bluuebunny/crossref_metadata_2025 huggingface dataset:
Responses of Regularly-Firing Aplysia R3-R13 Neurones to Normoxia and Hypoxia
Authors: Coyer Philip E.
Published: April 2021

Exposure of 10 R3-R13 neurones to a 115-min period of hypoxia resulted in depolarization of their membrane potentials (EM) from a mean of −46·9 ± 3·1 to −20·8 ± 4·4mV (S.E.). Intracellular potassium ion activities decreased significantly from 118·9 ± 5·1 to 67·7 ± 8·5 mm-K+. This is equivalent to a change in EK from − 70·9 mV to −54·5 mV, which is insufficient to account for depolarization of approximately 26 mV. During reoxygenation of the saline surrounding the ganglion, there was a continued depolarization of EM to − 11·5 ± 3·2 mV and progressive fall in to 49·2 ± 4·9 mm. Decreases in the membrane slope resistance were also observed in these depolarizing neurones. The depression in resistance remained irreversible for as long as experiments were conducted. Computations of PNa /PK ratios were made using a steady-state calculation. Increases in the PNa/PK ratio from 0·030 to 0·045 were observed during hypoxic depolarization using a modification of the Goldman equation which neglects the contribution of chloride ions. Subsequent depolarization and loss of a’K during reoxygenation elevated this value to 0·183. Whether or not the observed depression of the membrane resistance is linked to a change in either the sodium or potassium ion permeability is unknown. Release of neurotransmitter and related permeability changes cannot be ruled out as an effect of hypoxia.
Haemolymph Concentration and Apparent Permeability in Varying Salinity Conditions of Gammarus Duebeni, Chaetogammarus Marinus and Gammarus Locusta
Authors: Bolt Stephen R. L.
Published: April 2021

Haemolymph and external medium sodium concentrations have been investigated in three euryhaline amphipods, Gammarus duebeni (Lillje-borg), Chaetogammarus marinus (Leach) and Gammarus locusta (Linnaeus). These were subjected to various salinity regimes, including sudden and cycling salinity changes. The apparent permeability to water of these three species was investigated in various salinity regimes using THO as a marker. Of the three species, only G. duebeni demonstrated large and significant changes in apparent permeability to water. The bulk flow into and out of the animals was calculated showing a variation of responses in the three species, G. duebeni exhibiting the smallest bulk flow and G. locusta the largest.

These results were related to the ecology of the three species.
Electrical Potentials from the Regenerating Eye of Strombus
Authors: Gillary Howard L.
Published: April 2021

Following amputation of the eye of Strombus luhuanus, a morphologically equivalent one is regenerated. Early regenerates exhibited a relatively simple, single-peaked electroretinogram (ERG) that progressively matured to display two ‘on’ peaks, a ‘steady state’ during sustained illumination, and repetitive ‘off’ potentials. ERGs of regenerates were dependent on stimulus intensity, wavelength, light adaptation and temperature, as are those of mature eyes. Intracellularly recorded light-evoked depolarizations from retinas of early stages of regeneration tended to be simpler in waveform than those of more mature stages. In addition, certain cells exhibited light-evoked and electrically evoked action potentials, while others were hyperpolarized by light. Optic nerves of eyes in early stages of regeneration showed only ‘on’ activity, while those of later stages also exhibited ‘off’ responses.
Proprioceptive Reflexes Change When an Insect Assumes an Active, Learned Posture
Authors: Zill Sasha N. , Forman Robin R.
Published: April 2021

Imposed changes in activity of a joint angle receptor of the locust leg, the metathoracic femoral chordotonal organ, produce variable, phasic reflex responses in a leg extensor motoneurone in untrained animals. After training the locust to maintain a posture in extension beyond a minimum required joint angle, these reflexes are consistently tonic and excitatory. This plasticity of reflex responsiveness permits the locust to couple motoneurone firing to afferent activity when receptor input is behaviourally relevant.
Effect of Lanthanum Ions on Neuromuscular Transmission in Insects
Authors: Washio Hiroshi , Miyamoto Takenori
Published: April 2021

The effect of extracellular lanthanum on neuromuscular transmission was studied in cockroach leg muscle and larval mealworm ventral muscle by means of microelectrodes. Miniature excitatory postsynaptic potential (MEPSP) frequency was markedly increased after lanthanum was added, in the presence and absence of calcium. The potentiation by La3+ was suppressed in a high Ca2+ saline and enhanced in the absence of Ca2+. Lanthanum ions blocked neuromuscular transmission at a concentration as low as 0-1 mm. The quantal content estimated by the failure method was reduced by 80% in the presence of 0·1 mm-La3+. The reduction in the EPSP amplitude by La3+ may be due to a decrease in the amount of transmitter released by a nerve impulse. The response to L-glutamate applied iontophoretically was also reduced in the presence of La3+. It seems unlikely that La3+ and L-glutamate were competing for a common binding site on the postsynaptic membrane since the apparent maximum of the dose-response curve for glutamate-induced depolarization was reduced in the presence of La3+. External recording of MEPSPs showed that adding lanthanum to the bathing medium increased the time constant of decay of the potential. These results suggest that lanthanum does indeed have a postsynaptic action in addition to its prejunctional action in insect muscle fibres.
Cardiac Performance in thein SituPerfused Fish Heart During Extracellular Acidosis: Interactive Effects of Adrenaline
Authors: Farrell A. P. , Macleod K. R. , Driedzic W. R. , Wood S.
Published: April 2021

