bluuebunny/crossref_metadata_2025 huggingface dataset:
Muscular control of landing from unexpected falls in man
Authors: Jones G. Melvill , Watt D. G. D.
Published: December 2014

1. It was previously shown that the controlled landing from single steps to the ground is typically brought about by accurately timed motor activity, commencing before the actual landing, and completed before time would permit the participation of a useful stretch reflex response.

2. To investigate further the validity of this conclusion, subjects were dropped from an electromagnetic suspension at unexpected moments. Their gastrocnemius electromyographic (e.m.g.) responses and the forces applied to their feet were recorded throughout.

3. No useful contribution of a stretch reflex response was detected. Indeed, it was shown that a functionally effective reflex resulting from the mechanical event of landing would occur far too late to contribute to the muscular deceleration of the fall.

4. It was also found that a consistent muscular response occurred, commencing 74·2 msec (
S.E. of mean = 1·4 msec) after starting the fall, independent of height.

5. It is suggested that this response in the leg musculature is a reflex originating in the otolith apparatus. In addition, a possible mechanism for the control of repetitive hopping, and perhaps running, movements, involving the above reflex, is suggested.
The fine structural localization of cholinesterases in the carotid body of the cat
Authors: Ballard Kathleen J. , Jones J. V.
Published: December 2014

1. The distribution of cholinesterases in the carotid body of the cat has been investigated with the electron microscope to obtain a clearer picture of the localization of the enzyme. This is of relevance to the possible role of acetylcholine as a transmitter in the carotid body.

2. Tissues were fixed for short periods and incubated by the method of Karnovsky for the fine localization of cholinesterases.

3. The enzyme was found in two main sites. Butyrylcholinesterase was present on the type II cell membrane while acetylcholinesterase was found in groups of peripheral axons. No intracellular enzyme was found.

4. It is concluded that acetylcholine may be a transmitter in the carotid body and that it may be partly destroyed by enzymic hydrolysis. A possible explanation for some of the anomalous pharmacological findings is suggested.
Measurements of small variations in ‘absolute’ pitch
Authors: Wynn V. T.
Published: December 2014

1. Longitudinal studies on absolute pitch estimates have been observed in one male and two female subjects.

2. The female subjects underwent rhythmic variations in their estimates that were related to their menstrual cycles. One female subject, the more intensively studied of the two, also showed variations in her pitch estimates that were related to illness.

3. Relevant correlations between the menstrual cycle and known biochemical parameters are mentioned which suggest that the fluctuations in the female estimates are governed by changes in the electrical activity of the auditory nervous system.

4. The male subject showed similar fluctuations in his pitch estimates. A rhythm of approximately 20 days was observed.

5. A connexion between the fluctuations in the pitch estimates and the sex hormones in both the female and the male subjects is suggested as a possible explanation of the difference between two different types of absolute pitch.

6. The hypothesis is extended to show how the adrenal corticosteroids could account for the changes in the pitch estimates that occurred with illness.
Reflex respiratory and cardiovascular effects of stimulation of receptors in the nose of the dog
Authors: James Jennifer E. Angell , Daly M. de Burgh
Published: December 2014

1. In forty‐one out of forty‐seven dogs under chloralose—urethane or Nembutal anaesthesia, mechanical stimulation of the nasal mucous membrane caused a reduction or inhibition of respiration, bradycardia, variable changes of arterial blood pressure, and a small rise in venous pressure.

2. Simultaneous measurements of arterial and venous pressures, and also of blood flow in various arteries by means of an electromagnetic flowmeter indicate that the calculated vascular resistance increases in the intact limb, muscle, and skin, and the vascular beds of the vertebral, superior mesenteric, renal and splenic arteries. No changes in vascular resistance occur in the common carotid circulation.

3. Evidence is presented that the increase in vascular resistance is due to vasoconstriction, and occurs in the absence of changes in pulmonary ventilation.

4. Stimulation of the nasal mucous membrane causes a reduction in volume of the spleen.

5. The respiratory and cardiovascular responses are reflex in nature, being abolished by the application of a local anaesthetic to the nose or by combined division of the maxillary and ethmoidal branches of the trigeminal nerves. The cardiac response is mediated largely by the vagus nerves, and the vascular responses by sympathetic adrenergic fibres.

6. Cessation of the stimulus to the nose not infrequently results in the following temporary after‐effects: hyperventilation, tachycardia, hypertension, and vasodilatation in the intact limb and in muscle.
The hyperglycaemic response to stimulation of the hepatic sympathetic innervation in adrenalectomized cats and dogs
Authors: Edwards A. V.
Published: December 2014

1. The extent to which the hyperglaemic and glycogenolytic responses to splanchnic nerve stimulation depend upon the integrity of the hepatic innervation has been investigated in adrenalectomized dogs and cats.

2. In both species maximal stimulation of the hepatic nerves (20 c/s) produced changes in plasma glucose concentration comparable to those which have been found to occur in response to bilateral splanchnic nerve stimulation at the same frequency. Furthermore, the hyperglycaemic response to splanchnic nerve stimulation was very substantially reduced by section of the hepatic nerves, whereas the associated changes in haematocrit and mean aortic blood pressure were not significantly altered.

