bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in statistical parameters during facilitation at the crayfish neuromuscular junction
Authors: Wernig A. 
Published: December 2014

1. Transmitter release at excitatory neuromuscular junctions of the crayfish was studied at different frequencies of stimulation ranging from 1/sec to 20/sec.2. Over this frequency range the average number of quanta released per stimulus (m) increased with frequency by a factor of 6–7.3. Analysis of the fluctuations in quantal release using binomial statistics indicated that the increase in m was associated with increase in the average quantal release probability (p) at stimulation frequencies between 5/sec and 20/sec. Between 1/sec and 5/sec there was an apparent increase in the number of quanta available for release (n).
Vasopressin clearance and secretion during haemorrhage in normal dogs and in dogs with experimental diabetes insipidus
Authors: Errington M. L. , E Silva M. Rocha 
Published: December 2014

1. The secretion of vasopressin in response to haemorrhagic shock has been investigated in anaesthetized dogs.2. The changes in the plasma concentrations of vasopressin were followed over a period of 5 hr, during which the arterial blood pressure was kept constant at 40 mm Hg. It was found that vasopressin concentration in plasma rose to a high peak shortly after the onset of shock and gradually declined thereafter. Five hours later, it was still 3·5 times higher than control. Re‐transfusion of blood was followed by a return to control levels.3. The clearance of vasopressin was calculated before and during shock in normal dogs and in dogs with experimental diabetes insipidus. Soon after the onset of shock, the clearance rate dropped to one quarter of its normal level but slowly recovered, returning to near control values at the fifth hour of shock. Clearance rates did not vary as a function of infusion rates, suggesting that there is no maximal transport rate for the removal of the hormone over the entire secretory range found in normal and hypotensive dogs.4. From the clearance rates and from the plasma concentrations of endogenously secreted vasopressin it has been possible to calculate the approximate secretory rates of the hormone in response to shock. Secretion rose to a very high level, some 40 times greater than control, at the onset of shock. This was followed by a fairly constant secretory plateau. At the fifth hour of shock secretion was 3·5 times higher than control.5. The half‐life of vasopressin was measured in normal and hypotensive dogs. Control measurements confirm the generally accepted value of approximately 5 min. The half‐life was significantly higher in the early stage of shock, but returned to control values in the later stage.6. Haemorrhage experiments performed in normal and diabetic dogs suggest that vasopressin may play a part in the development of irreversible haemorrhagic shock: all normal animals died within a few hours of retransfusion, whereas four out of eight diabetic dogs similarly treated survived a 24 hr observation period. In a separate set of experiments, eight diabetic dogs were subjected to the haemorrhage procedure while receiving a constant infusion of vasopressin: only two of these survived. Surviving dogs showed none of the characteristic lesions of irreversible haemorrhagic shock.
Daily changes in foetal urine and relationships with amniotic and allantoic fluid and maternal plasma during the last two months of pregnancy in conscious, unstressed ewes with chronically implanted catheters
Authors: Mellor D. J. , Slater J. S. 
Published: December 2014

