bluuebunny/crossref_metadata_2025 huggingface dataset:
Command Fibres in the Circumoesophageal Connectives of Crayfish
Authors: Bowerman R. F. , Larimer J. L.
Published: April 2021

Several discrete postures have been generated by electrical stimulation at frequencies of 20–75 Hz of command interneurons within the circumoesophageal connectives of the crayfish. The behaviour patterns were recorded by cine photography. The similarity of the patterns in different individuals generated by stimulation of interneurons found in the same positions within the cord, strongly suggested that certain of the interneurons examined in this study were identical. A number of tonic command fibres were found, each of which evoked a specific body geometry. Tonic command units were classified on the basis of evoked cheliped, walking leg, and abdominal positions. The study concentrated on those command fibres which generated spatially distributed behaviour patterns involving both abdomen and appendages, and neglected command elements with more restricted outputs. The types of tonic command fibres characterized include the following: bilateral appendage promotion, ipsilateral appendage promotion, bilateral cheliped lift, ipsilateral appendage lift and flex, general flexion, abdominal extension, and both ipsilateral and contralateral turning. A movement-suppressing command fibre, ultimately termed the ‘statue fibre’ was found twice. Stimulation of this element terminated spontaneous activity by ‘freezing’ the animal, irrespective of position. An additional consequence of stimulation of the statue fibre was the overriding of the excitatory effect of mechanical stimulation which in the absence of the command drive would provoke the animal into activity. It is suggested that a restricted number of tonic command fibres could be functionally operative in the generation of their corresponding behaviour patterns. For the majority of tonic command fibres, however, it is felt that the unit is merely one of a group of elements each of which is activated simultaneously or sequentially for discrete behavioural performances.
Electrophysiological Responses of the Terminal Sensilla on the Maxillary Palps Of Locusta Migratoria (L.) To Some Electrolytes and Non-Electrolytes
Authors: Blaney W. M.
Published: April 2021

Three morphologically and functionally different types of sensilla on the maxillary palp tips of Locusta migratoria are distinguished and an electrophysiological study is made of the most commonly occurring type. Responses to stimulation with 0·1 M sodium chloride show impulses of one, two or three amplitude categories in different sensilla. Variability of response to a constant stimulus is appreciable, both between and within sensilla. Tests with a range of compounds indicate that individual neurones are capable of responses to compounds of different chemical classes. Specificity of sensilla is more marked than specificity of neurones. Methods of interpretation of results are evaluated and the results are discussed in the context of discrimination of food plant materials.
The Response of the Swim Bladder of the Goldfish (Carassius Auratus) to Acoustic Stimuli
Authors: Popper Arthur N.
Published: April 2021

The teleost swim bladder is a gas-filled chamber located in the abdominal cavity just below the vertebral column. It consists of one or more inter-connected chambers which may be partially divided into ‘subchambers’ by septa that are extensions of the inner lining of the swim-bladder wall (Demski, Gerald & Popper, 1973 ; Greene, 1924; Tavolga, 1962 and others).
The Effect of Swimming Activity and Section of the Vagus Nerves on Heart Rate in Rainbow Trout
Authors: Priede Imants G.
Published: April 2021

Heart rates associated with swimming activity were measured in intact and vagotomized fish at 6·5 and 15 °C. Low swimming speeds had no effect on heart rate but above a threshold speed it increased logarithmically with swimming speed up to the critical speed and maximum heart rate. Times for recovery after exercise increased rapidly above the critical speed. Bilaterally vagotomized fish at 6·5 °C showed high resting heart rates and erratic cardiac responses to exercise. In bilaterally vagotomized fish at 15 °C heart rates were normal except for a low maximum rate. It is concluded that the vagus nerve can function differently at different temperatures.
Light-Evoked Electrical Potentials from the Eye and Optic Nerve of Strombus: Response Waveform and Spectral Sensitivity
Authors: Gillary Howard L.
Published: April 2021

The neural processing of visual information by the retina is reflected in the light-evoked extracellular retinal potentials (electroretinogram or ERG) and the discharge pattern of the concomitant afferent impulses in the optic nerve fibres. The waveform of the ERG is often fairly complex, since it represents the summed activity of a large number of different neurons; this activity can include the photic stimulation of receptors, and synaptic excitation and inhibition (Brown, 1968; Werblin & Dowling, 1969). Examining the ERG and its relation to the optic nerve activity which encodes the visual information can help to reveal the underlying neural mechanisms (Kennedy, 1964). Molluscan eyes, which exhibit a vast range of anatomical complexity (Charles, 1966), have proven amenable to the electrophysiological investigation of these mechanisms (see Discussion for examples and references).
Neuromuscular Physiology of the Longitudinal Muscle of the Earthworm, Lumbricus Terrestris
Authors: Drewes C. D. , Pax R. A.
Published: April 2021

