bluuebunny/crossref_metadata_2025 huggingface dataset:
A Non-Linear Mechanical Model of A Non-Spiking Muscle Receptor
Authors: Berger C. S. , Bush B. M. H.
Published: April 2021

The sensory response of a mechanoreceptor is generally assumed to be a compound function of its mechanical and electrochemical properties. In a muscle receptor such as the mammalian muscle spindle or crayfish stretch receptor, the former depend upon the visco-elastic elements of the receptor muscle and its linkages with the sensory endings, while the latter properties reside within the sensory neurone itself. Analysis of these systems is complicated, however, by the difficulty in defining the precise stimulus obtaining at the site of transduction, and by the possible modifying influence of the impulse encoding process.
Vertical Banding Evoked by Electrical Stimulation of the Brain in Anaesthetized Green Sunfish, Lepomis Cyanellus, And Bluegills, Lepomis Macrochirus
Authors: Bauer Diana H. , Demski Leo S.
Published: April 2021

A pattern of dark vertical bands is a characteristic agonistic display in the green sunfish, Lepomis cyanellus and the bluegill, L. macrochirus. The rapidity with which the display can appear and disappear indicates that it is neurally controlled. Electrical stimulation of the brain was carried out in anaesthetized green sunfish and bluegills to map those regions from which this colour change can be elicited. Banding was evoked by stimulation of sites near the midline in the preoptic area, ventral thalamic-dorsal hypothalmic transition zone, the midbrain tegmentum (just dorsal to the nucleus prerotundus pars medialis), in and near the torus semicircularis, in the basal midbrain (region of the crossing tectobulbar tracts), and in the rostral basomedial medulla. A ‘transition’ zone was located basally in the middle medulla, caudal to which only paling was evoked. Areas found to be negative for evoked banding included the telencephalic lobe, the inferior lobe of the hypothalamus, the optic tract, the optic tectum, the body and valvula of the cerebellum and the caudal medulla. It is postulated that the vertical banding pattern is made up of a separate, selectively controlled system of dermal melanophores. The possible neural mechanisms controlling banding are discussed.
Relation Between Non-Bicarbonate Buffer Value and Tolerance to Cellular Acidosis: A Comparative Study of Myocardial Tissue
Authors: Hansen Henry Damm , Gesser Hans
Published: April 2021

There is a large variation in the tolerance of myocardial tissue to cellular acidosis. Assuming the cytoplasmic acid-base status to be mainly a result of intracellular processes, this variation could be produced by variations in the tissue non-bicarbonate buffer value. In the myocardial tissue from nine vertebrate species, the non-bicarbonate buffer value did not correlate either with ability to develop tension under hypercapnic acidosis or with the indirectly estimated capacity for anaerobic glycolysis. Therefore, differences in myocardial tolerance to acidosis must be explained either by an active pH regulation or by other compensatory mechanisms.
Structure and Electrical Properties of Eye Muscles in Cave- and Surface-Dwelling Crayfishes
Authors: Mellon Deforest , Lnenicka Gregory
Published: April 2021

The morphologies and passive electrical parameters of fibres in two eye muscles of a surface- and a cave-dwelling crayfish were compared. In the cave-dwelling form the muscles contained fewer fibres, of less diameter, and hence had a smaller cross-sectional area. Current-voltage relationships were similar in both species. Input resistance was higher in the cave-dweller, but the difference was not as great as would be expected on the basis of geometry alone. Accordingly, the specific membrane resistance of muscle fibres in the cave-dweller is 50–60 % smaller than that in the surface-dweller. This may account partially for the observation that identified excitatory junctional potentials in muscles of cave- and surface-dwellers have similar amplitudes. We conclude that a functional oculomotor system is maintained in cave-dwelling crayfish, and that this system confers some positive selective advantage.
Nervous Control of the Heartbeat in Octopus
Authors: Wells M. J.
Published: April 2021

The circulatory system of cephalopods is based on a trio of hearts, with two pairs of associated ganglia linked to the CNS by a pair of visceral nerves. The beat of the hearts was recorded from free-moving octopuses before and after surgical removal or disconnexion of elements of the nervous system. Severing the visceral nerves does not stop the hearts, which continue to beat in a powerful well co-ordinated manner in isolation from the CNS. The nerves seem to be concerned in raising the cardiac output in exercise, and with stopping the hearts when mantle movements cease, but they are not necessary for the initiation of maintenance of the normal rhythm. Removal of the fusiform ganglia severs all nervous connexions between the two gill hearts, and deprives the systemic heart of its nerve supply. The trio of hearts continues to beat as strongly as before. Removal or disconnexion of a cardiac ganglion disrupts the beat of the corresponding gill heart which now tends to contract in an ill-coordinated and rather feeble manner, though at much the same frequency as before ; with both cardiacs gone the systemic heart, which contracts only when it is filled, tends to drop in frequency and the mean aortic pressure falls. The system remains rhythmic, however, and the beat may recover, to the point where aortic pressures and frequencies approach those found in intact animals at rest ; even octopuses with both fusiform and both cardiac ganglia removed can survive for many hours. From the performance of the isolated branchial heart, the existence of a pulsating vesicle in each cardiac ganglion, the effects of cardiac ganglion removal and the remarkable steadiness of heartbeat frequency shown by intact animals under a variety of conditions, it is argued that the heartbeat rhythm is normally controlled by pacemakers in the branchial heart/ cardiac ganglion complexes, and perhaps, in intact animals, from within the cardiac ganglia themselves.

