bluuebunny/crossref_metadata_2025 huggingface dataset:
Calcium Conductance in An Identified Cholinergic Synaptic Terminal in the Central Nervous System of the Cockroach
Authors: Blagburn Jonathan M. , Sattelle David B.
Published: April 2021

Intracellular microelectrodes were used to study a cholinergic synapse between two identified neurones: the lateral filiform hair sensory neurone (LFHSN) and giant interneurone 3 (GI 3) in the terminal ganglion of the first-instar cockroach Periplaneta americana. The presynaptic cell, LFHSN, was impaled in a region of the axon which forms large numbers of output synapses.

The sign and magnitude of the LFHSN spike afterpotential were shown to depend on [Ca2+]o. l μmol l−1 tetrodotoxin (TTX) abolished LFHSN spikes but the addition of 0·l mmol l−1 4-aminopyridine (4-AP) enabled regenerative depolarizations to be evoked which were followed by large EPSPs in GI3. Addition of 20 mmol l−1 tetraethylammonium ions (TEA+) abolished the cholinergic EPSPs but resulted in long-duration LFHSN spikes. Intracellular injection of caesium ions (Cs+) into LFHSN enabled long-duration spikes to be evoked and had no effect on synaptic transmission. Long-duration LFHSN spikes were (1) increased in amplitude by increased [Caz+]o; (2) accompanied by an increase in conductance; (3) not abolished by replacement of external Na+ with Tris+ or choline+; (4) blocked by 1 mmol l−1 Cd2+ and 10 mmol l−1 Co2+; (5) not supported by substitution of Mg2+ for Ca2+; and (6) supported by Ba2+ substitution. They are thus considered to be Ca2+ spikes. The Ca2+ spikes were blocked by organic Ca2+ channel blockers at 0·5–1 mmol l−1.

The putative Ca2+ spike was followed by a hyperpolarizing afterpotential (HAP), the duration of which was proportional to the amplitude and duration of the Ca2+ spike. The HAP was (1) accompanied by a conductance increase; (2) reversed at potentials 30mV more negative than resting potential; (3) not supported by substituting Ba2+ for Ca2+; and (4) partially blocked by 150 mmol l−1 TEA+. The HAP is considered to result from an increase in Ca2+-dependent K+ conductance.

It is concluded that, in addition to Na+ channels and delayed rectifying K+ channels, Ca2+ channels and Ca2+-dependent K+ channels are present in the axonal membrane of LFHSN, in a region which forms many output synapses.
How does a Fly Cling to The Under Surface of A Glass Sheet?
Authors: Wigglesworth V. B.
Published: April 2021

The climbing of flies on glass is a problem that still lacks an agreed solution. West (1862), who introduced the term ‘tenent hairs’ for the trumpet-like structures on the pulvilli, regarded these as suckers which ensured adhesion by atmospheric pressure. But it is generally agreed that they are too small for that. Dahl (1885), studying adhesive organs in insects in general, favoured adhesion by ‘Capillarattraction’ but he considered that other forms of cohesion and adhesion were operating as well. Rombouts (1884) opted for surface tension. In the most recent paper, Walker, Yule & Ratcliffe (1985) give a new description of the adhesive organs in the blowfly Calliphora, and conclude from calculations that surface tension of the lipid secretion under the tenent hairs provides an adequate adhesive force.

The pad of setae at the lower extremity of the tibia of the first two pairs of legs, which is present in the adult of the blood-sucking bug Rhodnius and is used in climbing on a smooth surface (Gillett, 1932), has a totally different structure from that of the adhesive organ of the fly. In making a combined investigation (Gillett & Wigglesworth, 1932) we believed at first that surface tension in the lipid secretion between the oblique endings of the hairs and the surface would prove to be the adhesive force. But after experiments on insects and models, helped by discussions with N. K. Adam, we decided that direct intermolecular attraction, generated when the lipid film breaks down during sliding (i.e. seizure or partial seizure), was probably the more important force.

The tibial organ is present only on the first two pairs of legs of the adult Rhodnius, but these large (2 cm) insects can climb a steeply sloping sheet of glass. When the glass is vertical they slip down very slowly. In the experiments of Edwards & Tarkanian (1970), some Rhodnius adults held on to glass at angles greater than vertical, up to a mean of 109°. Beyond that they fell off. These are characteristic properties of the frictional forces dependent on molecular attraction, which do not resist separation by forces acting in the axis normal to the surface unless the areas in contact are molecularly smooth (Bowden, 1957). Edwards & Tarkanian (1970), in repeating the experiments on Rhodnius, accepted our interpretation – with the proviso that meniscus (surface tension) forces will, of course, be operating at the same time.
Modulated vibration-sensitivity of lamprey Mauthner neurones
Authors: Currie S. N. , Carlsen R. C.
Published: April 2021