The physiological integrity of the in situ perfused heart of the ocean pout was established by its ability to maintain cardiac output (Q̇) over a range of work loads, and by the dependence of Q̇ upon the filling pressure of the heart. Similar observations have been reported previously for the in situ perfused heart of the sea raven. Physiological levels of extracellular acidosis (pH 7·6/1% CO2 and pH 7·4/2% CO2) significantly depressed cardiac performance in sea raven and ocean pout hearts in situ. Negative chronotropic and inotropic responses were observed. Adrenaline (AD; 10−7M) under control conditions (pH7·9/0·5% CO2) produced a sustained tachycardia. The tachycardia reduced filling time of the ventricle and stroke volume was compromised because of the constant preload to the heart. Consequently, AD produced only an initial, transient increase in stroke volume and Q̇. Thereafter, stroke volume was reduced in proportion with the increase in heart rate, and Q̇ remained unchanged. The combined challenge of extracellular acidosis and AD demonstrated interactive effects between AD and acidosis in situ. Q̇ and power output were maintained in both species at both levels of extracellular acidosis during the combined challenge. Thus AD alone can maintain (but not improve upon) basal 0 during extracellular acidosis. The effects of extracellular acidosis, circulating catecholamines and venous return pressure to the heart are discussed in relation to the regulation of Q̇ following exhaustive exercise.
Graded Potentials and Spiking in Single Units of the Oval Organ, A Mechanoreceptor in the Lobster Ventilatory System
Authors: Bush B. M. H. , Pasztor V. M.
Published: April 2021

The peripheral dendritic arborizations of sensory units X, Y and Z of the oval organ have similar branching patterns. All three permeate the whole array of connective tissue strands without apparent regionalization or specialization. The analogue components of sensory responses elicited in fibres X, Y and Z when the connective tissue array is stretched show considerable diversity: fibre Z has a higher threshold than X and Y; the dynamic peak values of X and Y saturate at pulls mid-range for Z; X, Y and Z form a spectrum of increasing adaptation. Application of TTX abolishes impulse generation in fibre X earlier than in fibre Y, indicating diversity in spike initiating mechanisms from one fibre type to another. Fibre X only spikes between certain limits of membrane depolarization. Usually the response includes one to five spikes which occur during the dynamic phase of a trapezoidal stretch stimulus. Fibre Y fires throughout the stimulus duration for pulls of moderate amplitude and velocity. Spiking inactivation and a low maximum firing frequency (approximately 80s−1) limit the range of length sensitivity in fibre Y. Fibre Z attains higher firing frequencies than either X or Y (approximately 110 s−1). The initial burst frequency (velocity dependent) may equal the firing rate of the dynamic peak.
Graded Potentials and Spiking in Single Units of the Oval Organ, a Mechanoreceptor in the Lobsterventilatory System Iii. Sensory Habituation to Repetitive Stimulation
Authors: Pasztor V. M. , Bush B. M. H.
Published: April 2021

When the oval organ is stimulated repetitively at frequencies imitating normal scaphognathite beating the responses of the three sensory afferents decline. The number of spikes per response diminishes, the firing rate declines and the latency of the first spike may increase. The term ‘sensory habituation’ is proposed to describe the decline in response of a primary sensory unit to a repetitive train of identical stimuli. The decline in spiking performance is shown to be due to some or all of these underlying changes: (a) a decline in the rate of rise of the graded potential, (b) a decline in amplitude of the graded potential, (c) a decline in the rate of growth of the active process leading to spike initiation and (d) a rise in spiking threshold. The graded potential undergoes less of a reduction than impulse generation. Tetrodotoxin-treated fibres show little habituation to stretch. Normal fibres habituate to repetitive pulses of depolarizing current. It is suggested that during regular quiet ventilation the analogue signal alone provides feedback. Any extraneous perturbation or change in scaphog nathite rhythm restores spiking.
α-Bungarotoxin Blocks Excitatory Synaptic Transmission Between Cercal Sensory Neurones and Giant Interneurone 2 of the Cockroach,Periplaneta Americana
Authors: Sattelle D. B. , Harrow I. D. , Hue B. , Pelhate M. , Gepner J. I. , Hall L. M.
Published: April 2021

Autoradiographic localization of an 125I-α-bungarotoxin binding component revealed that specific binding was distributed mainly in the neuropile and to some extent in the periphery of the terminal abdominal ganglion of the cockroach, Periplaneta americana (L.). Action potentials recorded from the axon of GI2 under current-clamp conditions were not affected by exposure to 1·0 X 10−5M α-bungarotoxin. Excitatory postsynaptic potentials recorded from GI2, evoked by stimulation of cereal sensory neurones, were sensitive to block by relatively low concentrations (1·0 X 10−9-l·0x 10−7 M) of α-bungarotoxin. The timecourse for blockade was found to depend on toxin concentration and frequency of afferent stimulation. Excitatory postsynaptic potentials recorded from GI 2 were not affected by exposure to 1·0 X 10−6M quinuclidinyl benzilate. We conclude that at least a portion of the 12SI-α-bungarotoxin binding component represents cholinergic receptors which have a postsynaptic function at synapses between cereal sensory neurones and GI 2.
Patterns and Control of Neurosecretion for the Cytochromogenic Hormone in Blaberus Discoidalis Cockroaches
Authors: Hayes Timothy K. , Keeley Larry L.
Published: April 2021

