bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of cross‐innervation on the myoglobin concentration of tonic and phasic muscles
Authors: McPherson Angus , Tokunaga J.
Published: December 2014

1. The myoglobin concentrations of m. soleus and m. flexor digitorum longus (
F.D.L.) were estimated spectrophotometrically in normal cats.

2. In another group of cats the nerves to m. soleus and
F.D.L. were self‐united in one limb and cross‐united in the opposite limb and the myoglobin concentrations of m. soleus and
F.D.L. in both limbs were estimated 6 months later.

3. After self‐union of the nerves the
F.D.L./soleus myoglobin ratio was not significantly different from that of normal cats.

4. After cross‐union of the nerves the
F.D.L./soleus myoglobin ratio was significantly greater than that of both normal cats and cats after self‐union of their nerves.
Variations in small and large vessel volumes caused by cations, adrenaline and histamine*
Authors: Chacalos Elias H.
Published: December 2014

1. Plasma and blood cell volumes were measured simultaneously with [131I]albumin and [32P]erythrocytes, together with the arterial haematocrits, in acutely splenectomized dogs anaesthetized with sodium barbital. These measurements were made during control runs and after the administration of vasoactive substances.

2. With these data and previously derived equations the mean composite radius of all small vessels with a radius < 150 μ, the distribution of the blood volumes between small and large vessels, and other variables could be calculated.

3. Adrenaline, CaCl2 or vasopressin administration caused a reduction of the mean composite radius, a net shift of erythrocytes and plasma out of the small vessel volume, and an expansion of the large vessel volume. Histamine, KCl and MgCl2 produced opposite effects.

4. Adrenaline appeared to cause the release of sequestered erythrocytes into the active circulation.

5. The effects of CaCl2 and KCl persisted for several hours, while those of MgCl2 did not.

6. The effects of vasopressin could be reversed by histamine, those of adrenaline by splenic plasma or KCl, and those of CaCl2 by MgCl2.

7. It was suggested that the observed vasoactions are essentially the resultants of diverse combinations of direct and indirect actions on the capacitance section of the small vessel volume.
Further studies on intestinal active transport during semistarvation
Authors: Hindmarsh J. T. , Kilby D. , Ross B. , Wiseman G.
Published: December 2014

1. The effect of semistarvation (sufficient to produce a loss of 18‐28% of initial body weight) on the active transport of
D‐glucose and
L‐histidine by the rat, the guinea‐pig and the golden hamster has been investigated by the use of sacs of everted small intestine (from upper jejunum to lower ileum).

2. In the rat and the guinea‐pig the dietary restriction resulted in increased active transport in all regions of the small intestine. In contrast, it caused no alteration in active transport in the hamster.

3. The response in the rat was most impressive in the middle‐to‐lower ileum during
D‐glucose uptake. Whereas normal sacs from this area appeared unable to move the sugar against its concentration gradient, sacs from semistarved rats did so quite well.

4. Although there was a considerable loss (24‐29%) of intestinal dry weight in all three species when the food intake was reduced, shortening of the small intestine was not detectable in the guinea‐pig or the hamster and was present to only a minor extent in the rat.

5. Evidence is presented indicating that the enhanced active transport is not merely a reflexion of the thinning of the intestinal wall and that it occurs during complete as well as in partial starvation.
Intracellular sodium concentration and resting sodium fluxes of the frog heart ventricle
Authors: Keenan Mary J. , Niedergerke R.
Published: December 2014

1. Using 24Na to label the exchangeable sodium in the tissue and either [35S]sulphate or [14C]sucrose to label the extracellular spaces, the intracellular sodium concentration of frog heart ventricles was determined and found to be between about 5 and 10 m‐mole/kg cell water.

2. The intracellular potassium concentration, obtained by flame‐photometric analysis, was approximately 163 m‐mole/kg cell water.

3. Two different methods were employed to study the sodium tracer efflux of resting heart ventricles. One involved a double‐tracer technique, using 24Na to indicate the release of the exchangeable tissue sodium, and 35SO4 to indicate, approximately, the release of extra‐myocardial sodium. In the other a comparison was made of the sodium release from the tissue when it contained sodium either at the normal concentration or at a concentration enhanced by exchange with intracellular potassium.

4. The magnitude of the sodium efflux from heart fibres as measured by both methods was of the order 50‐100 p‐mole/cm2 sec. Simultaneously with this cellular efflux a substantial amount of sodium was released from extra‐myocardial spaces and tissues.

5. The net efflux of potassium ions from heart cells that occurred when heart ventricles were perfused with potassium‐depleted fluids was determined. The results were used to obtain an indirect estimate, of about 2‐3 p‐mole/cm2 sec, for the resting sodium influx.

6. The significance of these different values of sodium efflux and influx is discussed.
Calcium activation of frog slow muscle fibres
Authors: Costantin L. L. , Podolsky R. J. , Tice Lois W.
Published: December 2014

1. Skinned muscle fibres were prepared from the tonus bundle of the frog iliofibularis muscle and the contractile response elicited by applied calcium ions was studied. The fibre type was determined by electron microscopy.

2. Fast fibres shortened many times more rapidly than slow fibres, indicating that the slow contraction of slow fibres is an inherent property of the contractile mechanism.

