bluuebunny/crossref_metadata_2025 huggingface dataset:
Some properties of the smooth muscle of rabbit portal vein
Authors: Holman Mollie E. , Kasby C. B. , Suthers M. B. , Wilson Jane A. F.
Published: December 2014

1. The morphology of the smooth muscle of the rabbit portal vein and its innervation were studied with fluorescence and electron microscopy. Two layers of smooth muscle were observed in the tunica media: an inner layer of circularly arranged muscle cells and an outer layer consisting of bundles of smooth muscle cells arranged in a near longitudinal direction. The membranes of neighbouring smooth muscle cells were occasionally fused to form ‘tight junctions’.

2. Bundles of non‐myelinated nerve fibres were observed in the adventitia, and between bundles and layers of smooth muscle cells in the media. Studies on longitudinal sections with fluorescence microscopy revealed a network of varicose noradrenergic axons.

3. Electrical and mechanical activity was recorded from longitudinal strips of smooth muscle from the media of the vein with a sucrose‐gap apparatus.

4. The preparation was spontaneously active under minimal resting tension (less than 150 mg) and at temperatures above 28° C. Slow depolarizations led to a burst of spikes (multi‐spike complexes), which corresponded to rhythmic contractions. In 10% of preparations, the interval between multi‐spike complexes showed a slower depolarization, suggesting the record was from a pace‐maker region.

5. The frequency of spontaneous activity (3‐27 beats/min) was very sensitive to changes in temperature and tension.

6. Noradrenaline in low doses (0·01 μg) caused an increase in frequency of the multi‐spike complexes. Higher doses (0·1‐0·3 μg) initiated continuous high‐frequency spiking, while very high doses (0·6‐2·0 μg) caused maintained depolarization.

7. Responses to repetitive electrical stimulation of the vein were qualitatively similar to those in response to exogenous noradrenaline. The relation between the mechanical response and the various parameters of stimulation was consistent with the stimulation of sympathetic nerve fibres in the wall of the vein.

8. The actions of isoprenaline, phentolamine and propranolol indicated the presence of α ‘excitatory’ and β ‘inhibitory’ adrenotrophic receptors on the smooth muscle.
Water and electrolyte secretion by the perfused pancreas of the cat
Authors: Case R. M. , Harper A. A. , Scratcherd T.
Published: December 2014

1. A technique is described for perfusing the isolated cat pancreas with saline solutions.

2. Single doses of secretin, although present in the perfusate for only a short time, caused a prolonged flow of pancreatic juice.

3. In response to continuous secretin infusion, the preparation secreted for up to 6 hr a juice which was similar to that obtained in vivo, with the exception that the bicarbonate concentration decreased and the chloride concentration increased with time, even when the rate of secretion remained constant.

4. The osmolalities of perfusate and secretion were identical over a range of 450 m‐osmoles/kg, but the electrolyte concentration of the secretion was always slightly higher than that of the perfusate. Variations from perfusate isosmolality produced inverse changes in the secretion rate, over the range from 600 m‐osmoles/kg, at which secretion ceased, to 150 m‐osmoles/kg, at which the rate was highest. At perfusate osmolalities below 150 m‐osmoles/kg secretion rapidly declined.

5. Reduction in perfusate sodium chloride concentration, isosmolality being maintained with sucrose, caused a fall in secretion rate, but the sodium concentration of the juice remained constant until perfusate sodium concentration was reduced to about 70 m‐equiv/l. Below this level it declined and sucrose was detected in the juice in quantities almost sufficient to account for the equiosmolality of juice and perfusate.

6. Two hypotheses about the mechanism of water and electrolyte secretion by the pancreas are presented.
The dependence on external cations of the oxygen consumption of mammalian non‐myelinated fibres at rest and during activity
Authors: Rang H. P. , Ritchie J. M.
Published: December 2014

1. A study has been made of the effect of potassium and other cations on the oxygen consumption of rabbit desheathed vagus nerves at rest and during activity.

2. In normal Locke solution (containing 5·6 m
M‐K) the resting oxygen consumption, Qr, was 0·0903 μmole/g wet wt. min. The extra oxygen consumed as a result of stimulation, Qs, at 3 stimuli/sec was about 600 p‐mole/g.impulse; at 30 stimuli/sec it was less, being 240 p‐mole/g.impulse.

3. Only a fraction of Qr (18% at 5·6 m
M‐K) was sensitive to ouabain (1 m
M). The ouabain‐sensitive component, however, increased as the external potassium concentration was increased, in the range 0‐100 m
M. Qs was virtually abolished by ouabain.

4. Reduction of the external potassium concentration from 5·6 m
M to zero reduced Qr (by 10%) and increased Qs, but the changes were scarcely significant statistically.

5. The conclusions were drawn: that Qs reflected the pumping of cations to restore the ionic imbalance following activity, particularly reflecting the extrusion of sodium ions from the fibre; that this pumping was normally absolutely dependent on the presence of potassium externally and that no pumping could occur in its absence; and that Qs was not reduced to zero in ostensibly potassium‐free solutions because enough potassium was released into the periaxonal space during activity to maintain pumping.

6. Thallium, rubidium, caesium and lithium could replace potassium and allowed pumping to occur.
Onset of and recovery from diving bradycardia in ducks
Authors: Butler P. J. , Jones D. R.
Published: December 2014

1. No evidence was found of a ‘postural reflex’ in ducks. Neither the position of the head nor the water temperature affected the cardiac response to diving.