The picture of the control of the heartbeat that emerges from the study of free moving essentially intact animals is quite different from that arising from in vitro and acute preparation studies. It suggests that the conventional wisdom about the control of the heartbeat in cephalopods (and perhaps by implication, in other molluscs) may need to be considerably revised.
Heart Rate, Respiratory Frequency and Wing Beat Frequency of Free Flying Barnacle Geese Branta Leucopsis
Authors: Butler P. J. , Woakes A. J.
Published: April 2021

Two barnacle geese (Branta leucopsis) were successfully imprinted on a human and encouraged to fly behind an open-topped truck containing the foster parent. A two channel radio-transmitter was implanted into these geese so that heart rate and respiratory frequency could be recorded before, during and after flights of relatively long duration. The resting value for heart rate was 72 ±4 (10) beats min-1 and for respiratory frequency, 8.5±0.6(10) breaths min-1. Five flights of a mean duration of 14.4 ± 1.3 (5) min and at a mean air velocity of 18*7 ± 0.3 (54) m s-1 were performed. Both heart rate and respiratory frequency increased before the birds began to flap their wings for take off. Mean heart rate during flight was 512 ±4 (54) beats min-1 (7.24 x resting). At take off, wing beat frequency was 356 ± 7 (4) beats min-1 and respiratory frequency was 121 ± 10 (5) breaths min-1. Both of these variables then declined and reached average flight values of 287 ± 3 (37) beats min-1 and 99 ±2 (54) breaths min-1 (11.7X resting) respectively. There was no relationship between any of the measured variables and flight velocity. There was however, 3:1 correspondence between wing beat frequency and respiratory frequency and a tight phase locking between the two. The wings were fully elevated at 6.0 + 1.1(20)%, 40.5 + 1.1(20)% and 74.0+ 1.1(20)% of the respiratory cycle. On two occasions the birds slope soared on the air rising over the top of the cab for a mean duration of 52 s and at a mean air velocity of 14.2 ± 0.5 (4) m s-1. Heart rate was 261 ± 18 (4) beats min-1 and respiratory frequency was 68 ± 5 (4) breaths min-1. Upon landing, heart rate returned to its preflight value within 3 min. Respiratory frequency, however, increased as the birds began to pant and reached a maximum value of 255 ± 11 (5) breaths min-1 4 min after landing.
The Permeability of the Cuticular Lining of the Insect Alimentary Canal
Authors: Maddrell S. H. P. , Gardiner B. O. C.
Published: April 2021

The permeability of the cuticle lining the foregut and hindgut of adults of Schistocerca gregaria, Gromphadorhina portentosa, and Leucophaea maderae, and larvae of Manduca sexta was investigated. In Schistocerca, Manduca, Leucophaea, and Gromphadorhina the cuticle lining the foregut has a very low permeability, while that lining the ileum (Schistocerca, Manduca, Leucophaea, and Gromphadorhina) and the rectum (Schistocerca and Manduca) is much more permeable. The low permeability of cuticle lining the crop in the insects examined is suited to the crop’ s function as a temporary store of ingested material. In Schistocerca gregaria, the cuticular lining of the ileum and rectum were found to be equally permeable. Each allows relatively rapid passage of small neutrally charged hydrophilic molecules. Both, however, showed a reduced permeability to anions and an enhanced permeability to cations. The cuticular lining of the hindgut would thus not be a barrier to the reabsorption of useful substances known to appear in the fluid reaching the hindgut from the Malpighian tubules, but it would, to some extent, retain in the lumen the relatively large anions actively excreted by the Malpighian tubules. The cuticle lining the colon of Schistocerca gregaria has a much lower permeability than has that lining the rest of the hindgut. This accords with the idea that the colon is thought not to be involved in absorption.
Plasma Melatonin Levels in the Scincid Lizard Trachydosaurus Rugosus : The Effects of Parietal eye and Lateral eye Impairment
Authors: Firth B. T. , Kennaway D. J.
Published: April 2021

At a constant temperature of 24 °C there was a diel fluctuation in plasma melatonin concentration; highest levels occurring in the scotophase of a reversed daily light-cycle. Parietalectomy did not appear to affect melatonin titres under these conditions. When lizards were subjected to a photoperiod together with a thermoperiod (31 °C in the photophase, 24 °C in the scotophase), nocturnal plasma melatonin levels were almost twice as high as those in animals subjected to a photoperiod at constant temperature. Capping the lateral eyes of T. rugosus under these conditions did not alter the phase or amplitude of the rhythm in plasma melatonin content. However, removal of the parietal eye abolished the rhythm, owing mainly to reduced levels during the mid-scotophase and elevated levels during the midphotophase. It is concluded that plasma melatonin levels are regulated extraretinally, and that the parietal eye may help to mediate environmental input to centres secreting melatonin. It is suggested that the parietal eye may mediate thermal as well as photic information.
The Mechanics of Labriform Locomotion
Authors: Blake R. W.
Published: April 2021

