bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical Excitation of the Proventriculus of the Polychaete Worm Syllis Spongiphila
Authors: Anderson M. , Mrose H.
Published: April 2021

The myoepithelial cells of the proventriculus of Syllis spongiphila (which are composed of only one or two sarcomeres that may reach 40 μm in length) are innervated by excitatory and inhibitory nerve fibres. Experiments were performed to examine the chemical excitation of these cells. We found that acetylcholine (ACh) mimics the excitatory transmitter and that the postsynaptic receptors appear to be nicotinic. Bath application of ACh (10−5 to 10−4 M), carbamylcholine (Carb, 10−4 to 10−3 M) or nicotine (10−4 to 10−3 M), but not muscarine (10−4 to 10−3 M), elicited overshooting depolarizations followed by prolonged depolarized plateaus. Iontophoresis of ACh or Carb (0·1–1·0 M) elicited depolarizing responses which, when elicited in trains, exhibited increased rise times to peak and decreased amplitudes to a plateau level; these results suggest the occurrence of desensitization of the postsynaptic receptors. Depolarizations elicited by indirect stimulation or by iontophoresis of ACh were reduced in amplitude by D-tubocurarine (10−5 to 5 × 10−4 M) in a dose-related and reversible manner. Atropine (10−6 to 10−4M) had no effect on responses elicted by indirect stimulation. Small potential changes superimposed on responses to cholinergic agents applied in the bath or iontophoretically were abolished in Ca2+-free ASW, Ca2+-free+ 1 mm EGTA ASW or in ASW containing 4–6 HIM Mn2+. These small potential changes are likely to be from activity in neurones that receive cholinergic synapses. Carb and nicotine applied in the bath consistently induced more overshooting peaks than did ACh, and the plateaus of the responses to ACh were of lower amplitude than those of the responses to Carb. In addition, responses to iontophoretic pulses of ACh were prolonged in the presence of 10−4 and 10−3 neostigmine. These data suggest the presence of an esterase in the nerve-muscle junctions of the proventriculus.
The Hydrodynamics of Rheotaxis in the Plaice (Pleuronectes Platessa L.)
Authors: Arnold G. P. , Weihs D.
Published: April 2021

Plaice resting on the bottom of a flume respond to the current with a clearly defined pattern of behaviour. A simple hydrodynamic model which relates the slip-speed (Us) and lift-off speed (UL) to the physical forces acting on the fish has been verified experimentally using freshly killed fish and a rigid model. With an asymmetric semi-ellipsoid shape and a fineness ratio of 14 the plaice appears to be morphologically adapted to have minimum drag when heading into the current. As a result of this streamlined shape the lift force experienced by the fish is 10–20 times greater than the drag force, and the rheotactic behaviour therefore appears to be principally adapted to counteract hydrodynamic lift. Values of Us and UL, above which live fish must expend energy against the current, are exceeded for much of each tidal cycle in the southern North Sea. The model is of general application to benthic organisms in flowing water for Reynolds numbers between 104 and 106; outside these limits some modification of the constants is required.
The Metabolic Cost of Flight in Unrestrained Birds
Authors: Torre-Bueno J. R. , Larochelle J.
Published: April 2021

Oxygen consumption and carbon dioxide production were measured during flight in unrestrained starlings by a new method. Mean RQ after the first 30 min of flight was 0·691±0·08 ( ± S.D.). Mean rate of carbon dioxide production was 19·7±2·2 ml CO2/min, which corresponds to a metabolic rate of 8·9 ± 1 W. Metabolic rate during flight did not change significantly over a range of air speeds from 8 to 18 m/s and birds would not fly at speeds outside of this range. Current theories of bird flight predict a large change in metabolic rate over the same range of speeds. Wingbeat frequency was constant at 12 ±0·5 Hz. Wingbeat amplitude reached a minimum at a speed of 14 m/s and increased at both higher and lower speeds. Angle between the body and horizontal was least at high speeds and increased at low speeds. As existing theories do not take into account the change of drag resulting from changes in body attitude, this may be a cause of the discrepancies between theory and observation.
An Electromyographic Analysis of Forelimb Muscles During Overground Stepping in the Cat
Authors: English Arthur W.M.
Published: April 2021

The patterns of activity of 33 forelimb muscles during unrestrained over ground stepping in eight adult cats were analysed using intramuscular electromyography. Three general patterns were found. Some muscles began activity during the first extension epoch (E1) and ceased near the end of the third extension epoch (E3) and were considered extensors. Others, considered flexors, began activity just prior to the flexion (F) epoch and ceased at or just after the onset of E1. Other muscles showed a biphasic pattern of activation; one period of activity occurring during F, the other during the extension epochs. In all regions of the limb, individual muscles displayed variation in the onset and time course of activity. The results are interpreted in terms of a model of locomotor generation which proposes specific neural output to individual muscles. Muscles of the shoulder region are proposed to act mainly to produce translatory and rotatory movements of the scapula associated with lengthening the step. Muscles of the elbow region and antebrachium are interpreted as playing roles both in producing flexion extension movements and in the absorption of energy. The latter group are considered especially suitable to energy absorption because of their pennate arrangement of muscle fasciculi and their long tendons.
Quantitative Mapping of Cutaneous Receptive Fields in Normal and Operated Leeches, Limnobdella
Authors: Fett Michael J.
Published: April 2021