An earthworm saline commonly used in previous investigations of earthworm neuromuscular physiology has been shown to be inappropriate for such studies because the ionic composition of the saline does not correspond to that of earthworm body fluids. Problems encountered when using this saline include: increased excitability of motor axons innervating the longitudinal muscle, a decrease in the amplitude of external electrical responses of the muscle, an increased susceptibility of longitudinal muscle fibres to injury spiking, and a decrease in resting potentials of longitudinal muscle fibres (to a mean of – 36·1 mV). Such problems have been overcome by the development of a new physiological saline whose composition closely corresponds to the ionic composition of earthworm body fluids. In the new saline responses of the nerve-muscle preparation remain stable for more than 1 h. Resting potentials of longitudinal muscle fibres are also stable with time, the mean resting potential being – 47·9 mV.
Coupling of Transmural Flows of NaCl and Water in the Intestine of the EEL (Anguilla Anguilla)
Authors: Skadhauge Erik
Published: April 2021

An in vivo perfusion of the intestine of the yellow European eel (Anguilla anguilla) was used to measure the net absorption of NaCl and water, the osmotic permeability coefficient, the solute-linked water flow, and the osmolality difference against which the intestine could transport water as functions of the salinity of the surrounding water. The eels were adapted to fresh water, to sea water, and to strength sea water. The osmolality difference against which the intestine could transport water was observed to be linearly related to the net transmural flow of NaCl ; the solute-linked water flow had a constant hypertonicity in spite of differing net flows of NaCl. The findings are in agreement with the hypothesis of uphill water movement being caused by local osmosis due to the salt flow and with a shunt leak proportional to the transmural osmotic difference. An important part of adaptation to waters of higher salinity is a pronounced increase in the intestinal absorption of NaCl. The osmotic permeability coefficient varied from experiment to experiment without relation to the state of adaptation. An explanation for this finding may be that the osmotic permeability of the intestinal epithelium is of little importance for the total intestinal transfer of water.
Drinking Rate and Oxygen Consumption in the Euryhaline Teleost Aphanius Dispar in Waters of High Salinity
Authors: Skadhauge E. , Lotan R.
Published: April 2021

The drinking rate and the oxygen consumption were measured in Aphanius in sea water (SW) at 17, 20 and 24·5 °C and at 20 °C in 2-fold and -fold SW. Both untrained (shocked) and trained fish were used. In this species shock was observed to reduce the drinking rate. In trained fish the drinking rate was 11·0±1·0μl/g.h (mean μ S.E.) in SW at 20 °C. The oxygen comsumption was 346± 16 μl O2/g.h. These parameters were not significantly changed in 2 SW and SW. At 17 °C both drinking rate and oxygen consumption were reduced, and at 24·5 °C were increased. The results suggest that adaptation to waters of high salinity primarily involves a reduced effective osmotic permeability of the integument (the gills) and an increase in the transport rate of NaCl by the intestine, roughly proportional to the salinity.
Flow along the Gut and Intestinal Absorption of Salt and Water in Euryhaline Teleosts: A Theoretical Analysis
Authors: Kristensen K. , Skadhauge E.
Published: April 2021

In euryhaline teleosts the transmural salt and water flow and the flow and concentration changes along the gut were simulated by analogue computation. The purpose was to elucidate the interaction of and sensitivity to the parameters of the system particularly with respect to intestinal water absorption. The simulations were based on data obtained from the yellow European eel, the rainbow trout and the cyprinodont Aphanius dispar. When the experimental values for drinking rate, maximal NaCl absorption rate and concentration at half-maximal absorption rate, osmotic permeability coefficient, solute-linked water flow, and concentrations in the gut were used in the model, good consistency was achieved, and predictions could be made. The simulations demonstrated a close linkage between drinking rate and maximal NaCl absorption rate. A large water absorption was only possible close to an optimal drinking rate for each value of maximal NaCl transport rate. The water absorption was little sensitive to the osmotic permeability coefficient of the intestinal wall. As a means of adaptation to waters of high salinity an increase in maximal NaCl absorption rate was shown to be very costly for energetic reasons. This supports indirectly the concept that the osmotic permeability of the gills must go down. The increase in plasma osmolality was a useful part of the adaptation.
Gas Exchange and its Effect on Blood Gas Concentrations in the Amphibian, Xenopus Laevis
Authors: Emilio M. G. , Shelton G.
Published: April 2021

Unrestrained Xenopus with access to air had an oxygen consumption, as measured at 20 °C by manometric and electrode techniques, of approximately 4·5 ml O2 100 g−1 h−1 of which 1·1 ml was taken in through the skin. Measurements of body volume showed that the rate of oxygen uptake from the lungs was high when the animal was at the surface but fell rapidly during the first few minutes of a dive. Oxygen tensions in systemic (80 mmHg) and pulmocutaneous (60 mmHg) vessels provided evidence for separation of blood flows in the ventricle of the animal when breathing air. The tensions fell in all parts of the circulation throughout a dive. The above data, together with a conventionally determined oxygen dissociation curve, show that both blood and lungs are used to a limited extent as oxygen stores during a dive, the blood being more important. The stores do not permit tissue consumption to go on at a uniform rate throughout a normal breathing - diving cycle.
On the Mechanical Properties of the Vitelline Membrane of the Frog Egg
Authors: Mild Kjell Hansson , Løvtrup Søren , Bergfors Tommy
Published: April 2021

Cole’s method is employed to measure the internal pressure in body cavity eggs of Rana temporaria. In the interpretation of the results the effect of bending resistance is considered.

