bluuebunny/crossref_metadata_2025 huggingface dataset:
The metabolism of chylomicron fatty acids by isolated rat heart‐lung preparations
Authors: Simpson‐Morgan M. W.
Published: December 2014

1. An isolated rat heart—lung preparation is described. This preparation is perfused with the rat's own blood, in the absence of heparin or other anticoagulants, by the sustained efficient contractions of the heart. The preparation has only a small circulating blood volume and is stable for up to 3 hr.

2. Chylomicrons which were infused continuously into the circulating blood of the heart—lung preparation were removed from the circulation.

3. [14C]Palmitic acid incorporated into the chylomicrons was oxidized rapidly to CO2. Rates of oxidation of chylomicron fatty acids in excess of 3 mg/hr were measured and suggest that in the intact rat, the heart and lungs could account for up to 10% of the chylomicron fatty acids oxidized.

4. The infusion of glucose did not reduce the oxidation of the chylomicron fatty acids, whilst the infusion of sufficient quantities of chylomicrons in the absence of glucose spared some of the cardiac glycogen.
Activity of aortic chemoreceptors during electrical stimulation of the stellate ganglion in the cat
Authors: Mills Elliott
Published: December 2014

1. In anaesthetized cats, action potentials from aortic chemoreceptors were recorded during electrical stimulation of preganglionic sympathetic fibres to the decentralized right stellate ganglion. The rate of discharge in afferents in the ipsilateral but not in the contralateral aortic nerve increased when stimulus frequency was 4/sec or higher.

2. The post‐ganglionic fibres in the stimulated pathway originate in the right stellate ganglion. They leave the ganglion in the caudal limb of the ansa subclavia, and the results suggest that the ipsilateral aortic nerve and its branches distribute sympathetic fibres as well as afferents to aortic bodies.

3. In contrast, the rate of discharge of chemoreceptor fibres in the contralateral aortic nerve fell as blood pressure increased during sympathetic stimulation. Sympathetic pathways to the aortic bodies can maintain or increase chemoreceptor discharge during hypertension elicited by sympathetic activation.
The release of adenosine triphosphate from frog skeletal muscle in vitro
Authors: Boyd I. A. , Forrester T.
Published: December 2014

1. Active frog sartorius muscle in vitro liberates a substance into the bathing solution which has a pronounced stimulatory action on the frog heart.

2. The stimulatory effect is not due to an increase in the K+ concentration of the bathing solution, nor is it due to the liberation of catecholamines.

3. In a molecular sieve chromatography procedure the stimulatory substance can be eluted in a single fraction which shows a maximum absorption of U.V. light at a wave‐length of 265 nm, indicative of the presence of substances containing a purine ring.

4. Low concentrations (10−7‐10−8 g/ml.) of adenosine triphosphate (ATP), adenosine diphosphate (ADP) and uridine triphosphate (UTP) have a marked stimulatory action on the frog heart. The action of ATP and ADP on the heart is qualitatively very similar to that of the muscle bathing solution, while the action of UTP is distinctly different. The triphosphates of inosine, cytidine and guanosine stimulate the heart when in high concentration only. Adenosine and adenosine monophosphate do not stimulate the heart.

5. Incubation of the muscle bathing solution and of solutions of ATP with the enzyme apyrase for the same time produces a similar marked reduction in the stimulatory action of both on the heart. Apyrase catalyses the break‐down of nucleotide triphosphates to monophosphates.

6. The elution behaviour of the stimulatory substance determined by molecular sieve chromatography is the same as that for ATP.

7. The muscle bathing solution causes light to be emitted from firefly lantern extract, the pattern of light emission being similar to that produced by nucleotide triphosphates.

8. The concentrations of ATP having the same quantitative action on the frog heart and on firefly extract as a given muscle bathing solution are almost identical, whereas the matching concentrations of ADP and UTP in the two methods of assay are widely different.