It is likely that the ‘undulatory propulsora’ employed by many fish are capable of producing a usefully directed thrust force over most of the tail-beat cycle. In contrast, fish which employ the ‘paddling pectoral fin propulsor’ only produce thrust during the power stroke phase of their fin-beat cycle, after which a recovery stroke occurs, when little usefully directed thrust force is produced. However, in order to gain a complete understanding of the mechanics of the paddling propulsor it is necessary to investigate the recovery stroke fully.
Head Movements in Flies (Calliphora) Produced by Deflexion of the Halteres
Authors: Sandeman David C. , Markl H.
Published: April 2021

The heads of resting flies will twitch to the side if the haltere is deflected rapidly forwards. Head movements are always away from the stimulated haltere and do not occur if the haltere is deflected up, down or backwards. The anatomy and action of the neck muscles is described. Cobalt fills of the whole haltere nerve show that the sensory axons project to the neuropiles of the ipsi- and contralateral pro- and mesothoracic neuropiles, to the ipsilateral metathoracic neuropiles and to the cerebral ganglion. Cobalt fills of the nerves to the neck muscles and from the prosternal organs show that the central projections of these nerves end in the ipsilateral prothoracic neuropile. Recordings from the motoneurones to the neck muscles show that they are phasically activated by forward deflexion of the halteres after a latency of 2.5-3 ms. Spikes in the motoneurones follow the vibration of the haltere, one to one, up to 200 Hz. Recordings from the ipsilateral mesothoracic wing nerve (N. alae) show two large units which respond after a 2.5-3 ms latency to forward deflexion of the halteres. Behavioural observations of walking flies show that the presence or absence of halteres has a small but nevertheless significant effect on the animals’ ability to detect angular accelerations during walking or to orient with respect to gravity.
Exercise Training in Skeletal Muscle of Brook Trout (Salvelinus Fontinalis)
Authors: Johnston Ian A. , Moon Thomas W.
Published: April 2021

The differentiation of myotomal muscles in the brook trout (Salvelinus fontinalis Mitchill) has been investigated using p-phenylene diamine stained semi-thin sections and cytochemical and quantitative determinations of enzyme activities. Evidence is presented that the range of fibre size in white muscle represents stages in growth rather than distinct fibre types. Electromyography shows that both red and white muscles are recruited for sustained swimming. The threshold swimming speed for recruitment of white fibres is around 1·8 body length/s (L/s). White muscle citrate synthetase and cytochrome oxidase activities are 25–35% that of red muscle. Hexokinase, phosphorylase and phosphofructokinase activities are 2, 4 and 2 times higher in white than red muscles. It is considered that the aerobic capacity of white muscle is sufficient to support sustained swimming, and that blood glucose could be an important fuel source. Endurance exercise training has been investigated in fish swimming, continuously, for 21 days at 3 L/s. This training regime restricts spontaneous high-speed swimming activity and resulted in a general decline of white muscle glycolytic enzyme activities. Red fibres underwent hypertrophy relative to non-exercised controls (530± 64μm2 non-exercised, 901 ± 63 μm2 trained). Aerobic enzyme activities in red muscle and the fraction of fibre volume occupied by mitochondria (30·2± 0·8%) did not change in response to the training programme, but glycolytic enzyme activities were elevated. 3-OH Acyl Co A dehydrogenase activities increased in both red and white muscles indicating an enhanced capacity for fatty acid catabolism with training. Plasma and muscle lactate levels were not statistically different between tank-rested and trained fish swimming at 3 L/s. Adaptations of fish muscle to endurance training are discussed and compared with results for other vertebrates.
The Statistical Analysis of Pontaneous Transmitter Release at Individual Junctions on Cockroach Muscle
Authors: Washio H. M. , Inouye S. T.
Published: April 2021

Miniature excitatory post-synaptic potentials (MEPSPs) were recorded extra-and intracellularly from the coxal depressor muscle of the cockroach, Periplaneta americana. Statistical analysis of the time intervals between MEPSPs showed that the variance-to-mean curve for the extracellular data sets lay significantly above the line predicted for a Poisson process. A shuffling procedure, however, made the series almost random. The serial correlation coefficients for the extracellular data sets exceeded the confidence limits for various lags and most of them were positive. In comparison with the intensity function, the departure from the random process appeared to be mainly due to large positive correlation of intervals. It is concluded that in insect neuromuscular junctions, the spontaneous release of transmitter at individual sites is more clustered than that predicted by a Poisson process.
Water Balance and Urine Production in the Australian Arid-Zone Crab Holthuisana Transversa
Authors: Greenaway Peter
Published: April 2021

The permeability to tritiated water (hourly exchange fraction = 0·164) and the rate of urine flow (0·47% body weight/day) are lower than recorded in other freshwater decapods. The calculated net osmotic water flux (2·71 % body weight/day) is 5 times the water output in the urine, indicating that there is extrarenal excretion of water. Water balance is maintained in the absence of urine production, again indicating an extrarenal excretory site. Water turnover is greater for crabs in burrows than for crabs kept in air of 98% R.H., indicating relatively favourable conditions of moisture availability at the base of the burrow.
Burst Reset and Frequency Control of the Neuronal Oscillators in the Cardiac Ganglion of the Crab, Portunus Sanguinolentus
Authors: Benson Jack A.
Published: April 2021