The internal pressure in the undeformed egg in isotonic solution, at 25 °C, is 30 dyn/ cm2, corresponding to a stress resultant, or tension, in the vitelline membrane of 1-5 dyn/cm. In hypotonic solutions substantial increases in the pressure have been recorded.

When the pressure is studied as a function of temperature an anomalous high pressure is found at 16 °C for all the different incubation media employed.

A new method is applied to determine Young’s modulus of the membrane. The result obtained is 3·7 x 105 dyn/cm2 at 23° C.
Ventricular Outflow Dynamics in the Lizard, Varanus Niloticus: Responses to Hypoxia, Hypercarbia and Diving
Authors: Millard R. W. , Johansen K.
Published: April 2021

Blood flow and blood pressure have been measured in the right aorta and left pulmonary artery of the semi-aquatic lizard, Varanus niloticus, during normal breathing, during hypercarbic and hypoxic breathing and during voluntary diving. Mean pulmonary blood pressure during normal breathing was 19 · 5 ± 2 · 0 cmH2O while right aortic pressure was 118 · 0± 3·0 cmH2O. The high systemic blood pressure and high ratio of systemic to pulmonary vascular resistance (4·0−6·0) stand out among reptiles and approach values in homeotherm vertebrates. Pulmonary pressure rise preceded right aortic pressure rise by 120 msec at a heart rate of 25/min. Pulmonary ejection lasted 50% of the cardiac cycle compared to 25 % for aortic ejection during normal breathing. CO2 breathing increased right aortic vascular resistance by 120% while pulmonary resistance increased moderately by 30%. Carotid vascular resistance decreased during CO2 breathing. The pulmonary blood pressure increase was however much higher than the systemic, but at no time did systemic and pulmonary blood pressures overlap. Hypoxic breathing increased pulmonary blood pressure to 36·0 ± 4·0 cmH2O while right aortic pressure fell to 100·0± 10·0 cmH2O. Ejection time remained unchanged in the right aorta while pulmonary flow became continuous. Overall pulmonary vascular resistance increased markedly while systemic resistance changed little. Voluntary diving increased pulmonary blood pressure while the systemic blood pressure fell markedly. The results obtained are discussed in the light of ventricular outflow distribution in reptiles. Directional shunting of blood inside the heart of V. niloticus during cardiac systole must be reduced or absent. Intracardiac shunting during cardiac filling or by systolic residual volumes is small, placing varanid lacertilians haemodynamically closer to homoetherm vertebrates than other reptiles studied.
Directional Sensitivity of Microphonic Potentials Form the Perch Ear
Authors: Sand Olav
Published: April 2021

Microphonic potentials were recorded from the lagena and from different parts of the sacculus in the perch during horizontal and vertical vibration of the fish in air. This stimulation technique gives a good simulation of sound stimulation in water. The lagena was predominantly sensitive to vertical vibrations, whereas the anterior part of the sacculus was equally sensitive to vertical and horizontal vibrations. A gradient is seen along the sacculus, in that the more posterior positions show a tendency towards greater relative vertical sensitivity. By comparing the nervous output from the lagena and from the sacculus the fish might thus get information about the vertical direction of the sound source. The amplitude of the saccular Microphonic potentials evoked by horizontal vibrations was a function of the vibration direction. Maximal responses were obtained when this direction deviated about 20° from the long axis of the fish, which is approximately parallel to the long axis of the sacculi. The difference in response between the two ears might be utilized to give directional information about the horizontal position of the sound source. Sound-induced pulsations radiating from the swimbladder will be efficient in evoking saccular Microphonic potentials. This causes masking of the difference in response between the two ears, but directional information may still be obtained. It is proposed that the power of angle separation in the horizontal plane should be optimal for sound waves side on to the fish, and that a fish possessing a swimbladder may be able to detect the sound direction with higher accuracy in the vertical than in the horizontal plane. The relative effect in evoking Microphonic potentials of vertical compared to horizontal vibrations was frequency dependent, and it is concluded that the pattern of otolith movements during sound stimulation may also change with frequency. This phenomenon constitutes a possible basis for peripheral frequency analysis in fish.
Potassium-Induced Release of the Diuretic Hormones of Rhodnius Prolixus and Glossina Austeni: Ca Dependence, Time Course and Localization of Neurohaemal Areas
Authors: Maddrell S. H. P. , Gee J. D.
Published: April 2021

Exposure of neurohaemal areas to solutions of elevated K concentration (above 40 mM) causes a maximal release of diuretic hormone in Rhodnius prolixus and Glossina austeni. An involvement of Ca in hormone release is indicated by the reduction caused by low concentrations of this cation (below 2 mM) or by the presence of Mn. During prolonged treatment with K-rich solutions the rate of hormone release is initially high, but then declines. This response parallels that for Ca entry into squid giant axons during maintained potassium depolarization and suggests that the rate of Ca entry controls the rate of hormone release. Tetrodotoxin did not reduce the potassium-induced release of the hormone, suggesting that K acts directly on the neurosecretory axon endings in the neurohaemal areas.
Total Body Calcium and Haemolymph Calcium Concentrations in the Crayfish Austropotamobius Pallipes (Lereboullet)
Authors: Greenaway Peter
Published: April 2021