9. It is concluded that ATP is released from active frog skeletal muscle in vitro. This release may play an important part in the reactive hyperaemia of muscular exercise since ATP has a powerful vasodilator action.
The uptake and release of thyroxine and tri‐iodothyronine by the perfused rat heart
Authors: Hillier A. P.
Published: December 2014

1. The uptake and release of [131I]
L‐thyroxine and
L‐3,5,3′‐tri‐iodothyronine have been studied in the rat heart perfused by Krebs—Ringer bicarbonate solution.

2. After 30 min perfusion thyroxine equilibrates to a ‘space’ of 15 ml./g of heart (i.e. each gram of tissue accumulates thyroxine equivalent to 15 ml. of perfusion fluid). Tri‐iodothyronine takes about 120 min to equilibrate to a ‘space’ of about 75 ml./g of heart. These results are independent of the concentration of the hormone between 1 × 10−5 and 1·0 μg/ml.

3. The uptake of thyroxine at 17° C is almost identical with that at 37° C.

4. Radioactive thyroxine and tri‐iodothyronine are both released from the heart by two distinct exponential processes, viz. a rapid process with a half‐time of 14 min and a slow process with a half‐time of 60 min. About 30% of the total thyroxine and about 83% of the total tri‐iodothyronine are present in the slow‐release compartment.
The effect of fatty acid on the uptake of thyroxine by the perfused rat heart
Authors: Hillier A. P.
Published: December 2014

1. A study has been made of the effect of fatty acids on the uptake of thyroxine by the perfused rat heart.

2. Oleic acid increases the thyroxine uptake of hearts perfused by solutions containing serum. In the absence of serum, oleic acid is without action.

3. The thyroxine uptake of hearts perfused by 0·25% serum is approximately doubled by the addition of oleic acid at a concentration of 0·0025 m‐equiv/l. An effect on thyroxine uptake, however, is demonstrable at only one twentieth of this concentration.

4. Long‐chain fatty acids are much more effective than short‐chain fatty acids.
The influence of muscle length on the development of fatigue in toad sartorius
Authors: Aljure Emilio F. , Borrero Luis M.
Published: December 2014

1. Fatigue curves were obtained on muscles contracting at length (L) different from the optimal (Lo), and performing isometric tetani of fixed duration at regular intervals. Every sixth tetanus occurred at Lo, the remainder took place at L. The parameters of the fatigue curve were compared with those of controls contracting always at Lo. Fatigability was measured as the coefficient of exponential decrease of tension with time.

2. Fatigability varied linearly with length in shortened and lengthened muscles, but the slopes of the relations were significantly different for the two groups.

3. The tension values from single experimental muscles fell on two independent curves, one for those obtained at Lo, another for data at L. The same muscle showed, therefore, two different fatigue processes which followed independent temporal evolutions.

4. Points 2 and 3 of this Summary imply that fatigue is a process dependent on the actual setting of the myofilaments during contraction and not distributed uniformly within the sarcomere.

5. It is proposed that fatigue results from local changes taking place at discrete reactive points in the myofilament. The experimental results are discussed in terms of this hypothesis and of the sliding model of contraction.
The effects of chloralose‐urethane and sodium pentobarbitone anaesthesia on the local and autonomic components of the circulatory response to arterial hypoxia
Authors: Korner P. I. , Langsford G. , Starr D. , Uther J. B. , Ward W. , White S. W.
Published: December 2014

1. The circulatory and respiratory responses to severe arterial hypoxia were studied in normal rabbits, ‘de‐efferented’ rabbits without functioning autonomic effectors, and atropinized animals before anaesthesia and during chloralose‐urethane and sodium pentobarbitone anaesthesia. Net systemic autonomic activity and autonomic activity to the heart was assessed from a comparison of the responses of the various preparations.

2. In the normal spontaneously breathing animal each anaesthetic had a similar mode of action, and modified qualitatively the circulatory response present before anaesthesia. In the ‘de‐efferented’ animal the circulatory response was determined by the local effects of hypoxia, and was altered only quantitatively during anaesthesia.

3. In the normal unanaesthetized animal the reflex changes in autonomic activity during hypoxia consisted of a large increase in vagal efferent activity, a decrease in cardiac sympatho‐adrenal activity, and an increase in total sympatho‐adrenal constrictor activity.