3. Comparison of the changes in plasma glucose concentration in response to splanchnic or hepatic nerve stimulation at relatively low frequencies (1·0–2·0 c/s) showed that stimulation of either nerve produced closely similar responses in adrenalectomized animals of both species.

4. In adrenalectomized dogs maximal stimulation of the hepatic nerves (20 c/s) for shorter periods (30 sec) caused a significant rise in plasma glucose concentration whereas total occlusion of the portal vein for the same period in the same animals produced no statistically significant hyperglycaemic effect.

5. Maximal stimulation of the hepatic nerves (20 c/s) caused a rapid rise in plasma glucose concentration in hypoglycaemic adrenalectomized cats pretreated with a large dose of insulin (4 u./kg body wt.).

6. It is concluded that the hyperglycaemic response to stimulation of the peripheral ends of the splanchnic nerves in adrenalectomized dogs and cats is directly dependent upon activation of sympathetic efferent fibres to the liver.
The location of the fluid pump in the cornea
Authors: Maurice D. M.
Published: December 2014

1. Fluid transport across rabbit corneal tissue has been investigated by observing the movement of fluid interfaces under the microscope, or by mounting the tissue between two chambers and observing the displacement of menisci within capillary tubes.

2. In both cases, the endothelial layer supported on a thin sheet of connective tissue is capable of pumping fluid in a direction out of the cornea, against a head of pressure. The volume of fluid moved may amount to twelve times the thickness of the endothelial cells in an hour.

3. This active fluid movement accounts for the prevention of swelling of the normal corneal stroma. The hypothesis that corneal hydration is regulated by the sodium pump in the epithelial layer is not supported by these experiments.
The action of insulin on brown adipose tissue in vivo
Authors: Hardman M. J. , Hull D.
Published: December 2014

1. The action of insulin on the net exchange of glucose, free fatty acids and glycerol by brown adipose tissue of young rabbits was investigated.

2. Infusion of insulin (10,000 μu./kg.min I.V. for 10 min) caused a large increase in the uptake of glucose by brown adipose tissue of fed week‐old rabbits. The release of fatty acids fell but glycerol release was unchanged.

3. The brown adipose tissue of 9‐day‐old rabbits fasted in a warm environment had a high initial rate of fatty acid and glycerol release and low rates of glucose uptake. Insulin infusions (10,000 and 100 μu./kg.min) greatly reduced fatty acid release but had little or no effect on glucose uptake.

4. The brown adipose tissue of 9‐day‐old rabbits fasted in a cold environment was depleted of fat and took up free fatty acid as well as glucose from the circulation. Infusion of insulin (10,000 μu./kg.min) caused a large increase in glucose uptake accompanied by a reduction in fatty acid uptake.

5. The experiments support the view that insulin has a direct effect on fatty acid transport across the cell membrane.
Influence of adaptation level on response pattern and sensitivity of ganglion cells in the cat's retina
Authors: Yoon Myonggeun
Published: December 2014

1. The effect of background illumination on response pattern is correlated with its effect on visual sensitivity by analysing post‐stimulus time‐histograms obtained from single ganglion cells in the cat's retina at various levels of background illumination between zero and 2 × 106 photons (wave‐length 523 nm).sec−1.deg−2 (via 5·7 mm2 pupil).

2. If background illumination did not exceed a critical value, about 103 photons (523 nm).sec−1.deg−2 (via 5·7 mm2 pupil), stimulation of the centre of a receptive field resulted in either sustained excitation (i.e. increase in discharge rate) during ‘on’ and cessation of the excitation at ‘off’ (on‐centre unit), or sustained inhibition (i.e. decrease in discharge rate) during ‘on’ and cessation of the inhibition at ‘off’ (off‐centre unit). Within this low adaptational level, a ganglion cell maintained its maximum sensitivity regardless of whether the weak background light was presented or not.

3. When background level exceeded the critical value up to 2 × 106 photons (523 nm).sec−1.deg−2, however, the simple, sustained responses changed into compound responses with two transient components of opposite polarities, either excitation at ‘on’ and inhibition at ‘off’ (on‐centre unit), or inhibition at ‘on’ and excitation at ‘off’ (off‐centre unit), and also the sensitivity began to decrease as the background increased, approximately obeying Weber's law.

4. It is suggested that a ganglion cell gives simple‐sustained response when its gain control mechanism remains inactive at a low background illumination below a critical level, whereas it gives compound‐transient response when its gain control mechanism becomes active as background illumination exceeds the critical value.
Differences in sensitivity to vasoconstrictor drugs within the wall of the sheep carotid artery
Authors: Graham J. M. , Keatinge W. R.
Published: December 2014

1. Controlled heat damage was used to separate the responses of the outer innervated smooth muscle from those of the inner nerve‐free smooth muscle of the sheep carotid artery.

2. Preparations of smooth muscle from the inner part of the media gave 50% maximal contractions in response to approximately 1/15 the concentration of noradrenaline needed to produce similar responses from outer smooth muscle. The difference in sensitivity was greater in the lower than the upper parts of the dose—response curves.

3. Much of the difference in sensitivity was still seen in the presence of Desipramine and after chronic denervation, and so could not be attributed to uptake of noradrenaline by the nerve fibres in the outer smooth muscle; disappearance of the fibres after denervation was confirmed by fluorescence microscopy.