The receptive fields and physiological properties of the sensitive cutaneous mechanoreceptive neurones in the leech Limnobdella australis were found to be very similar to those previously described in Hirudo medicinalis. Following separation from the central nervous system (C.N.S.), the distal dendrite stump and cutaneous receptive field remained unchanged for at least 160 days. There was little spreading of receptive fields into regions of skin isolated from the C.N.S. for at least 184 days. Cutting one dendrite of a mechanoreceptive neurone which has two major dendrites produced little change in the receptive field of the intact dendrite. Abnormalities were found in most of the receptive fields of operated leeches, irrespective of the site of operation. These abnormalities were not seen in normal leeches.
The Dimensions of the Gills of Two Species of Loach, Noemacheilus Barbatulus and Cobitis Taenia
Authors: Robotham P.W.J.
Published: April 2021

The gill area to body weight relationship of two species of loach, Noemacheilus barbatulus (L.) and Cobitis taenia (L.) was measured. It was found that the secondary lamellar area and the total length of the gill filaments were independently related to the lengths of the fish in each of the species. Both these measurements were similar in the two species. The number of secondary lamellae per mm of gill filament was independent of fish length, and was greater in C. taenia than in N. barbatulus (45·5 and 36·4 respectively), being the main factor for the far greater total gill area/g calculated for C. taenia than for N. barbatulus (507·9 and 316 mm2/g respectively). These gill area measurements are, in general, higher than those of other freshwater fish. It is suggested that this is related to the sedentary burrowing habits of the two species.
The Relationship of the External Surface Area of Birds to Skin Surface Area and Body Mass
Authors: Walsberg Glenn E. , King James R.
Published: April 2021

Data from 12 bird species reveal that skin surface area averages 23 % larger than the external surface area of the plumage. Use of skin surface area instead of the area of the external plumage surface may produce large errors in heattransfer analyses.
Cilioexcitatory and Cilioinhibitory Processes Initiated by Light on Two Identifiable Neuronal Pigments in Mytilus Edulis
Authors: Paparo Anthony A. , Murphy Judith A.
Published: April 2021

Two neuronal chromoproteins (red-haemoprotein and yellow-caroteno-protein) initiate changes in ciliary activity on the gill of Mytilus. Photic, electrical and chemical stimulation of these chromoproteins correlate with fluctuations in ionic (calcium and iron) deposits in gill bulk tissue samples. Microspectrophotometric measurements of chromoprotein spectral band patterns reveal two or three absorption maxima for carotenoprotein and haemoprotein respectively. Under aerobic conditions, cilioinhibition and cilioexcitation results after activation of carotenoprotein or haemoprotein respectively. Carotenoproteins are only engaged during gradual anoxia. Immediate anoxia renders both chromoproteins inoperative. Changes in ciliary activity initiated by photic stimulation of neuronal chromoproteins are abolished by denervation of the gill. It is postulated that photoactivation and/or release of specific neurotransmitters lead to transformations in chromoproteins with subsequent neuronal regulation of gill ciliary activity.
Identification of Active Cell in Potassium Transporting Epithelium
Authors: Blankemeyer James T. , Harvey William R.
Published: April 2021

Epithelial ion transport regulates the environment of cells and modulates the environment inside them, making possible the evolution of eukaryotic organisms. Analysis of the transport process requires that the route taken by ions as they are actively transported across epithelia be known. The route can be determined by locating ion pumps electrically and by measuring transport pool sizes kinetically provided that the epithelial structure is simple enough to enable the results to be interpreted in cellular terms. The route by which potassium is actively transported across the lepidopteran midgut is demonstrated here by a combination of electrical and kinetic analyses.

Two sorts of cells, goblet and columnar cells, are distinguished by their electrical properties. The goblet cell is identified as the site of active potassium transport, the pump being localized in its apical membrane. The goblet cells are electrically coupled with columnar cells only when midguts that have been isolated from diet-reared larvae are short circuited. A corollary to this result is that the size of the pool of potassium which is involved in transport should be small when the goblet cells are not coupled with columnar cells and should become large when they are coupled. This corollary has been confirmed by direct measurement of the transport pools using isotope tracer kinetic analysis.

This is the first time that the cell type responsible for active ion transport in a polymorphic tissue has been identified directly by physiological means.
The Source of Short-Circuit Current Across Locust Rectum
Authors: Williams D. , Phillips J. E. , Prince W. T. , Meredith J.
Published: April 2021

Recta of desert locusts were mounted as flat sheets in ‘Ussing-type’ chambers and various parameters of tissue viability were monitored. The trans-epithelial resistance, the electropotential difference, the short-circuit current (Isc), and unidirectional fluxes of 22Na+, 36C1− and 42K+ all remained relatively constant during the 3rd and 4th h. The direction of the Isc indicated a net transport of either anions to the haemocoel, or cations to the lumen side. This current was abolished by KCN and was sensitive to temperature (Q10 = 2·4). There was a rapid decline in Isc over the first 2 h, which could be abolished by substituting NO3− or SO42− for Cl− in the bathing medium, indicating that this fall in current is due to a decline in the rate of Cl− transport. Measurements of 36C1− fluxes under short-circuit conditions confirm this interpretation. In the steady-state (3rd and 4th h), however, the same anion substitutions had no effect on Isc. Concurrent flux measurements indicated that net Na+ and K+ transport to the haemocoel side equals or slightly exceeds that of Cl−in the same direction. Consequently all of the Isc must be due to unidentified ion transport processes. Transport of H+ to the lumen, or HCO3− and organic anions to the haemocoel side, is proposed.
Sodium Fluxes and Exchange Pumps: Further Correlates of Osmotic Conformity in the Nerves of An Estuarine Bivalve (Mytilus Edulis)
Authors: Willmer P. G.
Published: April 2021