Variations in the concentration of calcium in the haemolymph and of total body calcium in Austropotamobius pallipes have been investigated. Haemolymph calcium concentration was independent of both body size and sex. During premoult the calcium concentration of the haemolymph rose from 11·8 mM/1 to 15·0 mM/l. After the moult the calcium concentration remained high during stages A and B but declined to the intermoult level during stage C. Total body calcium was directly proportional to fresh body weight. No difference was apparent between calcium content of male and female crayfish of similar body weight.
Respiratory Acidosis and Eggshell Resorption by the Chick Embryo
Authors: Crooks R. Jane , Simkiss K.
Published: April 2021

Eggs of the domestic fowl were injected with 45Ca and then subjected to normal incubation or to incubation in 9% carbon dioxide in air. The embryos, yolk, albumen and shell were analysed at various times after incubation had started. The results demonstrate that there is normally a resorption of the eggshell during the latter part of incubation but that this process is depressed by hypercapnia. The results are discussed in relation to the events in normal development and in relation to possible mechanisms of shell resorption.
The Effects of Sodium-Transport Inhibitors and Cooling on Membrane Potentials in Cockroach Central Nervous Connectives
Authors: Pichon Y. , Treherne J. E.
Published: April 2021

Cooling caused axonal depolarization in desheathed and urea-treated connectives, but induced hyperpolarizing responses (measured with microelectrodes and with the sucrose-gap) in intact preparations. Hyperpolarizing responses were also recorded with extracellularly-located microelectrodes in intact connectives. Strophanthidin (0·2 mm/1) caused axonal depolarization in desheathed preparations, ethacrynic acid being without appreciable effect. Ethacrynic acid (0·2 mm/1) induced apparent hyperpolarizations in intact connectives and abolished or reduced the effects of cooling. It is concluded that the axonal sodium pump is pharmacologically separable from that associated with the perineurial and/or the glial membranes: the former being inhibited by cardiac glycosides, the latter by ethacrynic acid. The results are discussed in relation to extra-axonal sodium regulation and the possible involvement of an electrogenic sodium pump associated with the perineurial or glial membranes.
Metabolic Rates Related to Muscle Activity in Bumblebees
Authors: Kammer Ann E. , Heinrich Bernd
Published: April 2021

Oxygen consumption, thoracic temperature, and action potentials from the fibrillar muscles were concurrently recorded in queens and workers of Bombus vosnesenskii. The oxygen consumption of ‘inactive’ bees (quiescent and/or producing fewer than 0·3 spikes/sec) was markedly temperature-sensitive, with a Q10 of 3·4 for thoracic temperatures of 25–35°C. The oxygen consumption of bees with active fibrillar muscles was directly correlated with spike frequency; a single spike was associated with the consumption of 2·3–2·6 μl O2/gth. No oxygen debt was observed. The oxygen consumption per spike during flight was similar to that during warm-up. Oxygen consumption per gram thorax was similar in queens and workers engaging in similar activity. The results are compared with those from other insects and their adaptive significance is discussed..
Renal Concentrating Ability in Selected West Australian Birds
Authors: Skadhauge Erik
Published: April 2021

The osmotic ratio between ‘urine’ (the supernatant of the ureteral part of the droppings) and plasma has been determined in a number of dehydrated West Australian birds. The U/P ratio was 1·4 in the Emu, 1·7 in two Columbidae (Senegal Turtle Dove and Crested Pigeon), 2·4 in two Meliphagidae (Singing Honeyeater and Red Wattle Bird), 2·6 in three Psittacidae(Bourke Parrot, 28-Parrot, and Galah), 2·7 in the Laughing Kookaburra, and 2·8 in the Zebra Finch. The Na+ and Cl− concentrations in the ‘urine’ ranged from 5 to 71 m-equiv./l, the K+ concentration from 92 to 201 m-equiv./l. There seems to be a rather narrow range for tire concentrating ability within each family, but the concentrating ability of xerophilic birds differs considerably.
Calcium Balance at the Premoult Stage of the Freshwater Crayfish Austropotamobius Pallipes (Lereboullet)
Authors: Greenaway Peter
Published: April 2021

The premoult stage in Austropotamobius pallipes is characterized by a net loss of calcium which increases from Do to a maximum of 0·83 /μmoles/g/h at D4. The concentration of ionized calcium in the haemolymph does not increase during the premoult stage although there is an increase in complexed calcium. The electrochemical gradient across the body surface is similar to that at the intermoult stage and favours calcium outflux. Possible routes for calcium net loss have been discussed and a mechanism for elimination of calcium has been proposed.
Physiology of Insect Ecdysis: Neural and Hormonal Factors Involved in Wing-Spreading Behaviour of Moths
Authors: Truman James W. , Endo Paul T.
Published: April 2021