Corpora cardiaca (CC) from immature and adult Blaberus discoidalis Serville of both sexes contained approximately equal amounts of activity for the cytochromogenic hormone (CGH), a neurohormone which stimulates cytohaem synthesis in fat body mitochondria on day 4 of adult life. CGH activity remained at a constant level in the CC of males during days 0 and 1 of adult life, decreased during days 2 and 3, and then returned to the original level by day 4. Female CC followed a similar pattern except that the period of low CGH activity occurred 1 day later. Variations in early adult feeding patterns or in daily photoperiod did not change the secretory pattern of CGH. However, injections of juvenile hormone III stimulated a precocious release of CGH on days 0–1. Thus, CGH and juvenile hormone may function in this insect as a coordinated endocrine sequence directing metabolic maturation of the fat body during early adult life.
The Disappearance of Moulting Fluid in the Tobacco Hornworm, Manduca Sexta
Authors: Cornell John C. , Pan M. L.
Published: April 2021

In Manduca sexta, and other insects, moulting fluid (MF) accumulates after apolysis in the exuvial space which underlies the old cuticle, and then most of it disappears shortly before ecdysis (see reviews by Zacharuk, 1976; Jungreis, 1979). Moulting fluid digests and weakens the old endocuticle so that the animal may free itself at ecdysis, and the digested components of the old endocuticle are reabsorbed. In M. sexta, Jungreis (1979) found that MF is produced between 30 and 12 h before the larval-pupal ecdysis (LPE) and it begins to disappear about 9 h before the LPE (LPE –9h). By LPE –3 h, most, but not all, of the MF has disappeared. We have found that MF represents a significant fraction of the total body water, 14·7% body weight (bw) [0·579 ± ·042 (5) ml, mean ± S.E. (N)] at LPE –6h.
Influence Of Some Common Methylxanthines on Contractile Responses and Calcium Mobilization of Ileal, Vas Deferens and Bladder Smooth Muscle
Authors: Huddart H. , Bayton E. , Shanklin J.
Published: April 2021

Caffeine and theophylline (0·1–5· MM) relaxed rat ileal muscle and reduced spontaneous rhythmicity. They inhibited the K-induced tonic contractures of rat vas deferens and bladder muscle strips but were without significant effect on the phasic responses to K. Theobromine (1·0–2·5 mm) induced contractures in ileal muscle and enhanced both the phasic and tonic components of K-induced contractures in vas deferens and bladder muscle strips. Theophylline and caffeine inhibited by varying degrees the 45Ca efflux from ileal, vas deferens and bladder muscle strips during the slow intracellular phase, but theobromine significantly stimulated 45Ca slow compartment efflux in all three types of muscle. Caffeine and theophylline both depressed, to varying degrees, the 45Ca influx into all three muscles while theobromine stimulated 45Ca influx in all cases. Caffeine and theophylline were either without much effect or slightly stimulated calcium binding by microsomes and mitochondria isolated from ileum, vas deferens and bladder, while theobromine significantly inhibited calcium binding by both sub-cellular fractions in all three muscles. The inhibitory action of caffeine and theophylline on these muscles appears to be due to inhibition of calcium influx coupled with some stimulation of intracellular binding. Theobromine’s excitatory action appears to be related to stimulation of calcium influx and inhibition of cellular calcium binding.
Actions of Cholinergic Pharmacological Agents on the Cell Body Membrane of the Fast Coxal Depressor Motoneurone of the Cockroach (Periplaneta Americana)
Authors: David J. A. , Sattelle D. B.
Published: April 2021

The pharmacological properties of cholinergic receptors on the cell body membrane of the fast coxal depressor motoneurone (Df) of the cockroach (Periplaneta americana) have been investigated. Parallel dose-response curves were obtained for the depolarizing actions of four bath-applied agonists, with the following order of effectiveness: nicotine > acetylcholine (ACh), in the presence of 1·0×10−7M neostigmine > carbamylcholine > tetramethylammonium. By contrast, dimethyl–4-phenyl piperazinium, suberyldicholine, D,L-muscarine, oxotremorine, acetyl-β-methylcholine and sebacinylcholine were practically ineffective. Of the three putative receptor-specific ligands used to date in binding studies on insect CNS tissues, α-bungarotoxin (α-BGTX) was much more effective (I50 = 6·4x 10−8M) in blocking the depolarization resulting from ionophoretic application of ACh, than either quinuclidinyl benzilate (QNB) (I50 =1·6×10−4 M) or decamethonium (I50 = 2·8×10−3 M). The order of effectiveness of ligands that were particularly effective in blocking ACh depolarization was β-BGTX > α-cobratoxin (α-COTX) > mecamylamine > dihydro-β-erythroidine > benzoquinonium. Less potent and almost equally effective were atropine, rf-tubocurarine, pancuronium and quinuclidinyl benzilate. Even less effective were hexamethonium, gallamine, decamethonium and succinylcholine, all requiring concentrations of ∼ 1·0× 10−3M and higher to produce a significant block of the ACh response. Not all reversibly acting antagonists were equally effective in preventing irreversible block of the ACh-induced depolarization by α-BGTX. Whereas α-COTX protected the receptors, mecamylamine did not. With the cell body of Df voltage clamped, the degree of antagonism of the ACh-induced current was assessed at potentials in the range −120 mV to −60 mV. a-BGTX, dihydro-β-eryth-roidine, benzoquinonium, QNB and décaméthonium appeared to be voltage-independent over this potential range, whereas J-tubocurarine and atropine were strongly voltage-dependent in their blocking actions. Sites of action of cholinergic antagonists at the insect ACh receptor/ion channel complex are discussed.
Properties of Ventral Cerebral Neurones Involved in the Feeding System of the Snail, Lymnaea Stagnalis
Authors: Mccrohan C. R.
Published: April 2021