2. In ducks with access to air through a tracheal cannula, submersion did not invariably cause apnoea until the water level reached the glottis. Heart rate was closely related to respiratory frequency, and bradycardia did not occur during submersion unless there was a reduction in respiratory frequency or a cessation of ventilation altogether.

3. When apnoea and bradycardia did occur during submersion, the first inspiration upon surfacing was 2‐3 times larger than normal and was accompanied by an instantaneous rise in heart rate.

4. Atropinization or cold block of the vagus abolished diving bradycardia. Only one vagal trunk was involved in cardiac chronotropic control at any one time. This vagal trunk also appeared to be more important in control of respiratory frequency.

5. β‐adrenergic receptor blockade did not affect either diving bradycardia or post‐dive tachycardia.

6. The results show that the cardiac chronotropic response both during and after submergence is controlled solely by changes in parasympathetic vagal activity.
Rhythmical and non‐rhythmical spontaneous activity recorded from the central cut end of the sinus nerve
Authors: Biscoe T. J. , Sampson S. R.
Published: December 2014

1. Two types of spontaneous nervous activities have been recorded from the central cut end of the carotid sinus nerve of the cat.

2. One type was composed of nerve potentials that exhibited a respiratory or cardiac rhythm, whose rate of firing was depressed by the pressor response to adrenaline, and that were found to arise from post‐ganglionic fibres of the superior cervical ganglion.

3. The other type of activity consisted of non‐rhythmical nerve potentials whose rate of discharge increased 10‐30 sec after the injection of adrenaline. The activity of these fibres also increased when the arterial oxygen tension was lowered or when the arterial carbon dioxide tension was raised.

4. It is conceivable that either of these two groups of fibres, rather than the chemoreceptor afferent fibres, could provide the source of the microvesicle‐containing nerve endings on the type 1 cells of the carotid body.

5. A nerve was also described coursing from the sinus nerve to the hypoglossal nerve; the activity in it was sympathetic in origin.
The sensations produced by electrical stimulation of the visual cortex
Authors: Brindley G. S. , Lewin W. S.
Published: December 2014

1. An array of radio receivers, connected to electrodes in contact with the occipital pole of the right cerebral hemisphere, has been implanted into a 52‐year‐old blind patient. By giving appropriate radio signals, the patient can be caused to experience sensations of light (‘phosphenes’) in the left half of the visual field.

2. The sensation caused by stimulation through a single electrode is commonly a single very small spot of white light at a constant position in the visual field; but for some electrodes it is two or several such spots, or a small cloud.

3. For weak stimuli the map of the visual field on the cortex agrees roughly with the classical maps of Holmes and others derived from war wounds. With stronger stimuli, additional phosphenes appear; these follow a map that is roughly the classical map inverted about the horizontal meridian.

4. The phosphenes produced by stimulation through electrodes 2·4 mm apart can be easily distinguished. By stimulation through several electrodes simultaneously, the patient can be caused to see predictable simple patterns.

5. The effects of the duration and frequency of stimulating pulses on the threshold have been explored.

6. For cortical phosphenes there is no sharp flicker fusion frequency, and probably no flicker fusion frequency at all.

7. During voluntary eye movements, the phosphenes move with the eyes. During vestibular reflex eye movements they remain fixed in space.

8. Phosphenes ordinarily cease immediately when stimulation ceases, but after strong stimulation they sometimes persist for up to 2 min.

9. Our findings strongly suggest that it will be possible, by improving our prototype, to make a useful prosthesis.
Firing patterns of gastrocnemius motor units in the decerebrate cat
Authors: Burke R. E.
Published: December 2014

1. The patterns of medial gastrocnemius (MG) motor unit firing in response to MG muscle stretch have been studied in decerebrate cats, using intracellular recording techniques. In most of the units, the motoneurone axonal conduction velocity and cell input resistance were measured, and the maximum amplitude and wave form of the group Ia composite EPSP evoked by MG nerve stimulation were determined. The mechanical properties of the muscle unit portion of each motor unit were also studied.

2. Motor unit firing patterns were classified into two groups, ‘tonic’ and ‘phasic’. With few exceptions, tonic motor units showed sustained firing throughout MG stretches of varying duration, while most phasic units did not fire at all to the same stimulus. Tetanization of the afferents did not convert any of the previously phasic units to tonic firing.

3. MG motor units in this study were divided into three groups on the basis of the muscle unit twitch properties. Units with short twitch time to peak values (< 35 msec) were subdivided into two groups according to twitch tension output: (a) type F, with twitch tension > 1·5 g, and (b) type F*, with twitch tension < 1·5 g. Units with slow twitch time to peak (> 35 msec) were classified as type S.

4. The presence or absence of tonic firing during sustained MG stretch was found to be significantly related to the following factors: (a) the motor unit twitch type, in that tonic firing was observed in 100% of type S, 70% of type F*, and only 10% of type F units; (b) the apparent motoneurone size, in that tonic units tended to have higher cell input resistance values and slower axonal conduction velocities than phasic units; and (c) the density and spatial organization of the group Ia synaptic input, in that the MG monosynaptic EPSPs found in tonic motor units tended to be both larger in amplitude and longer in duration than those found in phasic units.