In the tobacco hornworm, wing spreading involves a stereotyped series of movements which take 74 min to complete and which include two components, wing folding and wing inflation. Moths decapitated at the moment of eclosion show neither wing inflation nor wing folding. If decapitation is delayed until 5 sec after emergence, then the full wing-spreading behaviour is displayed. Newly emerged moths which are confined show intense digging-behaviour and delay the onset of wing spreading until after their release. Decapitated moths attempt to spread their wings immediately, regardless of whether or not they are confined. Surgical experiments showed that the brain was not required in a neural capacity in order for wing spreading to occur; it was needed only as a source of the eclosion hormone. The neural influence of the suboesophageal ganglion was required until immediately after eclosion. Newly emerged moths whose abdomens had been removed showed wing-folding behaviour. No inflation occurred and the duration of wing folding was much longer than normal. It was concluded that wing-folding behaviour was centrally programmed but that the abdomen could modify the length of the programme. Injections of bursicon into abdomenless moths reduced the duration of wing-folding behaviour to almost normal levels. Therefore, in some manner, bursicon has an important role in determining when wing-folding behaviour will come to an end.
Active Ion Transport in the Larval Hindgut of Sarcophaga Bullata (Diptera: Sarcophagi Dae)
Authors: Prusch Robert D.
Published: April 2021

The potential difference across the hindgut of Sarcophaga is 30 mV, in vivo, the lumen being negative with respect to the haemolymph. A potential difference of the same polarity exists in the isolated hindgut. The potential difference is not a simple diffusion potential, since it is maintained in the absence of any ionic concentration difference across the gut, and is dependent on energy supplies. The potential across the gut is the algebraic sum of two separate electrogenic pumping mechanisms; a cation system which moves K+ or NH4+ and an anion system which moves Cl− into the gut lumen. Since a potential exists across the gut, the rate or amount of cation and anion movement into the gut cannot be equal; alternatively, various shunt pathways may exist for one or more of the ions involved.
The Effect of External Potassium Ions On the Electrical Potential Measured Across the Gills of the Teleost, Dormitator Maculatus
Authors: Evans David H. , Carrier Jeffrey C. , Bogan Margaret B.
Published: April 2021

A technique has been developed for the measurement of electrical potentials (TGP ‘s) across the gills of free-swimming, Dormitator maculatus. Transfer of fish to various KC1 solutions is correlated with changes in the TGP, which are not of sufficient magnitude to account for the known potassium stimulation of sodium efflux from this species. Transfer to potassium-free sea water results in little or no change in TGP while previous results have shown that such a transfer is correlated with a 22% reduction of sodium efflux. Transfer to fresh water results in a reduction of TGP from + 17 mV (inside positive) to −36 mV which is sufficient to account for the instantaneous reduction in sodium efflux previously shown for this species. It is concluded that while changes in TGP can account for the ‘Na-free effect’ in D. maculatus they cannot account for the potassium effects on sodium extrusion. This supports the previous conclusion that sodium efflux and potassium influx are chemically linked in this species.
The Effect of Acoustic Signals On the Chirp Rhythm in the Bush Cricket Pholidoptera Griseoaptera
Authors: Jones M. D. R.
Published: April 2021

The effect of acoustic signals on the control of chirp production has been investigated using the insect ‘s own chirp to trigger artificial sound signals (100 msec, 70dB, 12 or 15 kHz) at predetermined phases of the chirp cycle. The signals appear to reset the phase of the chirp rhythm generator, and signals given late in the cycle are followed by the greatest phase shifts. The signals may also have excitatory after-effects which are usually small, but can summate to give a slow, longer lasting increase in chirp rate. This appears to happen during alternation with a natural or artificial partner.
Active Transport by Insect Malpighian Tubules of Acidic Dyes and of Acylamides
Authors: Maddrell S. H. P. , Gardiner B. O. C. , Pilcher D. E. M. , Reynolds S. E.
Published: April 2021

Insect Malpighian tubules carry out active transport of two types of organic anion: acylamides (such as p-aminohippuric acid) and sulphonates (such as indigo carmine and amaranth). There are separate mechanisms for the transport of these two classes of compounds.

The degree to which these compounds are concentrated depends critically on the passive permeability of the tubule wall. In the permeable Malpighian tubules of Calliphora, small transported molecules readily escape from the tubule lumen. At low rates of fluid secretion the net rate of dye transport is thereby very much reduced. As a result the rate of dye transport in this insect depends on the rate of fluid secretion, although the processes are not rigidly linked. In the less permeable tubules of Rhodnius and Carausius, dye secretion is not affected by the rate of fluid secretion.

The active transport of these two types of compounds is a means of clearing from the haemolymph the conjugated compounds which are the products of detoxication of potentially toxic products of metabolism.
Pharmacological Studies on A Locust Neuromuscular Preparation
Authors: Clements A. N. , May T. E.
Published: April 2021

The structure-activity relationships of agonists of the locust excitatory neuromuscular synapse have been reinvestigated, paying particular attention to the purity of compounds, and to the characteristics and repeatability of the muscle response. The concentrations of compounds required to stimulate contractions of the retractor unguis muscle equal in force to the neurally evoked contractions provided a measure of the relative potencies. Seven amino acids were capable of stimulating twitch contractions, glutamic acid being the most active, the others being analogues or derivatives of glutamic or aspartic acid. Aspartic acid itself had no excitatory activity. Excitatory activity requires possession of two acidic groups, separated by two or three carbon atoms, and an amino group α to a carboxyl. An L-configuration appears essential. The ω-acidic group may be a carboxyl, sulphinyl or sulphonyl group. Substitution of any of the functional groups generally causes total loss of excitatory activity, but an exception is found in kainic acid in which the nitrogen atom forms part of a ring. The investigation of a wide variety of compounds revealed neuromuscular blocking activity among isoxazoles, hydroxylamines, indolealkyl-amines, β-carbolines, phenazines and phenothiazines. No specific antagonist of the locust glutamate receptor was found, but synaptic blocking agents of moderately high activity are reported.
Control of Moulting and Metamorphosis in the Tobacco Hornworm, Manduca Sexta (L.): Growth of the Last-Instar Larva and the Decision to Pupate
Authors: Nijhout H. Frederik , Williams Carroll M.
Published: April 2021