3. The extent of spread of contraction following local calcium application was much greater in slow than in fast fibres, a difference which is consistent with the relative sparsity of the sarcoplasmic reticulum in slow fibres.

4. The ability of the sarcoplasmic reticulum of slow fibres to accumulate calcium was demonstrated by the in situ immobilization of calcium when oxalate solutions were added to the skinned fibre.
The oxygen consumption of mammalian non‐myelinated nerve fibres at rest and during activity
Authors: Ritchie J. M.
Published: December 2014

1. A study has been made of the oxygen consumption of non‐myelinated nerve fibres of rabbit desheathed cervical vagus nerves at rest and during activity.

2. The average resting oxygen consumption (Qr) was 0·0924 μmole/g. min at 21° C. Stimulation for 1‐3 min at 3/sec caused an extra oxygen consumption (Qs) of 816 p‐mole/g.shock.

3. When the frequency of stimulation was increased, to 10/sec and 30/sec, Qs fell. When the frequency was decreased, to 1/sec and 0·3/sec, Qs increased slightly.

4. When the temperature was decreased, Qr fell; when the temperature was increased, Qs also increased. Temperature similarly affected Qs with high frequencies of stimulation, but had relatively little effect on Qs at low frequencies of stimulation.

5. An isolated single shock seemed to produce an increase in oxygen consumption of about 1200 p‐mole/g, and this value was largely independent of temperature.

6. When part of the sodium in the Locke solution was replaced by barium, Qr decreased (by 12%) whereas Qs increased (by 87%).

7. Veratrine (1 μg/ml.) increased both Qr (by 142%) and Qs (by 361%).

8. Acetylcholine (1·7 m
M) increased Qr (by 32%).

9. When nerves were transferred to potassium‐free solutions there was little change in Qr, and Qs fell slightly (by 8%).

10. When the potassium concentration in the Locke solution was increased 4‐fold, Qr increased (by 27%).

11. Salicylate (1‐10 m
M) increased Qr (by 24%) and abolished Qs.

12. When the sodium of Locke solution was replaced by lithium, Qr decreased (by 19%) and Qs was abolished.

13. In sodium‐Locke solution ouabain (100 μ
M) decreased Qr (by 26%) and abolished Qs. In lithium‐Locke solution ouabain also decreased Qr (by 28%).

14. All or nearly all of the oxygen consumed at rest or during activity seemed to be used to pump potassium ions into, and sodium ions out of, the axoplasm.

15. The K/O2 ratio during pumping was about 5·0.
Altered temperature and taste responses from cross‐regenerated sensory nerves in the rat's tongue
Authors: Oakley B.
Published: December 2014

1. The chorda tympani nerve, which innervates the front of the rat tongue, was found to be much less responsive to tongue cooling than the IXth nerve, which innervates the back of the tongue. The two nerves also differed in their relative responsiveness to various taste chemicals.

2. Through cross‐union the IXth nerve was made to innervate the front of the tongue, and in other rats the chorda tympani nerve the back of the tongue.

3. After an average of 15 post‐operative weeks, electrophysiological recordings of whole nerve action potential discharges were made from normal, control regenerated, and cross‐regenerated nerves. Cooling, and chemical and mechanical stimulation of the tongue demonstrated that the control regenerated and cross‐regenerated nerves had established functional connexions.

4. Neither the response to cooling nor the relative taste responses were altered by either of two types of control chorda tympani nerve regeneration.

5. In contrast, the cross‐regenerated chorda increased its responsiveness to tongue cooling and the cross‐regenerated IXthe nerve lost much of its responsiveness to cooling.

6. Cross‐regeneration also caused the relative taste responses to change and appear quite similar to the responses obtained from the nerve which normally innervated that tongue region (e.g. the cross‐regenerated IXth nerve responded like a chorda tympani nerve).

7. It is suggested that the sensory response evoked in the chorda tympani and IXth nerves by tongue cooling or taste stimulation is at least partially dependent upon the character of the tongue tissue in which the nerve terminates—the epithelium at the front differs from that at the back of the rat tongue.

8. These results rule out the following two hypotheses: (a) that the nerve ending itself functions as a taste receptor in direct contact with applied chemicals and yet is uninfluenced by the character of the tissue in which it terminates, (b) that assuming the taste bud cells are an integral part of the receptive process, the taste nerve ending determines the chemical specificity of the taste cell which it induces, without any previous modification of the nerve by the tissue in which it terminates.
The role of α‐ and β‐adrenergic receptors in some actions of catecholamines on intestinal smooth muscle
Authors: Jenkinson D. H. , Morton I. K. M.
Published: December 2014

1. Experiments were carried out to determine the type of adrenergic receptor concerned in the action of noradrenaline in increasing the rate of exchange of potassium ions in the taenia of the guinea‐pig caecum. The preparations were bathed in potassium‐rich solutions in order to depolarize the muscle fibres and so eliminate changes in potassium flux secondary to alterations in membrane potential.

2. Noradrenaline was more effective than isoprenaline in increasing both the influx and efflux of 42K, suggesting that the α‐receptors were involved. This action on potassium permeability was abolished by the α‐blocking agent phentolamine (10−7 g/ml.), the β‐blocking agent pronethalol (10−7 g/ml.) being without effect.

