bluuebunny/crossref_metadata_2025 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.
Effect of neutral α‐ and ω‐amino acids and basic α‐amino acids on uptake of l‐histidine by intestinal mucosa, testis, spleen and kidney in vitro: a comparison with effect in brain
Authors: Neame K. D.
Published: December 2014

1. The effect of the
D‐ and
L‐isomer of neutral α‐amino acids, of ω‐amino acids, and of basic
L‐α‐amino acids on uptake of
L‐histidine in vitro has been investigated in intestinal mucosa, testis, spleen and kidney cortex, and compared with the effect in brain.

2. Neutral α‐amino acids produced inhibition that was in general greater the longer the carbon chain of the inhibiting amino acid. There were minor variations with different tissues.

3. ω‐amino acids produced little or no inhibition, with only slight variation between tissues. There was a tendency towards less inhibition the longer the carbon chain.

4. The effect of basic amino acids varied with different tissues. With one exception, all produced significant inhibition with intestinal mucosa and testis. With spleen and kidney, inhibition was slight or absent, and resembled the effect produced by the ω‐amino acids. With brain (previously reported elsewhere) the short‐chain amino acids produced considerable inhibition, those having longer carbon chains little or none.

5. Proline produced significant inhibition in brain and spleen, but none in the other tissues. Tryptophan had no effect with kidney.

6. The findings are considered as further evidence for a relation between the extent to which an amino acid can be taken up by a given tissue and the specificity of the transport systems in that tissue. They also support the view that the nature of certain transport systems may vary considerably between different tissues.
Decremental and incremental visual thresholds
Authors: Short A. D.
Published: December 2014

1. Extrafoveal decremental and incremental visual thresholds have been measured with a circular test‐object of 57′ diameter, an exposure time of 0·1 sec and background luminance ranging from 2·5 to 7·3 log. quanta (equivalent to 507 nm) per second per square degree at the cornea.

2. The decremental threshold is lower than the incremental threshold by factors up to 0·4 log. unit when the background luminance is low; and the two thresholds are virtually the same when the background luminance is high.
The extracellular space of the smooth muscle of the guinea‐pig taenia coli
Authors: Goodford P. J. , Leach E. H.
Published: December 2014

1. The measured extracellular space of the taenia coli is large when small ions or molecules are used for the determination, and small when large molecules are used, even with identical experimental procedures.

2. Extracellular hyaluronic acid has been detected histologically. It is apparently reduced by hyaluronidase.

3. The extracellular inulin space increases after the tissue has been pretreated with hyaluronidase, although the ionic composition and wet weight are unchanged.

4. It is suggested that the hyaluronic acid prevents the free entry of macromolecules such as inulin into the extracellular space by steric hindrance. Monatomic ions such as Na+, Li+, Cl−, Ca2+ therefore have a larger extracellular space available than is calculated on the basis of the inulin space.

5. A slight shrinkage of the muscle cells can be detected when the incubation period is prolonged.
An interaction between potassium and sodium in the smooth muscle of the guinea‐pig taenia coli
Authors: Goodford P. J.
Published: December 2014

1. The potassium content of the guinea‐pig taenia coli was 72 m‐mole K/kg fr. wt. after equilibration with normal Krebs‐type solution at 35° C in vitro.

2. It fell to 13 m‐mole K/kg fr. wt. when Ca2+ and Mg2+ were omitted from the bathing solution, but this fall was reversed in part when [Na+]o was also reduced.

3. The taeniae relaxed when Ca2+ and Mg2+ were omitted from the normal solution. However, they contracted if Na+ was also omitted.

4. Effects 2 and 3 may show some antagonism between sodium and divalent cations in smooth muscle.

5. The extracellular space of the same muscles was measured with [14C]sorbitol. It was 440 ml./kg fr. wt. in normal solution.

6. The uptake of 42K was measured in the same muscles at the same time. An initial rapid exchange was followed within 2 min by a slow (half‐time [unk] 50 min in normal solution) and presumably intracellular uptake of tracer.

7. In normal solution the initial rapid phase of 42K exchange corresponded to 3·0 m‐mole K/kg fr. wt. A value of 2·6 m‐mole K/kg fr. wt. would have been calculated from [K+]o and the [14C]sorbitol space, and these estimates did not differ significantly.

8. The [14C]sorbitol space fell slightly when [Ca2+]o, [Mg2+]o, and [Na+]o were reduced, but the amount of rapidly exchanging potassium increased significantly reaching 4·6 m‐mole K/kg fr. wt. in solutions from which Ca2+, Mg2+ and Na+ were omitted. The [14C]sorbitol space only accounted for 2·4 m‐mole K/kg fr. wt. under these conditions, a significantly smaller quantity.