5. The intrinsic properties of MG motor units, the characteristics of the group Ia synaptic input to the motoneurones and the unit firing patterns elicited by MG muscle stretch appear to be mutually interrelated, forming a pattern of motor units within the MG pool which is analogous to the pattern thought to characterize the motor units belonging to ‘slow’ and ‘fast’ muscles. In most respects this pattern of MG motor units appears to be a continuum without clearly separable subgroups.
The contribution of the arterial chemoreceptors to the stimulation of respiration by adrenaline and noradrenaline in the cat
Authors: Joels N. , White H.
Published: December 2014

1. Intravenous infusions of adrenaline and noradrenaline in doses averaging 0·8 μg/kg.min increased the respiratory minute volume of anaesthetized cats breathing room air. The mean increase in respiratory minute volume was 14% during adrenaline infusion and 8% during noradrenaline infusion.

2. In a small group of decerebrate cats infusions of adrenaline and noradrenaline increased ventilation by 19 and 27% respectively.

3. Intravenous catecholamine infusions also increased the respiratory responses of anaesthetized animals to the inhalation of 5% or 10% O2 in N2 and to the inhalation of 5% CO2 in air.

4. Adrenaline and noradrenaline infusions had no significant effect on the ventilation of animals breathing 100% O2, nor did they significantly alter the respiratory response to the inhalation of 5% CO2 in O2.

5. After section of the carotid sinus and aortic nerves, a blood‐pressure compensator being used to minimize changes in arterial pressure, catecholamines had no effect on the respiration of cats breathing air.

6. An increase in carotid body chemoreceptor discharge accompanied the increase in ventilation during catecholamine infusion.

7. Intravenous catecholamine infusions still produced an increase in ventilation and carotid body chemoreceptor discharge after both aortic nerves and both cervical sympathetic nerves had been cut.

8. Intra‐arterial infusions into one carotid artery of 0·2 μg/kg.min of adrenaline or 0·1 μg/kg.min of noradrenaline led to mean increases in respiratory minute volume of 9·9 and 11·5% respectively. No increase occurred after section of the corresponding carotid sinus nerve. Such infusions also evoked an increase in carotid body chemoreceptor discharge.

9. It is concluded that the hyperpnoea produced by adrenaline and noradrenaline infusions in the cat is predominantly reflex in origin and is mediated by the arterial chemoreceptors.

10. The increase in ventilation produced by adrenaline appears to have a component additional to its effect upon the chemoreceptors though the nature of this action has not been identified.
The response to stretch of muscle spindle afferents of baboon's tibialis anticus and the effect of fusimotor stimulation
Authors: Koeze T. H.
Published: December 2014

1. Systematic studies of the response of baboon's tibialis anticus muscle spindles to stretch were undertaken. Most of the spindle afferents studied had conduction velocities between 72 and 78 m/sec with a range from 39 to 93 m/sec. There was no clear bimodality in the histogram of the conduction velocity. Measurements were made of the axon diameters of the nerve to tibialis anticus. The largest number of the larger axons had diameters from 11 to 13 μ. The largest axon diameter measured 17 μ and there were very few of these.

2. The dynamic index for any given afferent tended to be greater for the more rapidly conducting afferents and lower for the more slowly conducting afferents. However, a statistically significant regression line of this relationship could only be drawn for a stretch velocity of 64 mm/sec.

3. The spindle afferent response to stretch was studied from different muscle lengths. It was found that the velocity sensitive portion of the response to phasic stretch decreased when the stretch extended up to or beyond the maximum physiological length of the muscle.

4. Dynamic and static fusimotor fibres were isolated. The response of the spindle afferent to stretch, while the dynamic fusimotor fibre was being stimulated, was the same as that reported for the cat by P. B. C. Matthews (1962). During static fusimotor stimulation the response of the spindle afferent to stretch was usually like that reported for the cat. In a single case, however, static fusimotor stimulation resulted in a lowering of the peak frequency of the response of the spindle afferent to the phasic portion of stretch.
Slow inactivation of currents in cardiac Purkinje fibres
Authors: Reuter H.
Published: December 2014

1. When membrane currents, associated with repolarization to the holding potential, were measured in cardiac Purkinje fibres after depolarizing voltage clamp steps to the plateau level of the action potential (‐20 to ‐10 mV), tails of inward current were observed which turned into outward current. Amplitude and duration of the tails of inward current increased when the preceding depolarization was progressively shortened. This current could only be recorded in Na‐containing solution which strongly supports the view that the inactivation of sodium conductance (gNa) has a slow and incomplete component.

2. Initial outward current (most probably chloride current (ICl)) during strong depolarization (beyond ‐20 mV) could be inactivated either by increasing the frequency of depolarizations or by applying a conditioning depolarizing prepulse.

3. In Na‐free solution a small, slowly decreasing inward current was recorded. This is most probably carried by calcium ions and is at least partly responsible for the negative conductance of the current—voltage relation in the voltage range ‐60 to ‐30 mV.

4. If a strong conditioning depolarization (V1) to the inside positive potential range preceded repolarizing clamp steps to different membrane potentials (V2) inward current (probably calcium current (ICa) could be activated in Na‐free and Na‐containing solutions. This current depended on the duration of V1 as well as on the potential level of V2. After the maximum inward current, increasing outward current occurred when the duration of V1 was increased. This current could be explained either by an inactivation of calcium conductance (gCa) with time or by a very slow activation of an additional outward current.