The vibration-sensitivity of larval lamprey Mauthner (Mth) neurones is dependent on behavioural state. Animals are maximally vibration-sensitive when at rest and less so when active or aroused. To demonstrate this effect in freely behaving larvae, we provided repeated vibratory or electrical stimuli to the vestibular labyrinths while animals made transitions between rest and activity. Stimuli which were adequate to elicit Mth spikes 100% of the time in a resting animal (recorded extracellularly from the spinal cord) were consistently subthreshold while the animal was swimming. The same effect was seen in semi-intact preparations, both moving and curarized, while recording intracellularly from Mth cell bodies. Mth vibrationsensitivity decreased abruptly with the onset of ‘arousal’, defined here by the presence of tonic, descending spinal cord discharge. During arousal, the Mth soma exhibited a slight depolarization (2–8 mV), an increased membrane conductance, and a strong depression of vibration-evoked excitatory postsynaptic potential (EPSP) amplitude. This Mth PSP depression (MPD) appears to underlie altered vibration-sensitivity.
The Behaviour of Dendrocoelum Lacteum
Authors: Ullyott Philip
Published: April 2021

Dendrocoelum lacteum can orientate itself to a lateral stimulation intensity of less than 7 ergs/cm.2/sec. when not stimulated by other light sources. This orientation is produced equally well by “diffuse” or by point sources of light. The threshold value of lateral stimulation, to which orientation is possible, is a function of the total stimulation to which the animal is subjected. Graber (1884) and workers after him found that if planarian worms were put into a Petri dish one-half of which had been darkened with black paper, they congregated in the darker half. This was described as a phobotactic or non-orientated response. It has been shown that if a random movement brings an animal into the darker half of the dish, it immediately moves in an orientated fashion away from the lighter half, on account of its extreme sensitivity to lateral illumination. In reality tropotaxis and not phobotaxis is responsible for the behaviour observed. A reinvestigation of photophobotaxis is necessary.
The Behaviour of Dendrocoelum Lacteum
Authors: Ullyott Philip
Published: April 2021

Stimulation by non-directional light produces in the animal an increase in random movements, that is to say an increase in the rate of change of direction (r.c.d.). This r.c.d. can be expressed as a function of the stimulating intensity. In total darkness there is a basal r.c.d. In constant stimulation the r.c.d. decreases as the animal becomes adapted. The “shock reaction” is not an essential part of the mechanism of phobotactic behaviour. Photophobotaxis occurs without it. The r.c.d. phenomena and the adaptation associated with them are sufficient to explain the mechanism of photophobotaxis. Alternate adaptation and stimulation occur when the animal is moving down or up a non-directional gradient, as a result of its random movements. This alternate stimulation and adaptation has an effect on the r.c.d. of such a kind that the animal is led automatically to the place of minimal intensity.
On the Spherical Form of the Mammalian Erythrocyte
Authors: Ponder Eric
Published: April 2021

Some time ago I published an account of the change in shape, from disc to sphere, which occurs when mammalian red cells, suspended in saline, are placed between a slide and a closely applied cover-glass (Ponder, 1929). Later I briefly described a similar transformation which occurs in plasma or serum to which small quantities of lecithin have been added, the normally discoidal cells again becoming perfect spheres without change in volume (Ponder, 1933), and recently I have observed a disc-sphere transformation in systems containing red cells and dyes of the fluorescein series. To avoid difficulties associated with the peculiar shape of the mammalian red cell, several observers have worked with the spherical form in lecithin-treated plasma (Ponder, 1933, for finding volumes, 1935, in conductivity studies; Race, 1934, in sedimentation experiments; Fricke and Curtis, 1935, in conductivity and capacity experiments) ; no detailed description of the phenomenon itself, however, has yet appeared, and the disc-sphere transformation which occurs with the dyes of the fluorescein series is altogether new.
The Digestive Enzymes of the Onychophora (Peripatopsis Spp.)
Authors: Heatley Norman G.
Published: April 2021

An investigation has been made of the digestive enzymes of Peripatopsis spp. The pH of the gut varies between 6·0 and 8·2; it is usually about 7·0. The salivary glands elaborate amylase, glycogenase, protease and carboxy-polypeptidase. The gut digestive enzymes consist of invertase, maltase, lipase, esterase, amino- and carboxypolypeptidase and dipeptidase. Gelatin is also liquefied by the gut, but at pH 3·0 only. The properties of some of the individual enzymes have been examined.
Regeneration in Clavelina Lepadiformis
Authors: Berrill N. J. , Cohen Arthur
Published: April 2021

The polarity of a developing isolated piece of stolon of Clavelina lepadiformis is the same as that of the zooid from which it came in the case of straight or simply branched pieces. In pieces with congested ampullary branches the original polarity is lost and a secondary polarity acquired. The number of rows of stigmata formed during the development of a stolon fragment varies directly with the size of the fragment. In very small pieces development may become arrested at almost any stage, the stage of arrest depending on the quantity of mesenchyme contained in the proximal region of the stolon piece. If sufficient is present to enable development to proceed to the formation of a functional heart, a circulation is established that includes food reserves in the distal part of the stolon and development proceeds to completion. In shorter pieces, less than 0-4 mm. long, development or regeneration does not begin. The total failure to develop is correlated with the absence of a region of relatively columnar epidermis, and it is suggested that the area of columnar epidermis in pieces that do develop is a visible indication of the presence and extent of a morphogenetic field.
Experimental Studies in Insect Parasitism
Authors: Salt George
Published: April 2021

Trichogramma evanescens is able to distinguish healthy from parasitised hosts, and when few hosts are available can restrain itself for 8 hours to the deposition of 5 per cent, of its available eggs.

As far as is yet known, the discriminative ability is perfect ; but the restraint is limited and, in a longer period of time or when several parasites are together, it breaks down and superparasitism occurs.