9. The observations have been interpreted on Wilbrandt & Koller's (1948) hypothesis that there may be a superficial anionic region in muscle cells. On this model the present results suggest that K+ rather than Na+ is favoured as a monovalent counter‐cation in the taenia coli.
Pharmacological studies on feline Betz cells
Authors: Crawford J. M. , Curtis D. R.
Published: December 2014

1. A study has been made of the sensitivity of single neurones in the pericruciate cortex of anaesthetized and unanaesthetized cats to cholinomimetics administered electrophoretically from multibarrel micropipettes.

2. A high proportion of deep pyramidal cells, including Betz cells, were excited by these substances, and the receptors involved have muscarinic characteristics.

3. Atropine specifically reduced the sensitivity of cortical neurones to acetylcholine, but no such action could be demonstrated for dihydro‐β‐erythroidine, gallamine or general anaesthetics.

4. The significance of these results is discussed in relation to the possible synaptic or non‐synaptic action of acetylcholine upon cortical neurones.
Skin temperature, thermal comfort, sweating, clothing and activity of men sledging in Antarctica
Authors: Budd G. M.
Published: December 2014

1. Three men were studied while dog‐sledging 320 km in 12 days in Antarctica. Conventional Antarctic clothing (‘sweaters and windproofs’) was worn. Four hundred observations were made of medial thigh skin temperature, thermal comfort, sweating, clothing, activity and environmental conditions.

2. Work occupied an average of 11·0 hr/day and sleep 7·5 hr. Estimated daily energy expenditure averaged 5100 kcal (range 2740‐6660 kcal).

3. Skin temperature fell on exposure to cold despite the clothing worn, but was not changed by the level of activity. Sweating, and thermal comfort, were directly related to both skin temperature and activity.

4. Inside the tent, the modal value of skin temperature was 33° C (range 27‐36° C) and the men were comfortable in 94% of observations.

5. During the 9·2 hr/day spent outdoors the modal value of skin temperature was 27° C (range 18‐33° C) and the men felt too cold (but did not shiver) in 11% (range 7‐20%) of observations, suggesting that cold stress was not negligible. However, they also felt too hot in 20% of observations and were sweating in 23%.
Body temperature, shivering, blood pressure and heart rate during a standard cold stress in Australia and Antarctica
Authors: Budd G. M. , Warhaft N.
Published: December 2014

1. Four men of European descent were exposed naked to an air temperature of 10° C for 2 hr in Australia, and again after 24 weeks' residence at Mawson, Antarctica.

2. Their ability to maintain rectal temperature during the test cold exposure significantly improved at Mawson. Shivering and cold diuresis did not change. The response of skin temperature did not change significantly except for a small increase in toe temperature. Bradycardia caused by the cold exposure was significantly greater at Mawson, but the rise in blood pressure did not change. Spontaneous fluctuations in rectal temperature that occurred during the cold exposure were intensified at Mawson.

3. The results confirm those of a previous study at Mawson, and are attributed to general acclimatization to cold. It is suggested that tissue insulation increased as a result of enhanced vasoconstriction.
Effect of 5‐hydroxytryptophan acting from the cerebral ventricles on 5‐hydroxytryptamine output and body temperature
Authors: El Hawary M. B. E. , Feldberg W.
Published: December 2014

1. In cats anaesthetized with intraperitoneal pentobarbitone sodium the third ventricle, the anterior or inferior horn of the left lateral ventricle, was perfused with 5‐hydroxytryptophan (5‐HTP) in different concentrations, and the effluent assayed for 5‐hydroxytryptamine (5‐HT) on the rat stomach strip preparation of Vane (1957).

2. On perfusion of the third ventricle with 5‐HTP the output of 5‐HT in effluent increased, the increase depending on the 5‐HTP concentration: with 1/50,000 it increased 44‐69 times (mean 55), with 1/25,000, 81‐83 times (mean 82) and with 1/10,000, 71‐200 times (mean 128). The 5‐HT output depended also on the initial output during the preceding perfusion with artificial c.s.f. The greater this initial output the greater was the maximum output reached during the 5‐HTP perfusion.

3. The increase in 5‐HT output during perfusion of the third ventricle with 5‐HTP was usually associated with shivering and a rise in rectal temperature. This association, however, was not invariably obtained, probably because of a central depressant effect of 5‐HTP itself.