4. Similar but generally smaller differences in sensitivity between inner and outer smooth muscle were seen with respect to histamine, angiotensin II and 5‐hydroxytryptamine.

5. Sympathetic denervation 10–14 days previously increased the sensitivity of outer strips to noradrenaline; it usually also increased their sensitivity to histamine, suggesting that the change largely represented non‐specific denervation super‐sensitivity.

6. The high sensitivity of the inner smooth muscle is likely to be of value in enabling it to respond to the relatively low concentration of noradrenaline reaching it in life.
The interaction at equilibrium between tetrodotoxin and mammalian non‐myelinated nerve fibres
Authors: Colquhoun D. , Ritchie J. M.
Published: December 2014

1. As a preliminary to chemical studies an estimate has been made of the equilibrium dissociation constant (K) for the interaction of tetrodotoxin (TTX) with the non‐myelinated fibres of the rabbit desheathed vagus nerve.

2. TTX causes a parallel shift to the right of the curves obtained when either the height or the conduction velocity of the compound action potential are plotted against the logarithm of the external sodium concentration.

3. A model has been formulated based on the independence principle and the Hodgkin—Huxley theory, and the experimental results shown to be consistent with it. On this basis, and on the assumptions that one TTX molecule blocks one sodium channel, and that binding is Langmuir, K was estimated to be about 3‐5 n
M at about 20° C. Other simple non‐Langmuir models gave essentially similar low values for K.

4. An alternative method of computing K that makes rather different assumptions gives a similar low value.

5. Despite the low value for K, a TTX concentration of at least 100 n
M is needed to block conduction completely and this seems to be related to the fact that conduction is not completely blocked until the external sodium concentration falls below 7% of its value in normal Locke.

6. The minimum sodium concentration needed to support conduction increased with temperature.
Transport of potassium at the blood—brain barrier
Authors: Bradbury M. W. B. , Segal M. B. , Wilson Janet
Published: December 2014

1. The pial surface of different regions of the central nervous system of the rabbit have been bathed with artificial cerebrospinal fluid (c.s.f.), containing different concentrations of potassium. The object has been to change the composition of the interstitial fluid with respect to this ion, where it is adjacent to subarachnoid c.s.f.

2. Two techniques, subarachnoid perfusion from the supracallosal space between the hemispheres to the cisterna magna and barbotage from the cisterna magna, have been used. If the artificial c.s.f. contains Evans Blue, the former procedure results in maximum staining of the pia and underlying nervous tissue of the pons‐medulla and spinal cord. The latter procedure results in maximum staining of the medial and supero‐lateral surfaces of the cerebral hemispheres, particularly anteriorly.

3. During subarachnoid perfusion at 0·06 ml./min with the potassium‐free fluid, most regions of the brain took up significantly greater amounts of 42K than was the case during perfusion with the fluids containing 3 and 10 m‐equiv/l. For blue cerebral cortex, the tissue subjected directly to the inflowing fluid and showing the biggest differences, the ratios, c.p.m. per g brain/c.p.m. per ml. plasma, were 1·71 ± 0·12 (+44%), 1·19 ± 0·05 and 1·07 ± 0·08 (−10%) during perfusion with the fluids containing, 0, 3 and 10 m‐equiv/l. respectively.

4. During barbotage, the uptake of 42K into pons‐medulla and spinal cord from blood plasma, the concentration in the latter being effectively kept near constant, was, at the end of 2 hr, greater when the fluid contained potassium, 0 m=‐equiv/l. rather than 10 m‐equiv/l. Thus the ratio, c.p.m per g brain/c.p.m. per ml. plasma was (0·99 ± 0·04 (+36%) as against 0·73 ± 0·05 for pons‐medulla where the difference was greatest.

5. Simultaneous measurements of the entry of [14C]urea from blood to different regions of the central nervous system revealed no significant differences due to the differing concentrations of potassium imposed by either barbotage or subarachnoid perfusion. This appears to exclude a non‐specific cause for the changes in 42K uptake, an example of which might be a changing blood flow.

6. Reasons are given for supposing that the big increase in 42K uptake due to the potassium‐free fluid must be due to events occurring at the blood—brain barrier. This might be some form of interaction, possibly the single file effect, such that a low potassium concentration in the interstitial fluid potentiates 42K influx across the blood—brain barrier. Alternatively it might be due to a low potassium concentration in this fluid greatly reducing active potassium movement from interstitial fluid to blood. The former explanation would conform neatly with the present results; but the latter would additionally be compatible with other evidence concerning the homoeostasis of potassium concentration in c.s.f. and the interstitial fluid of brain.
The effects of calcium and magnesium on sodium fluxes through gills of Carassius auratus, L
Authors: Cuthbert A. W. , Maetz J.
Published: December 2014

1. Removal of calcium from Carassius either with chelating agents or by adaptation to deionized water increased sodium influx through the gills twofold.

2. Treatment of fish with chelating agents increased sodium outflux, whereas adaptation to deionized water reduced sodium outflux. The effects on outflux do not appear to result from calcium removal.

3. Addition of calcium (2–20 m
M) reversed the effects on influx of chelating agents and of adaptation to deionized water.