Four identified neurone types (CV3, 7, 5 and 6), located in the ventral cerebral ganglia of Lymnaea stagnalis, are described. These cells have axonal projections in one or more of the nerves innervating the lips. In addition, they show rhythmic synaptic inputs leading to strong burst activity in phase with cyclic output from the buccal ganglia, suggesting a role in the control of the oral aperture during feeding. The innervation of lip muscle by one of the cell types (CV7) is confirmed electrophysiologically. The relationship of rhythmic activity in CV cells with that in the buccal feeding system is discussed.
The Ionic Basis of the Resting Potential in a Cross-Striated Muscle of the Aquatic Snail Lymnaea Stagnalis
Authors: Brezden B. L. , Gardner D. R.
Published: April 2021

The mean resting potential in the heart ventricle muscle cells of the freshwater snail Lymnaea stagnalis was found to be – 61·2±3·5(..)mV (ranging from –56mV to –68mV). The average intracellular potassium concentration was estimated to be 51·5 ± 14·6 (..) m (ranging from 27·8 m to 77·3 m). The membrane of the heart ventricle muscle cells appears to be permeable to both potassium and chloride, as changes in the extracellular concentration of either of these ions resulted in a change in the membrane potential. A ten-fold change in the extracellular potassium concentration was associated with a 50·4 ± 3·8 (..) mV slope when the potassium concentration was above about 6 m. Deviations from the straight-line relation predicted for a potassium electrode could be accounted for by introducing a term for sodium permeability. The ionic basis of the membrane potential in these cells can be described by a modified form of the Goldman-Hodgkin-Katz equation.
The Selective Permeability of Fleshfly Midgut to an Orally Toxic Cobra Venom Cardiotoxin
Authors: Fishman Lena , Primor Naftali , Zlotkin Eliahu
Published: April 2021

The permeability of the midgut of the fleshfly, Sarcophaga falculata, to the orally toxic polypeptide (Mr∼7000), a cobra venom-cardiotoxin, was investigated by LM and EM autoradiography, using the radio-iodinated toxin. The histology of the normal and toxin affected midgut was also investigated.

The midgut could be classified into segments that were permeable, partially-permeable and non-permeable to the toxin. Histological comparison between the epithelial cells of the permeable and non-permeable segments revealed strong differences in the form of the cells, and in the distribution, form and organization of their microvilli, organelles and basal foldings. The movement of the toxin in the permeable region of the gut is progressive and includes the crossing of the peritrophic membrane, penetration into the apical region of the cell through the microvilli (5 min), movement in the cell’s cytoplasm and finally the passage of the midgut as shown by its appearance in extraintestinal tissues (30 min). The data strongly suggest that the crossing of the midgut by cardiotoxin did not follow the common pattern of pinocytotic uptake and vesicular transport. When applied orally in superlethal doses (10 LD50 units per fly), cardiotoxin strongly affected the integrity of the epithelial cells in the toxin permeable segment, as expressed in their collapse, rupture and final disintegration. The toxin had no histopathological effect on any other region of the midgut.

These data are interpreted in terms of a postulated specific composition and arrangement of phospholipids in the outer plasma membranes of the epithelial cells in the cardiotoxin-permeable segment of the midgut.
Contraction Dynamics of Flight and Stridulatory Muscles of Tettigoniid Insects
Authors: Josephson Robert K.
Published: April 2021

Isometric contraction kinetics and force-velocity relations were examined in wing muscles of two tettigoniid insects, Neoconocephalus robustus and N. triops. The muscles were first tergocoxal muscles of the mesothoracic and metathoracic segments. The metathoracic muscle is a flight muscle. The mesothoracic muscle is used in flight and in stridulation. In the field, the wing stroke frequency during stridulation by N. triops is about 100 Hz ; the thoracic temperature during singing is about 30 C ; and the temperature gradient between the thorax and surround is about 15 C. Published data for N. robustus give the wing-stroke frequency during stridulation as about 200 Hz at a thoracic temperature of 35–40 C. The wing-stroke frequency during flight by both species is approximately 20 Hz at 25 C. The twitch time course is similar in equivalent muscles of the two species. At 35 C the twitch duration (onset to 50 % relaxation) is 5·5–6·5 ms for mesothoracic muscles and 11–13 ms for metathoracic ones. Twitch and tetanic tension per unit area are about twice as great in the metathoracic muscles as in the faster, mesothoracic ones. Despite the differences in isometric contraction kinetics, the maximum shortening velocity (Vmax) is similar in mesothoracic and metathoracic wing muscles. Vmax values (lengths per second, 35 C), determined by extrapolation of force-velocity curves, were 10·1 (mesothoracic) and 11·1 (metathoracic) for N. robustus; 12·2 (mesothoracic) and 16·1 (metathoracic) for N. triops. With N. triops, Vmax was also determined from the time taken to re-develop tension following quick release. The values obtained were somewhat higher than from extrapolation of force-velocity curves, but again similar for mesothoracic and metathoracic muscles. Twitch time course becomes more rapid and Vmax increases with increasing temperature. Neither twitch nor tetanic tension is greatly affected by temperature change in the range 25 – 35 C. As for many other fast muscles, force-velocity plots for these muscles have little curvature. It is suggested that the relative straightness of these plots is a consequence of internal viscosity.
Juvenile Hormone Involvement in Pupal Diapause of the Flesh Fly Sarcophaga Crassipalpis: Regulation of Infradian Cycles of O2 Consumption
Authors: Denlinger D. L. , Shukla M. , Faustini D. L.
Published: April 2021