Analysis of sodium loss from Mytilus cerebro-visceral connectives indicated a slow efflux component attributable to movement across the cellular membranes. This component was significantly slowed at 4 °C, or by treatment with DNP, ouabain or K-free media; this implies that a conventional Na/K exchange pump contributes to cellular efflux. Dose-response curves for the effects of ouabain on cellular Na efflux gave preliminary indications of a significant increase in the sodium pump frequency in connectives from mussels adapted to 25 % salinity relative to those from too % salinity. Assays of ATPase activity in the connectives showed a 63 % increment in the Na/K-activated enzyme in 25 %-adapted tissues, with no significant change in the magnesium-activated enzyme. The Na/K-ATPase also exhibited a marked shift in its optimal sodium requirement, from 100 mM at 100% salinity to 50mM at 25% salinity; these figures are close to the respective values of [Na+]i determined for the axons under such conditions. [3H]ouabain binding studies confirmed that there was an increment in active sodium pumping sites (in this case of 76 %) in dilute-adapted nerves. Pump frequencies were in the range of 1000–4000 sites/μm2, in agreement with previous studies of invertebrate nerve membranes. The significance of extra pumping capacity for sodium (and potassium) ions in the dilute adapted tissues is considered in relation to the electrophysiological functioning, volume regulation and solute balance of the nerves of an osmoconformer.
Forces on the Tail Surface of Swimming Fish: Thrust, Drag and Acceleration in Bluefish (Pomatomus Saltatrix)
Authors: Dubois Arthur B. , Ogilvy Christopher S.
Published: April 2021

Pressures on the right and left sides of the tails of swimming bluefish were measured and found to have a range of +5·9 to −5·9 cm H20. The pressures were resolved into their forward and lateral vectorial components of force to allow calculation of forward and lateral force and power at speeds ranging from 0·26 to 0·87 m/s. The peak to peak changes in force of acceleration of the body, measured with a forward accelerometer averaged 209 g or 2·05 N at 0·48 m/s, and were compared with the maximum to minimum excursions of forward tail force averaging 201 g or 1·97 N at the same speed. The mean difference was 8 g, S.D. of the mean difference ±29, S.E. of mean difference ± 10 g. Mean tail thrust was calculated as the time average of tail force in the forward direction. It averaged 65 g, or 0·64 N, at 0·48 m/s. The mean forward power was 0·34 N m/s at 0·48 m/s. The drag of the gauges and wires accounted for 10% of this figure. The mean lateral power of the tail was 1·28 N m/s at a mean speed of 0·48 m/s. The propulsive efficiency of the tail, calculated as the ratio of forward power to forward plus lateral power, was found to be 0 20 S.D. ± 0·04, S.E. ±0·01 and was not related to speed. This suggests that 80% of the mechanical power of the tail was wasted. Turbulence in the water may have contributed to this large drag and low tail efficiency.
Oxygen Consumption in the Lizard Genus Lacerta in Relation to Diel Variation, Maximum Activity and Body Weight
Authors: Cragg Patricia A.
Published: April 2021

Diel recordings of under a 12 h Light/12 h Dark regime, constant light or constant dark reveal a strong endogeneous diurnal rhythm in L. sicula. L. vivipara show an exogeneous rhythm with activity occurring only in the light whilst L. viridis have a weak endogeneous rhythm that is modified by behavioural factors and inhibited by dark. Standard (or basal) can only be attained after several hours in an ‘indifferent’ environment, shielded from extraneous stimuli. Measurements must be at night (light or dark) for unrestrained L. sicula and in the dark (day or night, restrained or unrestrained) for L. vivipara and L. viridis. Intrageneric std (ml h−1 STPD) = 0·328 W0·76 or 0·216 W0·77 for 1- or 3-days starvation at 30 °C for 0·2 to 34 g Lacerta. Intrageneric maximum (determined for 30 to 60 s of provoked activity during the day) = 2·66 W0·747at 30 °C for 1-days starvation. Respiratory exchange ratio, R = 0·75 or 0·85 for std after 1 or 3 days starvation and 0·95 and 1·45 for mean daily and max . High R values are considered a result of anaerobic metabolism and hyperventilation during activity.
Measurement of Single Nephron Filtration Rate in the Kidney of the River Lamprey, Lampetra Fluviatilis L
Authors: Moriarty R. J. , Logan A. G. , Rankin J. C.
Published: April 2021