5. The main conclusions from these experiments are that (i) slow and incomplete inactivation of gNa are important features for the plateau of the action potential and (ii) calcium ions carry additional charge during this phase of the action potential. Chloride conductance (gCl) should be largely inactivated at a heart rate of 90/min.
Sodium fluxes in diaphragm muscle and the effects of insulin and serum proteins
Authors: Creese R. , Jenden D. J.
Published: December 2014

1. Thin diaphragm muscles in dialysed serum maintained their total sodium at values similar to those found in vivo. The fibre sodium exchanged with a half‐time of 5 min, and the flux was 10 p‐mole.cm−2.sec−1. The internal sodium was less than 10 μmoles/g fibre water and the ratio of external to internal sodium was at least 15. The calculated energy expenditure for sodium extrusion was less than 2% of the resting metabolism.

2. In physiological saline the half‐time for exchange of fibre sodium was similar to that in serum, but in saline there was an increase in sodium permeability and a raised total and fibre sodium.

3. Muscles treated with insulin (0·02 u./ml.) showed a more rapid exchange of sodium compared with muscles in saline, with no change in the permeability to sodium. Insulin also affected sodium movements in the absence of external glucose.

4. In saline the fraction of sodium which exchanged rapidly occupied 0·33 by volume of the muscle, after corrections for diffusion, and this value was similar to the mannitol space.

5. Fibre diameters were measured in frozen sections. Muscles prepared by fixation and embedding showed marked shrinkage.
A down then up staircase in frog ventricle due to altered excitation—contraction coupling
Authors: Brown A. M. , Orkand R. K.
Published: December 2014

1. Repetitive stimulation of frog ventricle strips bathed in low calcium (< 1m
M) fluids produced a decrease followed by an increase in successive tension responses which was not due to changes in the amplitude or the duration of the cardiac action potential.

2. The depression of contraction reached its peak 5‐10 sec after a conditioning contraction and decayed to one half in about 0·5 min; it was greater during a series of 5‐10 stimuli when the frequency was increased from 3/min to 12/min.

3. Lowering the external calcium concentration increased the amount of depression.

4. The initial depression could be converted to facilitation by: (a) increasing the external calcium; (b) lowering the external sodium; (c) lowering the external potassium; and (d) the addition of strophanthidin.
The constancy of the energy expended by rats on spontaneous activity, and the distribution of activity between feeding and non‐feeding
Authors: Morrison S. D.
Published: December 2014

1. Methods were developed and described for partitioning the total daily energy expenditure of rats into compartments attributable to rest, total spontaneous motor activity and feeding activity.

2. In terms of energy expenditure feeding appeared as a form of motor activity which was at least as costly as other spontaneous activity.

3. The compartment attributable to total spontaneous activity within a 24 hr period was about 25% of total energy expenditure and was not altered by body weight, food intake or feeding mode (e.g. solid or liquid food).

4. The compartment attributable to feeding activity varied with food intake and with feeding mode in such a way that non‐feeding activity varied inversely with feeding activity. By a given feeding mode non‐feeding activity varied inversely with food intake.

5. It is concluded (a) that food deprivation does not induce increased total activity by the rat, but does produce a complementary increase in non‐feeding activity; (b) that measurement of a specific motor activity does not give a valid estimate of change in total activity; and (c) that the complementary relationship between the energy expended on feeding activity and that expended on non‐feeding activity is responsible for the decline in food intake with increasing non‐feeding activity that has been shown to occur at low habitual levels of spontaneous activity.
Thermal studies of the rates of the reactions of carbon dioxide in concentrated haemoglobin solutions and in red blood cells. A. The reactions catalysed by carbonic anhydrase. B. The carbamino reactions of oxygenated and deoxygenated haemoglobin
Authors: Kernohan J. C. , Roughton F. J. W.
Published: December 2014

1. The initial rates of uptake of carbon dioxide by bovine Hb and HbO2, in solutions and in intact red cells at 25° C, pH 6·8‐7·4, have been measured by the continuous flow rapid calorimeter in the presence and absence of the carbonic anhydrase inhibitor acetazolamide.

2. Over the time range 0‐10 msec the only significant reaction, in the presence of acetazolamide, was the carbamino combination of CO2. In the absence of acetazolamide there was a much larger heat evolution owing to the simultaneous catalysis of CO2 to bicarbonate due to the enzyme, carbonic anhydrase. Subtraction of the former rate from the latter gives the catalysis of the CO2 hydration per se. The mode of calculating the actual amount of chemical change from the observed heat evolution is described in detail.

3. The carbonic anhydrase activity was found to vary about threefold between individual blood samples, as in previous work on dilute bovine enzyme solutions, but to be independent of the state of oxygenation of the haemoglobin. Comparison of the enzyme activity in solution and in the red cell seemed to show a discrepancy of the order of 30% in favour of the latter when approximate allowance was made for the difference of pH and Cl− content in the two cases. This 30% difference might be reduced if exact corrections could be applied.

4. No significant difference was observed between the rates of the carbamino CO2 reactions in concentrated Hb solutions and red cell suspensions, provided that approximate allowance was made for differences of pH in both cases.