When the superparasitism is slight and only two or three eggs are laid in a host, the competition between the parasite progeny leads to the victory and emergence of one; but when it is severe either a dwarfed or imperfectly developed individual or none at all emerges.

As the density of parasites in a fixed population of hosts is increased, more and more superparasitism occurs, and the following effects on the populations are observed : The number of hosts that escape steadily decreases; but even at high densities of parasites some hosts occasionally escape.The number of hosts that die without yielding either hosts or parasites steadily increases.The number of parasite progeny reaches a maximum and then decreases.The number of progeny of the individual parasites steadily decreases.An increasing proportion of the emergents are imperfectly developed.An increasing proportion of the emergents are males.
The Role of Divalent Cations and Ionic Strength in the Osmotic Sensitivity of Glutamate Oxidation in Oyster Gill Mitochondria
Authors: Ballantyne James S. , Moyes Christopher D.
Published: April 2021

The biochemical mechanism responsible for the osmotic sensitivity of glutamate oxidation in oyster (Crassostrea virginica Gmelin) gill mitochondria was examined. The relative roles of osmotically induced changes in matrix divalent cation concentration and ionic strength were determined. The calcium-magnesium ionophore A23187 inhibited glutamate oxidation in both low-(40% of control rate) and high-(25 % of control rate) osmolarity media. Addition of MgCl2 reversed A23187 inhibition, but at each MgCl2 concentration (1–5 mmoll−1) the rate of glutamate oxidation in the high-osmolarity medium was about 45 % that in the low-osmolarity medium. EDTA (4 mmol l−1) stimulated glutamate oxidation at both osmolarities (more pronounced at high osmolarity), removing the dependency on assay medium osmolarity. The stimulation in response to EDTA was correlated with mitochondrial swelling, which required the presence of monovalent cations for maximal effect. These data suggest that osmotically induced changes in matrix [Mg2+] or [Ca2+] are not responsible for the osmotic sensitivity of glutamate oxidation by oyster gill mitochondria in vitro. Changes in extramitochondrial [Mg2+] may be involved in regulating the rate of glutamate oxidation in vivo, through effects on mitochondrial volume. The maximal rate of glutamate dehydrogenase was not very sensitive to the ionic strength of the assay medium. The rate of electron transport was highly dependent on ionic strength, with the maximal rate occurring in 50 mmol l−1 salt. The osmotic sensitivity of glutamate oxidation in oyster gill mitochondria is apparently due to the effects of changes in matrix ionic strength on the rate of electron transport.
Maximum Lift Production During Takeoff in Flying Animals
Authors: Marden James H.
Published: April 2021

Maximum lift production during takeoff in still air was determined for a wide variety of insects and a small sample of birds and bats, and was compared with variation in morphology, taxonomy and wingbeat type. Maximum lift per unit flight muscle mass was remarkably similar between taxonomic groups (54–63 N kg−1), except for animals using clap-and-fling wingbeats, where muscle mass-specific lift increased by about 25 % (72–86 N kg−1). Muscle mass-specific lift was independent of body mass, wing loading, disk loading and aspect ratio. Birds and bats yielded results indistinguishable from insects using conventional wingbeats. Interspecific differences in short-duration powered flight and takeoff ability are shown to be caused primarily by differences in flight muscle ratio, which ranges from 0·115 to 0·560 among species studied to date. These results contradict theoretical predictions that maximum mass-specific power output and lift production should decrease with increasing body mass and wing disk loading.
Swimming Patterns and the Activity of Identified Equilibrium Interneurones in the Shore Crab, Carcinus Maenas
Authors: Fraser P. J. , Bévengut M. , Clarac F.
Published: April 2021

Swimming behaviour in crabs is electromyographically described in relation to the involvement of the discharge of the equilibrium interneurones. In intact crabs or crabs with only the fifth legs remaining, swimming consists of cyclic out-of-phase sculling movements of the last pair of pereïopods (P5). In these legs, all muscles are involved within a single swimming cycle; antagonistic muscles burst alternately, as do bilateral pairs of muscles. Bursting in the four proximal muscles ensures the appendage rotation while distal muscles set the scull in the best propulsive position.

Swimming evoked by tilt in the sagittal plane starts with symmetrical remotor activity before alternate bursting begins. Tilt in the plane of a statocyst vertical canal leads to asymmetrical onset of remotor bursting, starting with the muscle contralateral to the stimulated statocyst.

Tilt in defined vertical planes elicits the discharge of identified equilibrium interneurones. Of these, interneurones C and D are active before and during swimming. Sensory inputs from the statocysts and/or the leg proprioceptors to these interneurones are both adequate to drive swimming. Moreover, our experiments suggest that cell C activity is strongly involved in the onset and the maintenance of swimming behaviour.