3. In contrast, isoprenaline was about 30 times more active than noradrenaline in inhibiting calcium contractures of the depolarized taenia, suggesting that here the β‐receptors were concerned. This was confirmed by showing that this action of noradrenaline was effectively antagonized by pronethalol, again at 10−7 g/ml., but not by the same concentration of phentolamine.

4. Carbachol contractures in quiescent preparations bathed in Krebs solution at 17° C could be inhibited by both noradrenaline and isoprenaline. Noradrenaline was found to be more active under these conditions, and this action was antagonized by phentolamine (and piperoxane), but not by pronethalol, at the same concentrations as before.

5. These findings confirm that the α‐ and β‐receptors are quite distinct in their actions. Nevertheless, under physiological conditions, both may contribute to the inhibitory actions of catecholamines on intestinal smooth muscle.
The laminar organization of dorsal horn and effects of descending impulses
Authors: Wall P. D.
Published: December 2014

1. An examination of the physiological properties of cells in cat lumbar dorsal horn shows that there are three horizontal laminae which correspond approximately to Rexed (1952) laminae 4, 5, and 6.

2. A summary diagram (Fig. 9) suggests the relation of the laminae to each other and to afferent and descending fibres. All three laminae respond to cutaneous stimulation but only lamina 6 responds to movement. By comparing responses of cells in decerebrate and spinal preparations, it is shown that the brain stem inhibits cutaneous responses and enhances movement responses. Pyramidal tract stimulation affects cells in laminae 4, 5, and 6.

3. Cells in lamina 4 have small cutaneous receptive fields and respond as though many different types of specific cutaneous afferents converge on them. Cells in lamina 5 respond as though many cells of lamina 4 converge on them. In the decerebrate animal the responses of lamina 5 cells habituate to repeated light pressure stimuli but the cells remain responsive to new stimuli in other parts of their receptive field. Impulses descending from the brain stem can switch the modality of lamina 6 cells from cutaneous to proprioceptive.
The relative roles of the aortic and carotid sinus nerves in the rabbit in the control of respiration and circulation during arterial hypoxia and hypercapnia
Authors: Chalmers J. P. , Korner P. I. , White S. W.
Published: December 2014

1. The respiratory and circulatory effects of graded arterial hypoxia, alone or with superadded hypercapnia, were studied in four groups of unanaesthetized rabbits including normal animals and those with selective section of the aortic nerves, selective section of the carotid sinus nerves and section of both sets of nerves.

2. When measured 2‐4 days after selective section of the carotid sinus nerves the resting respiratory minute volume and arterial PO2 were lower and the PCO2 higher than normal. These effects were not observed after selective section of the aortic nerves. Selective aortic nerve section, and selective carotid sinus nerve section each produced a similar increase in the resting arterial pressure and heart rate, but were without effect on the resting cardiac output.

3. During arterial hypoxia reflex respiratory and circulatory effects ascribable to arterial chemoreceptor stimulation (hyperventilation, bradycardia, vasoconstriction) were mediated for the most part through the carotid sinus nerve. In animals with only the aortic nerves intact the circulatory response was determined largely by the opposing effects of aortic baroreceptor reflexes and the local peripheral dilator action of hypoxia.

4. The circulatory effects of hyperventilation induced by hypercapnia during arterial hypoxia, in animals with both aortic and carotid sinus nerves cut were small.

5. The results suggest that relatively few chemoreceptor fibres originate from the aortic region in the rabbit, though the carotid sinus and aortic nerves both contain baroreceptor fibres.
Excitation of afferent cardiac sympathetic nerve fibres during myocardial ischaemia
Authors: Brown A. M.
Published: December 2014

1. Occlusion of the main left coronary artery of lightly anaesthetized cats provoked a pseudaffective reaction. The afferent pathway was in the cardiac sympathetic nerves.

2. The compound action potential evoked in the inferior or middle cardiac nerves by stimulation of the thoracic sympathetic trunk contained two elevations, a small Aδ wave and a much larger sC wave. Occasionally a B wave was present.

3. During coronary occlusion, the Aδ elevation was reduced by 35‐55%, indicating afferent activity in these fibres. Multifibre preparations also showed increased afferent discharge during occlusion.

4. It seems probable that the afferent activity in these fibres was mainly responsible for signalling the pseudaffective response elicited by coronary occlusion.

5. Myocardial ischaemia produced by coronary occlusion was probably the stimulus for the increased activity.
The innervation of sheep mesenteric veins
Authors: Holman Mollie E. , McLean A.
Published: December 2014

1. An isolated preparation of sheep mesenteric vein is described from which contractions of the longitudinal smooth muscle of the adventitia have been recorded in response to stimulation of intramural and periarterial nerves.

2. The preparation did not respond to single stimuli but the relation between amplitude of response and frequency of stimulation was characteristic of that described for other smooth muscles innervated by sympathetic nerves.

3. Responses were blocked by tetrodotoxin, guanethidine, and by a number of α‐receptor blocking drugs. Responses to peri‐arterial stimulation were unaffected by hexamethonium. It was concluded that the longitudinal smooth muscle is supplied with post‐ganglionic noradrenergic motor nerves and the presence of such fibres in the adventitia was confirmed by fluorescence microscopy.