4. Magnesium (2–10 m
M) was without significant effect on sodium influx, but increased the outflow in fish adapted to deionized water.
The dependence of plateau currents in cardiac Purkinje fibres on the interval between action potentials
Authors: Hauswirth O. , Noble D. , Tsien R. W.
Published: December 2014

1. The influence of diastolic interval on ionic currents that may determine the action potential duration in cardiac Purkinje fibres was investigated. As the diastolic interval is shortened from about 5 sec, the first effect on the action potential is to reduce and then abolish the notch at the beginning of the plateau.

2. This effect corresponds to the influence of diastolic interval on the magnitude of a transient outward chloride current known as the ‘dynamic current’.

3. Further shortening of the diastolic interval produces a slight shortening of the action potential until intervals less than about 500 msec are used. The action potential then becomes considerably shorter. The ‘time constant’ of decay of this major influence of one action potential on the duration of the subsequent action potential is about 200 msec.

4. This effect corresponds to the time course of decay of an outward (mainly K) current known as ix1.

5. It is shown that variations in the magnitude of ix1 may be responsible for the alternation in action potential duration at the beginning of a train of stimuli known as ‘electrical alternans’.

6. The results in general are consistent with the view that ix1 is the main current involved in determining the interval—duration relation although they cannot exclude the possibility that an inward current with a reavailability time course similar to the decay time course of ix1 might also be involved.
The frequency response of frog muscle spindles under various conditions
Authors: Kirkwood P. A.
Published: December 2014

1. Nerve impulses were recorded from afferents from non‐contracting spindles from the isolated extensor longus dig. IV muscle of the frog during small sinusoidal changes in muscle length at frequencies from 0·001 to 100 Hz. A computer of average transients was used to average the spike distribution during a number of cycles, and hence to determine the spindle response in impulses/sec at different phases of the cycle.

2. At any one frequency the response could be described by a sinusoid, whose amplitude was approximately proportional to the amplitude of the stretch and whose phase was approximately constant, together with a non‐linearity dependent principally upon non‐linearities in the static response.

3. The frequency response was estimated from the sinusoid responses. In conventional terms, it consisted of a straight line of positive slope below 2 Hz and a maximum between 7 and 16 Hz.

4. The slope of the frequency response was dependent on the mean length of the preparation, typically varying from zero to about 0·5 (3 db/octave) over the physiological range of the passive muscle. The shape of the peak appeared to depend on the mean firing frequency.

5. The responses to ramp stretches of one second duration and up to 2 mm in amplitude were also measured. Responses predicted from the sinusoid measurements were the same shape as the measured responses, but were larger by a factor of about 1·4.

6. The shapes of both the frequency responses and the responses to ramps were hardly affected by an operation that removed most of the polar parts of the spindles.

7. The results are discussed in terms of internal spindle mechanisms.
The slowing of gastric emptying by four strong acids and three weak acids
Authors: Hunt J. N. , Knox M. T.
Published: December 2014

1. Test meals of 750 ml. water containing a range of concentrations of hydrochloric, nitric, sulphuric, cyclamic (cyclohexylsulphamic), tartaric,
L‐ascorbic and citric acids were instilled into the stomachs of sixteen healthy subjects.

2. The greater the concentration of an acid in the instilled meal, the greater was the volume of meal recovered after a fixed interval.

3. For the weak acids, tartaric, ascorbic and citric, the concentrations which gave a recovery of 450 ml., out of the 750 ml. instilled, increased with increase in the molecular weight of the acid.

4. For the strong acids, hydrochloric, nitric, sulphuric and cyclamic, the concentrations which gave a recovery of 450 ml., out of the 750 ml. instilled, were approximately equal. These concentrations were less than those for weak acids.

5. The strong acids with high molecular weights were slightly more effective in slowing gastric emptying than were those with low molecular weights.

6. The approximate equality of effectiveness of nitric, sulphuric and cyclamic acids to hydrochloric acid is attributed to the presence of chloride ion in the duodenal contents. Thus all the strong acids instilled produce an environment of hydrochloric acid around the receptor.

7. A model for a duodenal receptor responding to acids is proposed.
The visual evoked potential as a function of contrast of a grating pattern
Authors: Campbell F. W. , Kulikowski J. J.
Published: December 2014

1. It was shown that the potentials evoked by using a grating pattern alternated in phase at 8 Hz is proportional to the logarithm of the supra‐threshold contrast. Other functions were considered, but they did not describe the data so parsimoniously.

2. The same logarithmic function described the results when a grating was simply flashed on and off; therefore, the apparent movement accompanying the phase alternations is not necessary to evoke the potential.

3. The contrast at which the evoked potential reached the theoretically zero voltage (C0) was compared with the psychophysical contrast threshold, determined by means of proportion‐of‐time seen measurements; the C0 contrast corresponded to 50% time seen.

4. The potential, corrected for the proportion‐of‐time seen, was found linearly related to contrast.
Quantitative investigations of the adhesiveness of circulating polymorphonuclear leucocytes to blood vessel walls
Authors: Atherton Anne , Born G. V. R.
Published: December 2014

1. A new simple method is described for quantitating the adhesiveness of circulating polymorphonuclear leucocytes, or granulocytes, to the walls of blood vessels. The cheek pouch of anaesthetized hamsters or a small part of the mesentery of anaesthetized mice were prepared for continuous microscopic observation of selected venules. Those granulocytes which moved sufficiently slowly to be individually visible were counted for 1 or 2 min periods as they rolled past a selected point on one side of a vessel. The velocity distribution of these cells was determined by analysing films. Films were used also to measure mean blood flow velocity in the venules by observing embolizing platelet thrombi induced by the iontophoretic application of adenosine diphosphate. Emigration of granulocytes into the tissues was quantitated by enumerating them in standard areas of stained histological sections.