The reliability of [3H]inulin as a reference substance for the measurement of glomerular filtration rate (GFR) in river lampreys was investigated. Simultaneously measured renal clearances of [3H]inulin and [14C]-polyethylene glycol (PEG) were not significantly different. Recoveries of [3H]inulin in the urine following its injection into the proximal tubule and urinary duct averaged 83·5 ± 4·0% (n = 14) and 93·0 ± 4·6% (n = 9) respectively. No evidence was obtained to suggest penetration of the tubular wall by [3H]inulin following its introduction into peritubular capillaries. Gel-filtration of lamprey plasma and urine produced no signs of any significant degradation of the inulin to fructose. [3H]inulin recoveries, though significantly below 100% (P < 0·001), were considered adequate to justify its use after allowing for possible sources of error. A mean single nephron filtration rate (SNGFR) value of 7·02 ± 0·27 nl/ min (n = 89) was obtained from the kidneys of anaesthetized freshwater lampreys. [51Cr]EDTA was found to be totally unsuitable for the measurement of GFR in this species.
The Effect of the H-ion Concentration on Protozoa, as Demonstrated by the Rate of Food Vacuole Formation in Colpidium
Authors: Mills Sylvia M.
Published: April 2021

In a short communication to the British Association at Leeds (1927) Saunders pointed out that the average number of vacuoles ingested by Colpidium in a given time, when fed with suspensions of Indian ink, varied with the H-ion concentration. The present series of experiments represent an attempt to analyse in greater detail the effect of the hydrogen-ion concentration on Colpidium, particularly in respect to its effect on the formation of food vacuoles. The work was carried out under the direction of Mr J. T. Saunders, to whom I owe my thanks for much help.
The Growth of Fish
Authors: Gray J. , Setna S. B.
Published: April 2021

Certain scales of Salmonoid fish exhibit a series of concentric ridges or circuli, the number of which increases with the size of the whole fish. Each year of normal growth is recorded on the scale of a salmon by a concentric band which is more or less sharply divided into two regions, (i) in which the concentric ridges are relatively wide apart, (ii) in which the ridges are closer together. It is tolerably certain that the first region is formed whilst the fish is in the sea, and the second region whilst the fish is in estuarine or fresh water ; roughly speaking the two regions mark the summer and winter periods respectively. The factor or factors responsible for the difference between winter and summer circuli are not fully understood. There are two possibilities. The variation in width may be dependent on an inherent rhythm upon which external factors may exert little or no control ; or the variation may be due to variations in the external environment of the fish. In view of the high economic importance of the facts, curiously little experimental data are available for a solution of the problem.
The Adaptation of Gunda Ulvae to Salinity
Authors: Pantin C. F. A.
Published: April 2021

Whereas it is well known that most organisms cannot survive sudden large changes in the salinity of the external medium yet estuarine organisms have developed powers of resistance to them. Recent work, particularly that of Schlieper (1929), has thrown some light on the behaviour of estuarine animals in diluted sea water.
A Lamarckian Experiment Involving A Hundred Generations with Negative Results
Authors: Agar W. E.
Published: April 2021

The experiment was devised to find out whether regeneration of the dorsal branch of the second antenna of Simocephalus and Daphnia, repeated for many generations, would result in an improvement in the regeneration (which is very imperfect) or in any other alteration in the process. Neither the character nor extent of the regeneration was influenced in any measurable degree in any of the experimental lines, even after 100 generations, nor was the normal growth of the antenna affected.

A similar experiment, except that selection was practised in addition, likewise produced negative results, confirming both the lack of the Lamarckian effect and the inefficacy of intraclonal selection.
The Effect of Salinity Changes on the Water Content and Respiration of Marine Invertebrates
Authors: Beadle L. C.
Published: April 2021

Schlieper’s theory of the function of increased oxygen intake by “homoi-osmotic” marine invertebrates in dilute sea water in maintaining their body fluids hypertonic to the surrounding water is discussbd, and objections are brought forward to the methods used in the experiments on which his conclusions were based. By periodic weighings, and measurements of respiratory rate (under narcotic) by Barcroft manometers, it was found that the weight of N. diversicolor, on transference to water of low salinity, at first increases and then falls, and that the respiratory rate is at first increased and later tends to decrease. With N. cultrifera the weight increases to a higher value and does not subsequently fall, and the respiratory rate is also increased but to a lesser extent than with N. diversicolor. These differences in the amount of increase in respiratory rate are more marked in water containing only 16·6 per cent, sea water than in water containing 25 per cent, sea water. N. diversicolor maintains its activity while N. cultifera becomes practically inert in dilute water. The latter does not actually die in 25 per cent, sea water after 100 hours, but dies in 16·6 per cent, sea water after about 50 hours. Exposure to Mjiooo KCN or to anaerobic conditions in dilute water tends to break down the mechanism by which the free osmotic inflow of water in N. diversicolor is prevented, and the weight curves under these conditions approach the N. cultrifera form. The respiratory rate of G. ulvae increases progressively with dilution of the sea water, and is roughly proportional to the initial difference of osmotic pressure inside and outside the animal. The swelling of Gunda in dilute water is due to swelling of the gut cells, which become much vacuolated. The other tissues appear unaltered. M/1000 KCN or anaerobic conditions cause a greater amount of swelling in Gunda in a given salinity than normally occurs. These experiments seem to give reasonably good support to Schlieper’s hypothesis. The mechanism responsible for this “osmotic resistance” in N. diversicolor must be of a somewhat different nature from that in G. ulvae. A rigid distinction between “homoiosmotic” and “poikilosmotic” marine animals cannot be supported.
Growth in the Larvae of Tenthredinidae
Authors: Miles Herbert W.
Published: April 2021

From a study of the larvae of some twenty-eight species of Lepidoptera, Dyar(1) concluded that growth, as indicated by the growth of the head in successive instars, follows a regular geometrical progression. Fisher (2), working on Tortrix pronubana Hb., applied the findings of Dyar and worked out the growth ratio, which he found to be 1·37. The following table indicates how the growth ratio is arrived at: Table I.(Fisher, 1924.)