4 In hypoxia during anaesthesia the vagal efferent activity no longer increased, but the change in sympatho‐adrenal activity to heart and systemic circulation was the same as before anaesthesia in the spontaneously breathing animal. During anaesthesia with controlled ventilation systemic sympatho‐adrenal activity increased further, and bradycardia again developed. The bradycardia was now due exclusively to reduction in cardiac sympathetic activity and not to an increase in vagal efferent activity.
The effect of vasopressin on hormone secretion and blood flow from the thyroid vein in sheep with exteriorized thyroids
Authors: Falconer I. R.
Published: December 2014

1. Vasopressin has been shown to activate the thyroid in some species, and also to be released into the bloodstream after emotional and other stresses.

2. Emotional stimuli applied to sheep have previously been shown to increase thyroid secretion and the possible influence of vasopressin in this process has been investigated. Sheep bearing exteriorized thyroid glands were used, so that thyroid vein blood could be collected in undisturbed conscious animals.

3. 125I or 131I (50 μc) was injected
I.M. into the sheep; 4‐7 days later, samples of thyroid vein blood were collected at 10 min intervals for 4 hr, and the concentration of total and protein bound 125I or 131I was measured. Intravenous infusions of 0·3, 3·0 or 31 m‐u./min arginine or lysine vasopressin, or close arterial infusions of 3·0 or 31 m‐u./min arginine vasopressin were administered 1·5 hr after commencement of blood sampling. Blood flow from the thyroid was measured by a plethysmographic technique during similar experiments.

4. No significant changes in thyroid hormone secretion were observed as a result of vasopressin infusion, and it was concluded that vasopressin release does not play a part in the activation of the thyroid resulting from emotional stimulus in the sheep.
The influence of ions on the labelling of adenosine triphosphate in red cell ghosts
Authors: Lant A. F. , Whittam R.
Published: December 2014

1. The ionic composition of human red cell ghosts and suspending Ringer solutions have been varied independently. Measurements were made of the incorporation of [32P]o‐phosphate (32Pi) into ATP associated with different concentration gradients of Na and K across the membrane.

2. Some incorporation of 32Pi was always found irrespective of the ionic composition of ghosts or media. However, additional labelling of energy‐rich phosphate occurred when low Na, high K ghosts were incubated in a high Na, K‐free medium. This did not occur when there was only a gradient of either Na or K. Downhill movements of both Na into and K out of the ghosts were needed for the extra labelling.

3. Even in the presence of suitable ionic gradients, the extra incorporation was prevented by ouabain or by adding a small amount of external K sufficient to facilitate normal operation of the Na pump.

4. Increase in internal Pi stimulated the incorporation.

5. The results show that the conditions for forward and backward running of the ATPase system associated with the Na pump are such that both reactions cannot proceed optimally at the same time.
Histological and electrophysiological investigation of lizard skeletal muscle
Authors: Proske U. , Vaughan P.
Published: December 2014

1. The patterns of innervation and electrical properties of muscle fibres in a skeletal muscle of the blue tongue lizard Tiliqua nigrolutea have been investigated.

2. Gold impregnation of nerve terminals and staining of muscle fibre junctional areas for cholinesterase showed that there are two histological types of muscle fibre in scalenus muscles of the lizard: (a) those usually receiving single en plaque innervation, and (b) those that receive multiple en grappe terminations.

3. In normal solution and in solutions to which small doses of curare were added, two types of subthreshold post‐junctional response were recorded following nerve stimulation, (a) potentials with rapid rates of rise and a half‐decay time of less than 10 msec and (b) responses with fast rise times and long half‐decay times (50 msec or more).

4. Fast time course subthreshold responses often gave rise to propagated action potentials. In curarized preparations ((+)‐tubocurarine 0·4‐1·0 μg/ml.) action potentials failed, giving way to junction potentials of decreasing amplitude, when stimulation was maintained at rates of 5/sec or more. The decay phases of fast time course potentials were closely approximated by error functions.