2. In control experiments with hamster cheek pouch venules, the rolling granulocyte count usually passed through a maximum shortly after the preparation was set up and then fell to a low constant value. In mouse mesentery venules the count remained at a low approximately constant value from the beginning for at least 3 hr.

3. The mean velocity of blood flow in the venules was between 900 and 200 μ/sec. All rolling granulocytes moved much more slowly; in hamster cheek pouch venules the mean velocity was about 20 μ/sec and in mouse mesentery venules about 10 μ/sec. Around these means the velocity distribution of individual cells was narrow.

4. Rolling of granulocytes was abolished by superfusing ethylenediamine tetra‐acetate (EDTA, 0·1
M) suggesting that the phenomenon depends on calcium or magnesium ions.

5. Agents were applied locally to the observed venules. Human serum albumin, trypsin or histamine in high concentrations did not affect the rolling granulocyte count.

6. The rolling granulocyte count was increased during the application of Hammarsten casein or Escherichia coli culture filtrate which are chemotactic to granulocytes in vitro. These agents did not cause alterations in mean blood flow velocity in the observed venules which might have accounted for the effect on the rolling granulocyte counts. When E. coli culture filtrate was perfused through mouse intestine the increase in rolling granulocyte count in the draining venous blood was proportional to the logarithm of the concentration of filtrate.

7. The rolling granulocyte count was also increased by the local application of plasma globulin permeability factor or lymph node permeability factor.

8. Granulocyte counts in standard histological sections showed no significant increases in control preparations but considerable increases following the application of Hammarsten casein.
An electrophysiological demonstration of the axonal projections of single spinal interneurones in the cat
Authors: Jankowska Elżbieta , Roberts W. J.
Published: December 2014

1. Single interneurones excited from group Ia afferents and located in the ventral horn of the spinal cord in the cat were activated antidromically by stimulation of their axons with one micro‐electrode while recording extracellularly close to their somas with a second micro‐electrode. The interneurones studied were those which, according to previous indirect evidence, should mediate the reciprocal Ia inhibition of motoneurones.

2. Two subgroups of these interneurones were studied: those excited from group Ia afferents in the quadriceps (Q) and posterior bicepssemitendinosus (PBSt) nerves. Most of them could be activated from a number of separate loci in the PBSt and Q motor nuclei respectively and from the ventral or lateral funiculi.

3. The location of the axonal branches and the extent of their branching in the motor nuclei were reconstructed by comparing the latencies of the responses and the thresholds (0·1–5 μA) for antidromic activation of single interneurones from different electrode positions in a number of tracks, having previously established the relation between the threshold and the distance from the stimulated fibres. For the main branches in the white matter the conduction velocity was found to be about 70 m/sec.

4. The axonal projections of the investigated interneurones were found to be fully consistent with the hypothesis that they mediate reciprocal inhibition of motoneurones.
Inotropic responses of the left ventricle to changes in aortic arch pressure in anaesthetized dogs
Authors: Hainsworth R. , Karim F.
Published: December 2014

1. Inotropic changes in the left ventricle in chloralose anaesthetized dogs were determined in response to changes in non‐pulsatile pressure perfusing the vascularly isolated aortic arch.

2. Inotropic responses were assessed by measuring the maximum rate of change of left ventricular pressure (dP/dt max) in preparations in which heart rate, mean ascending aortic pressure and brachiocephalic (i.e. carotid sinus and cerebral) perfusion pressure were held constant.

3. dP/dt max increased (average +43%) when aortic pressure was reduced from a level above that which produced maximum depression of the myocardium to a level below which no further responses could be obtained; responses occurred as aortic arch pressure was changed between 250 and 90 mm Hg.

5. In the same preparations changes in the brachiocephalic artery perfusion pressure with aortic arch pressure held constant resulted in similar inotropic responses.

6. It is suggested that aortic arch baroreceptors may be of importance in the control of the inotropic state of the heart.
Ionic fluxes and permeabilities of cell membranes in rat liver
Authors: Claret M. , Mazet J. L.
Published: December 2014

1. Intracellular ion concentrations, measured in rat liver perfused with saline solutions were, at steady state:

[K]1 = 113; [Na]1 = 16·4; [Cl]1 = 25·5 m‐mole l.−1 of cells.

2. Intracellular Cl concentration was measured when both [Cl]o and membrane potential were changed. The experimental values were close to the predicted ones by the Nernst equation, indicating a passive distribution of this ion across the cell membrane.

3. Fluxes were determined by means of radioactive tracers and had the following values:

mK = 6·6; mNa = 12·4 and mCl = 8 × 10−12 mole cm−2 sec−1.

4. When Na was replaced by Li in the perfusing solutions, the Na efflux was decreased by 3·3 × 10−12 mole cm−2 sec−1. This was attributed to a Na‐for‐Na exchange (exchange‐diffusion).