A cyclic pattern of juvenile hormone (JH) activity is retained during pupal diapause in the flesh fly, Sarcophaga crassipalpis. Cycles of JH activity correlate with infradian cycles of O2 consumption. JH activity progressively increases during a 4-day cycle and appears to trigger the onset of an peak. During the first 2 days of an cycle, pupae are insensitive to an application of JH analogue, but when JH analogue is applied during the last 2 days of the cycle, rises and the cyclic pattern is destroyed. When JH analogue is applied to third instar larvae, O2 consumption is sustained at a steady, high rate throughout pupal diapause. The cycles persist in abdomen-ligated pupae but disappear following head ligation.
Temperature-Induced Changes in Blood Gas Equilibria in the Albacore, Thunnus Alalunga, a Warm-Bodied Tuna
Authors: Cech Joseph J. , Laurs R. Michael , Graham Jeffrey B.
Published: April 2021

Samples of unbuffered, whole blood from freshly-caught albacore (Thunnus alalunga Bonnaterre) were equilibrated at 5, 10, 15, 20, 25, 30 and 35 °C and at 0 and 1 % CO2 for construction of oxygen dissociation curves. A strong Bohr effect (− 1·17), a negligible Root effect, and a reverse temperature effect (ΔH = +1·72 for 0 % CO2 and +·26 for 1 % CO2) characterized these hyperbolic (Hill’s n = 1·1) curves. The unusual reverse temperature effect was especially pronounced when blood was quickly warmed or cooled, simulating passage through the heat exchanging, countercurrent vascular rete system of this warm-bodied fish. A diagrammatic model of blood gas dynamics in the rete incorporating these in vitro data illustrates protection of arterial oxygen from premature haemoglobin dissociation and consequent loss to the venous circulation as blood warms in the rete. More conventional temperature effects on the carbon dioxide equilibria of albacore blood lower the of venous blood being cooled in the rete. This reduces the venous-arterial gradient, thereby minimizing the diffusion of CO2 to arterial blood with resulting haemoglobin-oxygen dissociation via the strong Bohr effect. The temperature range (10–30 °C) over which the albacore haemoglobin-oxygen binding exhibits the reversed thermal effect closely matches the maximum thermal gradient (ambient water-core body temperature) typically present in this fish, suggesting that its highly specialized haemoglobin-oxygen dissociation characteristics evolved within – and now establishes thermal limits upon – the existing geographic distribution of this species.
Viscoelasticity of Holothurian Body Wall
Authors: Motokawa Tatsuo
Published: April 2021

Stress-relaxation tests and creep tests were performed on the bodywall dermis of two sea cucumbers, Actinopyga echinites (Jäger) and Holothuria leucospilota Brandt. These viscoelastic connective tissues had mechanical properties which agreed well with those of a four-element mechanical model composed of two Maxwell elements connected in parallel. The elastic stiffness of the dermis of Actinopyga was 1·7 MPa and that of Holothuria was 0·42 MPa. The viscosity of the dermis showed great variation of more than two orders. Chemical stimulation with artificial sea water containing 100 mm potassium increased the viscosity but not elasticity. The viscosity change is suggested to be caused by the change in weak (non-covalent) bonds between macromolecules which constitute the dermis.
The Effect of Size and Swimming Speed on Locomotor Kinematics of Rainbow Trout
Authors: Webb P. W. , Kostecki P. T. , Stevens E. Don
Published: April 2021

During swimming at constant speed the frequency (f), amplitude (a) and depth (d) of the tail trailing edge, and the length of the propulsive wave (λ) were measured for rainbow trout ranging in total length (L) from 5·5 to 56·0 cm. Fish were tested in a water flume using increasing velocity tests to sample a range of swimming speeds, V. λ was independent of V and related to size by: so that wavelength was relatively larger in smaller fish. 3.f was related to L and V according to: a was independent of V but was relatively smaller in larger fish: d was also independent of V but relatively larger in larger fish: Thrust power (= drag power) calculated using Lighthill’s small amplitude bulk momentum model was two to three times the theoretical minimum of a flat plate of equivalent length and area moving parallel to the flow with a presumed turbulent boundary layer. Froude efficiency increased with swimming speed, and it is shown that this is the usual relationship for fish studied so far. Froude efficiency was essentially independent of size at the critical swimming speed. Estimated aerobic efficiency increased with size at the critical swimming speed, implying that muscle efficiency also increases with size.
Distribution of Flow and Plasma Skimming In Isolated Perfused Gills of Three Teleosts
Authors: Olson K. R.
Published: April 2021

Distribution of flow and red cells between the efferent (epibranchial) and venous pathways was examined with an isolated perfused gill adapted to collect the two effluents separately. Gills from two fish species (Ictalurids) with abundant prelamellar arteriovenous anastomoses (AVAs) were compared with those of the trout which contain few AV As. The gills were perfused with Ringer or Ringer containing 51Cr-tagged red cells (blood).