Swimming can be altered by autotomy of legs on one side performed a few days in advance, and leads to the same turning tendency as does contralateral cutting of a connective. This may be due to modification in the strength of the remaining central connections to compensate for those lost.
Telemetered Electromyography of the Fast and Slow Extensors of the Leg of the Brown Lemur (Lemur Fulvus)
Authors: Anapol F. C. , Jungers W. L.
Published: April 2021

Quantitative telemetered electromyography from the four heads of the quadriceps femoris (vastus medialis, rectus femoris, vastus intermedius and vastus lateralis) during normal postures and locomotion (quadrupedal resting, walk/run, gallop and leaping) is presented for the brown lemur, Lemur fulvus. The vastus intermedius is the sole contributor to muscle recruitment during quadrupedal resting postures. It exhibits consistently high levels of electrical activity during all locomotory behaviour. The vastus medialis is recruited least among these muscles during walk/run and tends to be ‘saved’ for galloping and leaping. The rectus femoris and vastus lateralis are recruited at similarly high levels during all phasic activities. The rectus femoris appears to be used eccentrically, storing ‘elastic strain energy’ during all phasic activities. The vastus lateralis combines exceptionally high potential effective force with relatively high potential velocity and resistance to fatigue and probably develops the majority of force in all phasic activities. These results support previously documented structural and histochemical data that imply a functional division of labour among these muscle synergists.
Interactions Between Acid-Base Balance and Cutaneous Ion Transport in Larval Ambystoma Tigrinum (Amphibia: Caudata) in Response to Hypercapnia
Authors: Stiffler Daniel F. , Ryan Sandra L. , Mushkot Robert A.
Published: April 2021

Larval Ambystoma tigrinum (Green) were cannulated non-occlusively in the truncus arteriosus and allowed to recover for 20–24 h. They were then subjected to 24 h of hypercapnia in three groups : those adapted to tap water, 100 mmol l−1 NaCl or running distilled water. The animals in tap water displayed a 32% compensation for the respiratory acidosis in that [HCO3−] and strong ion difference (SID) were elevated to return pH back towards the control level. The animals in 100 mmol l−1 NaCl behaved similarly. However, the animals in running distilled water were unable to compensate by increasing either [HCO3−] or strong ion difference until NaCl was added to the medium. The clear requirement for NaCl in the medium of salamanders that are compensating for a respiratory acidosis led to measurements of Na+ and Cl− fluxes. The influx of Na+ increased by 123 % in animals immersed in NaCl and by 39% in animals in Na2SO4. The influx of Cl− decreased by over 50% in animals immersed in NaCl and by over 30% in those in choline chloride. The transcutaneous potential difference increased rapidly and reversibly during hypercapnia and the increase was blocked by propranolol. These data suggest that the cutaneous active transport of Na+ into the extracellular space is stimulated and that the active transport of Cl− is simultaneously inhibited during hypercapnia. Measurement of circulating interrenal steroids (RIA) revealed a clear increase in aldosterone concentration during hypercapnia and a possible accompanying increase in corticosterone. The results suggest that the compensatory response to hypercapnia in larval A. tigrinum involves alterations in cutaneous ion transport which increase the extracellular SID. These cutaneous responses may be under the shortterm control of catecholamines and under the long-term control of interrenal steroids.
The Sexually Dimorphic Jamming Avoidance Response in the Electric Fish Eigenmannia (Teleostei, Gymnotiformes)
Authors: Kramer Bernd
Published: April 2021

Eigenmannia’s, jamming avoidance response (JAR) is a frequency change of its electric organ discharge (EOD) in response to an electric stimulus of similar frequency (small ΔF; ΔF = FFish – FStim). It is assumed that the response to an unclamped stimulus, ΔR = FResponse – FRest, is stereotyped and non-habituating, and improves the fish’s electrolocation performance in the presence of a jamming stimulus, such as the EOD of a nearby conspecific.

Adult females gravid with eggs (N = 3) gave good responses (frequency decrease of at least 3 Hz) to – ΔF (stimulus frequency higher than fish frequency), but no response or only weak responses (<0·5 Hz) to + ΔF (stimulus frequency lower than fish frequency). After 2·75 years, a sexually mature female still showed the same behaviour, whereas an immature female (see below) had changed its behaviour considerably on becoming sexually mature.

Large males (N = 4) did not give JARs to +ΔF, and no JARs or only weak ones to – ΔF (| ΔR| < 0·7 Hz). Increasing the stimulus intensity by +10 or +20 dB did not change this result. After 2·5 years, two large males were still found to be almost unresponsive. However, large males gave rapid frequency modulations (‘short rises’ and ‘interruptions’), which have been described from threatening fish likely to attack, even at the weakest stimulus intensity.

One group of juveniles (N=4; probably females) gave only a weak increase in frequency (AR <0 ·9 Hz) in response to +ΔF but a strong frequency decrease (|ΔR|>2Hz) in response to –ΔF. Another group of juveniles (N=4; probably males) gave strongest responses (ΔR >3 Hz) to ΔF = 0Hz. In these juveniles, the ‘equilibrium point’ of no response was at ΔF ≈ – 0·6 Hz to – 1Hz instead of at ΔF = 0 Hz. They thus increased, rather than decreased, their EOD frequency even at small – ΔFs, which would have been more economical. A decrease in frequency was weaker than an increase. A significant frequency change could even be elicited by stimuli of ΔF = 0 Hz that are phase-locked to the EOD.

The accuracy of assessment of ΔF, as determined in juvenile fish giving good + ΔRs and – ΔRs, was not better than ±0·3 Hz (at ΔF = – 0·6 Hz). The JAR showed strong habituation.

Dedicated to Professor Kurt Fiedler on his 60th birthday.