1. The fluid sacs and bladders of ten foetuses and the allantoic sacs of five foetuses were catheterized between 79 and 96 days gestational age and daily samples were withdrawn until lambs were born naturally at ∼147 days. Maternal jugular plasma obtained daily allowed the nutritional status of each ewe to be regulated and monitored. All lambs were observed for 7 weeks, and at post‐mortem no abnormalities were seen in those operated upon in utero.2. The osmolality, [Na+], [K+], [Cl−], [glucose], [fructose], [urea], [amino acid] and pH of all samples were measured.3. Foetal surgery seemed to affect the actual concentrations of some solutes, but gestational trends in foetal fluid composition were unaltered.4. Until about 7 days before birth the foetal urine osmolality, [Na+], [Cl−] and [fructose] decreased, its [urea], [amino acid] and pH remained relatively constant, and from about 120 days gestational age the [K+] increased. During the last 7 days there was a marked increase in the osmolality and the concentrations of all these solutes, and a decrease in pH.5. Entry of foetal urine into the fluid sacs tended to decrease the osmolality, [Na+], [K+], [Cl−] and [glucose] of both foetal fluids and the [amino acid] of allantoic fluid, and tended to increase the [fructose] and [urea] of both fluids and the [amino acid] of amniotic fluid.6. Changes in urine composition suggested large daily variations in the secretion of foetal antidiuretic hormone and also a rapid increase in its secretion during the last 7 days, and particularly the last 2–4 days before birth.7. Changes in the [Na+]/[K+] ratios of foetal urine and allantoic fluid were parallel during post‐operative recovery, during the course of pregnancy and immediately before birth, and this was consistent with a simultaneous action of foetal plasma corticosteroids on the foetal kidneys and chorioallantois.8. Variations in the [fructose] of foetal urine and allantoic fluid were parallel to changes in their [Na+]/[K+] ratios and suggested an involvement of foetal corticosteroids in the regulation of the [fructose] of foetal plasma.9. Further evidence has been presented supporting the hypothesis that maternal induced foetal hypoglycaemia effects a relative increase in the secretion of foetal corticosteroids having an action on the chorioallantois. Also, high concentrations of maternal plasma corticosteroids may decrease the permeability of the placenta to glucose.
The pharmacology and ionic dependency of amino acid responses in the frog spinal cord
Authors: Barker J. L. , Nicoll R. A. 
Published: December 2014

1. The isolated frog spinal cord was used to study the action of amino acids and their antagonists on primary afferent terminals and motoneurones. The direct effects of these substances were observed by bathing the cord in 20 m
M magnesium sulphate (thus blocking synaptic transmission) and recording the polarization level of the dorsal and ventral roots.2. γ‐Aminobutyric acid (GABA) and glutamic acid depolarized the dorsal root and reduced dorsal‐root potentials, while glycine produced only weak and variable effects. Glutamic acid also depolarized the ventral root; GABA usually produced either a hyperpolarization or had little effect, while glycine caused variable effects.3. Bicuculline and picrotoxin antagonized all the synaptic potentials recorded on the dorsal root, as well as the GABA responses on both dorsal and ventral roots.4. All the synaptic potentials examined remained and were markedly prolonged in the absence of external chloride except the ventral root‐dorsal root potential. Replacement of the physiologic complement of chloride during chloride‐free perfusion restored the potentials to their original time courses.5. Depolarizing amino acid responses remained in the absence of external chloride, while hyperpolarizing responses were reversed into depolarizations. Return to normal Ringer solution re‐established the hyperpolarizations.6. Removal of external sodium reversibly abolished the amino acid depolarizations but had little effect on the depolarizations in response to applications of high external potassium concentrations.7. The results support the hypotheses (a) that GABA mediates presynaptic inhibition by depolarizing primary afferent terminals and (b) that the GABA‐mediated depolarization is sodium dependent.8. The results also indicate that GABA utilizes different ionic mechanisms to mediate presynaptic inhibition (sodium) and post‐synaptic inhibition (chloride) in the amphibian (and presumably in the mammal).
Nervous activity of afferent cardiac sympathetic fibres with atrial and ventricular endings
Authors: Malliani A. , Recordati G. , Schwartz P. J. 
Published: December 2014

1. We recorded the electrical activity of single afferent cardiac fibres isolated from the third and fourth left thoracic sympathetic rami communicantes of anaesthetized cats. Their conduction velocities ranged from 12 to 32 m/sec.2. The endings of each fibre were localized to one cardiac chamber by mechanical probing of the opened heart performed at the end of the experiment.3. The impulse activity was spontaneous and, in fibres with atrial or ventricular endings, it was in phase with a particular atrial or ventricular event.4. This nervous activity increased during increases in pressure occurring in the chamber where the endings were located. Conversely, decreases in pressure were accompanied by decreased nervous discharge.5. In some experiments the left coronary artery was perfused at different flows and pressures. Brief decreases or increases in coronary flow and pressure decreased or increased, respectively, the discharge of fibres with atrial or ventricular endings. Fibres were excited by intracoronary injections of veratridine.6. Cessation of coronary pump flow increased the discharge of fibres with atrial or ventricular endings only when myocardial ischaemia was accompanied by signs of heart failure.7. These afferent cardiac sympathetic fibres which provide the spinal cord with continuous specific information on cardiac events are likely to contribute to the neural control of circulation.
Chronotropic and inotropic effects on the dog heart of stimulating the efferent cardiac sympathetic nerves
Authors: Furnival C. M. , Linden R. J. , Snow H. M. 
Published: December 2014