5. The rate of carbamino combination with Hb appeared to be about twice that with HbO2 at the same pH. Possible explanations for this difference are discussed.
Mammary and whole animal metabolism of glucose and fatty acids in fasting lactating goats
Authors: Annison E. F. , Linzell J. L. , West C. E.
Published: December 2014

1. Measurements were made of milk yield, mammary blood flow and mammary arteriovenous differences during the measurement of substrate entry rate by the isotope dilution method using [U‐14C]glucose, acetate, palmitate, stearate or oleate in conscious lactating goats after 24 hr starvation.

2. As previously reported, in fasting, milk yield fell to 40 ± 3·4 (
S.E.)%, lactose secretion to 31 ± 3·4%, milk fat secretion to 81 ± 6·7% and mammary blood flow fell to 53 ± 7·5% of the values before fasting. Mammary O2 uptake was only 45 ± 5% of the mean value in fed animals and there were marked falls in the uptakes of glucose, acetate and triglycerides, a smaller fall in β‐hydroxybutyrate uptake, and a large increase in free fatty acid uptake.

3. Glucose was found to enter the circulation of the fasting animal at 1‐1·6 mg/min/kg body wt. (entry rate) and it gave rise to 3‐5% of the total CO2. The udder took up 10·7‐16·1 mg/min/kg of tissue and 8‐10% of mammary CO2 was derived from glucose, although only 5‐10% was oxidized. Mammary uptake accounted for 35‐43% of the total glucose entering the circulation.

4. In the whole animal acetate entry rate was 1‐1·4 mg/min/kg and 9‐10% of total CO2 was derived from it. The udder used 0·8‐2·4 mg/min/kg of tissue and 9‐13% of mammary CO2 was derived from acetate, 46‐79% of that taken up being oxidized. Mammary uptake accounted for only 2‐6% of the total acetate entry rate. Negligible quantities of isotope were found in milk fatty acids and there was a fall in the proportion of milk fatty acids of chain length up to C14 which in fed animals are synthesized from acetate and β‐hydroxybutyrate.

5. Palmitate, stearate and oleate entered the circulation as free fatty acids at 0·94‐6·8 mg/min/kg and 6‐9% of total CO2 was derived from each. The udder took up 3·0‐5·7 mg/min/kg of tissue and 4‐8% of mammary CO2 was derived from each acid. In the udder 8 and 5·5% of stearate and oleate were oxidized and 25% of palmitate. Mammary uptake of stearate was 31·5% of the total entry rate, palmitate 1%, and oleate 7·5%. Only long chain milk fatty acids were labelled.

6. During fasting the mammary
R.Q. was 0·85 ± 0·045 compared with a value in fed animals of 1·24 ± 0·02, when the udder is synthesizing fatty acids from acetate. The total mammary uptake of lipid precursors was only 74% of the rate of milk fat secretion and there was an 18% shrinkage in empty udder volume, suggesting the use of endogenous mammary tissue substrates.
The after‐effects of repetitive stimulation on the isometric twitch contraction of rat fast skeletal muscle
Authors: Close R. , Hoh J. F. Y.
Published: December 2014

1. The peak tension and time course of isometric twitch contractions of rat extensor digitorum longus muscle in vitro (35° C) have been measured at various stages of potentiation following repetitive stimulation at 20 c/s and 300 c/s.

2. Potentiation of the peak twitch tension increases with an increase in the number of repetitive stimuli up to a maximal level of about 1·9 times the control value. The relation between potentiation and numbers of stimuli is dependent on the frequency of stimulation.

3. Potentiation of peak twitch tension is maximal shortly after the end of repetitive stimulation and subsequently decays exponentially at a rate which is dependent on the number of stimuli in the train and the frequency of stimulation.

4. Short trains of stimuli bring about nearly maximal potentiation with little or no change in contraction time and a small decrease in half‐relaxation time.

5. Long trains of stimuli increase the contraction time, the half‐relaxation time and the twitch duration in addition to potentiating the peak tension. The changes in twitch time course are dependent on the number of repetitive stimuli and the frequency of stimulation.

6. The results are discussed in relation to possible mechanisms of post‐tetanic potentiation and the degree of activation of mammalian and amphibian muscle fibres.
The effect of adrenaline on the tension developed in contractures and twitches of the ventricle of the frog
Authors: Graham J. A. , Lamb J. F.
Published: December 2014

1. The effect of adrenaline on contracture and twitch tension in frog's ventricle has been examined, using the superfused preparation.

2. In 1 m
M‐Ca Ringer, contractures induced with excess KCl concentrations from 50 to 200 m
M, are reduced by 1 × 10−6 g/ml. adrenaline to an average of 0·62 of control values, in marked contrast to the well known positive inotropic effect of adrenaline on the heart twitch. This effect of adrenaline is directly dose dependent. Increasing [Ca]o diminishes the effect of adrenaline on contracture tension, and on the twitch tension.

3. Adrenaline has a significantly greater effect on the KCl contracture tension than noradrenaline or isoprenaline.

4. In 1 m
M‐Ca Ringer, Na‐free contractures are reduced to 0·72 of controls by 1 × 10−6 g/ml. adrenaline. Adrenaline also significantly reduces tension in contractures induced by 50 c/s alternating current.

5. The action of adrenaline on contracture tension is largely complete in 1–2 min at various rates of stimulation and calcium concentrations. A similar time course has been found for the effect of adrenaline on membrane potential.

6. Pronethalol blocks the action of adrenaline on both twitch and contracture. The action on the contracture can also be blocked by ouabain (1 × 10−5
M), and exposure of the tissue to K‐free or Na‐free Ringer solution.