None of the 14 fish showed a frequency difference vs response curve close to optimal for the purpose of jamming avoidance. An alternative function of the JAR in social communication is considered.
Effects of Trimetaphan on Locust Muscle Glutamate Receptors
Authors: Ashford M. L. J. , Boden P. , Ramsey R. L. , Shinozaki H. , Usherwood P. N. R.
Published: April 2021

Effects of trimetaphan have been tested on locust retractor unguis and extensor tibiae nerve–muscle preparations. Trimetaphan reversibly reduced the neurally evoked twitch amplitude of the retractor unguis muscle, dependent upon dose and partly upon stimulus frequency. Contractions evoked by both glutamate (10−4moll-1) and L-quisqualic acid (10− 4moll− 1) were abolished by Immoll− 1 trimetaphan. Dose-response curves for ionophoresis of L-glutamate were shifted to the right by trimetaphan, with a reduction in peak glutamate potential amplitude. The depression of the ionophoretic glutamate potential was partly dependent upon previous stimulation history, and this action was eliminated by concanavalin A. Trimetaphan had no effect on transmitter release. Within certain limits, trimetaphan reduced the extracellular postsynaptic current (EPSC) amplitude and rise time in a concentration-dependent and voltage-dependent manner. At high concentrations (>5x 10− 4mol l− 1) its effectiveness was reduced with large hyperpolarizations. The EPSC decay was prolonged and usually biphasic in the presence of trimetaphan, although at some junctional sites a mixture of biphasic and apparently monophasic EPSC decays was seen. It is concluded that trimetaphan exerts more than one effect on locust muscle glutamate receptors. It is likely that it enhances desensitization and also blocks the receptor channel when in the open state.
Swimming in the California sea lion: morphometrics, drag and energetics
Authors: Feldkamp Steven D.
Published: April 2021

During swimming, the California sea lion, Zalophus californianus (Lesson), generates thrust forces solely by means of its pectoral flippers. This study examines the drag, energetic cost and efficiency associated with this method of locomotion. Sea lions are highly streamlined, with a fineness ratio of 5·5 and maximum girth at 40 % of body length. This profile leads to reduced drag and swimming power requirements. Films of gliding animals showed the drag coefficient (based on wetted surface area) to be 0·0042 at a Reynolds number of 20×106. This value is comparable to that found for other aquatic vertebrates and suggests that the sea lion ‘s morphology helps to delay turbulent separation and maintain laminar flow over the forward portion of its body.

Swimming metabolism was measured in a water flume at velocities up to 1·3 ms−1. Effective swimming speeds up to 2·7ms−1 were attained by increasing each animal ‘s drag. Oxygen consumption rose exponentially with velocity and for two animals was best described as where is in ml O2 min−1 kg−1 and U is in ms−1. Minimum cost of transport for these animals was 0·12 ml O2 kg−1 m−1 at a relative speed of 1·4 body lengths s−1. This is 2·5 times that predicted for a fish of similar size. Swimming efficiencies were determined from these results using power output values calculated from the measured drag coefficient and standard hydrodynamic equations. At the highest velocity, aerobic efficiency reached a maximum of 15 % while mechanical efficiency of the foreflippers was 80%. The results demonstrate that foreflipper propulsion is a highly efficient and comparatively inexpensive method of locomotion in aquatic mammals.
Physiological features of the opercularis muscle and their effects on vibration sensitivity in the bullfrog Rana catesbeiana
Authors: Hetherington T. E.
Published: April 2021

The amphibian opercularis muscle connects a movable otic element (the operculum) to the pectoral girdle and can act in reception of ground vibrations. Various physiological parameters of the opercularis muscle of the bullfrog Rana catesbeiana were measured and compared with similar measurements on the iliofibularis muscle of the hindlimb. The opercularis muscle is a very slowly contracting muscle, with a Vmax of 1·81 muscle lengths s−1 compared to a Vmax of 6·24 muscle lengths s−1 for the iliofibularis muscle. The opercularis muscle develops tension slowly, taking about 10 s to attain maximum isometric tension when stimulated at 100 Hz. The muscle can retain high levels of tension for several minutes, and following stimulation has a time to half-relaxation of about 4–6s. The slow velocity of contraction, slow rate of tension development, fatigue-resistance and slow rate of relaxation of the opercularis muscle support morphological evidence that it consists mostly of tonic muscle fibres. Experiments were also made to examine the effects of muscle tension on reception of ground vibrations as measured by inner ear microphonics. Severing the nerve supplying the opercularis muscle produced slight decreases of no more than 2dB in responses to vibrations from 25 to 200 Hz. Artificial stimulation of the opercularis muscle after severing the nerve supplying the muscle increased responses to vibration across the entire frequency range. Higher tension levels produced greater increases in responses; at the highest tensions used (about 120 kN m−2) responses were increased by as much as 4· 5 dB. The opercularis muscle is therefore specialized for slow but prolonged contractions, and tension is important in its sensory function. A tensed opercularis muscle appears to transmit faithfully motion of the forelimb, produced by vibrations, to the operculum such that the latter moves relative to the inner ear fluids.
Intracellular Recording from Receptor Cells of the Temporal Organ of the Japanese House Centipede, Thereuonema Hilgendorfi: Receptor Potential and Conductance Changes
Authors: Yamana Kenjiro , Toh Yoshihiro
Published: April 2021

The primary process of carbon dioxide reception in the temporal organ of the Japanese house centipede Thereuonema hilgendorfi has been studied by means of intracellular recording.