In the above table the measurements are given in millimetres, and the modes of the observed widths of the head capsules of the first and second larval instars are taken as the basis of calculation. By dividing the mode for the head widths of the second instar larvae by that for the first instar larvae, a figure representing the ratio of increase is found. By further calculation it is possible to estimate the width of the head capsule for any subsequent instar. The close approximation of calculated and observed measurements furnishes the student of life history of Lepidoptera with a means of checking larval ecdysis and development.

Morphologically the larvae of Tenthredinidae bear a close resemblance to those of Lepidoptera, hence it seemed possible that the same general laws with regard to growth might be followed. Material was obtained, therefore, to test the application of Dyar’s law for growth in the larvae of Lepidoptera to growth in the larvae of the Tenthredinidae.
The Influence of Temperature on the Rate of Growth of Sporotrichum Garnis, From −10° C. TO +30° C
Authors: Haines R. B.
Published: April 2021

This mould is of frequent occurrence on stored carcases and in cold stores. The lean portions of carcases which have been kept for eight or ten weeks below zero centigrade but above –10° C. are frequently covered with mould growth. No such growth has been so far observed on carcases stored at – 20° C. Brooks and Hansford, in reviewing mould growth on cold-store meat, found that some strains of Cladosporium herbarum developed and grew at – 6° C. (Brooks and Hansford, 1923). They also suggested that other moulds including Sporotrichum, would probably grow between o° C. and – 6° C. It is therefore of interest to attempt to determine the precise growth limits of this mould. Two cases have to be investigated: the influence of temperature upon growth per se, and also the effect of physical changes in the medium consequent upon freezing. The present communication is concerned with the first of these only, all measurements below zero having been made on supercooled media: i.e. media cooled below their freezing-points but from which ice crystals had not separated.
The Physiology of Excretion in A Blood-Sucking Insect, Rhodnius Prolixus (Hemiptera, Reduviidae)
Authors: Wigglesworth V. B.
Published: April 2021

A theory of uric acid excretion is put forward according to which potassium or sodium acid urate is secreted in solution in the upper part of the Malpighian tube, and water and base reabsorbed from the lower part of the tube, leading to a precipitation of free uric acid; so that the same water and base are circulated and used repeatedly. The evidence for this theory is presented under four heads:

General evidence from the histology of the Malpighian tube and the relative solubility of uric acid and urates. Experiments with vital dyes. Thus, neutral red is taken up from the blood by the upper segment of the Malpighian tube, and from the lumen of the tube in the lower segment. It is suggested that water follows the same route. The application of ligatures to the tubes at different levels shows that uric acid is not secreted by the lower segment. Experiments with indicators show that the contents of the tube are faintly alkaline (pH 7·2) in the upper segment, and acid (pH 6·6) in the lower segment. Uric acid in solution has a pH about 6·5.

It is suggested that the terminal ampullae of the Malpighian tubes, and possibly the rectal glands, also play a part in the reabsorption of water.
Direct Measurements of Instantaneous Lift in Desert Locust; Comparison with Jensen’s Experiments on Detached Wings
Authors: Cloupeau M. , Devillers J. F. , Devezeaux D.
Published: April 2021

Instantaneous values of lift in the locust Schistocerca gregaria, flying in a wind tunnel, were measured by means of a piezo-electric probe. The airflow velocity was adjusted to be equal to that which would have been experienced by the freely flying insect.

In order to obtain the true aerodynamic forces, the inertial forces must be subtracted from the gross forces measured. These inertial forces were calculated from the movement of the centre of gravity and from the mass of the different wing sections.

The lift curves obtained have a shape similar to the curves deduced by Jensen from measurements on isolated wings in steady flows, but an approximately doubled amplitude. These amplitude differences appear to be caused by the existence of significant unsteady effects.
The Relationship of the Central Motor Pattern to the Feeding Cycle of Lymnaea Stagnalis
Authors: Rose R. M. , Benjamin P. R.
Published: April 2021

Electromyographic recordings from the buccal muscles of Lymnaea during feeding has shown that there are 4 component phases in the feeding cycle. Cinephotography of feeding cycles has confirmed that these correspond to protraction, 2 phases of retraction, and an inactive phase. The 4 phases of muscle activity can also be related to the cycle of neural activity described previously (Benjamin & Rose, 1979). Thus types 6, 4 group, and type 8 cells are motoneurones involved in protraction and the two retraction phases, while the type 5 cell fires in the inactive period. The combination of physiological and anatomical approaches has led to the suggestion that the single and double input cells described by Benjamin & Rose (1979) are involved with the control of buccal and oesophageal activity respectively.
Inhibition and Excitation in the Locust DCMD Receptive Field: Spatial Frequency, Temporal and Spatial Characteristics
Authors: Pinter Robert B.
Published: April 2021