5. Slow time course responses summated during repetitive stimulation, but action potentials were never produced. The decays of slow junction potentials were well fitted by exponentials. It is suggested that fibres in which they were recorded received distributed, en grappe innervation.

6. Fibres in which fast time course junction potentials were recorded were excited by direct stimulation via an intracellular micro‐electrode. They had apparent membrane resistance and capacity of about 4000 Ω. cm2 and 7 μF/cm2.

7. Fibres exhibiting slow junction potentials could not be excited directly, even when depolarizing pulses were preceded by hyperpolarizations of 50 mV or more for more than 20 msec. Such fibres had an apparent membrane resistance of 31 × 103 Ω.cm2 (mean) and a capacity of less than 3 μF/cm2 (eight fibres).

8. Curarized muscles developed tension in response to nerve stimulation at frequencies of 5/sec or more. The tension profile was smooth at even the lowest frequencies at which a response was elicited. Normal fusion frequency was around 50/sec.

9. It is suggested that fibres exhibiting slow junction potentials were functionally similar to amphibian tonic fibres.

10. Some fibres were found in which action potentials could be elicited by stimulation of one or more axons. Their subthreshold responses and passive properties were not determined and it remains uncertain to which of the two structural types they belong.
The effect of acidaemia on the response to stimulation of the autonomic nerves to the heart
Authors: Linden R. J. , Norman J.
Published: December 2014

1. The effects are described of an acidaemia produced either by an inhalation of carbon dioxide or by an infusion of hydrochloric acid on the response of the heart to stimulation of the ansae subclaviae and right vagus nerve in anaesthetized dogs.

2. The results show that during an acidaemia (pH 6·95) of up to 2 hr duration the response to stimulation of the right vagus nerve was enhanced and that the inotropic response to stimulation of sympathetic nerves was not changed; the chronotropic response was depressed during acidaemia only at the low end of the range of responses, from 0 to 40 beats/min. The importance of preventing acidaemia when investigating reflex heart rate responses is discussed.

3. It is suggested that in the intact animal with an innervated heart the response of the heart to stimulation of the sympathetic nerves is unaltered in acidaemia and that the reported effects of changed cardiovascular response during acidaemia may in part be explained by the enhanced response to vagal stimulation and an altered response of the peripheral vessels.
Reflexes to sacral parasympathetic neurones concerned with micturition in the cat
Authors: de Groat W. C. , Ryall R. W.
Published: December 2014

1. Reflexes to sacral parasympathetic neurones were studied by electrophysiological techniques in decerebrate, in chloralose‐anaesthetized, and in chronic spinal cats.

2. Excitatory reflexes from pelvic nerve and sacral somatic afferent nerve fibres were present before and after chronic transection of the spinal cord, but the latencies differed markedly. It was concluded that the long‐latency reflexes observed when the spinal cord was intact involved long‐loop reflexes to the brain‐stem. The weak, short‐latency reflexes in the chronic spinal cat were never observed when the spinal cord was intact and could be due to reorganized spinal connexions. The short‐latency reflexes are probably unimportant in normal micturition.

3. Stimulation of afferent fibres in the pelvic or sacral somatic nerves produced short‐latency inhibitory post‐synaptic potentials (IPSPs) and inhibition of discharges in parasympathetic neurones. This inhibition was due to a spinal reflex.

4. A local reflex was demonstrated in the pelvic plexus. This was probably a cholinergic axon reflex, but the remote possibility that it was a local cholinergic reflex involving sensory neurones in the bladder wall has not been excluded.
Effect of prolonged saline‐exposure on sodium transport across frog‐skin
Authors: Hornby R. , Thomas S.
Published: December 2014

1. Differences in Na transport between skins from Rana temporaria and R. esculenta maintained for up to several weeks in water or 0·7% saline (0·7 g NaCl in 100 ml. H2O), with and without daily injections of 4% saline (4 g NaCl in 100 ml. H2O), were measured, in vitro.

2. In saline‐treated skins, the following changes were found:

(a) An increased Na content.

(b) A consistent decrease in short‐circuit current (Isc).