4. Acetylcholine also caused contractions. Although a direct excitatory action on the smooth muscle could not be excluded, results suggest that acetylcholine may release noradrenaline from the axons of the sympathetic ground plexus.
Influence of phospholipase C on some electrical properties of the skeletal muscle membrane
Authors: Albuquerque E. X. , Thesleff S.
Published: December 2014

1. A study was made of the effects of phospholipase C (PhC) on the resting membrane potential, input resistance, action potential and acetylcholine sensitivity of innervated and chronically denervated single muscle fibres of the rat.

2. In doses higher than 1·5 μg/ml. PhC significantly increased the ionic permeability of the muscle membrane (indicated by a fall in input resistance) and reduced the resting membrane potential of innervated fibres. The ‘fast’ or ‘white’ extensor digitorum longus muscle was the most sensitive and the ‘slow’ or ‘red’ soleus the least sensitive muscle. A similar difference was observed among ‘fast’ and ‘slow’ muscles of the chicken, the posterior latissimus dorsi being far more sensitive than the ‘slow’ anterior latissimus dorsi muscle. Chronically denervated muscles were more resistant to these actions of PhC than innervated ones but even after denervation the ‘fast’ muscles remained more sensitive than the ‘slow’ muscles.

3. The action‐potential generating mechanism in the ‘fast’ and ‘slow’ muscle was completely and irreversibly blocked by 1·5 μg/ml. of PhC within 1 hr. Furthermore the innervated and chronically denervated muscles were equally sensitive to this effect of PhC. The enzyme caused a gradual increase in the threshold for excitation, reduction in the rate of rise and the amplitude of the action potential. The input resistance and the resting membrane potential were not reduced by this dose of PhC.

4. Acetylcholine sensitivity of chronically denervated muscles was not affected by PhC in doses that abolished the electrical excitability of the membrane. When PhC reduced the input resistance and the resting membrane potential a decrease was also observed in the response to applied acetylcholine.

5. The results suggest that PhC by acting at the polar heads of membrane phospholipids interferes with the ionic carrier mechanism which generates the action potential. The differences in sensitivity between ‘fast’ and ‘slow’ muscles and between innervated and chronically denervated ones are tentatively explained on the basis of heterologous membrane phospholipids and/or variations in their stereochemical arrangement.
Spatial interaction in human cone vision
Authors: Westheimer Gerald
Published: December 2014

1. The adaptation state of a uniformly illuminated patch of human cone retina was determined by finding the threshold for a small, brief light spot seen flashing in its centre.

2. When the illuminated patch of the retina is increased in diameter, the adaptation state is first raised, and beyond a critical background diameter, lowered.

3. This is interpreted as a manifestation of excitatory and inhibitory interaction of adaptation stimuli: illumination of retinal regions in the immediate neighbourhood of the area tested acts to raise the adaptation level, and of those further removed acts to lower it.

4. The critical area beyond which adapting light produces inhibition is about 5 min of arc in diameter in the eye's object space for foveal observation. For peripheral cone vision it increases much as the minimum angle of resolution.

5. The inhibiting action of outlying areas is substantially reduced, or perhaps even eliminated, by lowering the background luminance.

6. Surrounding the retinal patch with a pair of juxtaposed narrow concentric black and white rings superimposed on a uniform field, simulating a border, irrespective of diameter, does not influence the threshold of the probing spot. This argues against a possible threshold raising effect of the border of the background.

7. The inhibiting action on a patch of cone retina of a surrounding annulus occurs only when the annulus is seen by the same eye and not when it is seen by the other eye: the site of inhibitory interaction is, therefore, retinal.
Body temperature responses in cats and rabbits to the monoamine oxidase inhibitor tranylcypromine
Authors: Feldberg W. , Lotti V. J.
Published: December 2014

1. In unanaesthetized cats tranylcypromine (1‐10 mg/kg) had scarcely any effect on rectal temperature when injected intraperitoneally, yet such injections prevented the deep and long‐lasting fall in rectal temperature which normally occurs when the cat is anaesthetized by intraperitoneal pentobarbitone sodium or intravenous chloralose. The anaesthesia itself, however, was not affected. In some of the experiments with pentobarbitone sodium rectal temperature even rose to fever level.

2. In anaesthetized as well as in unanaesthetized cats injections of tranylcypromine (0·1‐1 mg) into the cerebral ventricles caused a rise in rectal temperature.

3. In rabbits, rectal temperature was scarcely affected when surgical anaesthesia was produced by intravenous infusions of pentobarbitone sodium under the same condition in which, in cats, intraperitoneal pentobarbitone sodium produced a deep and long‐lasting fall in temperature, i.e. when no external heat was applied but excessive dissipation of heat was prevented by placing the rabbit on a cotton‐wool pad. However, when it was placed on the metal surface of an operating table, the anaesthesia was associated with a deep fall in rectal temperature.

5. In anaesthetized and unanaesthetized rabbits tranylcypromine had no effect on rectal temperature when injected intraperitoneally (10 mg/kg) or into the cerebral ventricles (1 mg).

5. These results are discussed in relation to the theory that the three monoamines in the hypothalamus, 5—hydroxytryptamine (5‐HT), adrenaline and noradrenaline, act as central transmitters in temperature regulation.
The effect of withdrawal of visual presentation of errors upon the frequency spectrum of tremor in a manual task
Authors: Sutton G. G. , Sykes K.
Published: December 2014

1. When a subject attempts to exert a steady pressure on a joystick he makes small unavoidable errors which, irrespective of their origin or frequency, may be called tremor.