5. A mathematical model was applied to the perfused liver. It allowed estimation of the actual fluxes across the membrane. Corrections resulting from the application of the model remain small.

6. The permeability coefficients were calculated from the passive fluxes and were:

PK = 7·6; PNa = 4·0; PCl = 12·3 × 10−8 cm sec−1, corresponding to relative permeabilities of PNa/PK = 0·52 and PCl/PK = 1·6.

7. The membrane potential calculated from the Goldman equation was significantly different from the measured one. This may be accounted for by an electrogenic activity of the Na—K pump. Applying the Mullins & Noda equation, the ratio of active Na flux to active K flux becomes 3/2.
Effects of sugar and amino acid transport on transepithelial fluxes of sodium and chloride of short circuited rat jejunum
Authors: Munck B. G.
Published: December 2014

1. Using the Ussing Zerahn (1951) technique the relation between short circuit current (Isc) and unidirectional ion fluxes across the short circuited rat jejunum has been examined.

2. These parameters of jejunal function have been measured in absence of sugars and amino acids and at 10 m
M glucose, 28 m
M glucose, 28 m
M galactose and 20 m
M proline. Sulphate has been used as substituent for chloride on both sides of the gut wall and potassium has been used on the serosal side to substitute for sodium. With regard to the effects of proline on Isc and ion fluxes, investigations were made to see whether sulphate and potassium substitutions significantly affected proline transport.

3. The purpose of the study was to examine the Isc seen in sugars and amino acid free conditions and the Δ Isc induced by these substances. Further, it was our purpose to examine the validity of extending to amino acids and sugars in general the suggestion that jejunal transport of these substances stimulates an electroneutral secretion of sodium chloride.

4. In the absence of sugars and amino acids at least two‐thirds of an Isc of 50–70 μA/cm2 are accounted for by a process of chloride secretion located in the deep parts of the epithelium. The remaining one third or less of the Isc can be accounted for in terms of net flux of sodium. The results further indicate that a state of hypoxia in the deep part of the epithelium is the cause of the very low Isc, p.d. on electrical resistance usually found for sacs of everted rat jejunum.

5. The increase in Isc induced by proline and glucose is best accounted for by the simultaneously induced increase in mucosa to serosa flux of sodium. There is no compelling evidence that proline should increase Isc by a stimulation of chloride secretion.

6. Proline, glucose (and galactose) stimulate unidirectional fluxes of sodium and chloride. The effects on serosa to mucosa fluxes equal or exceed those on mucosa to serosa fluxes. The effect of proline on mucosa to serosa flux of thiourea exceeds by far that on serosa to mucosa flux. This and the effects of potassium and sulphate substitution lead to the conclusions in (7) and (8).

7. Transport of sugars and amino acids induces or stimulates in rat jejunum in vitro an electroneutral secretion of sodium chloride.

8. This effect suffices to explain why, in spite of marked increases in Isc, increments in net flux of sodium are not induced by transport of proline and glucose. It also explains why the effects of sugar and amino acid transport on water transport in vitro are much less than in vivo.
The uptake and hydrolysis of p‐nitrophenyl phosphate by red cells in relation to ATP hydrolysis by the sodium pump
Authors: Cotterrell D. , Whittam R.
Published: December 2014

1. The hydrolysis of p‐nitrophenyl phosphate has been studied in human red cells, ghosts and haemoglobin‐free membranes to see whether hydrolysis was related to the functioning of the sodium pump.

2. The cell membrane restricted p‐nitrophenyl phosphate entry into cells and was rate‐limiting for hydrolysis by the large amount of intracellular soluble phosphatase. The uptake was inversely proportional to the external chloride concentration, and inhibitors (phloretin and persantin) of inorganic phosphate uptake also reduced p‐nitrophenyl phosphate uptake and hydrolysis. The entry mechanism of p‐nitrophenyl phosphate appears to be similar to that of inorganic phosphate.

3. p‐Nitrophenyl phosphate was hydrolysed in cells almost entirely by ouabain‐insensitive phosphatases, both soluble and membrane bound. In ghosts containing less soluble enzyme than cells there was still no component of p‐nitrophenyl phosphate hydrolysis that was related to the sodium pump in being sensitive to external potassium or ouabain.

4. Haemoglobin‐free membranes lacking soluble p‐nitrophenyl phosphatase required potassium for optimum p‐nitrophenyl phosphate hydrolysis and this part was inhibited by ouabain as was also ATP hydrolysis by the sodium pump. The rates of potassium‐dependent and potassium‐independent hydrolysis were each increased about threefold on decreasing the electrolyte concentration from 150 to 25 m
M. The response was found whether the main electrolyte was potassium chloride, sodium chloride, choline chloride or Tris chloride. In contrast, the changes were not found when the osmotic pressure was varied to the same extent with non‐electrolytes. p‐Nitrophenyl phosphate hydrolysis was thus activated on lowering the ionic strength. The soluble enzyme was similarly affected and the effect was reversible.

5. The membrane ATPase activity was unaffected by the changes in ionic strength which markedly altered p‐nitrophenyl phosphate hydrolysis.