7. Adrenaline hyperpolarizes the membrane potential with a range of [K]o from 0 to 200 m
M. This effect is blocked by pronethalol and ouabain. After exposure to ouabain, adrenaline causes a significant decrease in the membrane potential. This may be due to an increase in the sodium permeability.

8. At low values of the [Ca]/[Na]2 ratio, adrenaline takes a relatively constant number of beats for full action, but at high values of the ratio the development of full effect is largely time dependent.

9. The time course of the effect on the twitch of changing from 0·5 to 2 m
M‐Ca Ringer has been studied at various rates of stimulation. The equilibration time has been found to depend on the heart rate.

10. The effect on the contracture suggests that adrenaline decreases the calcium permeability. It is further suggested that the development of twitch tension is not due to direct Ca entry but is due to the release of Ca from a local store within or between the cells. The inotropic action of adrenaline is explained in terms of this store.
The minimum latency of the a‐wave
Authors: Arden G. B. , Ikeda Hisako
Published: December 2014

1. Intense flashes of light evoke early and late receptor potentials from albino rat eyes.

2. When the temperature is lowered the amplitude of the early receptor potential (e.r.p.) is found to decrease much more than that of the a‐wave. Below 5° the a‐wave can be seen without a preceding negative e.r.p.

3. The a‐wave, but not the e.r.p., is suppressed by an intense flash, so that subsequent stimuli only evoke e.r.p.s.

4. The responses of such light‐adapted eyes have been used to determine the contribution of the a‐wave to the response of dark‐adapted eyes.

5. These calculated a‐waves begin during the e.r.p. with an initial portion which is biphasic.

6. The initial portion has a temperature dependence similar to that of the a‐wave. It is not related to the photoreversal of rhodopsin caused by the stimulating flashes.

7. The minimum latency of the a‐wave, extrapolated to body temperature, is approximately 300 μsec.

8. The site and mode of generation of the a‐wave is discussed.
Myelinated afferent fibres innervating the primate skin and their response to noxious stimuli
Authors: Perl E. R.
Published: December 2014

1. The functional characteristics of cutaneous receptors in the squirrel monkey were determined by recording discharges of single myelinated afferent fibres in peripheral nerves with micro‐electrodes or from fine filaments prepared by dissection. One hundred and sixty‐nine fibres of the posterior femoral cutaneous nerve and 209 of the superficial radial nerve with conduction velocities between 4 and 88 m/sec were classified according to the nature of the most effective stimulus, discharge characteristics, adaptation rate and organization of the receptive field.

2. Twenty per cent of the fibres innervating either hairy or glabrous skin required strong mechanical stimuli for activation; thresholds ranged from moderate to overtly damaging pressures. This class showed little or no sensitivity to thermal changes including noxious heat. Their receptive fields consisted of numerous, mechanically‐excitable points or spots. All such fibres gave higher impulse frequencies to noxious than to innocuous mechanical stimuli and a large fraction were considered to be nociceptors because they responded only to noxious deformation. The conduction velocities of nociceptors were distributed between 5 and 28 m/sec.

3. All but a few of the other fibres encountered responded vigorously to innocuous stimuli and were readily identified as corresponding to one of the receptor types known to exist in either the primate or the cat. These sensitive receptors were systematically tested by intense cutaneous stimuli; their response to injurious stimuli always could be mimicked by innocuous ones.

4. Therefore, in the primate a particular class of slowly‐conducting myelinated fibres is partially responsible for signalling mechanically‐induced cutaneous damage. The probable relation between such afferent fibres and certain kinds of cutaneous pain is explored.
An examination of the effects of osmotic pressure changes upon transmitter release from mammalian motor nerve terminals
Authors: Hubbard J. I. , Jones S. F. , Landau E. M.
Published: December 2014

1. When the frequency of miniature end‐plate potentials (m.e.p.p.s) was measured at neuromuscular junctions in rat diaphragm nerve preparations in vitro bathed in solutions having osmolarities between 200 and 700 m‐osmoles/l. it was found that m.e.p.p. frequency was transiently increased by exposure to osmotic gradients exceeding 75 m‐osmoles/l., and then declined, within 1 hr, to a steady level slightly higher than the control level of frequency. Smaller osmotic gradients caused a maintained increase in m.e.p.p. frequency. E.p.p. quantal content was initially increased and later profoundly decreased upon exposure of preparations to solutions with an osmotic pressure of 500 or 600 m‐osmoles/l. but was unaffected by less hypertonic solutions.

2. Variation of the Ca or Mg content of the bathing solutions did not alter these effects of osmotic pressure on the early transient increase in m.e.p.p. frequency or e.p.p. quantal content but affected the late steady increase in m.e.p.p. frequency.

3. The value of the transient increase in m.e.p.p. frequency was exponentially related to the osmotic gradient in the range 0‐300 m‐osmoles/l. with a Q10 of 1·95 (range 11‐34° C). Greater osmotic gradients did not further increase m.e.p.p. frequency. Variation of the ionic strength of the bathing medium did not influence osmotic effects upon frequency.

4. The discrepancy between the effects of osmotic gradients upon spontaneous and nerve‐impulse induced transmitter release was explained by an occlusion of the osmotic effects by depolarization of nerve terminals. Time‐course studies showed that in the presence of 20 m
M‐KCl the m.e.p.p. frequency increase in response to an increase in osmotic pressure was small and was followed by a reduction in frequency to below control levels while osmotic pressure changes had no immediate effect upon m.e.p.p. frequency in solutions containing 30 m
M‐KCl.