2. Frequency analysis shows that low frequencies always contribute much more to the total error than high frequencies. If the subject is not allowed to check his performance visually, but has to rely on sensations of pressure in the finger tips, etc., the error power spectrum plotted on logarithmic co‐ordinates approximates to a straight line falling at 6 db/octave from 0·4 to 9 c/s. In other words the amplitude of the tremor component at each frequency is inversely proportional to frequency.

3. When the subject is given a visual indication of his errors on an oscilloscope the shape of the tremor spectrum alters. The most striking change is the appearance of a tremor peak at about 9 c/s, but there is also a significant increase of error in the range 1‐4 c/s. The extent of these changes varies from subject to subject.

4. If the 9 c/s peak represents oscillation of a muscle length‐servo it would appear that greater use is made of this servo when positional information is available from the eyes than when proprioceptive impulses from the limbs have to be relied on.
Acetate metabolism in the isolated sheep foetus
Authors: Alexander D. Pauline , Britton H. G. , Nixon D. A.
Published: December 2014

1. Sheep foetuses over the age range 105‐142 days and maintained on an extracorporeal circuit removed exogenous acetate at 2·0‐4·9 mg/kg.min.

2. Urinary loss of acetate was less than 12·5% of the administered amount.

3. The rate of acetate removal appeared to be unaffected by the addition of glucose to the circuit. The removal of glucose also seemed to be unaffected by the presence of acetate.

4. A decline in the plasma concentration of free fatty acids and ketone bodies was also observed during the perfusion.

5. It is concluded that under these conditions acetate may have accounted for about one half of the oxygen consumption. The contribution of free fatty acids and ketone bodies must have been small. The relevance of these findings to the nutrition of the foetus in utero is discussed.
The effect of a non‐ionic detergent (Triton WR 1339) on the removal of triglyceride fatty acids from the blood of the rat
Authors: Otway Sheila , Robinson D. S.
Published: December 2014

1. The initial rate of removal from the circulation of injected [14C] labelled chylomicron triglyceride is much slower in rats that have been injected with the non‐ionic detergent, Triton WR 1339, than in normal animals. Pre‐incubation of the lipid with Triton before its injection causes a further reduction in removal rate.

2. After the injection of [14C]labelled chyle triglyceride into animals given Triton, the rate of disappearance of radioactivity falls markedly as the percentage of the labelled material remaining in the blood declines.

3. A much smaller decrease in the rate of removal of injected chylomicron triglyceride occurs with increase in the size of the injected dose and with increase in the time interval between Triton and chylomicron triglyceride injections.

4. Serum triglycerides labelled with 14C are removed from the circulation of rats that have been given Triton at a much slower rate than [14C] labelled chylomicron triglycerides.
The effect of very frequent milking and of oxytocin on the yield and composition of milk in fed and fasted goats
Authors: Linzell J. L.
Published: December 2014

1. The effect of milking goats 1‐4 times an hour for 3‐12 hr on the yield and composition of milk has been studied in fed and fasted animals at all stages of lactation.

2. It was essential to inject oxytocin (50‐400 m‐u.
I.V.) just before each milking to remove all the milk already in the udder and then the yield was similar to that obtained on twice daily milking (105 ± 2·1
S.E.%). There were no significant differences between goats or between the two glands of one goat, even if one had been denervated by autotransplantation. However, the variation from hour to hour was 1·5 times greater than from day to day.

3. The claim of Zaks (1964) and Zaks, Natochin, Sokolova, Tanasichuk & Tverskoy (1965) that milking every 15 min always produces a large rise in milk Na and a fall in K and lactose, which is characteristic of alveolar milk, is not substantiated. In high yielding goats milking gently by hand or with a cannula caused a small change in K only, but vigorous hand milking exacerbated this fall and also caused a fall in lactose and a rise in Na and Cl. Still larger changes were produced by using excessively large doses of oxytocin (2500 m‐u.) when there was also a rise in citrate and total nitrogen. Hourly milking in goats fasted for 24 hr had the same effect.

4. In fasted goats the milk yield fell to 90% within 8 hr and to 56 ± 2·1% of the previous level by 24 hr. It remained at this level for a further 10‐12 hr on twice daily or on hourly milking. The yields of autotransplanted glands usually fell slightly but significantly more than that of the glands in situ. In most goats mammary blood flow was halved but in all animals there were large falls in mammary uptake of glucose, acetate and amino acids and greatly increased uptake of free fatty acids. There were significant differences between fasted goats on hourly milking.

5. It is concluded that, in spite of changes in milk composition, milking hourly can be a useful technique for studying milk secretion. The striking effects of a short fast in a lactating animal are emphasized.
The effect of subthreshold potentials on the membrane current in cardiac Purkinje fibres
Authors: McAllister R. E. , Noble D.
Published: December 2014

1. In sodium‐containing solutions, up to 60% of the slow outward current in Purkinje fibres can be activated by depolarizations which are too small to activate the fast sodium conductance responsible for the depolarization phase of the action potential. This result reinforces the view that the slow outward current results from slow activation of the potassium conductance rather than from slow inactivation of the sodium conductance.