6. These results with red cell membranes show that the ionic strength under physiological conditions largely prevents the hydrolysis of p‐nitrophenyl phosphate, but not of ATP. A possible mechanism is discussed in terms of the effect of different structures of water in electrolyte and non‐electrolyte solutions on the enzymic activity of the sodium pump.
Mechanical response with reversed electrical response to noradrenaline by Ca‐deprived arterial smooth muscle
Authors: Keatinge W. R.
Published: December 2014

1. When sheep carotid arteries had become electrically active after 30 min in Ca‐free saline, noradrenaline 0·1 m
M caused almost as much contraction as it did with Ca 1·25 m
M present; it also caused slight electrical depolarization, usually with increased spike frequency, followed by electrical quiescence.

2. In Ca‐free saline with EDTA the arteries became profoundly depolarized, and their mechanical responses greatly reduced, within a few minutes. The mechanical responses to noradrenaline that remained were accompanied by electrical repolarization or, after longer periods in EDTA, by no electrical change.

3. This residual mechanical responsiveness to noradrenaline, always tested at 36° C, declined on average 26 times as rapidly during exposure to EDTA at 36° C as at 5° C and was not reduced by increasing the concentration of EDTA from 1·25 to 12·5 m
M. This temperature‐sensitivity was significantly too high to be explained by a diffusion‐limited process.

4. The results suggest that most of the tissue Ca responsible for contractility in simple Ca‐free saline was either free in the extracellular space or in cellular stores that were discharged within a few minutes when free extracellular Ca was removed. They also indicate a small resistant Ca store which did not communicate with the exterior by diffusion, and part of which noradrenaline could utilize for contraction by means not dependent on depolarization conducted from the cell membrane.
Changes in plasma volume and protein content during exposures of working men to various temperatures before and after acclimitization to heat: separation of the roles of cutaneous and skeletal muscle circulation
Authors: Senay L. C.
Published: December 2014

1. Ten male subjects were trained in stair stepping for 2 weeks. Group A (six subjects) was thereupon sequentially exposed for 45 min to dry bulb temperatures of 20, 40 and 30° C, a vapour pressure of 10–11 mm Hg and a wind speed of 1 m/sec in a climate tunnel. While temperature changes were being effected the subjects rested in an antechamber. Group B (four subjects) was exposed to a sequence of 40, 20 and 30° C. Work rate was the same for all subjects, i.e. 216 kg m/min (≃ to an oxygen consumption of 0·9 l./min). Duplicate experiments were run on both groups of subjects before and after acclimatization to heat.

2. Throughout, periodic samples of venous blood, water and protein movement into or out of the extravascular compartment was assessed during exercise periods wherein blood flow was increased to exercising muscles (Group A, 20° C) or to both exercising muscles and skin (Group B, 40° C; Groups A and B, 30° C.)

3. Mild exercise in a cool environment before and after acclimatization to heat was accompanied by expansion of the vascular volume and an increase in the amount of circulating protein.

4. Mild exercise in a warm environment for 45 min was accompanied by haemoconcentration and loss of protein from the vascular volume before subjects were heat acclimatized. The results were reversed following heat acclimatization; i.e. exposure of Group B to 40° C and of Groups A and B to 30° C was accompanied by haemodilution and addition to (or maintenance of) plasma protein concentration.

5. Effects of heat acclimatization on exposure of Group A to 40° C were also noted.

6. The effects of heat acclimatization were ascribed to:

(a) a change in permeability of cutaneous capillaries to large molecules,

(b) an increased availability of translocatable protein within cutaneous interstitial spaces, and

(c) a combination of both a and b.

7. Further, the results supported a previous suggestion that addition or loss of water and protein from the vascular volume is dependent on the ratio of cutaneous to muscle blood flow.
Studies on the mechanism of action of angiotensin on ion transport by kidney cortex slices
Authors: Munday K. A. , Parsons B. J. , Poat Judith A.
Published: December 2014

1. A study has been made of the effects of cyclic AMP, phosphodiesterase inhibitors and protein synthesis inhibitors on the response of rat kidney cortex slices to physiological doses of angiotensin.

2. The additions of cyclic AMP, dibutyryl cyclic AMP and/or phosphodiesterase inhibitors to the incubation medium (conditions which would be expected to increase intracellular cyclic AMP levels) were without effect on sodium or potassium transport by kidney slices.

3. Actinomycin D (an inhibitor of the transcription stage of protein synthesis), at concentrations which inhibit RNA synthesis by 75%, has no effect on either control or angiotensin stimulated sodium transport.

4. Cycloheximide or puromycin (inhibitors of the translation stage of protein synthesis), at concentrations which inhibit protein synthesis by 70–80%, have no effect on control sodium and potassium transport by kidney slices, but completely block the angiotensin stimulation of these processes.

5. These findings are discussed in relation to the possible involvement of cyclic AMP and protein synthesis in the mechanism of action of angiotensin on kidney sodium and potassium transport.
The temperature sensitivity of the Type I slowly adapting mechanoreceptors in cats and monkeys
Authors: Duclaux Roland , Kenshalo Dan R.
Published: December 2014

1. The sensitivity of Type I slowly adapting mechanoreceptors in cat and monkey skin to temperature and changes in temperature was investigated.

2. Multiple receptors innervated by a single axon appeared to be more frequent in the monkey than in the cat skin.

3. The responses of these receptors to thermal stimulation at static skin temperatures from 27 to 40° C were similar in cats and monkeys. At 43° C the monkey receptors showed a higher steady‐state activity than the cat receptors.