The descending contralateral movement detector (DCMD) of the locust responds vigorously to small target (ca. 5°) stimuli; this response is inhibited by simultaneous or subsequent rotation of a radial grating (windmill) pattern (subtending 19-90° of visual angle) and suppressed by earlier rotation, The excitation produced in the DCMD by rotation of a radial grating pattern depends only on the spatial frequency of the stripes of the pattern, and is independent of pattern size, and of temporal frequency over the range of low values used. The inhibition produced by this same stimulus similarly depends only on the spatial frequency of the stripes of the pattern, independent of pattern size, and of temporal frequency over the range of low values used. As the radial grating excitation decreases with increasing spatial frequency, the inhibition increases until limited by optical and neural resolution. For spatial frequencies of the radial grating pattern below 0·05 cyc/deg the radial grating patterns become excitatory. Above 0·05 cyc/deg they are inhibitory. This is the point in spatial frequency below which inhibitory grating ‘backgrounds’ become excitatory targets. Inhibition decreases as the size of the radial grating pattern is decreased below 19° visual angle; at 8° or less no inhibition can be found at any spatial frequency. Inhibition is greater in the posterior than anterior regions of the receptive field, and greater in the ventral than the dorsal regions. Inhibition decreases as the distance between small target and the radial grating is increased, but this is influenced by the local variations of excitation and inhibition. Habituation is often greater for small target and low-frequency radial grating response than for inhibited small target and high frequency grating response. These results substantiate previously proposed lateral inhibition models of the acridid movement detector system.
Epithelial Conduction in Salps: I. Properties of the Outer Skin Pulse System of the Stolon
Authors: Anderson Peter A. V.
Published: April 2021

The Outer Skin Pulse (OSP) system of the stolon of Salpa fusiformis was studied histologically and electrophysiologically. The cells of the conducting epithelium are cuboidal, 4–10 μm in diameter and are connected by gap and tight junctions (Fig. 1). They have resting potentials of − 75 to − 96 mV. Outer Skin Pulses are conducted as overshooting action potentials 84–104 mV in amplitude which are characterized by the absence of a hyperpolarizing undershoot during the repolarizing phase (Fig. 2 A). When OSPs are evoked at frequencies in excess of 2 s−1 a pronounced plateau appears in the repolarizing phase (Fig. 2C). Tetrodotoxin blocks OSPs in a manner which suggests that a sodium current is responsible for activation of the action potential. Addition of 15 mM manganese to the bath blocks OSPs. This effect was initially accompanied by a reduction in OSP amplitude and an increase in duration (Fig. 5). This observation was interpreted as indicating the presence of a calcium influx during the action potential. The results are compared with those obtained from epithelial conduction systems in other organisms, other embryonic tissues and excitable cells in other non-vertebrate chordates.
Epithelial Conduction in Salps: II. The Role of Nervous and Non-Nervous Conduction System Interactions in the Control of Locomotion
Authors: Anderson Peter A. V. , Bone Quentin , Mackie George O. , Singla Chaman L.
Published: April 2021

The control of locomotion in Salpa fusiformis was studied by intracellular recordings from motor neurones and swimming muscles. Regular, synaptically driven, volleys of action potentials were recorded from motor neurones. This pattern of activity was consistent with that expected from the waveform of the compound junctional potentials associated with contraction of the swimming muscles. A second class of brain neurone was identified. These cells were synaptically driven. In some, their firing rate was increased while in others it was decreased by activity in an epithelial conduction system, the Outer Skin Pulse (OSP) system. Cells of the outer epithelium were impaled and OSP’s were recorded intracellularly as conventional action potentials. The records from many of these cells showed many depolarising synaptic potentials. Numerous gap junctions were observed throughout the outer epithelial layer and several neuroepithelial synapses were found. The distribution of these synapses coincided with that of the epithelial cells from which synaptic events were recorded.
Ventilatory Mechanisms of the Amphibian, Xenopus Laevis; The Role of the Buccal Force Pump
Authors: Brett S. S. , Shelton G.
Published: April 2021

Lung pressures, buccal pressures, lung volumes, and EMGs from respiratory muscles were measured in unrestrained Xenopus laevis to analyse their roles in the lung ventilation cycle. Lung pressure was always maintained above atmospheric levels and a buccal pumping mechanism was used to fill the lungs in Xenopus, as in other Amphibia. Xenopus, unlike other amphibians, does not ventilate the buccal cavity between lung ventilations. Expiration of gases from the buccal cavity is aided by muscles which decrease buccal cavity volume. Other anurans increase buccal cavity volume during expiration. The buccal phase of inspiration occurs after expired air has passed from the lung and buccal cavity, in comparison to the ranids and bufonids which inspire fresh air into the buccal cavity before expiration.
Ventilation, Oxygen Uptake and Haemolymph Oxygen Transport, Following Enforced Exhausting Activity in the Dungeness Crab Cancer Magister
Authors: McMahon B. R. , McDonald D. G. , Wood C. M.
Published: April 2021