5. It was concluded that increased osmotic gradients could release transmitter by a mechanism independent of Ca and of nerve terminal depolarization.

6. It is suggested that the initial transient effects of changes of osmotic gradient upon transmitter release are related to flow of water through the nerve terminal membrane, while the later effects are related to nerve terminal volume changes.
The responses of goats to the experimental induction of hypocalcaemia with cation‐exchange columns
Authors: Symonds H. W. , Treacher R. J.
Published: December 2014

1. Ionic calcium was selectively removed from the circulating blood of three anaesthetized goats by means of columns of cation‐exchange resin. Concentrations of other ions were not directly affected by the column.

2. A calcium extraction rate of 0·35 m‐equiv/min caused a fall in plasma total calcium of up to 40% in 35 min. Plasma calcium concentration returned to normal within 2 hr of the end of calcium removal.

3. Mobilization rates reached a maximum between 15 and 20 min after calcium removal commenced, declining rapidly after it had stopped.

4. Removal of calcium by EDTA infusion results in a similar calcium mobilization pattern to that produced by Ca removal by ion‐exchange.

5. A smaller variation appears to exist between goats in maximum calcium mobilization rates than in maximum phosphorus mobilization rates and goats may be able to mobilize phosphorus relatively faster than calcium.
The mechanism of the pyrogenic effect of streptococcus cell wall mucopeptide
Authors: Mašek K. , Rašková Helena , Rotta J.
Published: December 2014

1. The intravenous injection into rabbits of 25‐50 μg of a preparation of cell‐wall mucopeptide (SM) from group A streptococcus produced a rise in rectal temperature and a fall in the number of circulating granulocytes in the blood.

2. The pyrogenic response to SM is not dependent on the circulating granulocytes since it occurred also in rabbits made leucopenic by nitrogen mustard (HN 3).

3. The pyrogenic response to SM was enhanced after an intravenous injection of 5‐hydroxytryptophan (5‐HTP).

4. Pre‐treatment with reserpine caused a much greater attenuation of the pyrogenic response to SM than pre‐treatment with α‐methyl‐para‐tyrosine (AMPT).

5. As the reserpine reduced the 5‐hydroxytryptamine (5‐HT) and noradrenaline level in the hypothalamus, whereas the AMPT reduced only the noradrenaline level, it is concluded that 5‐HT may be involved in the pyrogenic response and the way in which 5‐HT may exert this function is discussed.
Compensatory reactions to a lack of metabolizable glucose
Authors: Himsworth R. L.
Published: December 2014

1. Following the injection of adrenaline into rats pre‐treated with thyroxine, there is a pronounced and prolonged increase in their oxygen consumption. On this basis a method is described for following increases in the rate of secretion of adrenaline in response to physiological stimuli in rats.

2. Using this method the onset and the cessation of the increased rate of secretion of adrenaline during insulin induced hypoglycaemia has been found to correspond to a blood glucose concentration of approximately 40 mg/100 ml.

3. 3‐Methylglucose (3‐O‐methyl‐
D‐glucopyranose) is shown to cause a marked and sustained increase in the blood glucose concentration.

4. This action of 3‐methylglucose can be accounted for by an increase in the rate of secretion of adrenaline, as it is accompanied by a rise in oxygen consumption in thyroid treated rats and is prevented by interruption of the central nervous connexions of the adrenal medulla.

5. These findings can be explained by 3‐methylglucose's acting upon the receptor which reacts to insulin hypoglycaemia by bringing about the secretion of adrenaline. It is shown that the effective stimulus to this receptor is not a low blood glucose concentration. The stimulus is possibly a depressed rate of utilization of glucose by the receptor tissue.
The effect of prolonged exercise on the components of the blood fibrinolytic enzyme system
Authors: Bennett N. B. , Ogston C. Marie , Ogston D.
Published: December 2014

1. The levels of the blood components of the fibrinolytic enzyme system were measured before, during and after a 4 hr period of exercise in eight subjects.

2. Mean plasminogen activator level rose progressively over the first 3 hr with little further change during the 4th hr of exercise. Following the period of exercise there was a rise in a circulating anti‐activator which was still present 20 hr after completion of the exercise.

3. There was no alteration in the mean blood level of plasminogen, fibrinogen, anti‐plasmin or a serum inhibitor of plasminogen activation during or following the exercise.

4. The significance of the findings in relation to the mechanism of interaction of the components of the fibrinolytic system is discussed.
The role of left atrial receptors in the diuretic response to left atrial distension
Authors: Ledsome J. R. , Linden R. J.
Published: December 2014

1. The diuretic response to distension of the whole left atrium caused by obstruction of the mitral orifice has been compared with the effects of distension (by means of small balloons) of the left pulmonary vein/left atrial junctions.

2. Distension of the pulmonary vein/atrial junctions caused an increase in heart rate and a diuresis similar to but smaller than that caused by mitral obstruction.

3. Section of both ansae subclaviae prevented the increase in heart rate produced by distension of the pulmonary vein/left atrial junctions but had little effect on the diuretic response either to pulmonary vein distension or to mitral obstruction.