During adaptation to air containing no carbon dioxide, the membrane potential of receptor cells in the temporal organ ranged from –25 to –59 mV with an average of –39mV (N = 21). Input resistance ranged from 10 to 46MQ with an average of 22-6MQ (N= 16). Receptor cells responded to a carbon dioxide stimulus with a graded hyperpolarizing receptor potential, which reduced impulse frequency. The decrease in steady-state frequency was proportional to the amplitude of the receptor potential. During the receptor potential, the input resistance increased. Injection of hyperpolarizing current resulted in an increase in amplitude of receptor potential, while depolarizing current caused a decrease. These results suggest that the receptor potential is caused by a decrease in membrane permeability to ions whose equilibrium potential is more positive than the membrane potential adapted to 0 % carbon dioxide.
Intersegmental Coordination of Central Neural Oscillators for Rhythmic Movements of the Walking Legs in Crayfish, Pacifastacus Leniusculus
Authors: Sillar Keith T. , Clarac François , Bush Brian M. H.
Published: April 2021

The neuronal circuits underlying rhythmical movements of the walking legs in crayfish Pacifastacus leniusculus are organized into central oscillators within each thoracic hemiganglion. These segmental networks are coupled in different modes of coordination during activities such as walking and limb waving. This paper examines the nature of the coupling between hemisegmental oscillators in the absence of sensory feedback, and the effect of phasic input from a major limb proprioceptor.

In isolated preparations of the thoracic nerve cord, adjacent ipsilateral hemiganglia can generate a rhythmic motor output pattern in which homologous motor roots discharge approximately synchronously (the ‘in-phase’ rhythm). In contrast, contralateral hemiganglia show no evidence of any such phase-locking in their activity. A single proprioceptor at the base of each limb, the thoracic-coxal muscle receptor organ (TCMRO), can influence the timing and intensity of the rhythmic output of two or more ipsilateral thoracic ganglia. Rhythmical stretch-release of the TCMRO of the fourth ganglion on one side can entrain the motor rhythms of both the third and fourth ipsilateral hemiganglia, in the in-phase pattern of coordination. The TCMRO also elicits intra- and intersegmental reflexes during expression of the in-phase motor rhythm. These reflexes are centrally modulated in a phasedependent manner. Thus mechanical stimulation of the TCMRO co-activates homologous sets of motoneurones in adjacent ipsilateral hemiganglia only during their active (spiking) phase in the motor rhythm.

We discuss the implications of these results for the generation and coordination of walking and other rhythmic behaviour of the thoracic limbs in decapod Crustacea. Our data shed further light on the properties of the motor rhythm generator for walking in crayfish, and suggest that the concept of a central pattern generator cannot be rigorously applied in this system.
Spontaneous and Evoked Eye Movements in Polyphemus Pediculus (Cladocera: Crustacea): A Case of Open-Loop Tracking?
Authors: Young Stephen , Taylor Victoria A.
Published: April 2021

Polyphemus eye movements were recorded in both pitching and yawing planes, both in a static visual environment and with a sinusoidally moving stimulus. Spontaneous eye movements (average amplitude 1·7°) had different properties in the two planes, with trembling movements predominating in the pitching plane. A contour-sharpening function is proposed for these movements. An attempt to analyse the eye movement response system using a Bode diagram shows a very poor fit to the data, leading to the conclusion that a closed-loop control system is an inappropriate model in this case. The evoked eye movements are most convincingly represented by a model in which the time the stimulus takes to traverse a restricted sensitive zone in the central region of the eye controls the duration of a subsequent constant angular velocity saccade. The direction of the response movement follows the direction of the stimulus. A small-object tracking function is proposed for these movements.
Energy-Dependent Facilitation of Transcuticular Water Flux Contributes to Evaporative Cooling in the Sonoran Desert Cicada, Diceroprocta Apache (Homoptera: Cicadidae)
Authors: Toolson Eric C. , Hadley Neil F.
Published: April 2021

Terrestrial arthropods exhibit an array of impressive adaptations for conserving water, including highly waterproof cuticles, the ability to reduce excretory losses by resorption of water from the faeces and, in some species, the ability to absorb water vapour from subsaturated atmospheres (Edney, 1977). The possibility of an additional adaptation has been inferred from the observation that gravimetric water loss rates of many terrestrial arthropods increase significantly following death, even when body openings, e.g. spiracles, are sealed. This increase, which may be as large as five-fold (Toolson & Hadley, 1979), has been interpreted as evidence for an energy-dependent process that actively retards loss of water through the cuticle (Winston & Beament, 1969). The mechanistic basis for the phenomenon, however, is controversial (Berridge, 1970; Riddle, 1981; Machin, Lampert & O’Donnell, 1985).
Contributions of anaerobic metabolism to pH regulation in animal tissues: theory
Authors: Pörtner Hans-Otto
Published: April 2021

Proton balance is analysed in relation to the anaerobic and aerobic metabolism of carbohydrates, carbonic acids, amino acids and fat by considering oxidation, carboxylation, decarboxylation and phosphorylation reactions, as well as the influence of ammonium, on the acid—base status of animal tissues. The functional role of the adenylates, phosphagens and inorganic phosphate in acid-base balance is investigated with respect to differences in the physicochemical properties of organic and inorganic phosphates.