1. The chronotropic and inotropic responses of the dog heart to stimulation of the ansae subclaviae were studied.2. The maximum rate of rise of pressure in the left ventricle (dP/dt max) was used as an index of the inotropic changes.3. In experiments in which the secondary inotropic effects of changes in heart rate and blood pressure were prevented it was shown that, using stimuli which produced the same chronotropic response, stimulation of the left ansa subclavia resulted in an inotropic change which was about eight times greater than that which resulted from stimulation of the right ansa subclavia.4. In experiments in which heart rate and blood pressure were allowed to change freely it was shown that the secondary inotropic effects of changes in blood pressure and heart rate amounted to about 70% of the total inotropic change when the right ansa subclavia was stimulated and about 20% of the total change when the left ansa subclavia was stimulated.
The visual areas in the splenial sulcus of the cat
Authors: Kalia Madhu , Whitteridge D. 
Published: December 2014

1. The extreme periphery of the visual field is represented in the upper wall of the splenial sulcus where the sulcus is horizontal, and in its anterior wall more posteriorly where the sulcus runs downwards and laterally. About half the cells whose fields lie between 50 and 90° from the area centralis have a sharply horizontal preferred orientation.2. Beyond the lateral edge of visual I there is a narrow band of visual cortex in which the receptive fields return towards the area centralis as one moves 1–1·5 mm laterally. Their receptive fields are usually about 20–30° degrees across, but all orientations are found. The more central fields may be binocular and those at the area centralis may be as small as 1° in diameter.3. This band has been called the splenial visual area. It does not seem to have properties corresponding to those of visual II nor of visual III.
The formation of synapses in mammalian striated muscle reinnervated with autonomic preganglionic nerves
Authors: Bennett M. R. , McLachlan Elspeth M. , Taylor R. S. 
Published: December 2014

1. A study has been made of the formation of synapses during reinnervation of the hemidiaphragm of adult rabbits with preganglionic fibres of the thoracic vagus, using histological, ultrastructural and electrophysiological techniques.2. Following reinnervation with preganglionic axons, silver‐stained nerve terminals were found in association with cholinesterase‐stained end‐plates only in the region of the muscle corresponding to the original innervation band.3. The fine preganglionic axons retained their normal structure in striated muscle, but were found to synapse over discrete areas of dimensions not larger than those of the original end‐plates.4. The regenerated varicose preganglionic nerve terminals were observed with the electronmicroscope in positions either overlying or in the vicinity of the old synaptic folds.5. Spontaneous potentials and evoked synaptic potentials were recorded only in the middle of the muscle fibres after vagus reinnervation.6. In a few cases, multiple synaptic potentials with similar time courses were recorded, suggesting that several axons had formed synapses at a single site on a muscle fibre.7. It has been shown that, during reinnervation of adult mammalian striated muscle fibres with nerves other than those of the somatic system, synapses are formed preferentially in the region of the old end‐plates.
Ionic mechanism for the photoreceptor potential of the retina of Bufo marinus
Authors: Brown J. E. , Pinto L. H. 
Published: December 2014