The five large and four small neurones in the cardiac ganglion of the crab, Portunus, are electrotonically coupled and behave as a single relaxation oscillator, exhibiting periodic bursting activity in vitro. Recorded from the large neurone somata, this activity consists of 200–400 ms slow depolarizations called ‘driver potentials’ (Tazaki & Cooke, 1979a), accompanied by attenuated action potentials and EPSP’s from small neurone input. There is a strong positive correlation between the duration of the driver potential and the duration of the following interburst interval in the spontaneously active ganglion. This correlation is preserved during prolonged depolarization and hyperpolarization. When a driver potential is prematurely terminated by an injected current pulse, the following interburst interval is shortened in direct proportion to the decrease in driver potential duration. When a driver potential or a burst of high-frequency action potential activity is evoked by a depolarizing current pulse, the cardiac oscillator resets to the point of maximum hyperpolarization of the burst cycle, and the following interburst interval is of normal duration. Resetting following an evoked driver potential is complete. Partial resetting occurs only after short, evoked action potential bursts in the absence of a driver potential. Reset of the oscillator causes phase shifts in the subsequent cycles of activity, which vary with the phase of application and duration of the injected current pulse. Response curves have been constructed for a comprehensive range of durations and intensities of hyperpolarizing and depolarizing current pulses applied at all phases of the oscillator cycle. The phase shifts are composed of contributions from the duration of the current pulse, from the premature initiation of the slow depolarizing pacemaker potential due to early termination of the burst, and from the change in interburst interval correlated with truncation of the driver potential. Considering the cardiac ganglion as a relaxation oscillator, frequency control by entrainment to periodically applied current pulses was quantitatively predicted from the phase-response curves and experimentally confirmed. A high concentration (10−5 M) of octopamine can inhibit driver potential activity in the large neurones. This was used to examine possible frequency modulating effects of electrotonic feedback from the large neurone driver potentials onto the small neurone pacemaker activity. The observations are discussed in relation to the ionic model for driver potentials and slow pacemaker potential activity in the cardiac ganglion, as proposed by Tazaki & Cooke (1979a, b).
The Regulation of Sodium, Potassium and Chloride in an Aphid Subjected to Ionic Stress
Authors: Downing N.
Published: April 2021

The aphid Myzus persicae has been cultured on the sea aster, Aster tripolium, which was grown in fresh water or sea water nutrient medium. Samples of sieve tube sap, obtained through the severed stylets of feeding aphids, haemolymph, and honeydew were analysed for sodium, potassium and chloride content. On fresh water plants the blood sodium level of the aphids was found to be exceptionally low. At 0·2 mmol 1−1 it is the lowest recorded sodium concentration in the blood of any animal. The result is discussed in relation to the functioning of the insect’s nervous system. Under the sea water condition all three ions are maintained in the blood at levels below those found in the imbibed or excreted fluid.
Small Motor Axons in Orthopteran Insects: A Reinvestigation of the Innervation of the Femoral Retractor Unguis Muscle in a Stick Insect and two Species of Locust
Authors: Walther Christian
Published: April 2021

The motor innervation of the femoral retractor unguis muscle in a stick insect and two species of locust was investigated morphologically and electrophysiologically. In all three insects a somewhat variable number of axons with diameters less than 2 μm, some even less than 0·5 μm, accompany much larger ones in the motor nerve supplying the muscle. In the stick insect Carausius probably more than six motoneurones, including at least one inhibitory, control the muscle. In the two species of locust two populations of muscle fibres, ‘red’, and ‘white’, can be distinguished according to their respectively high and low levels of succinate dehydrogenase and their different patterns of innervation. The ‘red’ muscle fibres in Schistocerca have, in addition to one or two ‘fast’ excitors, two inhibitors, and in Locusta ‘red’ fibres receive a further one or sometimes two ‘slow’ excitors, giving a more complex innervation pattern of the ‘red’ compared to the ‘white’ fibres. An additional neurosecretory control by at least one neurone is indicated by the presence of characteristic nerve endings throughout the muscle. Of the two ‘fast’ motor axons in both locusts, one innervates the ‘red’ and the other the ‘white’ muscle fibres but both axons, to a lesser extent, also synapse with muscle fibres of the other type. The synaptic responses they evoke here are, however, only of small or intermediate amplitude. The existence of ‘slow’ excitatory innervation in Locusta ‘red’ fibres shows that functional synaptic contacts from one motoneurone can be restricted to a small region of a muscle fibre whilst those from other motoneurones are present along almost the entire length of the same fibre. Some of the difficulties in comparing morphologically demonstrated numbers of axon profiles with electrophysiologically derived numbers of motoneurones are discussed.
Direct Microprobe Evidence of Local Concentration Gradients and Recycling of Electrolytes During Fluid Absorption in the Rectal Papillae of Calliphora
Authors: Gupta Brij L. , Wall Betty J. , Oschman James L. , Hall T. A.
Published: April 2021