2. These subthreshold changes in membrane conductance are probably responsible for the dependence of the action potential and pace‐maker potential durations on small changes in membrane potential in the subthreshold region.
Energetics of cardiac contractions
Authors: Gibbs C. L. , Mommaerts W. F. H. M. , Ricchiuti N. V.
Published: December 2014

1. The average resting heat production of a muscle under zero tension is 24·8 mcal/g muscle .min at 20° C. In the majority of muscles examined the resting heat production increases when the resting tension and muscle length are increased.

2. The relation between actively developed tension and heat produced is similar to that existing in skeletal muscle. The plot of heat against developed tension can be obtained either by altering muscle length or by varying the stimulus frequency.

3. The mean maximum total efficiency work/(work + heat) in the work experiments was 11·6%. The total energy produced (work + heat) correlates with the load rather than with the work done.

4. In isotonic contractions more heat is liberated than the heat versus tension plot predicts. This extra heat is load‐dependent.
Effects of water content upon the respiration and the cations of kidney slices
Authors: Little J. R. , Robinson J. R.
Published: December 2014

1. Cortical slices from the kidneys of adult rats were incubated aerobically at 38·5° C in Warburg manometers in an ordinary balanced saline medium and also in ‘low‐ion’ media consisting of 20 m
M Tris buffer to which 0‐30 g polyethylene glycol (‘PEG 6000’)/100 ml. was added to control the swelling of the tissue.

2. Oxygen uptake in the low ion media containing less than 2 m‐equiv/l. of Na+ and K+ was maximal when the water content of the slices was kept normal by 14% PEG 6000 in the medium, and was about two thirds of the oxygen consumption in a balanced saline medium.

3. Slices respiring in the low‐ion media retained potassium in concentrations 10‐20 times the concentration in the medium; the ratio of tissue to external concentration of K+ was inversely related to the water content of the tissue.

4. Ratios of K+/Na+ concentration in tissue water were maximal and equal to 10‐25 when water content was near normal and the ratio Na+/K+ in the medium was between 1·5 and 2·0.

5. Cryoscopic measurements showed that 14% of PEG 6000 contributed 140 m‐osmole/kg to the osmolality of the low‐ion media in which slices maintained a normal water content.

6. It was not possible to interpret the volume of the cells as determined by the balance between the osmotic effect of PEG 6000 in the medium and the colloid osmotic pressure of intracellular proteins.
Influence of the ionic environment on the membrane potential of adrenal chromaffin cells and on the depolarizing effect of acetycholine
Authors: Douglas W. W. , Kanno T. , Sampson S. R.
Published: December 2014

1. Intracellular recordings were made from chromaffin cells isolated from adrenal medullae of gerbils to examine the effects, on membrane potential, of changes in the ionic environment that are known, from other experiments, to influence the rate of catecholamine secretion.

2. Depolarization in response to acetylcholine fell linearly with the logarithm of the extracellular sodium concentration over the range 154‐3 m
M and reached a value, in sodium‐free medium, of about 30% of the control value.

3. The depolarizing effect of acetylcholine in sodium‐free media increased linearly with the logarithm of the extracellular calcium concentration over the range 1‐117 m
M.

It is concluded that depolarization in response to acetylcholine involves inward movement of both sodium and calcium ions.

4. Depolarization was also observed in response to the secretagogues, excess potassium and barium, both in sodium‐rich and sodium‐free media. The effect of barium was antagonized by calcium, and it is suggested that these two cations interact at the level of the plasma membrane.

5. Depolarization does not appear to be tightly coupled to secretion, for acetylcholine or excess potassium still depolarized the chromaffin cells when the environment was calcium‐free or contained an excess of magnesium, conditions that inhibit secretion. Furthermore, although acetylcholine had some depolarizing effect in sodium‐free media, the level to which the membrane potential fell was not below the control ‘resting’ potential since the cells in sodium‐free medium were hyperpolarized; yet, secretory responses are augmented in such conditions.

6. It is proposed that depolarization in response to acetylcholine may be no more than the electrical sign of increased permeability to ions such as sodium and calcium, and that depolarization is not, in itself, a key event in stimulus—secretion coupling. The evidence is held to favour the view that movement of calcium into the chromaffin cells on exposure to acetylcholine is responsible for evoking secretion.
Potassium‐stimulated respiration and intracellular calcium release in frog skeletal muscle
Authors: Van Der Kloot William G.
Published: December 2014

1. In 1931 Fenn showed that the respiration of frog twitch muscles increases when [K+]o is raised. The present paper is a further study of potassium‐stimulated respiration. Stimulation depends on membrane potential, since respiration is also stimulated by elevated [Rb+]o or [Cs+]o in direct relation to their ability to depolarize.

2. When [K+]o is elevated to 25 m
M there is an increase in respiration which is sustained for hours. If [K+]o is 30 m
M or above, there is a transitory burst of stimulated respiration, followed by a decline back to the basal level.

3. If [K+]o is raised in steps from 20 to 30 m
M, there may never be a burst of increased oxygen consumption. Often a rise in [K+]o from 20 to 24 m
M decreases respiration.

4. The response to elevated [K+]o can be blocked by divalent cations or by local anaesthetics; the blocking agents do not interfere with the depolarization of the membrane. The blocking agents act rapidly; they probably take effect soon after they contact the cell membrane.