1. Membrane potentials were recorded from single rods in the isolated retina of Bufo marinus while the ionic composition of the extracellular medium was rapidly changed. Substitution of 2 m
M aspartate− for Cl− produced a prompt depolarization of horizontal cells, but no modification of either resting potential or response to light in receptor cells. This implies that feed‐back from horizontal cells to receptor cells was not active.2. During substitution of choline+ or Li+ for Na+, and during isosmotic substitution of sucrose for NaCl, the resting potential of receptor cells became more negative and responses to light were abolished. During exposure to K+‐free medium, the resting potential became slightly more negative and the responses to light became larger and developed small after‐depolarizations. Exposure to [K+]out of four times normal resulted in permanent diminution of response magnitude and permanent change of response waveshape. Removal of Mg2+, four times normal [Mg2+]out or substitution of methylsulphate− for Cl− had no effect on resting potential or responses to light. With the exception of the small effects seen with altered [K+]out these results are consistent with the receptor potential being generated by a light‐induced decrease of membrane conductance to Na+.3. Exposure to decreased [Ca2+]out caused both a depolarization of the receptor membrane in the dark and an increase in the magnitude of the maximal response that could be evoked by a test stimulus. The magnitude of the increase in response equalled the magnitude of the depolarization. Exposure to increased [Ca2+]out or steady background light caused both a steady hyperpolarization and a decrease in the magnitude of the maximal response that could be evoked by a test stimulus. For steady hyperpolarizations greater than 3·5 mV, whether caused by elevated [Ca2+]out or steady background light, the decrease in response magnitude exceeded the magnitude of the hyperpolarization. These results imply that externally applied Ca2+ ions mimic the effects of steady background lights, but the applied Ca2+ ions must do more than merely decrease membrane conductance to Na+.
The afferent discharge pattern of atrial mechanoreceptors in the cat during sinusoidal stretch of atrial strips in situ
Authors: Arndt J. O. , Brambring P. , Hindorf K. , Röhnelt M. 
Published: December 2014

1. The differences in spike discharge from atrial mechanoreceptors in vivo suggest the existence of different receptor types. To test this possibility, and to see how atrial receptors compare with other mechanoreceptors, their response was studied under comparable stimulus conditions.2. Sinusoidal length changes, with frequencies from 1 to 10 Hz and amplitudes of 1·5–5·0 mm at a given static extension, were imposed in situ on strips of atrial receptor areas of cats.3. The receptor response was evaluated from functional single fibres in terms of number of spikes per stimulus period, average discharge rate, instantaneous spike frequency, and phase angle between forcing function and instantaneous frequency.4. Irrespective of the fibre type, atrial fibres appear to originate from identical mechanoreceptors which sense length at low stimulus frequency and low stimulus amplitudes, but also sense velocity in the high frequency range and with large stimulus amplitudes.5. The difference in the discharge pattern and in the functional behaviour of the atrial fibres in vivo can be explained on the basis of identical receptors.6. The difference in the temporal occurrence of the atrial burst is still open to debate, but probably is related to the site of the receptor.
Raising rabbits in a moving visual environment: an attempt to modify directional sensitivity in the retina
Authors: Daw N. W. , Wyatt H. J. 
Published: December 2014

1. Rabbits were raised inside drums with vertical stripes painted on the inside. The rabbits were held stationary while the drum rotated continually around them: rotation was always in the same direction for any one animal. Rabbits in one litter were put in the drum for 15 min/day from 10–15 days after birth to about 60 days after birth, with the drum rotating to the right. Rabbits in another litter were put in for 15 min/day with the drum moving left. Rabbits in three other litters were put in for 2‐3 hr/day with the drum moving right. All rabbits were kept in the dark when not in the drum.2. Optokinetic nystagmus was measured by photographing eye movements during drum rotation at various stages of development. The response to rotation in both directions was measured in a few adult animals. Only small differences were found in the adult animals between optokinetic nystagmus in response to a drum moving right compared to a drum moving left.3. Recordings were made from ganglion cells in the retina and their receptive fields were mapped. A total of 607 cells from deprived rabbits were analysed. The percentages of on‐centre and off‐centre centre‐surround types, on‐off directionally sensitive types, and on‐directionally sensitive types were not significantly different from normal.4. The percentages of directionally sensitive cells responding in the anterior, posterior, superior and inferior directions were normal. The fall‐off in sensitivity for these cells with change in direction from the preferred direction was normal.5. A few orientation sensitive cells were found responding to horizontally oriented bars.6. We conclude that this selective deprivation of rabbits had little effect on the optokinetic response and no effect on the organization of the retina.
On the repetitive discharge in myotonic muscle fibres
Authors: Adrian R. H. , Bryant S. H. 
Published: December 2014

