bluuebunny/crossref_metadata_2025_split huggingface dataset:
Histological evidence against the view that the cat's optic nerve contains centrifugal fibres
Authors: Brindley G. S. , Hamasaki D. I. 
Published: December 2014

1. Degeneration that can be shown by the Nauta—Gygax technique in the orbital part of the cat's optic nerve does not begin until 10 days after intracranial transection of the nerve, though after enucleation of the eye it is conspicuous in 4 days.2. We were not able to tell, by any silver‐staining technique applied to an optic nerve at any interval after an operation, whether at that operation the nerve had been cut peripherally only or both peripherally and centrally.3. From these and subsidiary observations we conclude that either the cat's optic nerve contains no centrifugal fibres detectable by silver staining and light microscopy, or, if there are such fibres, they are much less susceptible to prograde (Wallerian) degeneration and much more susceptible to retrograde degeneration than most of the centripetal fibres. The former is the simpler and, we suggest, the more likely conclusion.
The reflex excitation of the soleus muscle of the decerebrate cat caused by vibration applied to its tendon
Authors: Matthews P. B. C. 
Published: December 2014

1. Vibration was applied longitudinally to the fully innervated soleus muscle of the decerebrate cat by attaching its tendon to a vibrator. Vibration at frequencies of 50‐500/sec with amplitudes of 10 μ upwards caused the muscle to contract reflexly for as long as the vibration was maintained. The response was recorded myographically by a myograph mounted upon the vibrator, and electromyographically by gross ‘belly‐tendon’ leads. The reflex contraction produced several hundred g wt. of tension and involved too many motor units for their discharges to be separable. The maintained reflex was abolished by making the preparation spinal or by anaesthetizing it with pentobarbitone, but it persisted after removing the cerebellum.2. The minimum latency for the appearance of the reflex response at the beginning of a period of vibration was about 10 msec. The latency of cessation of the response at the end of vibration was similarly short.3. On increasing the amplitude of vibration at any particular frequency in the range 100‐300/sec the resulting reflex tension increased to an approximate plateau for amplitudes of vibration of 100‐200 μ. Further increase in the amplitude decreased the size of the contraction, though there was no such reduction in records of the ‘integrated’ electromyogram.4. Such large amplitudes of vibration also reduced the tension, and shortened the duration, of a twitch contraction of the muscle elicited by stimulating its nerve. The strength of a tetanic contraction was much less affected by vibration than was that of the twitch contraction, and the muscle action potential elicited by stimulation of the nerve was unaffected. Thus, large‐amplitude vibration influenced the contractile mechanism of the muscle (cf. Buchtal & Kaiser, 1951).5. Increasing the frequency of vibration increased the value of the plateau tension reached on increasing the amplitude. The effect was, however, relatively small and the largest increase seen was 3 g wt. of contractile tension per c/s increase in vibration frequency.6. The primary afferent ending of the muscle spindle is considered to be the receptor whose excitation leads to the reflex response to vibration. The vibration reflex thus appears to be the well‐known stretch reflex, elicited by a rather unusual form of stretching. The size of the vibration reflex and its variation with frequency are discussed in relation to the servo theory of muscular contraction.
The action of calcium on neuronal synapses in the squid
Authors: Miledi R. , Slater C. R. 
Published: December 2014