General principles are established for different anaerobic metabolic pathways in species from several phyla. It is concluded that proton release from the substrate, which is always involved in substrate-level phosphorylations, is essential for the mechanism of ATP formation. Anaerobic metabolism, which is characterized by incomplete oxidation of carbon chains and an accumulation of acidic groups, supports pH regulation in facultative anaerobes by minimizing the amount of accumulated protons. High levels of phosphagens mean high proton absorption during hydrolysis and an increase in the intracellular buffer value. Decarboxylation reactions in catabolic pathways are equivalent to proton consumption. The degradation of carbonic acids during anaerobiosis, therefore, contributes to pH regulation. Release of ammonia or ammonium ions in catabolism is also linked to the buffering of protons originating from the formation of carboxyl groups and net cleavage of ATP. Net disposal of amino groups or ammonium ions by transamination, reductive amination or ion exchange does not change this general picture. The proton, bicarbonate and CO2 turnover in metabolic pathways is discussed with respect to the interrelationships between pH and metabolic regulation.
Substrate Interactions Affecting Motor Growth Cone Guidance During Development and Regeneration
Authors: Westerfield Monte
Published: April 2021

Most serious injuries of spinal nerves or roots in man and other higher vertebrates lead to permanent loss of control of skeletal muscles. In some cases this may be due to a failure of motor axons to regenerate, although even when functional neuromuscular connections are re-established, coordinated use of body and limb muscles may be absent. In both mammals and lower vertebrates, damaged motor axons usually regrow and reform functional connections with muscles, although these connections are often inappropriate. The selectivity of reinnervation is improved by maintaining alignment of the severed ends of the nerve. Thus, factors operating near the lesion site may direct regenerating motor axons into fascicles in the distal nerve stump that lead to inappropriate muscles. The identity of some of these factors is suggested by recent studies of developing systems which have shown that motor axons are directed in their growth, (a) The filopodia of their growth cones sample a limited region of the periphery. If motor growth cones extend too far from their normal pathways they establish connections with inappropriate muscles, (b) Motor growth cones normally extend into regions of embryos rich in the extracellular matrix molecule laminin, and avoid regions containing fibronectin. Moreover, motor growth cones extend on laminin but not on fibronectin substrates in vitro. In peripheral nerves, these two molecules are differentially distributed; laminin is expressed by Schwann cells in the endoneurium whereas fibronectin is expressed by fibroblasts primarily in the perineurium. These studies suggest that regenerating motor growth cones may be directed to appropriate muscles if their original fascicles within the distal nerve stump are within filopodial reach but may not be able to escape the fibronectin-rich perineurial sheath once directed into an inappropriate fascicle.
Nerve Growth Factor in Neuronal Development and Maintenance
Authors: Misko Thomas P. , Radeke Monte J. , Shooter Eric M.
Published: April 2021

One of the major roles of nerve growth factor (NGF) is to mediate the selective survival of a proportion of the developing sympathetic and sensory neurones as they innervate their particular target tissues. The underlying basis of this phenomenon is the synthesis of limited amounts of NGF in the target, its secretion around, and uptake by, the nerve terminal and its retrograde transport along axons to the neuronal cell bodies. The cascades of reactions which lead to neuronal survival and maintenance are initiated by signal transduction somewhere in this pathway. Retrograde transport and the initial signal transduction step begin when NGF binds to NGF receptors on the nerve terminal. Receptor-mediated internalization and the survival and maintenance function of NGF are mediated by the higher affinity receptors. These receptors have relative molecular masses of approx. 145 000 and are trypsin-resistant when occupied. In contrast, the larger population of lower affinity receptors have relative molecular masses of 85 000 and are rapidly degraded by trypsin. Clustering of the lower affinity receptors by a variety of agents gives them many of the characteristics of the higher affinity receptors, suggesting receptor interconversion may play a role in NGF actions. The structure of the lower affinity NGF receptor, determined by gene transfer and cloning, shows it to be a unique, heavily glycosylated protein. The extracellular domain is rich in cvsteine-containing repeat units while the intracellular domain lacks the consensus sequence for an endogenous kinase activity. It is likely that the higher affinity receptor contains this protein as the NGF binding subunit together with a second protein which determines both the nature of the signal transduction mechanism and the process of internalization.
Neurite Outgrowth and Synapse Formation by Identified Leech Neurones in Culture
Authors: Chiquet Matthias , Nicholls John G.
Published: April 2021