1. Muscle fibres from myotonic goats respond to injected constant currents with a train of action potentials. If the number of action potentials in an evoked train exceeds 10–15, stopping the current does not stop the repetitive firing of action potentials.2. Normal muscle fibres (goat) in a chloride‐free Ringer respond in the same way to constant current.3. In the absence of self‐maintained activity both myotonic fibres and normal fibres in chloride‐free Ringer show an after‐depolarization which is proportional to the number of driven impulses. The half‐time for the decay of this after‐potential is about 0·5 sec.4. Tubular potassium accumulation resulting from the initially driven activity and the known low chloride conductance of myotonic muscle fibres appear to account for the initiation of the myotonic discharge.
The formation of synapses in reinnervated and cross‐reinnervated striated muscle during development
Authors: Bennett M. R. , Pettigrew A. G. 
Published: December 2014

1. A study has been made of the formation of synapses in reinnervated and cross‐reinnervated developing striated muscles which normally receive either a focal or distributed innervation, using histological, ultrastructural and electrophysiological techniques.2. The focally innervated mammalian tibialis anterior muscle, denervated soon after birth, was reinnervated at both the original end‐plates as well as on the new muscle added during the period of denervation; but not on the muscle present at the time of denervation. Nearly all the synapses which had formed, other than at the original end‐plates, disappeared by 6 weeks post‐natal.3. The avian anterior latissimus dorsi muscle (ALD), which receives a distributed innervation, was denervated during the first week post‐hatched, and became reinnervated both at the original synaptic sites as well as on the new muscle added during the period of denervation; all these synapses were spaced approximately 200 μm apart along the length of individual muscle cells.4. The myofibres of the ALD muscle cross‐reinnervated at hatching with the superior brachialis nerve, which contains fast motor axons that normally form a focal innervation, were each focally innervated by a single ‘en plaque’ terminal; these synapses had the same electrical properties as normal synapses formed by fast motor axons.5. Many of the myofibres of the avian posterior latissimus dorsi (PLD), which normally receive a focal innervation, received a distributed innervation from ‘en grappe’ terminals when cross‐reinnervated with the ALD nerve at hatching.6. It is suggested that during development the nerve type determines the pattern of synapses over an effector; this is achieved by the nerve, after forming the initial synaptic contact, making the rest of the muscle cell membrane refractory to further synapse formation for some distance, this distance being determined by the nerve type.
Synapse formation during embryogenesis on ganglion cells lacking a periphery
Authors: Landmesser Lynn , Pilar G. 
Published: December 2014

1. The development of transmission was studied in chick ciliary ganglia that had been deprived of their periphery during early embryonic development.2. Peripherally deprived neurones in the ganglion differentiate in normal numbers and send functional axons into the post‐ganglionic nerve.3. Ganglion cells lacking a periphery follow the normal developmental sequence sending out transient dendrites at the time ganglion cell synapses are formed, and later retracting them when calyces appear.4. Synapses, which appear functionally and ultrastructurally normal, form on all ganglion cells at the normal time and transmission is normal until Stage 34. Therefore information from the periphery is not required for ganglion cell synapse formation per se.5. From Stages 35 to 38 most cells die, so that only 8% of the original number of cells remain in the operated ganglion. Transmission fails in many cells during this same time, but precedes cell loss by only a short time, so that deafferentation probably does not contribute substantially to cell death.6. Both ciliary and choroid cells achieve full cytologic differentiation and are distinct from each other, indicating that the periphery is not required for the elaboration of the distinctive characteristics of these cells. Presynaptic fibres also differentiate into typical bouton as well as calyciform endings. Therefore, the type of preganglionic ending does not depend on ganglion cells establishing proper peripheral contacts.7. It has not been possible to ascertain whether ganglion cell specificity is affected by the periphery.8. Peripheral removal affects ganglion cell migration, so that two ganglia are formed. Approximately half of the cells migrate into the remnant optic cup forming a second misplaced ganglion. Ciliary and choroid cells occur in both ganglia and these cells go through the typical sequence of events described above.