Scaphognathite and heart-pumping frequencies, ventilation volume, cardiac output, oxygen uptake and oxygen transport by haemolymph have been studied in unrestrained Dungeness crabs (Cancer magister) before, immediately after, and during recovery from 20 min of enforced exhausting activity. Exercise increased oxygen uptake 4-fold. This increase was achieved by more than 2-fold elevation of both ventilation volume and cardiac output and by greater participation of haemocyanin in oxygen delivery. The elevated ventilation volume resulted entirely from an increase in scaphognathite pumping frequency, while the rise in cardiac output resulted largely from increase in stroke volume. Prior to exercise haemocyanin accounts for less than 50% of the oxygen delivered to the tissues. Following exercise this increases to over 80%, the additional oxygen release being mediated by a depression of prebranchial oxygen tension and a substantial Bohr effect resulting from build up of lactate ion in the haemolymph and subsequent fall in pH. These changes allowed% oxygen extraction from branchial water to be maintained at 28% despite a 2-fold increase in ventilation volume, and allowed an increase in%. oxygen extraction by the tissues. Despite these changes oxygen supply fell below demand during exercise, and considerable anaerobic metabolism resulted, as evidenced by a 9-fold increase in haemolymph lactate concentration. The resulting oxygen debt required 8–24 h for repayment. Aerobic metabolic scope, and mechanisms of increasing oxygen uptake and transport in this crab are compared with those of a range of fish species.
Thermoacclimatory Changes in the Ionic Microenvironment of Haemoglobin in the Stenothermal Rainbow Trout (Salmo Gairdneri) and Eurythermal Carp (Cyprinus Carpio)
Authors: Houston Arthur H. , Smeda John S.
Published: April 2021

Haematological characteristics (erythrocyte number, haematocrit, haemoglobin, mean erythrocytic volume and haemoglobin content) and plasma and packed red blood cell water and electrolyte (Na+, K+, Ca2+, Mg2+, Cl−) levels were determined in summer and winter populations of rainbow trout acclimated to 2, 10 and 18 °C, and for carp held at 2, 16 and 30 °C. Erythrocyte electrolyte concentrations and ion: haemoglobin ratios were calculated from these data. Modest increases in red cell abundance and reductions in mean erythrocytic volume were the most obvious haematological changes accompanying acclimation to higher temperatures. Haemoglobin levels in carp also tended to increase with temperature. In winter trout plasma sodium and potassium were elevated following acclimation to increased temperature. No significant changes in plasma composition were observed in summer fish. Carp held at higher temperatures were characterized by increases in plasma chloride and calcium and reductions in sodium and magnesium levels. Red cell potassium and magnesium and K+:Hb and Mg2 +:Hb ratios tended to be higher in winter than in summer trout, with the converse being true of chloride and calcium and Cl−:Hb and Ca2+. Hb. Only potassium and K+: Hb were significantly altered following acclimation; rising at higher temperatures. In carp, potassium and K+:Hb were relatively thermostable, but sodium and chloride and Na+:Hb and Cl∼:Hb increased with temperature while magnesium and Mg2+:Hb decreased. Changes in the ionic composition of carp red cells support the suggestion that cellular pH is reduced in the warm-acclimated animal. These variations may be of adaptive value. Increases in chloride and hydrogen ion commonly reduce haemoglobin-oxygen affinity, and should facilitate oxygen unloading at the tissue level. Reductions in cellular magnesium, by maximizing organophosphate modulator levels, should produce much the same effect. In both species reductions in mean erythrocytic volume took place at higher temperatures despite increases in cellular ion content which exceeded those of plasma. It is probable that reductions in cellular volume, which should favour branchial oxygen loading, were achieved by export of some as yet unidentified solute or solutes.
Aerodynamics and Hydrodynamics of the ‘Hovering’ Flight of Wilson’s Storm Petrel
Authors: Withers Philip C.
Published: April 2021

Wilson’s storm petrel (Oceanites oceanicus) characteristically feeds by ‘hovering ‘over the water surface, but its technique for this is unlike that of other flying vertebrates. The kinematics and aerodynamics of this ‘hovering’ flight were investigated to determine the possible sources of lift ; various nonaerodynamic sources of lift were discounted. It is suggested that the storm petrel soars into an ambient, horizontal wind, and thus is not hovering in the usual sense. Such soaring into a horizontal wind is only possible if some thrust component counteracts the bird’s aerodynamic drag, and it is shown that the hydrodynamic drag of the feet through the water is adequate to balance aerodynamic drag. The bird is thus analagous to a kite, where the tension in the string counterbalances the aerodynamic drag of the kite.

The movements of the storm petrel’s wings during ‘hovering’ suggest that the bird may use the wing-flip mechanism for generation of high lift coefficients (Weis-Fogh, 1973, 1976). Such high lift coefficients are required for the bird to ‘hover’ under calm conditions, when ambient wind velocity is less than 5 m s −1. Use of the wing-flip mechanism would enable the bird to ‘hover’ at lower ambient wind velocities. Ground effect also contributes to the bird’s ability to ‘hover’.

This analysis of the flight behaviour of Wilson’s storm petrel indicates that its ‘hovering’ is an energetically inexpensive foraging stragegy which is probably available only to small, surface-feeding birds with low wingloading.
Central Generation of Bursting in the Feeding System of the Snail, Lymnaea Stagnalis
Authors: Benjamin P. R. , Rose R. M.
Published: April 2021

The central generation of burst activity was investigated in the buccal ganglia of Lymnaea. Eight different patterns of burst activity were generated by one or two consecutive phases of compound synaptic potentials resulting from activity of neurones outside the population of recorded neurones. These inputs acted upon the different endogenous properties of buccal neurones such as post-inhibitory rebound and spike adaptation. Effects of synaptic inputs were reinforced by electrotonic coupling of some buccal neurones of the same type.
Metabolic Control of Neuronal Pacemaker Activity and the Rhythmic Organization of Central Nervous Functions*
Authors: Chaplain R. A.
Published: April 2021