The dynamics of growth and the timing of release of the brain ‘s pro-thoracicotropic hormone (PTTH) in final instar larvae of Manduca sexta are consistent with the following hypothesis. When a 5th-stage larva reaches a critical weight of about 5 g an unidentified process is initiated which requires 24 h to be completed. At the completion of this process the brain is rendered competent to release PTTH. The actual release of PTTH is gated by the photoperiod and occurs when the gate opens during the very next photophase.
Nitrogen Metabolism in the American Cockroach: an Examination of Whole Body and Fat Body Regulation of Cations in Response to Nitrogen Balance
Authors: Mullins Donald E. , Cochran Donald G.
Published: April 2021

The effects of nitrogen balance on uric acid/urate, K+ and Na+ storage or mobilization were examined in the American cockroach Periplaneta americana (L.). Cockroaches on a high nitrogen diet increased in whole body uric acid/urates, K+ and Na+. Those on a semi-starvation diet maintained fairly constant levels of uric acid/urates, K+ and Na+. However, those on a low nitrogen diet mobilized stored uric acid/urates and K+, but not Na+. Analyses for uric/urates K+, Na+, Ca2+ and Mg2+ in fat body tissue from insects maintained on 12 diets containing different concentrations and sources of dietary nitrogen showed that only K+ concentration could be correlated with fat body uric acid/urate storage. Whole body storage and mobilization of uric acid/urates, K+ and Na+ were reflected in the faecal/dietary ratios of K+ and Na+. A model for a uric acid/urate ion sink which might be associated with ionic and osmotic balances is proposed, and some evidence for its existence is discussed.
Interneurones in Crab Connectives (Carcinus Maenas (L.)): Giant Fibres
Authors: Fraser Peter J.
Published: April 2021

Five interneurones with cell bodies and dendritic trees in the brain have axons 40–60μm diameter in one oesophageal connective. The fibres are phasic and multimodal, responding to visual and tactile stimuli. They have complex adaptation properties and two are suppressed completely during certain movements of the animal. The role of the fibres in overt behaviour has not been revealed by electrical stimulation or by examination of output in free walking animals. Several smaller intemeurones in the connective are briefly described anatomically and physiologically.
Effects of Acetylcholine on Resting and Action Potentials, and On Contractile Force in the Ventricle of Dolabella Auricularia
Authors: Hill Robert B.
Published: April 2021

Acetylcholine (2 ×10−8 to 2 × 10−3 M) depolarized the isolated ventricle of Dolabella auricularia. The depolarization was accompanied by a negatively inotropic effect from 2 × 10−8 M to 2 × 10−4 M, and by a positively ionotropic effect from 2 ×10−4 M to 2 × 10−3 M. The interaction of acetylcholine and 5-hydroxytryptamine was studied by artificially prolonging the plateau of the cardiac action potential by treatment with 5-HT. Acetylcholine had the effect of shortening the plateau established by 5-hydroxytryptamine. Force was reduced correspondingly.
Water Uptake and Hatching in the Potato Cyst Nematode, Heterodera Rostochiensis, and the Root Knot Nematode, Meloidogyne Incognita
Authors: Ellenby C.
Published: April 2021

The second-stage larva of the plant parasitic nematode Heterodera rostochiensis shows very little movement while confined to the egg; on the other hand, the larva of the closely related Meloidogyne incognita is very active Using interference microscopy, it is shown that the water content of the Heterodera larva increases immediately it is liberated from the egg while that of the Meloidogyne larva remains constant. It is suggested that the Heterodera larva is physically constricted by the egg shell and that this restricts both its movement and its water content. Measurement of larval and egg volume in both forms supports this hypothesis. The Meloidogyne larva has about 30% of free space inside the egg shell while the Heterodera larva fits it completely. It is suggested that these differences can be correlated with differences in the distribution and life-history of the two forms.
The Reduced Glucose Permeability of the Isolated Malpighian Tubules of the Blowfly Calliphora Vomitoria
Authors: Knowles G.
Published: April 2021

The excretion of several sugars by the isolated Malpighian tubules of Calliphora vomitoria has been investigated. The isolated tubules do not excrete glucose or trehalose at rates similar to those of sugars of the same molecular weight. Trehalose can be hydrolysed to glucose as it traverses the tubule wall. It is proposed that glucose can be reabsorbed by the tubule. Evidence is presented to suggest that glucose reabsorption can be saturated. Phloridzin was found to increase the rate of glucose excretion by the isolated Malpighian tubule.
Motor patterns in the stomatogastric ganglion of the lobster Panulirus argus
Authors: Hartline Daniel K. , Maynard Donald M.
Published: April 2021