The concentrations of sodium, potassium and chloride and dry mass were measured by electron-probe X-ray micro-analysis in 1 μm thick frozen-hydrated sections from Calliphora rectum in 5 different states of absorptive function. In all cases the average concentrations of sodium + potassium + chloride was consistently higher in the fluid in the lateral intercellular spaces than in the cytoplasm, the average ratio being 2:1 in water-fed flies and higher in water-deprived flies. The highest concentration of electrolytes was found in the extracellular channel of complex lateral membrane stacks, which is consistent with the histochemical localization of major cation pumps at these sites (Berridge & Gupta, 1968). This concentration exceeded the electrolyte concentration in other tissue compartments by some 80 m-equiv/1 H2O in water-fed flies and about 700 m-equiv/1 H2O in water-deprived flies. The potassium and sodium concentration ratio of this extracellular fluid was nearly 1:1 in water-fed flies, 3:1m water-deprived flies with KC1 in the rectal lumen, and 0·5:1 with NaCl in the rectal lumen. Results suggest that the extracellular fluid is generated in membrane infoldings along the intercellular channels, and that this fluid gains water and sodium, but loses a variable amount of potassium and chloride, as it passes to the haemolymph, thus supporting the idea of local osmosis and ion recycling.
Effects Of pH on Sodium Uptake in Norwegian Brown Trout (Salmo Trutta) from An Acid River
Authors: McWILLIAMS Philip G.
Published: April 2021

Sodium uptake rates were measured in wild and hatchery reared Norwegian brown trout (Salmo trutta) exposed to media of a range of pH. Sodium uptake was strongly dependent on external acidity, being reduced in media of low pH. Wild fish from the naturally acid R. Tovdal (S. Norway) were more tolerant of acid media than hatchery reared fish. The effects of increasing external sodium concentrations were strongly influenced by low external pH. The results are discussed with respect to brown trout population decline in certain areas of S. Norway.
Acclimation To an Acid Medium in the Brown Trout Salmo Trutta
Authors: McWILLIAMS P. G.
Published: April 2021

Data are presented which demonstrate acclimation of brown trout (Salmo trutta) to an acid medium. Sodium fluxes, transepithelial gill potentials and plasma electrolyte concentrations were measured in brown trout exposed to an acid medium of pH 6·0 for a period of 6 weeks.

Sodium loss rates in acid exposed fish are reduced compared to normal fish, and sodium uptake is insensitive to external pH following long-term acid exposure.

Changes in gill potential and sodium turnover rate following acid exposure can be accounted for by changes in the relative permeability of the gills to sodium and chloride. In neutral media the permeability ratio ϕNa+/ϕC1_ = 1·12 but this falls to 0·76 during acid exposure.

The ability to acclimate to acid conditions seems to depend largely on changes in gill permeability to sodium.
Ca-Induced K+-Outward Current in Paramecium Tetraurelia
Authors: Satow Youko , Kung Ching
Published: April 2021

Late K-outward currents upon membrane depolarization were recorded in Paramecium tetraurelia under a voltage clamp. A Ca-induced K-outward component is demonstrated by subtracting the value of the outward current in a pawn A mutant lacking functional Ca-channels (pwA500). The Ca-induced K-outward current activates slowly, reaching a peak after 100 to 1000 ms. The current then remains steady or reaches the steady state after a decline of several seconds.

EGTA2− injection experiments show that the Ca-induced K-outward current is dependent on the internal Ca2+ concentration. The current is shown to depend on the voltage-dependent Ca conductance, by study of the leaky pawn A mutant (pwA132), which has a lowered Ca conductance as well as a lowered Ca-induced K-current. The Ca-induced GK is thus indirectly dependent on the voltage. The maximal GK is about 40 nmho/cell at + 7 mV in 4 mm-K+.

The Ca-induced K current is sustained throughout the prolonged depolarization and the prolonged ciliary reversal.
Calcium Metabolism in Bullfrog Tadpoles (Rana Catesbeiana)
Authors: Baldwin Geraldine F. , Bentley P. J.
Published: April 2021

Non-feeding bullfrog (Rana catesbeiana) tadpoles can maintain their body Ca concentration in artificial pond waters containing a range of Ca concen-trations. The rate of uptake of 45Ca increases when the tadpoles are pre-adapted to a low-Ca pond water and declines when they are pre-adapted to high Ca. Measurement of drinking rate shows that drinking could account for only 5% of the influx. From in vitro experiments, it is estimated that about 70% of the influx occurs accoss the gills, and about 25% through the skin. Calcitonin decreases accumulation of 45Ca while 1,25-(OH)2 vitamin D3 increases it; parathyroid hormone was without effect. Efflux of 45Ca was unchanged by calcitonin or parathyroid hormone.
The Effects of Substance P and Baclofen on Motoneurones of Isolated Spinal Cord of the Newborn Rat
Authors: Otsuka Masanori , Yanagisawa Mitsuhiko
Published: April 2021

The effects of substance P (SP) and baclofen were studied in the isolated spinal cord of newborn rats. Potential changes generated in motoneurones were recorded extracellularly from the ventral root (L3-L5). When SP (8×10− 5 M) was introduced into the bath, the depolarization of motoneurones began with a delay of 1·1 s. A large part of this delay can be explained as a time needed for SP to reach the site of action on spinal neurones.

When the preparation was perfused with artificial cerebrospinal fluid (CSF) containing low Ca (0·1 mm) and high Mg (1·6–3·5 mm), the spinal reflexes induced by dorsal root stimulation and recorded from the corresponding ventral root were completely abolished. The depolarizing action of SP (10−7 M) on the motoneurones was potentiated in the low-Ca medium, suggesting that SP acts directly on the motoneurones.