1. The isolated stellate ganglion of the squid (L. pealii) was studied with intracellular and extracellular micro‐electrodes. Three or four nerve fibres in the preganglionic nerve establish synaptic relations with the giant axon in the last stellar nerve. Accordingly, 1‐3 small presynaptic spikes (< 1 mV) could be recorded from within the post‐synaptic axon.2. A micro‐electrode was inserted in the presynaptic fibre and used to polarize and record simultaneously. In the distal (giant) synapse, hyperpolarization of the ending produced an increase in the size of the presynaptic action potential and post‐synaptic potential (PSP). Depolarization had the opposite effect. These effects of polarization took more than 10 sec to develop fully, and declined with a similar time course at the end of polarization. Analogous results were obtained with two other preganglionic fibres, which make contacts in the proximal synaptic region.3. The second of a pair of preganglionic impulses evoked a PSP larger than the first. This facilitation of PSP was sometimes accompanied by a small increase in the size of the second action potential in the presynaptic axon. At some shorter intervals, the second presynaptic action potential was reduced in amplitude, but the PSP was still increased. Hyperpolarization of the presynaptic terminal increased the size of both PSPs in a pair and abolished the facilitation. With stronger hyperpolarization the second PSP was even smaller than the first.4. Removing or reducing the Ca in the bathing fluid reversibly abolished the post‐synaptic response. The small presynaptic spikes remained practically unaffected. In these conditions a nerve impulse still invaded the ending and normal action potentials could be recorded from the pre‐synaptic terminal. This shows that electrical coupling between pre‐ and post‐synaptic axons is insufficient to account for synaptic transmission.5. In low‐Ca solution synaptic transmission could be restored locally by extracellular ionophoretic application of Ca to a small portion of the synapse. At sensitive spots a post‐synaptic current (recorded with the Ca pipette) and PSP could be detected earlier than 1 sec after commencing the application of Ca.6. Ca was ineffective when injected intracellularly into the presynaptic fibre at a spot where extracellular ionophoresis of Ca restored the PSP.7. The results indicate that synaptic transmission in the squid stellate ganglion is not electrical but due to the release of an unidentified transmitter. Release of this transmitter by the presynaptic nerve impulse requires the presence of Ca in the external medium. During the impulse Ca would combine with a ‘Ca‐receptor’ in the membrane and initiate the reactions which lead to transmitter release. It appears that the ‘Ca‐receptor’ is only accessible from the outside of the membrane.
Observations on temperature distribution in the cardiovascular system, thorax and abdomen of monkeys in relation to environment
Authors: Grayson J. , Irvine M. , Kinnear T. 
Published: December 2014

1. Thermo‐electric observations of temperature distribution in the ‘core’ area of monkeys and baboons are reported.2. Temperature gradients were shown to exist in the inferior vena cava, temperatures rising by a mean value of 0·2° C at the entry of the renal veins and again by a further 0·2° C at the level of the hepatic veins.3. Temperatures in the right atrium were on average 0·1° C lower than in the inferior vena cava due to the return of relatively cooler blood from the superior vena cava.4. Net heat exchanges in the thorax were small. Right atrial and aortic blood temperatures were not significantly different and it was concluded that heat losses in the thorax were balanced by heat production in lungs and heart.5. The mean liver temperature was 0·1° C higher than that of the aortic blood irrespective of the environment.6. The mean temperature recorded from the lumen of the jejunum was 0·2° C warmer than the aorta in the ‘warm’ environment and 0·4° C hotter than the aorta in the ‘cool’ environment. In both environments intrajejunal temperature was higher than the liver but the differential was increased by exposure to a ‘cool’ environment.7. Evidence is adduced to suggest that the gastro‐intestinal tract in the body at rest is a major heat producer contributing about double the amount of heat generated by the liver.8. It is suggested that blood flow redistribution in the splanchnic area on exposure of the body to cold is the main cause of the change in aortic—jejunal and jejunal—liver differentials. Metabolic factors have, however, not been excluded.
The effect of an intravenous infusion of hypertonic saline on renal mechanisms and on electrolyte changes in sheep
Authors: Potter B. J. 
Published: December 2014

1. The ability of the sheep to tolerate excess sodium chloride has been investigated by subjecting sheep to an intravenous infusion of a 10% solution of sodium chloride.2. Inulin and diodrast clearances failed to show any consistent changes in glomerular filtration rate but the effective renal plasma flow was slightly more. Plasma levels of sodium and chloride increased by 20‐25% and potassium decreased by 30%. Urinary levels for sodium and chloride showed a corresponding increase and potassium excretion was reduced.3. The rates of re‐absorption of sodium and chloride from the renal tubules were found to be proportional to their rates of filtration at the glomerulus, but this ratio was reduced after the hypertonic saline infusion. No such correlation could be established for potassium.4. Osmolar clearances indicated that continued re‐absorption of osmotically free water from the kidney tubular fluid occurred during and after the hypertonic saline. Excretion of urine, hyperosmotic to plasma, was thus maintained and water conservation supported.5. Possible renal mechanisms associated with these effects are discussed.
The role of a central temperature receptor in shivering in man
Authors: Johnson R. H. , Spalding J. M. K. 
Published: December 2014