In Ringer-perfused gills, efferent outflow decreased as efferent pressure increased. Epinephrine prevented the decrease in efferent flow at elevated efferent pressures. In all species around one-third of the control blood perfusing the gill drained via the venous pathway. At constant efferent pressure epinephrine increased and acetylcholine decreased efferent outflow. These results suggest that tonic adrenergic stimulation is necessary for normal branchial perfusion.

The haematocrit of efferent effluent was greater than venous effluent in all species. No consistent effects of epinephrine or acetylcholine on plasma skimming were observed. Comparison of measured microhaematocrit and haematocrit values calculated from 51Cr red cell space suggests that the red cells in the venous effluent are larger than those from the efferent pathway and supports the concept of a nutritive function for the venous pathway.
On the Excitation of Crustacean Muscle. I
Authors: Pantin C. F. A.
Published: April 2021

A brief account is given of the present position of the problem of neuro-muscular action in the Crustacea. A method is described by which the leg of Carcinus maenas may be perfused and stimulated. By this method the muscle remains in good condition for some 8 hours. By stimulating the nerve in Carcinus leg with alternating currents of increasing intensity a series of varied responses is obtained. Above the threshold a contraction is developed of a comparatively slow type. With increase of intensity of the stimulus the response fails, owing to the excitation of inhibitory nerves. But at still greater intensities contraction reappears. This contraction, however, is very rapid. Tetani developed from the slow contraction are easily inhibited. Tetani developed from the rapid contraction cannot be inhibited by superimposed stimuli. The relation of the quick and slow contractions is considered. It is not possible to fatigue one without fatiguing the other. Experiments show that on suddenly releasing the tension of the muscle during a tetanus, the tension always redevelops in a manner similar to the development of tension in the quick contraction, even though the tetanus be developed initially by the slow contraction. The same contractile mechanism is involved in both cases. The latent period of contraction on stimulation of the nerve is very long, and ranges from 300σ at the threshold. That for direct stimulation of the muscle is 7–10σ. Above the threshold the latent period shortens rapidly with increasing stimulus. Over this region the contractions are of the slow type. The latent period becomes asymptotic to 50σ as the intensity is increased. At this value the contractions are of the quick type. Inhibition is effective where the latent period begins to approach its asymptotic value. It is suggested that all the varied phenomena observed are related to the power of summation of crustacean muscle ; that the slow contraction in response to a battery of stimuli is not due to a different contractile mechanism from the quick one, but that it is a summation effect by which a statistically increasing number of muscle fibres are brought into action as successive impulses pass down the nerve.
The Osmotic Pressure of the Colloids in Fish Sera
Authors: Keys Ancel , Hill R. M.
Published: April 2021

Measurements of colloid osmotic pressure and refractive index of five species of teleost fishes are recorded. A number of observations were made on eels which had been starved for two months. With the exception of the eel, the colloid osmotic pressures were less than half the characteristic level for mammals, the average being about 100 mm. H2O. Normal eels showed serum colloid osmotic pressures within the mammalian range, the starved eels showed values less than half as great but showed no signs of oedema.

A comparative table of colloid osmotic pressures for the vertebrates studied so far is presented.

The relation between refractive index and the colloid osmotic pressure is discussed briefly.
Some Effects of Fasting on the Composition of the Blood and Respiratory Exchange in Fowls
Authors: Henry Kathleen M. , Magee H. E. , Reid E.
Published: April 2021

It has been shown that the blood sugar in the adult fowl, male or female, after falling during the first 2 days of fasting, rises on the 3rd or 4th day and then declines rapidly so that a well-defined peak is formed (Henry, Macdonald and Magee, 1933). This change was so constant in its occurrence that experiments were undertaken in the hope of throwing light on the immediate cause. As all the original glycogen stores are almost certainly exhausted after fasting for 3 or 4 days, the increase in blood sugar could only have come from protein or fat. A study was therefore made in fasting fowls of the uric acid and non-protein nitrogen contents of the blood, in the hope that, if any marked change in the metabolism of protein occurred, it would be reflected in alterations in the amounts of these present in the blood. In regard to fat the metabolites chosen were cholesterol and lecithin. The significance of these substances in fat metabolism is not very clear at present; but, as they can be readily and accurately estimated in small amounts of blood, they were preferred to blood fat as possible indicators of change in fat metabolism. The liver and muscle glycogen of fowls killed after different periods of fasting were also determined, as well as the effect of fasting on the respiratory exchange. Marked qualitative alterations in energy metabolism would, it was thought, be associated with corresponding changes in the R.Q. None of these lines of study threw any direct light on the problem we set out to solve ; but the results obtained were considered to be of sufficient interest in themselves to merit publication.
Cellular Transfer of Substances, Especially Neurohumors
Authors: Parker G. H.
Published: April 2021