Baclofen at 10−6 M depressed the monosynaptic reflex by about 75%. The SP-induced depolarization of motoneurones was greatly depressed by baclofen in both normal and 0·1 mm-Ca mediums. The effects of baclofen (10−5 M) on the responses to various depolarizing agents were compared with that on the response to SP in artificial CSF containing 0–1 mm-Ca and 1·6–2 mm-Mg. The SP response was reduced by about 80%, whereas the responses to acetylcholine and glycine were not appreciably affected, and those to L-glutamate, GABA and noradrenaline were depressed by 10–22% by baclofen. These results suggest that baclofen blocks transmission at certain primary afferent synapses by antagonizing the action of SP that is released as a transmitter.
A Cellular Basis for the Differences in Regulation of Synthesis and Secretion of Acth/Endorphin Peptides in Anterior and Intermediate Lobes of the Pituitary
Authors: Rosa Patricia A. , Policastro Paul , Herbert Edward
Published: April 2021

The focus of research in our laboratory over the past few years has been the regulation of synthesis, processing and release of the ACTH/LPH family of peptides. These peptides are derived from a common precursor protein that is found in both the anterior and intermediate lobes of the pituitary (Roberts et al. 1978) and in the hypothalamus (Liotta et al. 1979). In the anterior lobe this protein gives rise to α (1–39)ACTH, β-lipotropin and an N-terminal fragment of undefined function. In addition, a variety of intermediate lobe pituitary peptides can be derived from the precursor by further processing of ACTH and β-LPH. In this paper we compare the structure of the precursor in the anterior and intermediate lobes of mouse and rat pituitary. Processing of the precursor to its constituent hormones is then contrasted in primary cultures of anterior and intermediate lobe cells using pulse label and pulse chase techniques with radioactive amino acids and sugars. Finally, we discuss the difference in behaviour of anterior and intermediate lobe cells in culture with regard to their rates of secretion and intracellular turnover of hormones and regulation of these processes by hypothalamic factors, glucocorticoids and catecholamines.
Factors That Influence Regeneration of the Neuromuscular Junction
Authors: McMAHAN U. J. , Edgington D. R. , Kuffler D. P.
Published: April 2021

Regeneration of neuromuscular junctions after trauma occurs in an orderly way and relies on communication between nerve and muscle. This paper summarizes evidence that factors which direct the growth and differentiation of both pre- and postsynaptic components of regenerating neuromuscular junctions are associated with the extracellular matrix of muscles.
On Some Cellular Reactions to X-Radiation
Authors: Butler Elmer G.
Published: April 2021

The wall of the developing neural tube of young chick embryos contains two types of cells; one type, the germinal cells, with nuclei conspicuously active in mitosis, is restricted to the innermost layer of the neural wall; the other type of cell with nuclei in the resting state and none in division, forms the main mass of the neural wall, the mantle layer. A study of the neural tube after radiation with a single non-lethal dose of X-rays reveals a series of cellular changes: an initial period of mitotic depression during which mitotic figures in the germinal cells disappear entirely; a period of pseudo-recovery during which mitotic activity reappears; a period of degeneration characterised by severe nuclear changes among the cells in the resting state; and a period of remarkable regeneration and recovery resulting in a return of the tissue to its normal condition.
On the Vitelline Membrane of the Egg of Psammechinus Miliaris and of Teredo Norvegica
Authors: Hobson A. D.
Published: April 2021

It has been assumed very generally that the unfertilised eggs of many animals are surrounded by a clear surface layer, discontinuous with the general protoplasm, which is known as the vitelline membrane. In marine forms this layer is commonly supposed to be separated from the true surface of the egg at the time of, or soon after, fertilisation and then becomes the fertilisation membrane.
The Osmotic Properties of Medusae
Authors: Bateman J. B.
Published: April 2021

Medusae show no osmotic regulation. The total water of the jelly disc is osmotically free; it follows that nearly all the electrolyte present is also uncombined. Gortner’s statement that the medusae contain 99·8 per cent, water is contradicted.
Studies on the Pituitary
Authors: Hogben Lancelot , Charles Enid
Published: April 2021

The injection of fresh saline suspensions of ox pituitary produces a prolonged fall in the calcium content of the serum of normal female rabbits and rabbits deprived of their ovaries. After sexual excitement there is a fall of blood calcium in the female rabbit beginning within 4 hours from association with the buck, followed by a secondary rise at the time when ovulation occurs with a further fall subsiding by the time the corpus luteum is fully formed. The removal of the ovaries from sexually mature rabbits does not produce any significant change in the calcium or magnesium level of the serum.
Iodine Compounds and Fertilisation
Authors: Carter G. S.
Published: April 2021

The analysis of the secretions which diffuse from the eggs of Echinoderms and other marine invertebrates is a subject which has attracted the attention of many biologists, who have approached it from many different points of view. As a result, there is available a large amount of varied work on the subject and the conclusions which have been drawn from this work have also been varied. There can be no doubt that the secretions are always complex, in the sense that they always contain more than a single chemical substance, and very little doubt that the secretions of different species are to some extent different in nature. In spite of this variability in the nature of the secretions and of the lack of agreement between the workers who have experimented with them, some broad conception of the constitution of the secretions has been obtained and may be summarised as follows.
Phosphagen and Protozoa
Authors: Needham Dorothy Moyle , Robertson Muriel , Needham Joseph , Baldwin Ernest
Published: April 2021