4. On perfusion of the anterior or inferior horn of the left lateral ventricle with 5‐HTP, the output of 5‐HT in the effluent also increased, but to a lesser extent than in the effluent from the third ventricle. There was no association with shivering nor with a rise in rectal temperature.

5. An injection of 1 or 2 mg 5—HTP into the cerebral ventricles of unanaesthetized cats produced a biphasic rise in temperature, shivering, constriction of the skin vessels followed by vasodilatation, tachypnoea, wiping and scratching movements, miaowing and long lasting sleep.

6. The biphasic rise in temperature is explained as the result of two opposing effects: increased formation of 5‐HT which would raise body temperature, and a central depressant effect of 5‐HTP itself or of one of its metabolites which would lower body temperature.

7. The initial rise in temperature and the shivering in response to an intraventricular injection of 5‐HTP varied from cat to cat. In those in which these effects were strong the 5‐HT output during a subsequent perfusion of the third ventricle with artificial c.s.f. was higher, and the maximum 5—HT output reached on perfusion with 5‐HTP was greater than in those in which these effects had been weak.
Location of sites of 5‐hydroxytryptamine storage and metabolism by radioautography
Authors: Gershon M. D. , Ross L. L.
Published: December 2014

1. A technique for the radioautographic identification, localization, and study of the turnover of cellular depots of 5‐hydroxytryptamine (5‐HT) has been evaluated. A light microscopic survey was made of the uptake and turnover of 5‐HT, synthesized in vivo from its administered tritium‐labelled precursor, 5‐hydroxytryptophan (5‐HTP).

2. 5‐HT was taken up rapidly and retained for long periods of time by adrenal medullary chromaffin cells, gastric enterochromaffin cells, blood platelets, thyroid parafollicular cells, beta cells of pancreatic islets, mast cells, and septal cells of the lung. Reticulo‐endothelial cells of liver and spleen took up radioactive 5‐HT more slowly but also retained it for days.

3. Specific uptake, and a rapid turnover of radioactive 5‐HT, was found in pancreatic exocrine cells, neurones of the superior cervical ganglion, terminal axons of gastro‐intestinal myenteric plexus, carotid body cells, and pinealocytes.

4. A supranuclear localization of radioactive 5‐HT in renal proximal tubular cells may represent tubular secretion of 5‐HT.

5. The localization of 5‐HT by radioautography generally corresponds to that found by formaldehyde‐induced fluorescence. It makes possible the study of 5‐HT turnover and is capable of greater resolution than the fluorescence technique. Freeze‐drying may also be avoided.
An analysis of spontaneous impulse activity of units in the striate cortex of unrestrained cats
Authors: Griffith J. S. , Horn G.
Published: December 2014

1. Recordings were made from sixty‐five cells in the visual cortex of unanaesthetized, dark‐adapted cats and transferred automatically to computer input paper tape.

2. The activity of each cell was measured as a function of time (the running mean). The unit of time used was inversely proportional to the mean firing rate, in order to give comparable results for different cells.

3. For sixty‐nine sections of discharge from fifty‐two cells, the length of time recorded was sufficient to test for the long‐term stability of the running mean. In twenty‐six sections, various kinds of trend and long‐term irregularity were found.

4. The interspike interval histogram was computed for the forty‐one sections (from thirty‐one cells) in which there were more than 2000 discharges. Only eight histograms approximated closely to the exponential form. A test was also made of the distribution of the longer intervals alone and in twenty‐five sections they did not deviate significantly from the exponential form.

5. There was no significant correlation between the behaviour of the longer interspike intervals and the long‐term stability or otherwise of the running mean.
Optical quality of the human eye
Authors: Campbell F. W. , Gubisch R. W.
Published: December 2014

1. Optical quality of the eye was measured at eight pupil sizes between 1·5 and 6·6 mm diameter by recording the faint light emerging from the eye; this light was reflected from the bright image of a thin line on the fundus.

2. The nature of the fundus reflexion was examined; it was found that the fundus acts very much like a perfect diffuser while retaining polarization.

3. Using the result that the fundus acts like a diffuser, the recorded line images were Fourier analysed to provide modulation transfer functions. These functions indicate an optical quality considerably higher than that found in previous physical studies.

4. Linespread profiles were then derived from the modulation transfer functions. These profiles are 40% narrower than those of previous physical studies for a 3·0 mm pupil. The narrowest profile occurred with a 2·4 mm pupil.