1. Five subjects with spinal cord transections and one subject unconscious from a head injury have been studied when the deep tissue temperature (‘central’ temperature) was artificially lowered but normally innervated skin was kept warm, usually 34‐36° C.2. Shivering and/or increased metabolism was evoked when the central temperature was 34·9‐37° C.3. These observations are compatible with the view that there is a central receptor which can cause shivering when stimulated by a fall in central temperature.
The depressor reflex arising from the left coronary artery of the cat
Authors: Brown A. M. 
Published: December 2014

1. The main left coronary artery of the cat was perfused through its own common carotid artery. Changes in perfusion pressure were produced from a pressurized reservoir.2. In cats anaesthetized with pentobarbital, increased coronary artery pressure always caused a reflex reduction of the discharge in sympathetic nerves. A reflex fall in blood pressure occurred less frequently. In cats anaesthetized with chloralose, increased coronary artery pressure caused a reflex bradycardia without any primary change in sympathetic activity.3. The afferent fibres of the coronary depressor reflex are in the vagus nerves. The efferent fibres were both sympathetic and vagal.4. It seems likely that the coronary depressor reflex is initiated by excitation of the coronary mechanoreceptors. It also seems likely that the reflex response to the intracoronary injection of 1 μg veratridine (Bezold—Jarisch effect) was initiated at least in part by excitation of these same receptors.
The effect of haemorrhage on venous return and regional blood flow in the anaesthetized cat
Authors: Greenway C. V. , Lawson Anne E. 
Published: December 2014

1. In cats under pentobarbitone anaesthesia, a venous long‐circuit technique was used to measure the blood flows in the superior vena cava and the hepatic, renal and iliac segments of the inferior vena cava. The sum of these flows gave the venous return (minus coronary and bronchial flows).2. In these preparations, the mean venous return was 130 ml./kg. Of this 28% came from the superior vena cava and 37% from the hepatic, 23% from the renal and 12% from the iliac segments of the inferior vena cava.3. After haemorrhage, the flows from all the venae cavae segments decreased. The quantitative changes varied with the particular cat, the degree and duration of the haemorrhage and whether the animal had been subjected to a previous haemorrhage.4. The proportion of the reduced venous return draining from the superior vena cava and the hepatic segment increased, that draining from the renal and iliac segments decreased. Vasoconstriction occurred in all vascular beds, but was greatest in the kidney and hind limbs. Thus the blood flow through the head and liver was partially maintained at the expense of that through the kidneys and hind limbs.5. Autoregulation of blood flow in the kidneys was usually seen immediately after the first removal of blood but with the onset of renal vasoconstriction it was reduced or abolished for the remainder of the experiment.
The effect of androgenic hormones on creatinine secretion in the rat
Authors: Harvey Alice M. , Malvin Richard L. 
Published: December 2014

1. The stop flow procedure was used to compare the urinary creatinine: inulin ratios in male and female rats; to confirm previous evidence for secretion of creatinine by the renal tubule in the male rat, and to assess the effect of androgenic hormones on this property of the renal tubule in the female rat.2. The creatinine:inulin ratios in free flow and all stop flow samples in the female rat were close to unity, confirming the absence of secretion of creatinine.3. In the male rat the ratios in the free flow samples exceeded 1·2. In samples proximal to the sodium minimum the ratio rose to a peak of 1·56, and then declined to the free flow level.4. Female rats pre‐treated with androgenic hormones exhibited a male type pattern. A single intramuscular dose of testosterone, or daily injections of progesterone for 1 month, had a similar effect. The free flow ratios rose to 1·2 and on stop flow a proximal secretory peak was seen.5. Two conclusions may be drawn—the creatinine clearance is a valid measure of glomerular filtration rate in the female rat, but not in the male; and the secretion of creatinine is a function of the proximal tubular cells which can be influenced by androgenic hormones in the rat.
Transmission from intramural excitatory nerves to the smooth muscle cells of the guinea‐pig taenia coli
Authors: Bennett M. R. 
Published: December 2014