The comparative investigations of Eggleton and Eggleton(6), Meyerhof and Lohmann (11), Meyerhof(10), and Needham, Needham, Baldwin and Yudkin(12) have established a considerable body of information concerning the distribution of the phosphagens in the animal kingdom, and the character and implications of this knowledge have recently been analysed by Needham and Needham (13). But from all discussions hitherto, any mention of the Protozoa has been absent. This gap in our knowledge is unfortunate for two reasons, firstly because from a phylogenetic point of view it would be very desirable to ascertain the lower limit of distribution of such important compounds, and secondly because the Protozoa, or at least certain examples of them, would afford an interesting test of any possible association between phosphagen metabolism and ciliary, as well as muscular movement. With regard to the first of these reasons, the Coelenterates yielded interesting results in the work of Needham, Needham, Baldwin and Yudkin(12), for whereas a Cteno-phore, Pleurobrachia pileus, contained considerable amounts of arginine phosphate (43 per cent, of the free and labile water-soluble phosphorus), none was discoverable in the Actinozoa, Anthea rustica and cereus. Further work on the phosphagen of the Coelenterates would be very useful, but it is perhaps significant in this connection that Kutscher and Ackermann (9), though able to isolate free arginine from many marine invertebrates, could only obtain guanidine and agmatine from Geodia gigas. The question whether phosphagen was to be found elsewhere than in the Metazoa clearly merited examination. And with regard to the second of the reasons given above, some indications were found by Needham, Needham, Baldwin and Yudkin (12) that phosphagen might occur in situations primarily characterised by ciliary activity, e.g. the swimming gastrulae and plutei of echinoids.
The Heart Rate of the Developing Chick
Authors: Bogue J. Yule
Published: April 2021

Several authors have measured the heart rate of the chick embryo, but in all cases their methods involved opening the egg. The effect of this procedure on the heart rate is unknown, and therefore the writer investigated the possibility of recording the electrical variation of the embryo heart and thus obtaining a record of the heart rate with the minimum of interference with the embryo.
Experimental Studies on the Struggle for Existence
Authors: Gause G. F.
Published: April 2021

Although the phenomena of variation and heredity have in recent years become amenable to quantitative treatment, our knowledge of the struggle for existence has been increased to an almost negligible extent during the past fifty years. In the present paper an account is given of a series of experiments which constitute an attempt to apply experimental methods to the study of the struggle for existence. The work has been carried out with two species of yeast, and observations have been made on the effect of the presence of one species on the rate of reproduction of another. This situation has recently been considered from a mathematical point of view by Lotka (1925) and by Volterra (1931).
Fertilisation in the Rabbit
Authors: Pincus G. , Enzmann E. V.
Published: April 2021

In a previous paper (Pincus, 1930) it was concluded that for the fertilisation of the ovum of the rabbit it takes the spermatozoa from 2 to 3 hours after ovulation, to reach and effectively fertilise the egg. This conclusion was based on experiments in which ova, taken from the tubes at various intervals after fertile matings, were cultured in vitro. It was found that “the proportion of ova from fertile matings that divide in culture is very low for ova recovered between 11 and 12 hours after copulation, increases for ova obtained from 12 to 13 hours after copulation, and practically all ova recovered from 14 hours after copulation onward divide in culture.” Since ovulation in the rabbit normally occurs at about 10 hours after copulation there is a period from ovulation to about 3 hours later when the significant events associated with sperm penetration occur. It was decided therefore to examine with some care the state of rabbit ova as recovered from the tubes during this critical period.
Observations on Digestion in the Ruminant
Authors: Magee H. E.
Published: April 2021

Present-day knowledge of the physiology of digestion in ruminants is very limited and to a great extent it is based on anatomical deductions. Some of these are doubtless correct ; but many of them must be regarded merely as speculations until such time as adequate experimental proof is brought forward. It was with the object of providing this proof that the present work was undertaken. The experiments were concerned chiefly with the progress of the food through the alimentary canal, and, consequently, with the movements of the different sections of the canal itself. The ruminant owes its unique position amongst mammals to the anatomical complexity of the stomachs, and, for this reason, attention was directed particularly to the movements of these viscera. It will be an advantage, before taking up the experimental part of this paper, to consider certain important1 anatomical features and postmortem appearances and to discuss the physiological significance which it is believed can be attributed to them.
The Functional Design of the Insect Excretory System
Authors: Maddrell S. H. P.
Published: April 2021

Insects have a slowly operating excretory system in which the passive rate of movement of haemolymph solutes into a slowly secreted primary excretory fluid is restricted by a reduction in the area available for passive transfer. They may have come to possess such an energy-saving system as a result of their evolution as small animals in osmotically and ionically stressful environments. Although the possession of a waxy cuticle is a major element in their ability to live in such environments, insects have a very high surface-area/ volume ratio and this is likely to have conferred a selective advantage on individuals able to withstand unusually variable extracellular conditions. Among their major adaptations evolved to allow them to tolerate such conditions are the lack of a blood-borne respiratory pigment to be affected and the development of a system whereby their most sensitive tissues are protected by the regulatory activities of special covering epithelia. Because of these features it follows that there has been less evolutionary pressure for rapid excretory control of the haemolymph composition. With an excretory system that only slowly filters the haemolymph, less energy expenditure is involved in the production of the primary excretory fluid and in reabsorption of useful substances from it. In addition, insects are able to maintain in circulation high concentrations of substances such as amino acids, trehalose, and lipids. They can also eliminate excess fluid at very high rates with the loss of only trace amounts of haemolymph solutes. It is argued that terrestrial insects owe much of their success to their ability to recover virtually all the water from the slow flow of primary excretory fluid. The hindgut cells that are responsible for this recovery are aided by their cuticular lining which protects them from contact with the very high concentrations of potentially interfering compounds in the excretory material.
A Sodium-dependent ‘Twitch’ Muscle in a Coelenterate: The Ectodermal Myoepithelium of the Gastrozooids in Agalma SP. (Siphonophora)
Authors: Chain Benjamin M.
Published: April 2021