5. Our results demonstrate that physical and psychophysical studies can yield similar estimates of optical quality. The influence of optical factors not common to both techniques is discussed. Evidence for the existence of neural ‘image sharpening’ mechanisms is reviewed.
Potassium contractures in single muscle fibres of the crayfish
Authors: Zachar J. , Zacharová Daria
Published: December 2014

1. Contractures were evoked in isolated muscle fibres of the extensor carpopoditi muscle of the crayfish (Astacus fluviatilis) by increasing [K]o at constant [Cl]o or at constant [K]o[Cl]o product.

2. The relation between tension and log [K]o is S‐shaped with a less steep slope if [K]o was increased at constant [Cl]o. This is due to a smaller drop in membrane potential for a given change in [K]o in the latter case.

3. The curves relating the tension to the membrane potential overlap in either case. In the linear part of the curve, the slope is around 0·3 kg cm−2m V−1.

4. The mechanical threshold of contracture is about ‐55 mV and mechanical saturation is at ‐20 mV.

5. Fibres exert the greatest tension when stretched to 1·25 lo (8 kg/cm2), where lo is the length at which the fibres are just taut in the solution. Tension falls on either side of this optimal length. Tension vanishes when the fibre is stretched to 1·95 lo.

6. Sarcomere length at optimal fibre length is 10·5 ± 0·3 μ. The A band is 3·95 ± 0·8 μ long and does not alter during stretch.

7. The crayfish muscle fibres were of the phasic type, since they relaxed spontaneously at maintained high [K]o.

8. At [K]o near saturation point, contractures attain the maximum tension in 5 ± 1·3 sec and the time to half decay is 8·1 ± 0·5 sec.

9. If the contracture is allowed to relax spontaneously, it is not possible to obtain initial tension until after 20‐30 min. When the contracture is terminated by a return to low [K]o after reaching its maximum, but before spontaneous relaxation appears, the fibre is capable of repeatedly exerting the initial tension.

10. The rate of recovery after a spontaneously relaxed contracture depends on [K]o in the solution, in which the fibre lies before evoking the test contracture. The relation of recovery upon log [K]o is S‐shaped and the tension is the greater, the lower the [K]o in the solution in which recovery is taking place.
Properties of stretch receptors in cat extraocular muscles*
Authors: Bach-Y-Rita P. , Ito F.
Published: December 2014

1. The properties of fifty‐two stretch receptors in the extraocular muscles were studied in thirty cats. Between ten and twenty‐eight receptors were observed in each preparation.

2. In four preparations, spontaneously discharging receptors were observed, with afferent fibre conduction velocities ranging from 16·9 to 41·1 m/sec.

3. In the remaining twenty‐six cats, the minimal threshold receptors ranged from 3 to 130 g, with a peak distribution between 10 and 20 g, and afferent fibre conduction velocities ranging from 6·5 to 52·0 m/sec, the peak being between 10 and 15 m/sec. Of these receptors, nineteen were quickly adapting and seven were slowly adapting.

4. The dynamic and static indexes of all the receptors were essentially similar; they both increased markedly on increasing the initial length. This suggests that the receptors do not lie in contact with regions of reduced viscosity on the muscle fibres comparable to the equatorial region of the intrafusal muscle fibres.

5. All of the receptors were located in the muscle; none was located in the tendon. Forty‐seven of forty‐nine receptors were in parallel and two receptors were in series with the contractile elements.

6. The properties of all the receptors studied appeared to be similar, suggesting that a single type of stretch receptor is located in the inferior oblique muscle of cats.
Kidney composition and renal concentration ability in young rabbits
Authors: Forrest J. N. , Stanier Margaret W.
Published: December 2014

1. The water, sodium, urea, potassium and ammonia concentrations of the kidney cortex and inner medulla of adult rabbits, and of rabbits 1, 4, 14 and 21 days old, were measured after mild dehydration. The urine osmolarity and serum and urine urea concentrations were also measured.

2. Potassium and ammonia showed no consistent variation in the different parts of the kidney or at the different ages. Sodium concentrations expressed as m‐equiv/100 g fresh weight were about twice as high in the medulla as in the cortex at all ages.

3. The medulla/cortex ratio of urea concentration increased markedly between the fourteenth and twenty‐first day after birth. So also did the urine osmolarity of the mildly dehydrated animals.

4. The rise in the medulla/cortex urea ratio between birth and 21 days, and the even higher ratio found in adult animals, was due to a decrease in the concentration of urea in the cortex rather than to an increase in its concentration in the medulla.
Effects of sodium extrusion and local anaesthetics on muscle membrane resistance and potential
Authors: Harris E. J. , Ochs S.
Published: December 2014

1. Membrane potentials and resistances of K‐depleted muscles were measured in the cold and again after warming in K‐containing media so that active ion movements occurred.