After injury, neurones in the central nervous system (CNS) of the leech regenerate with a high degree of specificity. The aim of our experiments has been to study the sequential steps involved in neurite growth and synapse formation using isolated identified neurones in culture. An important requirement for sprouting of leech neurones is the substrate. Neurites grow only slowly and sparsely on polylysine or vertebrate laminin. The extracellular matrix of leech ganglion capsules contains a protease-sensitive factor which can be extracted with urea. With this material as substrate, growth proceeds rapidly in defined medium. Another neurite-promoting substrate is provided by the plant lectin concanavalin A (Con A). The activity of Con A, but not of the capsule matrix factor, is blocked by the Con A-specific hapten methyl cr-D-mannoside. The morphology and branching pattern of the neurites in culture depend on the specific substrate and on the type of neurone. During stimulation, less Ca2+ uptake occurs into growth cones than in cell bodies. The mechanism of neurite growth seems not to depend on activity-mediated Ca2+ influx or on interactions between neuronal cell surfaces. However, even without profuse outgrowth, electrical and chemical synapses develop between neighbouring neurones. The type of synapse depends predictably on the types of neurones within the cell pair. Since the development of a synapse can be followed with time in culture, the sequential events can each be studied separately for this multi-step process.
Tinkering With Successful Synapse Regeneration in the Leech: Adding Insult to Injury
Authors: Muller K. J. , McGLADE-McCULLOH E. , Mason A.
Published: April 2021

In the leech, synapse regeneration in adults and synapse formation during embryonic development can be studied in single, identifiable cells that make precise connections with their targets. Certain cellular components, such as synaptic targets and glia, were selectively destroyed to study how the regenerating axons locate their targets, what triggers axons to start growing and what stops them. The results showed that glia and targets play only a limited role in synapse regeneration and in axon degeneration. For example, contact with the synaptic target may inhibit sprouting and availability of targets may promote it. Comparative studies on axon growth and synapse formation by interneurones in embryos showed that regeneration does not simply recapitulate embryonic development. There are clearly separate constraints on the two processes. Axon survival is a different problem. Although isolated axon segments can survive for up to a year in the leech, temperature is a major factor in survival. Axon segments in a tropical leech that regenerates synapses well at 31 °C degenerated within 2–3 weeks at this elevated temperature, even when regeneration was prevented. In similar leeches at room temperature (22°C), segments survived for months. Overall, results in the leech support the idea that degeneration as well as regeneration share fundamental mechanisms with other invertebrates and the vertebrates, including mammals. Perhaps long-lived axon segments and other features of the leech that speed or encourage functional regeneration can now be made to operate in repair of the mammalian nervous system.
Glial Cells in the Rat Optic Nerve and Some Thoughts on Remyelination in the Mammalian Cns
Authors: Raff Martin C. , Ffrench-Constant Charles , Miller Robert H.
Published: April 2021

Studies on the rat optic nerve in the past 5 years have produced two surprises. First, they demonstrated that there are two biochemically, developmentally and functionally distinct types of astrocytes in the optic nerve, and probably in white matter tracts throughout the CNS: one seems to be responsible for inducing endothelial cells to form the blood–brain barrier while the other seems to service nodes of Ranvier. Second, they showed that oligodendrocytes and type-2 astrocytes develop from a common bipotential (O-2A) progenitor cell that seems to migrate into the developing optic nerve, and may well migrate all over the CNS to wherever myelination is required; this implies that the neuroepithelial cells of the optic stalk are restricted to forming type-1 astrocytes.

Some of the findings in the optic nerve may be relevant to the problem of CNS regeneration after injury. These include the following. (1) Reactive gliosis in white matter tracts seems to be mainly a function of type-1 astrocytes. (2) Proliferating O-2A progenitor cells are present in the adult CNS, raising the possibility that they may be able to produce new oligodendrocytes and type-2 astrocytes following injury and thereby aid regeneration. (3) Type-1 astrocytes seem to be able to respond to environmental signals and form localized barriers that block the migration of O-2A progenitor cells; it is conceivable that the same barriers block the migration of regenerating axonal growth cones.
Mechanisms of Glial Regeneration in an Insect Central Nervous System
Authors: Smith P. J. S. , Howes E. A. , Treherne J. E.
Published: April 2021

As in other repairing systems, glial regeneration in insect central nervous connectives, following selective chemical lesioning, involves both exogenous and endogenous elements. Our current evidence, including that obtained with monoclonal antibodies, indicates that the reactive, granule-containing cells are derived from a sub-population of circulating haemocytes which, within 24 h, invade, and are restricted to, the lesion zone. The granule-containing cells are involved in the initial repair of the perineurial region. They also contribute to the first stage in the restoration of the blood-brain barrier and are responsible for recruiting reactive endogenous glia, apparently from the vicinity of the anterior abdominal ganglion. The granule-containing cells transform into or are replaced by functional glia between 3 and 5 days after selective glial disruption, coincident with the appearance in the lesion zone of dividing reactive cells.
Motor Activity During Searching and Walking Movements of Cockroach Legs
Authors: Delcomyn Fred
Published: April 2021

Rhythmic motor activity may be recorded in the legs of cockroaches during the execution of several different types of behaviour that involve leg movements. It was examined in detail during searching and walking. During walking, motor activity always consisted of a series of bursts separated by silent periods. During searching, it was usually continual, but modulated in frequency. Sometimes, the motor pattern recorded from a searching leg was burst-like rather than modulated. In these cases, it could nevertheless be reliably distinguished from the motor pattern recorded during walking by a simple analysis of the burst pattern. An analysis of the motor pattern recorded during righting indicated that this pattern was more like that for walking than that for searching. Therefore, searching is not simply walking that lacks certain periodic sensory input due to leg contact with the ground. It is concluded that walking and searching can be reliably distinguished from one another on the basis of an analysis of a record of motor activity in a single leg muscle only. An ability to distinguish between similar types of behaviour on the basis of the motor pattern may prove useful in a variety of experiments.