(c) An increased d.c. resistance, R, the consistency of which varied with the anion content of the Ringer solution.

(d) A highly significant fall in Na influx, accounting for the reduced Isc; a small reduction in Na efflux was not significant, statistically.

(e) The Pitressin‐induced increment in Isc was usually considerably lower compared with that in water‐exposed skins; considered relative to the pre‐Pitressin values, however, there were no clear differences.

(f) By calculation from the changes in resistance (R) caused by replacement of outer Na2SO4 Ringer by K2SO4 Ringer solution,

I. E0, the electromotive force of the active sodium transport system, was moderately, but significantly, reduced,

II. R shunt, the shunt path resistance, was moderately, but significantly, increased, and

III. Rser, the series path resistance, was considerably, and highly significantly, increased.

(g) K influx from outer K2SO4 Ringer solution was reduced.

3. Differences between skins from water‐exposed and saline‐treated frogs persisted, in vitro, despite the occurrence of anionic‐dependent acute changes after mounting in Ringer solution.

4. There were seasonal changes in Isc, and in the effects of saline treatment.

5. The findings are discussed in terms of decreased permeability of outer barriers to ion‐diffusion, and reduced activity of a Na pump.
Blood volume changes in outdoor exercise of 8‐10 hour duration
Authors: Pugh L. G. C. E.
Published: December 2014

1. Blood volume was measured with carbon monoxide on six hill‐walkers before and immediately after a 28‐mile walk on two occasions. The subjects had free access to food and fluid.

2. Blood volume increased and haematocrit fell significantly on both occasions compared with the control observations. The mean increase of blood volume was 204 ml. or 3·9% (P < 0·01) and the mean reduction of haematocrit was 2·1% (P < 0·02). Plasma volume calculated from these results increased by 233 ml. or 7·3%. There was no significant change in red cell volume or plasma protein concentration.

3. These changes are the opposite of those taking place in short‐term exercise and suggest that in the absence of dehydration a compensatory adjustment of blood volume takes place during exercise of many hours duration.
Cutaneous thermoreceptors in primates and sub‐primates
Authors: Iggo A.
Published: December 2014

1. Cutaneous thermoreceptors were examined electrophysiologically in primates (monkey, baboon) and in sub‐primates (dog and rat) by recording from single units dissected from peripheral nerves.

2. Thermal stimuli were delivered from thermodes in contact with the skin.

3. Primate ‘cold’ receptors had spot‐like receptive fields and were found in both hairy and glabrous skin. The conduction velocities of the axons ranged from 0·6 to 15·3 m/sec.

4. The discharge from the primate receptors characteristically appeared in bursts with intervals of silence within the range temperatures of 18‐40° C. Static and dynamic sensitivity curves were established, with maxima about 30° C.

5. Cold receptors in the lip of the dog had maximal sensitivity at 31‐37° C. The axons were myelinated with conduction velocities less than 20 m/sec.

6. ‘Warm’ receptors, with maximal sensitivity at 40° C and non‐myelinated axons, were abundant in the scrotal nerve of the rat. The ‘cold’ receptors had maximal responses at 23‐28° C.

7. The ‘spurious’ thermoreceptor behaviour of slowly adapting mechanoreceptors is described and the way in which they may distort integrated potential records from whole nerves is analysed.
A quantitative analysis of the responses of certain dorsal horn neurones to mechanical stimulation of the large foot pad in cats
Authors: Fuller D. R. G. , Gray J. A. B.
Published: December 2014

1. Responses of single units in the dorsal horns of the spinal cords of cats to mechanical stimulation of the large foot pad have been recorded.

2. The observations made with different single stimuli belonging to the set under different conditions of excitability have included: the numbers of impulses per response, their means and variation; the frequency distributions of impulse numbers; the time distribution of activity during a response and in particular the probability of an impulse occurring in each successive time interval.

3. The observations with two stimuli were designed to measure the [ill] of the whole response contributed by the second stimulus and [ill] relate the size of this contribution to the interval between the stimuli and their distance apart.