5. Either extracellular Ca2+ or Sr2+ is important for the stimulation of respiration. The burst produced by 50 m
M [K+]o is transformed into a sustained rise in respiration when [Ca2+]o or [Sr2+]o are also raised. If a muscle is stimulated with 25 m
M [K+]o in the absence of extracellular calcium, respiration is elevated as usual, but now the rise is transitory unless Ca2+ or Sr2+ are added back to the extracellular solution.

6. Depolarization seems to stimulate respiration by causing the release of Ca2+ into the sarcoplasm. Since respiration is increased by a depolarization below the threshold for producing a contracture, respiration is more sensitive than contraction as an indicator of sarcoplasmic calcium concentration.

7. A model for the relation between sarcoplasmic calcium and membrane potential is proposed. The model accounts for the time course of the stimulation of respiration and also for much of the available data on potassium contracture. In the model, Ca2+ is released into the sarcoplasm from a store in the cell. With depolarization, the release of Ca2+ from the store is increased, but the rate at which extracellular Ca2+ can replenish the store is decreased. The ability of the longitudinal reticulum to pump Ca2+ from the sarcoplasm does not vary with membrane potential.
An electrophysiological study of single vagal efferent units associated with gastric movements in sheep
Authors: Iggo A. , Leek B. F.
Published: December 2014

1. A method for obtaining reticulo‐ruminal movements for up to 19 hr in halothane‐anaesthetized sheep is described. The duration, wave form and frequency of the movements resembles those in the conscious animal except that ruminal movements have a lower amplitude.

2. A method of recording for up to 5½ hr single efferent unit discharges from fibres presumed to innervate the reticulo‐rumen is described.

3. At least seven distinguishable types of discharge pattern were recorded. By relating these temporally to movements of the reticulum and rumen it was concluded that Types I, II and III occurred in fibres innervating the reticulum or associated structures, Type IV the rumen and Types V, VI and VII other gastric structures not yet identified. Apart from Type VII units there was no ‘resting discharge’ in efferent fibres during the quiescent phase of the gastric cycle.

4. We conclude that the co‐ordination of the complex sequence of gastric movements in ruminant animals is a function of the ‘gastric centres’ in the hind‐brain through their ability to determine the pattern, durations, spike frequencies and temporal interrelationships of discharges in gastric motoneurons innervating the different parts of the forestomach.
Nervous factors influencing the membrane activity of intestinal smooth muscle
Authors: Kuriyama H. , Osa T. , Toida N.
Published: December 2014

The effects of various chemical agents on the spontaneous membrane activities and those electrically elicited in the smooth muscles of small intestine were investigated.

1. The effects of various chemicals on the spontaneously active membrane might be summarized as follows. (a) Cholinergic agents; atropine slightly hyperpolarized the membrane and reduced the amplitude of slow potential changes even in aged preparations. Prostigmine depolarized the membrane, and enhanced the amplitude and prolonged the duration of the slow potential changes. Atropine prevented the actions of prostigmine on the membrane. (b) Ba2+ depolarized the membrane, and enhanced the amplitude and prolonged the duration of the slow potential changes. The spike frequency was initially increased, then reduced. Atropine and tetrodotoxin partially prevented the action of Ba2+ on the membrane activities.

2. Effects of chemical agents on the membrane activity elicited by electrical stimulation might be summarized as follows. (a) Short pulse stimulation (0·5‐1 msec) generated the spike as a direct response of the muscle cell membrane, then it was followed by slow depolarization, delayed hyperpolarization, i.e. the ‘inhibitory potential’, and post‐inhibitory rebound successively. (b) The slow depolarization and the post‐inhibitory rebound were reduced in amplitude by treatment with atropine, and enhanced by treatments with prostigmine and Ba2+. Tetrodotoxin blocked all activities except the spike.

3. When repetitive stimulation (20 c/s) was applied to the membrane, the membrane hyperpolarized; then, after 3‐5 sec, it gradually depolarized even if the stimulation was continued, and triggered spikes. The hyperpolarization always preceded depolarization. The duration and the amplitude of the delayed depolarization was proportionally increased by the increased intensity and duration of stimulation. Atropine and tetrodotoxin blocked the generation of the post‐inhibitory rebound.

4. Effects of repetitive stimulation on the stored tissues were observed. The responses to repetitive stimulation of the membrane of muscles which had been stored 50 hr at 4 °C, were the same as those observed in the fresh tissue. The response of the tissue which had been stored 100 hr was the same as that observed in the fresh tissue treated with tetrodotoxin, i.e. all activities except the spikes were blocked.
The effect of progressive hypoxia on the respiratory and cardiovascular systems of the chicken
Authors: Butler P. J.
Published: December 2014

1. During the initial stages of progressive hypoxia the intact, unanaesthetized chicken shows increases in heart rate and respiratory frequency with no change in arterial blood pressure and oxygen consumption. During the later stages, heart rate, diastolic and mean blood pressure and oxygen consumption fall, while respiratory frequency increases further.

2. Following bilateral cervical vagotomy and adrenergic β‐receptor blockage there is no tachycardia, but the late bradycardia and fall in blood pressure do occur during progressive hypoxia. Respiratory frequency remains at a low level after vagotomy.