Activity patterns arising from the thirty cells of the stomatogastric ganglion of Panulirus argus are described for both a semi-intact preparation and an isolated one. The thirty or so cells can be divided so far into two functional groupings: the gastric mill group, with at least ten motor elements, and the pyloric group with at least fourteen. There is some, but not extensive, interaction between groups. The main gastric mill activity is arranged in two sets of elements, each of which is composed of reciprocating elements innervating antagonistic muscles. Thus alternation in activity between the single LC and the two LG neurones results in alternate closing and opening of the lateral teeth; alternation between the four GM and single CP units results in alternate protraction and retraction of the medial tooth. The two sets are phased to each other in such a way that they cause gastric mill teeth to operate effectively to masticate food. The main pyloric activity is arranged in a three-part cycle with each of three sets of units active in sequence. Activity in two PD and one AB unit is followed by bursts in IC and LP units followed in turn by activity in up to seven PY units. Activity in a single VD neurone is locked to this cycle in a more complex pattern.
The Role of the ‘Walking Legs’ in Aquatic and Terrestrial Locomotion of the Crayfish Austropotamobius Pallipes (Lereboullet)
Authors: Pond Caroline M.
Published: April 2021

The hydrodynamic drag acting on the crayfish Austropotamobius pallipes is measured and it is concluded that, in the range of velocities used in walking, the drag is independent of the posture of the limbs and the direction of motion of the body. At swimming velocities the streamlining caused by promotion of the legs reduces the drag losses to half that of a crayfish moving in the forwards walking posture at the same speed. The forwards walking of intact crayfish is compared with that of the same animal after amputation of one or more pairs of legs. It is concluded that the third and fourth pair of legs provide most of the propulsion under water and the second pair is not essential to locomotion under any of the conditions tried.
Activity and habituation in the brain of the polyclad flatworm Freemania litoricola
Authors: Koopowitz Harold
Published: April 2021

A variety of spontaneously active units was measured in the brain of the polyclad flatworm Freemania litoricola. Following application of MgCl2 there was both a decrease in number of active units and a decrease in frequency of firing of those cells which persisted in their activity. Receptors which respond to vibration stimuli evoke potentials in the posterior part of the brain. Repetitive stimulation leads to habituation, the extent of which is dependent on both the number of times stimulated and the strength of the stimulus. Weaker stimuli habituate more rapidly than strong stimuli. Habituated responses can be dishabituated by tactile stimuli and also by stronger intensity stimuli of the same modality. The vibration-evoked potentials appear to occur in at least second-order cells, since vibration responses are abolished by the application of MgCl2. Tactile responses can also be elicited from the posterior portion of the brain when the stimulus is applied to the periphery of the animal. These responses are insensitive to MgCl2. Both vibration and tactile evoked responses are able to evoke further barrages of spike activity. The presence of a dual sensitizing and inhibitory system during habituation is discussed.
The Optokinetic Responses of the Mysid Shrimp Praunus Flexuosus
Authors: Neil D. M.
Published: April 2021

The optokinetic responses of the mysid shrimp Praunus flexuosus in the horizontal and vertical-transverse planes have been studied. The horizontal optokinetic nystagmus is fragmented, and eyestalk following speed is a function of stimulus speed. The vertical optokinetic response is not a nystagmus, but involves maintained eyestalk, deviations. These deviations, and eyestalk following speed are both functions of stimulus speed. The velocity gain (eye speed/slip speed) of the responses in both dimensions has a constant value between drum speed z°/sec and 40°/sec, which suggests that they subserve a simple rheotactic function. The vertical optokinetic response is modulated by statocyst input, and possible mechanisms underlying this effect are discussed.
The cardioregulatory system of crayfish: The role of circumoesophageal interneurones
Authors: Field L. H. , Larimer J. L.
Published: April 2021

Interneurones located in the circumoesophageal commissures were found to control the activity of the cardioinhibitor and cardioaccelerator regularity neurones. These interneurones (cardiac command fibres) fell into three classes: (1) strong inhibitors, which caused cardiac arrest, (2) weak inhibitors, which caused bradycardia, and (3) accelerators, which caused tachycardia. When the positions of interneurones were plotted collectively, they formed distinct clusters, suggesting that each cluster was represented by one command unit in an individual preparation. Twenty strong inhibitor units and 16 accelerator units were found. Weak inhibitors did not form clusters. Stimulus threshold characteristics were as low as 3·0 V and 3 Hz for the strong inhibitor units (mean range 4·7−7·1 and 14−V 30 Hz). Higher values were found for weak inhibitors and accelerators. The strong inhibitor command drives always showed a positive bias toward the contralateral cardioinhibitor neurone, relative to the ipsilateral cardioinhibitor. Plots of command neurone stimulating frequency versus evoked cardioinhibitor activity displayed steep positive slopes for strong inhibitor command units and shallow positive slopes for weak inhibitor units. Reciprocity between the cardioinhibitor and cardioaccelerator neurones occurred during both inhibitory and acceleratory command drives. This is not likely to be a property inherent in the command units themselves because reciprocity was earlier observed during chemical and tactile reflex inhibition of the heart. (Field & Larimer, 1974a).
Thermoregulation in Small Flies (Syrphus Sp.): Basking and Shivering
Authors: Heinrich Bernd , Pantle Curt
Published: April 2021