4. The results are discussed and it is concluded that the observed transformations allow representations of successive events to exist at the same time and that the purpose of the transformation may therefore be to allow particular types of interaction between successive events. A model of mechanism which is consistent with many of the observations is also discussed.
Relationship between growth hormone and muscular work in determining muscle size
Authors: Goldberg A. L. , Goodman H. M.
Published: December 2014

1. Growth hormone reduced the loss of weight or induced net growth of denervated soleus and plantaris muscles in hypophysectomized rats.

2. Growth hormone did not alter the weight of the denervated muscle relative to its contralateral control, i.e. the hormone increased the sizes of denervated and control muscles proportionately.

3. Similarly treatment with the hormone appeared to cause proportional growth in muscles undergoing work‐induced hypertrophy and their contralateral controls.

4. It is suggested that muscle size is determined by at least two independent factors, growth hormone and muscular work. Growth hormone appears to act as a biochemical ‘amplifying system’ for the cell's anabolic machinery and determines the absolute changes in muscle size which result from changes in muscular work.
Retardation of protein synthesis in rat foetal liver on inhibiting rate of histamine formation
Authors: Grahn B. , Hughes Rosanne , Kahlson G. , Rosengren Elsa
Published: December 2014

1. The rate of protein synthesis, as gauged by the incorporation of [14C]leucine, has been determined in vitro in foetal and 5‐day‐old rat liver, tissues with respectively high and low histidine decarboxylase activity.

2. Incorporation of [14C]leucine was considerably faster in foetal liver than in liver of the young.

3. Following inhibition of histamine formation by α‐methyl histidine, a specific inhibitor of histidine decarboxylase, the rate of incorporation of [14C]leucine was substantially diminished in foetal but not in liver of the young.

4. The retarded incorporation of [14C]leucine consequent on inhibition of endogenous histamine formation could not be restored by extracellular histamine, i.e. by adding histamine to foetal liver tissue.

5. On complete inhibition of protein synthesis by puromycin in foetal and 5‐day‐old rat liver the rate of histamine formation was not affected.

6. The present observations support the view of endogenous histamine formation, ‘nascent histamine’, as an essential part of the metabolic machinery in some rapidly growing tissues.
The structure and function of a slowly adapting touch corpuscle in hairy skin
Authors: Iggo A. , Muir A. R.
Published: December 2014

1. Slowly adapting cutaneous mechanoreceptors, in the cat and primates, have been studied by histological and neurophysiological methods.

2. Each touch corpuscle is a dome‐shaped elevation of the epidermis, whose deepest layer contains up to fifty specialized tactile cells.

3. Nerve plates, enclosed by the tactile cell (Merkel cells), are connected to a single myelinated axon in the dense collagenous core of the corpuscle.

4. The corpuscle generated > 1000 impulses/sec when excited by vertical surface pressure. The response was highly localized and showed a low mechanical threshold, the frequency being dependent upon the velocity and amplitude of the displacement. There was a period of rapid adaptation before a sustained response which might continue for > 30 min.

5. A quantitative analysis of the responses to excitation by displacements of differing amplitude, velocity and duration is included.

6. The discharge of touch corpuscle units evoked by a mechanical stimulus was temperature‐sensitive, and was enhanced by a fall in skin temperature.
Force measurements in skinned muscle fibres
Authors: Hellam D. C. , Podolsky R. J.
Published: December 2014

1. Isometric force was measured in skinned segments of frog semitendinosus muscle fibres exposed to solutions in which the calcium ion concentration was controlled with EGTA.

2. The threshold for force development, calculated from an apparent stability constant for the CaEGTA complex of 106.69
M−1 at pH 7·0, was generally close to pCa 7·5. Maximum force was reached at about pCa 6·0.

3. Maximum force is proportional to the cross‐sectional area of the fibres.

4. The rate of force development was slower than that expected from simple diffusion of a substance from the bathing solution into the fibre. The delay appears to be due to slow equilibration of the EGTA buffer system during calcium uptake by the sarcoplasmic reticulum.

5. Addition of deoxycholate (DOC) to the bathing solution produced a reversible increase in the rate of force development. The steady force was also increased for values of pCa that gave less than maximum force, which shifted the force—pCa relation toward lower calcium concentrations by about 0·5 pCa unit.