4. A diuretic response to mitral obstruction could be demonstrated after all nerves from the lungs had been cut but not after the vagus nerves had been cut at levels likely to interrupt the majority of afferent fibres from left atrial receptors.

5. The results support the view that stimulation of left atrial receptors is a major factor in the production of a diuretic response to mitral obstruction.
The influence of the nasal mucosa and the carotid rete upon hypothalamic temperature in sheep
Authors: Baker Mary Ann , Hayward James N.
Published: December 2014

1. In chronically‐prepared sheep, intracranial temperatures were measured in the cavernous sinus among the vessels of the carotid rete and at the circle of Willis extravascularly, and in the preoptic area and in other brain stem regions. Extracranial temperatures were measured intravascularly in the carotid or internal maxillary arteries and on the nasal mucosa and the skin of the ear.

2. At 20° C ambient temperature, shifts in temperature of the hypothalamus and of other brain sites paralleled temperature shifts in the cerebral arterial blood which was cooler than central arterial blood. During periods of arousal and of paradoxical sleep, vasoconstriction of the nasal mucosa and the ear skin occurred and temperatures at the cerebral arteries and in the brain rose without a comparable rise in central arterial blood temperature.

3. Anaesthetic doses of barbiturate abolished the temperature oscillations in the cerebral arterial blood and the brain. When air was blown rapidly over the nasal mucosa in anaesthetized animals, temperatures dropped precipitously in the cavernous sinus, at the cerebral arteries, and in the brain, while central arterial temperature fell only slightly. Injections of latex into the facial venous system demonstrated a venous pathway from the nasal mucosa to the cavernous sinus.

4. When sheep were exposed to 45‐50° C ambient temperature, respiratory rate increased 5‐10 times and the temperature gradient between central and cerebral arterial blood widened.

5. It is concluded that venous blood returning from the nasal mucosa and the skin of the head to the cavernous sinus cools the central arterial blood in the carotid rete. This is an important factor in the maintenance of hypothalamic temperature in the wool‐covered, long‐nosed, panting sheep and undoubtedly affects hypothalamic thermoreceptors and temperature regulation in artiodactyls.
The components of the sodium efflux in frog muscle
Authors: Keynes R. D. , Steinhardt R. A.
Published: December 2014

1. In normal Ringer solution containing 2·5 m
M‐K only 37% of the efflux of labelled sodium from a freshly dissected frog muscle is blocked by treatment with ouabain; in sodium‐loaded muscles the ouabain‐sensitive fraction of the efflux increases to 75%.

2. Under all conditions, the ouabain‐insensitive component of the sodium efflux is markedly reduced if the sodium in the external medium is replaced by lithium; at least in sodium‐loaded muscles, the ouabain‐sensitive component is increased in lithium Ringer.

3. Only the ouabain‐sensitive component of the efflux is affected by the external potassium concentration.

4. In the presence of 2·5 m
M‐K the sodium influx in a freshly dissected muscle is not significantly altered by ouabain, but in a K‐free medium the influx and the efflux are both reduced by nearly 20%.

5. The sodium efflux can therefore be regarded as consisting of (1) a sodium‐potassium coupled component that is blocked by ouabain and involves a sodium‐sodium exchange in the absence of external potassium, and (2) a potassium‐insensitive component that is unaffected by ouabain and tends to reach saturation at relatively lower internal sodium concentrations.

6. The evidence is considered for attributing component (1) to an efflux of sodium from the sarcoplasm proper, and component (2) to an efflux from the sarcoplasmic reticulum. Although such an interpretation is consistent with many of the observations, a definite identification of the possible sodium compartments in frog muscle cannot yet be made.
Active transport of l‐glucose by isolated small intestine of the dietary‐restricted rat
Authors: Neale R. J. , Wiseman G.
Published: December 2014

1. The effect of semistarvation and complete starvation (sufficient to produce a loss of about 32 and 25% respectively of initial body weight) on the active transport of
L‐glucose has been studied by the use of sacs of everted mid‐small intestine of rats. The animals were allowed free access to water.

2. Sacs from animals on a restricted diet transported
L‐glucose against its concentration gradient, but sacs from fully fed rats did not. Even when sacs from fully fed rats were distended sufficiently to cause them to lose serosal volume, the
L‐glucose concentration in the final serosal fluid was never greater than that in the final mucosal fluid.

3. The
L‐glucose active transport was independent of net water movement, needed oxygen, was not demonstrable at 27° C, and required Na ions at a concentration of 83 m
M or greater. It could be completely inhibited by 10−6
M phlorrhizin, or 10 m
M L‐histidine, or 1·39 m
M D‐glucose. Phlorrhizin at a concentration of 10−8
M reduced, but did not prevent,
L‐glucose active transport.

4. It seems probable that
L‐glucose active transport is mediated by the mechanism that actively transports
D‐glucose.

5. Un‐incubated mid‐small intestine of fully fed rats contained 37·8 mg
D‐glucose/100 g wet wt. of tissue, whereas semistarved intestine had only 10·8 mg
D‐glucose/100 g. The lack of demonstrable active transport of
L‐glucose by normal intestine may possibly have been caused, at least in part, by inhibition of the process by endogenous
D‐glucose.

6. There appeared to be no metabolism of
L‐glucose by rat intestine, nor conversion to the
D‐form.

7. The hypothesis that sugars require the
D‐pyranose ring structure for active absorption is no longer tenable.