The dark longitudinal stripe (expanded melanophores) produced in the tail of Fundulus by a transverse denervating cut of 1 mm. length appears about half a minute after the cut is made, it reaches its maximum development in about an hour, and fades to the lightness (contracted melanophores) of the ordinary light fish in from 22 to 96 hours (average 29·7 hours). A dark longitudinal stripe similar to that described in paragraph 1, but from a 2 mm. cut, fades after 43–143 hours (average 78·3 hours). Light-tinted fishes, such as are noted in paragraphs 1 and 2, when put on a dark background, become fully dark, except for the stripe on the tail, in about 1·8 hours. Under such circumstances a 1 mm. stripe becomes dark within 17–27 hours (average 20·5 hours) and a 2 mm. stripe within 23–70 hours (average 37·4 hours). Dark-tinted fishes, when put on a light background, become fully light, except for the stripe on the tail, in about 4-6 hours. Under such circumstances, a 1 mm. stripe becomes light within 18–31 hours (average 26·4 hours) and a 2 mm. stripe becomes fight within 22–86 hours (average 51·6 hours). The darkening of the stripe (expansion of melanophores) and the fading of the stripe (contraction of melanophores) cannot be due to the nerves of the stripe, for these have been cut. The changes in colour are due to the gradual passage of an expanding neurohumor or of a contracting neurohumor from the adjacent regions into the stripe. This gradual change is much too slow for blood or lymph. It is believed to be due to a cell-to-cell transfer. Transfer of substances from cell to cell has been observed in plants (Kok), occurs in coelenterates, and is seen very probably in a number of instances in the human skin (spread of inflammation from radiated areas, erysipeloids, insect stings, and possibly vitiligo). Cell-to-cell transmission is a relatively slow process. Phylogenetically, it antedates transmission by blood and lymph.
Light Penetration Into Fresh Water
Authors: Pearsall W. H. , Ullyott Philip
Published: April 2021

In the last paper of this series (Pearsall and Hewitt, 1933) changes in the transparency of the water of Windermere were described. It was shown that the penetration of blue light (5100 Å to 4000 Å), as measured by the sulphuric acidiodide method, was very much greater in 1920 than it was in 1932. The present communication deals with the results of observations on changes in the transparency of the water of Windermere throughout the year March, 1932, to March, 1933. The causes of the differences in the light penetration at different times of the year are discussed.
The Fertilisation of Rabbit Ova in Relation to Time
Authors: Hammond John
Published: April 2021

By matings with fertile bucks at different intervals of time after a mating with a vasectomised buck (to induce ovulation) the time of insemination in the rabbit can be moved successively nearer to, at, and after the time of ovulation. From inseminations 5 hours before to 2 hours after ovulation the percentage of matings which are fertile, the average litter size, and average number of young per mating fall gradually and at a constant rate until absolute sterility is obtained. Does which produce large litters when mated normally (10 hours before ovulation) may be made to produce small litters by mating shortly before or after the time of ovulation. The ova are only capable of fertilisation while they are in, or as they leave, the plug at the top of the Fallopian tubes, i.e. up to about 6 hours after ovulation. They are incapable of fertilisation as they begin to move down the tube and acquire a layer of albumen around them. As a result of a mating made about the time of ovulation the apex of the “sperm swarm” arrives at the top of the tube in time to fertilise only those ova which still remain in the plug. The apex of the “sperm swarm” contains relatively few spermatozoa, and so small litters are produced. By “double matings,” of dominant and recessive coloured bucks on recessive coloured does, with a time interval between them, it is possible to measure the relative sizes of the “sperm swarms “at the tops of the tubes at different intervals of time after mating. The size of the “sperm swarm,” and so the interval of time over which it is possible to obtain fertilisation as a result of mating later than normal in relation to the time of ovulation, varies considerably in different males, The speed at which the sperms ascend the female tract is apparently not affected by the presence in them of male and female sex-determining elements. The duration of pregnancy is prolonged by reducing the size of the litter. With the prolongation of pregnancy the proportion of young born dead increases. Various possible causes for these facts are discussed. While there is but little constant increase in the weight of the individual young due to the prolongation of pregnancy from 31 to 34 days, there is a large increase in the individual weight due to reduction in the number of young in the litter. It is probable that the size of individual young is limited by the amount of some internal secretion or metabolic product of the mother.
Observations on the Fatty Constituents of Marine Plankton
Authors: Gunther E. R.
Published: April 2021