1. A study has been made of transmission from intramural excitatory nerves to the smooth muscle cells of the guinea‐pig taenia coli.2. Only ten cells out of eighty gave depolarizing (i.e. excitatory junction potentials,
E.J.P.S) on stimulating the intramural nerves, the remaining cells gave hyperpolarizing responses (i.e. inhibitory junction potentials,
I.J.P.S).
E.J.P.S were recorded in cells which were less than 1 mm away from cells which gave
I.J.P.S.3. In some cells stimulation of the intramural nerves with single pulses of maximal strength gave
E.J.P.S of about 20 mV amplitude after a latency of 100‐200 msec. In quiescent cells these
E.J.P.S gave rise to action potentials. Repetitive stimulation above 1 c/s depolarized the membrane for less than about 1 sec, and during the remainder of the stimulation no action potentials fired, even in spontaneous cells.4. In some cells stimulation of the intramural nerves gave an
I.J.P. The largest sized
I.J.P.S were generally only about half the size of the
I.J.P.S recorded in atropinized preparations. The decreased amplitude of the
I.J.P.S enabled rebound action potentials to be fired by successive
I.J.P.S when the intramural nerves were stimulated at about 1 c/s. At higher frequencies all spontaneous activity was suppressed.5. The effect of neostigmine (10−9‐10−7 g/ml.) on the transmission was studied. There was no detectable increase in the number of cells giving
E.J.P. responses in the presence of neostigmine.6. The electrophysiological characteristics of intramural excitatory and inhibitory nerve transmission are discussed.
Action of static and dynamic fusimotor fibres on secondary endings of cat's spindles
Authors: Appelberg B. , Bessou P. , Laporte Y. 
Published: December 2014

1. The effects exerted on secondary endings by repetitive stimulation of single static or single dynamic fusimotor fibres were studied in nine tenuissimus spindles in cats.2. The discharge of each secondary ending was recorded simultaneously with the discharge of the primary ending belonging to the same spindle.3. All the nineteen static fusimotor fibres studied activated secondary endings.4. Of eight dynamic fusimotor fibres, seven had no action on secondary endings. One dynamic fibre activated an atypical secondary ending which displayed some phasic sensitivity.5. No difference in conduction velocity was found between static and dynamic fibres.6. The implications of these observations for the mechanism of action of static and dynamic fusimotor fibres are discussed.
The effects of somatic stimuli on the bladder in the cat
Authors: McPherson Angus 
Published: December 2014

1. Measurement of the intra‐vesical pressure in cats during contractions of the bladder was found to be a more reliable method of studying bladder function than the cystometrogram. Under suitable conditions the pressure curves of these bladder contractions were constant and could be examined statistically.2. In the anaesthetized cat cold decreased the pressure developed by bladder contractions and shortened the interval between them. There was no evidence that this effect was reflex in nature.3. In the anaesthetized cat stimulation of the sural nerve sometimes produced contraction of the bladder or increased the pressure developed by spontaneous contractions.4. In the anaesthetized cat stimulation of any hind‐limb nerve from muscles with conduction velocities of approximately 50 m/sec inhibited bladder contractions.5. In the acute spinal cat somatic stimuli had no effect on bladder activity.6. In the chronic spinal cat cutaneous stimuli produced reflex contraction of the bladder or the augmentation of a spontaneous contraction. Stimulation of nerves from hind‐limb muscles, however, had no effect on bladder activity.7. In the decerebrate cat cutaneous stimuli increased bladder activity, and this was probably ‘reflex’ in nature. Stimulation of nerve fibres from hind‐limb muscles either produced bladder contractions or augmented spontaneous contractions.
Vesico‐somatic reflexes in the chronic spinal cat
Authors: McPherson Angus 
Published: December 2014

1. In cats anaesthetized with chloralose whose spinal cords were transected 6–7 weeks previously, spontaneous contractions of the bladder had no effect on mono‐ or polysynaptic reflexes recorded electrically from the cut lumbar ventral spinal roots.2. In the same cats contractions of the bladder decreased hind‐limb extensor and flexor reflexes recorded myographically.3. The effects of (a) pelvic nerve stimulation and distension of the bladder on mono‐ and polysynaptic reflexes and (b) the effects of bladder contractions on hind‐limb reflexes recorded myographically in acute and chronic spinal, decerebrate and anaesthetized cats are discussed.4. The sites of interaction between vesical and somatic reflexes are discussed and further evidence is presented that bladder contractions affect the γ‐loop.
The effects of hypoxia on neuromuscular transmission in a mammalian preparation
Authors: Hubbard J. I. , Løyning Y. 
Published: December 2014