The endogenous rhythmic activity of isolated pacemaker neurones of Aplysia californica appears to be controlled by the operation of a substrate cycle. The recycling of fructose-6-phosphate is mediated by two membrane-bound enzymes: phosphofructokinase (PFK) and fructose-1,6-diphosphatase (FDPase). Allosteric effectors which promote the PFK-FDPase system either increase the regular beating activity or induce bursting discharges, while inhibitory effectors reduce pacemaker activity. Associated with the PFK-FDPase cycle are slow oscillations in membrane potential, the postulate being that changes in amplitude and time period of the waves are brought about by the cyclic fluctuations of H+ ions and ATP in the immediate vicinity of the membrane. Other enzyme reactions which affect the concentrations of gluconeogenic substrates or PFK effectors can modulate the oscillatory driving input, a good example being the neurogenic amino acid glutamate. Modifiers of FDPase and PFK are equally effective in changing pacemaker activity within the intact neuronal network and, hence, the rhythmic body function connected to this network. This has been demonstrated with pacemaker neurones governing cardiovascular activity in Aplysia, blood pressure or heart beat in the cat, and respiration or thermo-regulation in the rabbit. Nature appears to have achieved a functional differentiation between different pacemaker neurones by altering their response to at least one or two of the PFK and FDPase effectors. New periodicities can be entrained by current stimuli on the pre-existing rhythms of isolated Aplysia pacemaker neurones. Stimulus-induced resetting of the discharges is in fact accompanied by a redistribution between two kinetically distinct forms of PFK, and modifiers of this enzyme can stabilize the new periodicities or facilitate the conditioning effect of a stimulus. Memory facilitation and consolidation under PFK modifiers could also be demonstrated in avoidance and discrimination learning trials with honey bees and rats, which are consistent with the metabolic nature of the slow-wave rhythmicity in vertebrate microneurones thought to be the site of memory storage.
Oscillatory Contraction Activity in Physarum
Authors: Wohlfarth-Bottermann K. E.
Published: April 2021

The plasmodia of Physarum polycephalum show different oscillatory phenomena (time period approximately 1·3 min) in their contraction behaviour and their protoplasmic flow. The force generating system for these phenomena is cytoplasmic actomyosin. The biochemical nature and location(s) of the oscillator(s), i.e. the clock governing these phenomena are unknown.

The following locations are discussed as possible sites of the oscillator: (1) cytoplasmic actomyosin, (2) the energy supply system, (3) inner Ca2+ stores, and (4) the plasmalemma, which must be involved at least in modulating the force generated by the contractile machinery during a chemotactic response.

The following oscillatory phenomena were used to assess the effects of externally and internally applied substances (e.g. calcium antagonistic drugs, caffeine, D2O) on oscillating force output: persistance of longitudinal contractile activity of veins (for external application of test substances),persistance of radial activity of veins (for internal application of the test substances),de novo generation of contractile activity in protoplasmic drops (external application).

The data seem to exclude rhythmical Ca2+, Na+ or K+ transport across the plasmalemma as a triggering function for the oscillation. Contractile activity seems to represent a spontaneous, endogeneous oscillation which can be modulated via the plasmalemma during chemotaxis.
On Exploring The Basis For Slow Potential Oscillations in the Mammalian Stomach and Intestine
Authors: Connor John A.
Published: April 2021

The basic driving unit of oscillatory electrical activity in stomach and intestine is the slow wave, a propagating depolarization of myogenic origin. The slow wave controls contractile activity in the intestine by triggering action potential bursts, while in the stomach there is both action potential and spike-free slow wave activation. This review attempts to summarize recent characterizations of the slow wave and to explore in detail the evidence, which suggests that the mechanisms which generate the electrical oscillations are quite closely coupled to metabolic processes.
An Atlas of Cellular Oscillators
Authors: Rapp P. E.
Published: April 2021

Rapidly accumulating evidence suggests that periodic behaviour is not confined to a limited number of cell types but is a common property of most biological systems. The argument for this proposition is presented by systematically cataloguing an atlas of biological and biochemical oscillators with periods of an hour or less. The listing consists of eight principal sections .and includes oscillations in secretory cells, neural oscillators, oscillations in muscle cells and rhythmic behaviour in growth and development. Each entry states the experimental preparation, the periodic event (the observed oscillatory variable), the period and lists references to the experimental literature. Four hundred and fifty experimental papers are cited.
Oscillatory Membrane Potential Changes in Cells of Mesenchymal Origin: The Role of an Intracellular Calcium Regulating System
Authors: Nelson P. G. , Henkart M. P.
Published: April 2021

A number of mesenchymal cells (fibroblasts, macrophages and megakaryocytes) respond to a variety of stimuli with large hyperpolarizations lasting several seconds (the H.A. response). The H.A. responses can occur as repetitive trains or oscillations. These hyperpolarizations are due to an increase of the surface membrane permeability to potassium ions which is probably mediated by an increase in the cytoplasmic free calcium ion concentration. Evidence is discussed which suggests that the source of this increased calcium is, at least in part, an intracellular sequestering system, probably the endoplasmic reticulum. A model capable of producing oscillatory changes in membrane potential is proposed based on such an intracellular calcium sequestering and releasing system.