Flies of the genus Syrphus aggregated at specific sites in the field (Tecks’). Flies at leeks were always capable of ‘instant’ take-of, even at ambient temperatures of 10 °C or less. The flies regulated their thoracic temperature by a combination of basking and shivering. During hovering flight in sunshine thoracic temperature rose 12−14 °C above the ambient temperature. The flies engaged in frequent brief chases while at the leeks. At an air temperature > 18 °C the flies at the leek remained in hovering flight most of the time. The vibration frequencies of the thorax during shivering and flight ranged from about 100 to 200 Hz at 10−27 °C, though at a given temperature and spike frequency the vibration rate during warm-up was higher than the wing-beat frequency (assumed to be the same as thoracic vibration frequency) during flight. During shivering, but not in flight, there is a tendency for the indirect flight muscles to be activated in synchrony.
Stimulus-secretion coupling in an insect salivary gland: cell activation by elevated potassium concentrations
Authors: Berridge M. J. , Lindley B. D. , Prince W. T.
Published: April 2021

Fluid secretion by isolated salivary glands was stimulated by elevating the external potassium concentration. The stimulatory effect of potassium was dependent on external calcium and was potentiated by a subthreshold dose of 5-hydroxytryptamine (5-HT). During the action of 120 mM potassium there was a large calcium dependent decrease in transepithelial resistance similar to that produced with 5-HT at normal potassium concentrations. These results on Calliphora salivary glands are compared with other cases where cells are activated by high potassium. In most cases, the effect of high potassium is dependent upon calcium, suggesting that the latter plays a primary role in cell activation.
Effects of viscosity and ATP concentration on the movement of reactivated sea-urchin sperm flagella
Authors: Brokaw C. J.
Published: April 2021

Spermatozoa from the sea urchin, Lytechinus pictus, can be demem-branated with solutions containing Triton X-100 and 5 mM-CaCl2 and reactivated in ATP solutions containing low concentrations (10−9 M) of free Ca2+ ion to give symmetrical bending wave movements, even at very low ATP concentrations. At ATP concentrations of 0·01−0·02 mw the reactivated spermatozoa have beat frequencies near 1 Hz, nearly normal bend angles, and wave-lengths about 50% longer than normal. The effects of increased viscosity, obtained by addition of methyl cellulose to the reactivation solutions, on bend angle and beat frequency decrease with decreasing ATP concentration, and become almost undetectable at 0 ·01 mM ATP. On the other hand, the effect of increased viscosity on wavelength shows relatively little change with ATP concentration, although it is noticeably reduced at o-oi mM ATP. These observations suggest that the beat frequency at low ATP concentrations is determined by an intrinsic rate-limiting process, in contrast to the viscosity-limited behaviour at high beat frequencies. Quantitative agreement with the experimental results is obtained with a model in which ATP concentration and viscosity each determine the rates of one step in a two-step reaction cycle which determines the beat frequency. Two other models which can qualitatively explain the effects of ATP concentration and viscosity on flagellar beat frequency fail to show quantitative agreement with the experimental results. In one of these models, ATP concentration determines the maximum rate of shear between filaments. In the other, ATP concentration determines a time delay which is required to bring the active moment into phase with the elastic moments which would be expected to dominate the bending resistance at low beat frequencies.
Sodium activity of insect blood: physiological significance and relevance to the design of physiological saline
Authors: Treherne J. E. , Buchan P. B. , Bennett R. R.
Published: April 2021

The apparent activity coefficients for sodium (γ ′Na) in the blood of six insect species have been calculated from measurements made with sodium-selective electrodes and a flame photometer. In every case γ’Na was significantly lower than that for this cation in free solution (γ Na). In Periplaneta americana γ ′Na varied considerably, during a period of 90 days, so that a relatively constant sodium activity (aNa) was maintained in the blood in the face of large variations in the total sodium content measured by flame photometry. Despite the relative constancy of aNa (of around 0·088M) appreciable fluctuations were observed in the sodium and potassium content of nervous connectives over a period of 140 days. The values of aNa and aK were used to devise a satisfactory cockroach saline for use in experiments with isolated nerve cords.
The Withdrawal Response of a Freshwater Snail (Lymnaea Stagnalis L.)
Authors: Cook Anthony
Published: April 2021

Electrical stimulation of a variety of nerves towards the brain results in movements of the neck of the snail similar to those associated with the withdrawal response of the intact animal. The columellar and cervical nerves mediate most of the movements being measured. Repetition of the stimuli results in a decline in response amplitude which is complicated by a superimposed incremental process which is itself subject to a decremental process as stimuli are repeated. As stimuli are repeated the response latency increases. Consecutive stimulation of pairs of nerves indicates that the response decrement is specific to the nerve being stimulated. The involvement of the pleuro-pedal connectives in the response has been demonstrated both in a semi-intact preparation stimulated electrically and in a free-roaming animal treated surgically and stimulated visually. Visual stimuli associated with the withdrawal response are detected by photoreceptors on the head and in the mantle.