2. On warming there was a fall of resistance and a gradual rise of potential which passed through a maximum. Later measurements of resistance in a chloride medium showed that values were, if anything, higher than initially in the warm.

3. The excess potentials measured approximated to those required to induce passive inward movement of the K ions through the measured K resistance.

4. Permeabilities for K+ and Cl− were deduced. When cocaine, procaine, amytal or mepyramine were added or when K+ was replaced by Rb+ in the Cl−‐free solution the K+ permeability was eventually reduced. The same agents led to an enhanced initial response of potential to warming, but later the potentials in Cl−‐free media fell to less than the K+ equilibrium values.

5. A method for obtaining the resistivity of the membrane from measurements made in conditions of non‐linear voltage—current dependence was applied.
Effect of inhibitors and uncouplers on the Na pump of the Maia muscle fibre
Authors: Bittar E. E.
Published: December 2014

1. A study has been made of sodium efflux from single muscle fibres of the crab Maia squinado, and of the effect of inhibitors and uncouplers on this efflux, using the microsyringe technique.

2. (i) Externally applied ethacrynic acid or injected ethacrynic acid produces 50% inhibition. The inhibitory state due to externally applied ethacrynic acid is shown to be sensitive to 40 m
M‐K+ in the bathing medium.

(ii) Internally applied chlorpromazine causes 40% inhibition.

(iii) Internally applied ethyl alcohol causes a slight increase or a slight decrease in Na efflux or no effect.

(iv) Internally applied antimycin A produces a net inhibitory effect of almost 50%.

(v) Internally applied rotenone produces a 60% inhibitory effect while fibres that fail to contract initially show about a 90% fall in efflux.

(vi) The response pattern to internally applied oligomycin is similar to that of antimycin but the net inhibitory effect is only 25%.

(vii) Internally applied atractylate produces 45% inhibition.

(viii) Internally applied gramicidin A produces about 40% inhibition.

(ix) Internally applied valinomycin is without an effect, but in the presence of 40 m
M‐K+ in the external medium there is marked inhibition of Na efflux.

3. The evidence put forward suggests that the Na pump of the Maia fibre is divided into two parts, one the Na+‐K+‐ATPase, driven by ATP and arginine phosphate (ArP), and the other, an electrogenic mechanism, driven by respiration and possibly direct coupling of glycolytic energy. The process of reverse electron flow can be invoked as a reasonable explanation of some of the observations made.
Post‐tetanic hyperpolarization and electrogenic Na pump in stretch receptor neurone of crayfish
Authors: Nakajima S. , Takahashi K.
Published: December 2014

1. Two types of after‐potentials in the stretch receptor neurone of crayfish are described.

2. A short‐duration after‐hyperpolarization associated with a single spike or a few spikes is diminished and reversed on applying hyperpolarizing currents. However, a much longer‐lasting post‐tetanic hyperpolarization (PTH) is enhanced by conditioning hyperpolarization; thus, no reversal potential can be obtained.

3. No changes in membrane conductance occur during PTH.

4. Reducing K concentration in the bathing fluid diminishes PTH, while it shifts the reversal potential of the short after‐potential toward greater negativity.

5. Replacement of Na with Li, or addition of 2,4‐dinitrophenol in the bathing fluid suppresses PTH in a reversible manner.

6. Electrophoretic injection of Na into the cell induces a long‐lasting hyperpolarization.

7. No change in K‐equilibrium potential, as indicated by the reversal point of the short after‐potential, is detected during PTH.

8. It is concluded that the short after‐potential is caused by a permeability increase for potassium ion, whereas PTH is produced by an electrogenic Na‐pump.
Cholinergic mechanisms in the caudate nucleus
Authors: McLennan H. , York D. H.
Published: December 2014

1. Acetylcholine (ACh), and a number of cholinomimetic and cholinolytic agents, have been applied to single neurones of the caudate nucleus, and the effects compared with those produced by stimulation of nucleus ventralis anterior thalami (VA).

2. Neurones responding by excitation following ACh and VA stimulation, and others depressed by both ACh and VA stimulation have been observed. The two types of cell are located in different regions of the nucleus.

3. Both types of ACh effect, and the responses to VA stimulation, are prevented by atropine.

4. Taken with the earlier observation that the release of ACh from the caudate can be enhanced by VA stimulation, it has been suggested that the present results indicate a final cholinergic link in the pathway from VA to caudate.