4. A maximum steady‐state frequency of 5·5 impulses/sec occurred in both the cat and monkey receptors at a static skin temperature of 37° C.

5. The maximum dynamic response to cooling occurred at a skin temperature of 40° C. The response was near its maximum at 2° C cooling and increased but little with further increases in the intensity of cooling.

6. Dynamic responses to cooling disappeared after the skin had been heated to 51° C for 35 sec and to mechanical stimulation after heating to 53° C for 35 sec. Excitation by either mechanical or thermal stimulation did not reappear within 1–2 hr.

7. The response characteristics of the Type I slowly adapting mechanoreceptors to temperature and temperature changes differ from those of specific cold receptors.
The statistical nature of the acetylcholine potential and its molecular components
Authors: Katz B. , Miledi R.
Published: December 2014

1. When a steady dose of acetylcholine (ACh) is applied to an end‐plate, the resulting depolarization is accompanied by a significant increase in voltage noise.

2. The characteristic properties of this ACh noise (amplitude and time course) are examined under various experimental conditions. The voltage noise is analysed on the assumption that it arises from statistical fluctuations in reaction rate, and in the frequency of the elementary current pulses (‘shot effects’) produced by the action of ACh molecules.

3. The elementary ACh current pulse (amplitude approximately 10−11 A), arises from a conductance change of the order of 10−10 Ω−1 which lasts for approximately 1 ms (at 20° C), and produces a minute depolarization, of the order of 0·3 μV. It is associated with a net charge transfer of nearly 10−14 C, equivalent to approximately 5 × 104 univalent ions.

4. At low temperature, and during chronic denervation, the duration of the elementary current pulse increases, and the elementary voltage change becomes correspondingly larger.

5. Curare has little or no effect on the characteristics of the elementary event.

6. A comparative study of ACh and carbachol actions shows that carbachol produces considerably briefer, and therefore less effective, current pulses than ACh.
Pancreatic acinar cells: measurement of membrane potential and miniature depolarization potentials
Authors: Dean P. M. , Matthews E. K.
Published: December 2014

1. Intracellular recordings of membrane potentials have been made in vitro from the exocrine acinar cells of the mouse pancreas using glass micro‐electrodes.

2. The mean membrane potential of the acinar cells was −41·2 mV. Spontaneous miniature depolarization potentials of 0·5–5·0 mV amplitude and occurring at random intervals were often observed superimposed upon the resting membrane potential. Atropine 2·8 × 10−6
M decreased, and physostigmine 1·23 × 10−5
M increased, the frequency and amplitude of the miniature potentials.

3. Electrical stimulation of the pancreatic nerves depolarized the acinar cells. Acetyl β‐methylcholine 10−6
M produced a sustained depolarization. Atropine 1·4 × 10−6
M blocked the depolarization to both electrical stimulation and acetyl β‐methylcholine.

4. Pancreozymin depolarized the exocrine acinar cells but secretin did not.

5. These results suggest that the miniature depolarization potentials are of cholinergic origin and that depolarization of the pancreatic exocrine cells by nerve stimulation or pancreozymin may trigger secretion.
Oxygen consumption by the component layers of the cornea
Authors: Freeman Ralph D.
Published: December 2014

1. The structural integrity of the cornea is maintained by an active fluid transport system which depends on metabolism. Experiments were designed to establish the respiratory activity of each corneal layer.

2. A rapid micropolarographic technique was used to determine the oxygen consumptions of the individual layers of the rabbit cornea.

3. Inherent problems of the determinations have been made minimal by the use of both denuded and whole corneal tissue preparations. Four independent measures were obtained for each limiting layer (epithelium and endothelium).

4. Results show that the endothelium, epithelium and stroma use 21, 40 and 39% respectively of the total oxygen consumption of the cornea. On the basis of volumes of oxygen per unit volume tissue, epithelial oxygen utilization is about ten times that of the stroma and approximately 0·2 that of the endothelium.

5. The endothelium has a larger oxygen uptake than previously reported.

6. The present results, in conjunction with other studies, indicate that the ratio of glycolytic to oxidative activity in the rabbit cornea is 0·87:0·13.
The decline of potassium permeability during extreme hyperpolarization in frog skeletal muscle
Authors: Almers W.
Published: December 2014

1. The voltage‐clamp technique was used to separate the effects of K depletion in the T‐system from the decline in K permeability during hyperpolarization, and to characterize the time‐ and voltage‐dependence of the latter.

2. K permeability due to the inward rectifier can be described as being proportional to a parameter which diminishes when the membrane is hyperpolarized beyond −120 mV. The parameter obeys first‐order kinetics. At 24° C, it can change with a time constant of 49 msec at −150 mV and 25 msec at −65 mV. At −200 mV the fall in membrane conductance due to the permeability change is to 30% of its initial value. The Q10 for the rate of conductance change at that potential is about 2·8.

3. It is estimated that K inward current can lower the average K concentration in the T‐system by more than 50%, and that, on the average, the space enclosed by the T‐system should be less than 0·8% of the fibre volume. Assuming the T‐system space to be 0·3% of the fibre volume, it is calculated that on the average, and during hyperpolarization to about −150 mV, no more than 20% of the initial current should flow across the surface membrane.