Intracellular recordings were obtained from the ectodermal cells of the gastrozooids of the siphonophore, Agalma sp. Stimulated gastrozooids undergo rapid longitudinal contractions that are immediately preceded by a series of action potentials which propagate throughout the epithelium. These rapid potentials arise from a much slower graded depolarization. Both potentials are abolished in low sodium solutions. Fast action potentials persist in the presence of manganese ions but both the slow potentials and contraction are abolished.
Measurements of Unsteady Periodic Forces generated by the Blowfly Flying in a Wind Tunnel
Authors: Buckholz Richard H.
Published: April 2021

A technique was developed for the measurement of the instantaneous lift and drag forces generated by the blowfly, Sarcophaga bullata, flying fixed in a wind tunnel. Apparatus for the measurement of insect-generated forces was checked in part for mean force accuracy by measurement of the drag on a circular cylinder. Our experimental device detects the sum of the aerodynamic forces and wing inertial forces as experienced by the thorax. The streamwise and vertical force waveforms show a surprising lack of higher harmonic content. Wind speeds in the neighbourhood of the known preferred flying speed were used, without an explicit attempt to nullify the mean vertical and horizontal forces to simulate free flight. Several measurements of the phase angle between the force waveform and the wing beating kinematics indicated that vertical forces in the liftward direction achieved a maximum during the downstroke and thrustward forces achieved a maximum during the upstroke.
Song Energetics of the Bladder Cicada, Cystosoma Saundersii
Authors: Nally Ralph Mac , Young David
Published: April 2021

Males of Cystosoma saundersii produced their calling songs while tethered to holders. Oxygen consumption during singing was 0·136 ml min−1, equivalent to 45· 0 mW, an increase of 42· 55 mW over the resting metabolic rate. Maximum sound output was 90·6 dB at 20 cm. The whole sound-field was measured and represents a power output of 0·35 mW. The efficiency of sound production is 0·82%. Heat production, estimated from the weight of singing muscle, was 28·7 mW. This leaves 13·5 mW of output unaccounted for. Comparison with other species of insects suggests that none are more than an order of magnitude more efficient than C. saundersii.
Participation of an Unpaired Motor Neurone in the Bilaterally Organized Oesophageal Rhythm in the Lobsters Jasus Lalandii and Palinurus Vulgaris
Authors: Moulins M. , Nagy F.
Published: April 2021

The main oesophageal motor neurone (OD1) of the rock lobster is an unpaired bifurcating nerve cell. The cell body is located in the oesophageal ganglion and the left and right axonal branches pass through the left and right commissural ganglia to innervate all the oesophageal dilator muscles. Three types of potentials are recorded in the cell body in vitro; each type is associated with an extracellular spike recorded from the nerves connecting the ganglia. Comparison between the three types of potentials (and the extracellular spikes) and collision experiments shows that all three are spikes. Spontaneous collisions can sometimes occur and it is concluded that one spike is generated in the oesophageal ganglion (somatofugal a-spike) while the other two are generated in the left commissural ganglion (somatopetal b-spike) or the right commissural ganglion (somatopetal c-spike). Each spike initiating zone is synaptically driven. The commissural zones fire short phasic bursts; each burst is composed of only one type of spike (b-or c-). The oesophageal (a-) zone gives a tonic discharge interrupted when the other zones are firing. Finally, combined firing of the spike initiating zones can generate three different patterns of discharge. OD1 participates in the oesophageal motor rhythm produced by two oscillators (one in each commissural ganglion) which fire alternated series of bursts. It is concluded that the three axonal spike initiating zones enable the motor neurone (1) to follow the oesophageal motor rhythm at any time regardless of which oscillator is in operation and (2) to co-ordinate phasic and tonic activation of the oesophageal dilator muscles.
Temperature Regulation and Heat Balance in Flying White-necked Ravens, Corvus Cryptoleucus
Authors: Hudson Dennis M. , Bernstein Marvin H.
Published: April 2021

During level flight at 10 m.s−1 in a wind tunnel, white-necked ravens (Corvus cryptoleucus, mass 0·48 kg) exhibited an increase in body temperature to steady-state levels as high as 45 °C, exceeding resting levels by nearly 3 °C. This reflects the storage of up to half of the metabolic heat produced (Hp) during 5 min of flight. During steady-state flight, body heat was dissipated in part by respiratory evaporation and convection (13–40% of Hp) evoked by increases in ventilation proportional to body temperature. Remaining heat was lost by cutaneous evaporation (10 % of Hp) as well as by radiation and convection from the external body surface. The results suggest strategies that might be used by ravens during flight under desert conditions.