3. It is suggested that the initial tachycardia is dependent on both the sympathetic and parasympathetic nervous systems, and that the former helps maintain arterial pressure during the early stages of hypoxia. Bradycardia and hypotension seem to be due to anoxia itself, and the vagus is essential for the increase in respiratory frequency.
Observations on the site and mode of action of pyrogens in the rabbit brain
Authors: Cooper K. E. , Cranston W. I. , Honour A. J.
Published: December 2014

1. Leucocyte pyrogen has been injected bilaterally into various parts of the rabbit brain. It caused fever when injected into the pre‐optic area and the anterior hypothalamus, but not when injected into the posterior hypothalamus, the mid‐brain, the pons, the cerebellum or the cerebral cortex.

2. The mean time which elapsed between a leucocyte pyrogen injection into the anterior hypothalamus and the onset of fever was 7·8 min. For similar injections of bacterial pyrogen the time lag was 24·8 min. The mean time lag between bilateral injections of noradrenaline into the anterior hypothalamus and the onset of fever was 7·4 min.

3. The amount of leucocyte pyrogen required to cause fever when injected into the anterior hypothalamus was less than 1/100 of that required to cause a similar fever on intravenous injection. The quantity of bacterial pyrogen injected into the hypothalamus was of the same order as that which would cause a similar fever on intravenous injection.

4. Control injections of saline, plasma, cerebrospinal fluid, heated leucocyte pyrogen and red cells into the anterior hypothalamus did not cause fever.

5. After attempts to deplete the hypothalamus of its monoamine stores by intraventricular injections of reserpine, the rabbit had fever as a result of an intravenous injection of bacterial pyrogen.

6. We conclude that the anterior hypothalamus and the pre‐optic area are sites at which leucocyte pyrogen acts to cause fever in the rabbit. The mechanism of this febrile response is not clear, but it appears that part, at least, of the response could be mediated by a mechanism other than release of noradrenaline or failure to release 5‐HT.
Centrally evoked sympathetic discharge: a functional study of medullary vasomotor areas
Authors: Kahn Norman , Mills Elliott
Published: December 2014

1. The medulla oblongata was stimulated electrically in decerebrate cats following bilateral vagotomy. Changes in splanchnic nerve discharge evoked by stimulation of pressor and depressor areas in the medulla are correlated with changes in arterial pressure. An interaction of baroreceptor afferents with the efferent sympathetic system at the level of the medulla and/or spinal cord is demonstrated. Evidence is presented which suggests that it is possible to alter activity selectively in a given division (splanchnic) of the sympathetic outflow.

2. Evoked responses were categorized as follows:

(a) Sustained splanchnic activation; an immediate increase in total splanchnic activity occurred with only a small, gradual decline in activity during the stimulation period. Mild stimulation (150‐200 μA) raised systolic pressure by 60‐80 mm Hg and stronger stimulation (300‐400 μA) increased pressure by 100‐150 mm Hg. When comparable pressor responses were elicited from points on either side of the mid line, splanchnic excitation was greater with homolateral stimulation (left side).

(b) Unsustained splanchnic activation; an immediate increase in activity occurred which declined sharply as systolic pressure rose by 60‐100 mm Hg during stimulation. Such a decline was attributed to the influence of baroreceptor afferents. Thus, if previous carotid occlusion was maintained during stimulation, the decline in activity was minimized although the pressor response increased. It is suggested that the structures yielding unsustained responses differ from those yielding sustained responses in their functional relation with the baroreceptor afferents.

(c) Reduced splanchnic discharge during direct medullary stimulation; a partial or complete inhibition of splanchnic activity was obtained, which was sometimes accompanied by a 20‐40 mm Hg reduction in systolic pressure. However, the direction and magnitude of the systemic pressure change were not as consistently related to the splanchnic response as they were during activation. Even if splanchnic efferent activity were elevated by carotid occlusion, stimulation still reduced discharge.
The effect of oxytocin and adrenaline on blood flow in the hind limb of the dog following chronic lumbar sympathectomy
Authors: Lloyd Sybil , Pickford Mary
Published: December 2014

1. In a number of dogs the last two lumbar ganglia were removed unilaterally. At various dates up to the 56th day after operation the dogs were anaesthetized and the effect of oxytocin and adrenaline on hind‐leg blood flow studied. Oxytocin alone reduced leg flow in all dogs after operation.

2. Until approximately day 11 after operation oxytocin given during an infusion of adrenaline increased leg blood flow, as it does in normal dogs not given adrenaline infusion. After that date it reduced the flow even during adrenaline infusion. The timing of this change suggests that the normal response to adrenaline depends on the presence of undegenerated nerve fibres.

3. In one animal the sympathetic nerves were crushed between the last two lumbar ganglia and beyond the last, and hind‐leg blood flow frequently measured by means of venous occlusion plethysmography until day 204, when the animal was anaesthetized and acute observations made. Electrical stimulation of the sympathetic chain above the site of crushing caused a reduction in leg flow, indicating that at least some of the nerve supply had regenerated. However, oxytocin reduced leg flow when used alone and exerted no apparent effect in the presence of adrenaline.

4. It is suggested that sympathetic nerves to vascular smooth muscle have a function or functions other than transmitter release and that when crushed nerves regenerate the functions do not recover at the same rate.