1. The rat diaphragm‐phrenic nerve preparation in vitro failed to contract in response to nerve impulses after 10‐20 min exposure to solutions containing 95% N2 and 5% CO2 (hypoxic solutions) at temperatures between 33 and 38° C. Intracellular recording revealed that end‐plate potential (e.p.p.) amplitudes fell below the firing threshold for muscle fibres and then disappeared probably because of block of intramuscular nerve conduction.2. In curarized and Mg‐paralysed preparations the reduction in e.p.p. amplitudes was found to be due to a fall in their quantal content. In about half of the Mg‐paralysed preparations, however, and in curarized preparations after repeated exposures, there were increases in quantal content of e.p.p.s during hypoxia.3. Miniature end‐plate potential (m.e.p.p. frequency increased in a cyclic fashion during hypoxia and this increase was largely suppressed in the presence of a raised extracellular Mg concentration. M.e.p.p. amplitude increased (range 0‐100% of control value) after about 20 min hypoxia.4. Post‐tetanic potentiation of e.p.p. amplitudes and m.e.p.p. frequency was reduced after exposure to hypoxic solutions. During hypoxia the e.p.p. amplitude potentiation was reduced but the m.e.p.p. frequency potentiation was augmented.5. There was an increase in the post‐synaptic sensitivity to carbamylcholine after 20 min hypoxia which was sufficient to explain the increase in m.e.p.p. amplitude. Other post‐synaptic changes were a fall in membrane potential (average 6 mV after 20 min) and a fall in membrane resistance after 30‐60 min exposure to hypoxia.6. The effects of hypoxia upon neuromuscular transmission were partially explained by reduction of active transport of sodium and potassium ions and consequent depolarization of nerve and muscle.
Factors affecting the distribution of iodide and bromide in the central nervous system*
Authors: Bito L. Z. , Bradbury M. W. B. , Davson H. 
Published: December 2014

1. Even when a steady level of 131I− is maintained in the blood for long periods, the uptake by brain and spinal cord is very small, and the possibility that this is due to an active transport of I− from brain‐tissue to blood has been examined.2. Most of the phenomena, however, can be explained on the basis of a slow passive diffusion across the blood—brain barrier associated with an active transport of 131I− out of the c.s.f. across the choroid plexuses, so that, except possibly for the spinal cord, active transport from central nervous parenchyma into the blood need not be postulated. If it does occur, it contributes very little to the net exchanges between the three compartments, plasma, c.s.f. and extracellular fluid.3. The steady‐state distribution of bromide between plasma and c.s.f. is normally such that the concentration in the c.s.f. is only some 70% of that in plasma; it has been shown that this is most probably due to an active transport of Br− across the choroid plexuses.
The dispersion of indicator flowing through simplified models of the circulation and its relevance to velocity profile in blood vessels
Authors: Caro C. G. 
Published: December 2014

1. The distribution of velocity (velocity profile) was studied in water flowing through simple models of the circulation. Dye was injected and the distribution of velocity was assessed from indicator concentration—time curves recorded with a photomultiplier.2. Observations were made on straight and curved tubes and on a tube containing a short region with an elliptical cross‐section. With steady flow, the rate was varied over the range 24‐870 ml./min (Reynolds number 102‐3690). Sinusoidal pulsations were imposed on the steady flow in some experiments.3. Bends gave rise to large secondary flows. These caused mixing across the flow and a marked reduction in the variation of velocity over the cross‐section of the tube. The effect of bends on velocity distribution was maximal at a Reynolds number of ca. 1000. Similar, but far smaller, effects were seen in a region with an elliptical cross‐section and when the flow was made pulsatile. Secondary motion due to bends was capable of preventing a heavier‐than‐water indicator (sp.gr. 1·375) from settling out of the flow.4. The experimental findings suggest that there may be secondary flows in vascular beds. Under certain conditions, these would prevent the establishment of Poiseuille type laminar flow. The possible physiological importance of the findings is discussed.