Collections of phyto- and zooplankton made off the Isle of Man were examined for vitamin content, and for chemical and biological characteristics. The important species entering into the composition of the plankton are noted, and a new method of estimating plankton catches is described. Figures which represent the numbers of a species present in a given quantity of plankton are translated into figures representing the volume occupied by that species. Comparisons are drawn between the numerical and volumetric estimations of the various zooplankton species. The phytoplankton catches taken in May showed a fairly uniform composition throughout the collecting period, species of the genera Chaetoceros and Lauderia forming more than 90 per cent, of the material. The zooplankton taken in July consisted mainly of Copepoda. The catches were of two types : those having a higher percentage of Acartia, Calanus copepodid stages IV and III, and the Peridinian Ceratium ; and those containing less of these but rich in the adult and other stages of Calanus finmarchicus. By the use of curves correlating length and volume, measurements of important species are translated into factors representing numbers per c.c.; application of these factors converts the numerical estimation of a species into an estimation in terms of volume. The numerical and volumetric estimations of various species in four separate groups of plankton are compared and the yield of oil from each group is also recorded. The volumetric method conveys a significantly different picture of the plankton than is to be gained from the numerical method alone. Calanus finmarchicus is shown to constitute a relatively larger part of the plankton than other more numerous but smaller species and likewise its adult or sub-adult stages than its earliest copepodid stages. The correspondence of a good oil yield with those groups having a high Calanus content is held to be suggestive of a possible correlation between the two. Chemical and biochemical analyses of planktonic organisms by other investigators are reviewed and their results compared with those obtained during the present work. The rôle of plankton organisms in the nutrition of various other organisms is discussed.
Experiments on Embryonic Induction
Authors: Waddington C.H
Published: April 2021

The experiments to be described in this section were begun in October, 1931, but no successful experiments were performed until the end of 1932. A short note on the results obtained was published in Nature (Waddington, 1933 b). In the meantime, Bautzmann, Holtfreter, Spemann and Mangold (1932) had shown that in the Amphibia coagulated organisers are still able to exert the inductive capacities which they possess in the living state. This work followed on the earlier experiments of Marx (1931) who obtained inductions with narcotised organisers, and Spemann (1931 a) who found that the inductive capacity is retained when the organiser tissue is subjected to crushing. The same type of investigation into the nature of the inducing agent in the amphibian organiser has now been carried still further by Spemann, Fischer & Wehmeier (1933), Holtfreter (1933 a and b) and Waddington, Needham & Needham (1933 a and b), all of whom have prepared cell-free organising extracts. The last-named authors have been able to show that the active substance is ether-soluble, but Fischer & Wehmeier (1933) claim that the substance is glycogen.
The Relations Between Yolk and White in the Hen’s Egg
Authors: Smith A. J. M.
Published: April 2021

The white of the hen’s egg is in equilibrium with ice at a temperature of approximately − 0·45° C., the yolk, according to most observers, at approximately − 0·58° C. More surprising than the mere existence of such a difference in the newly formed egg is the fact that this difference seems to persist, although to a gradually decreasing extent, in eggs preserved for a considerable period. The phenomenon may be of biological significance in the fertile egg, in connection with the passage of water yolkwards during incubation.
Metabolic Changes Associated With Endo-Crine Activity and the Reproductive Cycle in Xenopus Laevis
Authors: Shapiro H. A. , Zwarenstein H.
Published: April 2021

Experiments are described which show that active extracts of ovarian tissue minus corpus luteum can be obtained which significantly raise the lowered level of the serum calcium in ovariectomised toads ; and also raise the serum calcium level in normal toads above the normal level. Injection of adequate doses of antuitrin (Parke, Davis and Co.), raises the lowered level of serum calcium in hypophysectomised toads almost to normal ; and of ovariectomised toads to the normal level. The effect is obtained more readily in the ovariectomised condition. Injection of pituitrin (Parke, Davis and Co.), depresses the serum calcium level in normal, ovariectomised and completely hypophysectomised toads. The effect is more readily obtained in the normal intact animal than in the ovariectomised or the totally hypophysectomised state, when the ovaries have undergone involution. It is suggested that there is evidence that the principles exerting a hormone-like action on calcium metabolism are not, in the case of the ovary, either oestrin or the luteal hormone, or in the case of the pituitary, the gonadotropic hormone.
Some Observations on the Respiration of Certain Tropical Fresh-Water Fishes
Authors: Willmer E. N.
Published: April 2021

The blood of the fish of the rivers and swamps of British Guiana is not all equally affected by CO2. A regular series can be shown to exist between the paku (Myleus setiger Müll and Troschel), an active river fish whose blood is considerably affected, and the electric eel (Electrophorus electricus (L.)), which is an air-breather, frequenting relatively stagnant and poorly oxygenated water, and whose blood is almost independent of the presence of CO2. The blood of all the fish examined was found to be acid, generally about pH 6·7. The CO2 combining power of the blood of the fish examined was found to be very much lower than in other animals, but higher than might be expected on theoretical grounds. The possibility of another type of buffering is suggested. In the one fish examined (the bom-bom, Pterodorasgranulosus (Vai.)) the CO2 contained in reduced blood was found to be no higher than in oxygenated blood. In spite of the low oxygen content of some of the waters, no fish examined showed a haemoglobin with any markedly increased affinity for oxygen, such as might enable it to be saturated more easily at low pressures. The yarrow (Erythrinus erythrinus (Schn.) or Hoplerythrinus unitaeniatus (Spix.)) was found to be a fish which could either use its gills or take in bubbles of air into its air-bladder as a means of respiration. This fish has been studied in detail and the conditions controlling its respiration are described. Three factors are concerned, pH, oxygen content of the water, and CO2 content of the water. Of the three the last is most often the limiting factor. Carbonic anhydrase was found in the blood of all the fish examined for its presence, which include practically all those mentioned in this paper. The bearing of these results on certain problems of general biological interest is discussed.