6. The length—force relation in partially activated preparations is similar to that reported for electrically activated intact fibres. This result suggests that in the region of myofilament overlap the affinity of the binding sites for calcium is uniform along the length of the calciumbinding myofilament.
The significance of the shape of the lens and capsular energy changes in accommodation
Authors: Fisher R. F.
Published: December 2014

1. A method for the estimation of the energy released by the anterior part of the lens capsule during accommodation is described. This includes

(i) A determination of the pressure required to distend the capsule by a standard volume.

(ii) The calculation from the photographed lens profiles of the degree of capsular contraction which occurs when the lens changes from the unaccommodated to the accommodated form.

(iii) Capsular volume changes in vitro are then related to the surface area changes calculated for the lens in vivo.

2. A correlation exists between the stored capsular energy per unit area or surface tension and the accommodation power of different species. The human lens capsule releases 1170 ergs/cm2 while the more spherical lenses of the cat and rabbit release 520 and 485 ergs/cm2 respectively for a 10% change in lens diameter. The amount of energy which can be stored depends on the degree of flatness of the lens and the volume of the anterior segment. The flatter the lens and the smaller the volume of the anterior segment, the greater the capsular surface tension.

3. The anterior surface of the human lens remains ellipsoidal throughout life. The changes of accommodation which occur in presbyopia may therefore be related to the lens profiles at various ages. It is found that a coefficient obtained by dividing the anterior volume of the lens by the 5th power of the equatorial radius of the lens modifies the degree of accommodation for a given change of lens diameter.

4. The loss of accommodation is proportional to the effective capsular surface energy until about the age of 45. The effective capsular surface energy can be defined as the energy which gives the same change in lens dioptric power per erg regardless of the lenticular profile changes which occur with age. It is obtained by multiplying capsular surface tension at a given age by a ratio. This is obtained by dividing the profile coefficient mentioned in paragraph 3 of the given lens, by the profile coefficient of the reference lens aged 15 (0·068). The effective surface energy of the entire lens falls from 110 ergs at the age of 15 to 50 ergs at 60. Assuming that ciliary power remains unaltered 55% of the loss of accommodation is accounted for solely by the fall in Young's Modulus of elasticity of the capsule and the changing shape of the lens with age.
Cardiovascular responses in apnoeic asphyxia: role of arterial chemoreceptors and the modification of their effects by a pulmonary vagal inflation reflex
Authors: James Jennifer E. Angell , Daly M. de Burgh
Published: December 2014

1. In the spontaneously breathing anaesthetized dog, the systemic circulation was perfused at constant blood flow; there was no pulmonary blood flow and the systemic arterial blood PO2 and PCO2 were controlled independently by an extracorporeal isolated pump‐perfused donor lung preparation. The carotid and aortic bodies were separately perfused at constant pressure with blood of the same composition as perfused the systemic circulation.

2. Apnoeic asphyxia, produced by stopping the recipient animal's lung movements and, at the same time, making the blood perfusing the systemic circulation and the arterial chemoreceptors hypoxic and hypercapnic by reducing the ventilation of the isolated perfused donor lungs, caused an increase in systemic vascular resistance.

3. While the systemic arterial blood was still hypoxic and hypercapnic, withdrawal of the carotid and aortic body ‘drive’ resulted in a striking reduction in systemic vascular resistance. Re‐establishing the chemoreceptor ‘drive’ immediately increased the vascular resistance again.

4. Apnoeic asphyxia carried out while the carotid and aortic bodies were continuously perfused with oxygenated blood of normal PCO2 had little or no effect on systemic vascular resistance.

5. The systemic vasoconstrictor response produced by apnoeic asphyxia was reduced or abolished by re‐establishing the recipient animal's lung movements, and this effect occurred in the absence of changes in the composition of the blood perfusing the systemic circulation and arterial chemoreceptors. This abolition of the vasoconstriction was due to a pulmonary reflex.

6. Apnoeic asphyxia slowed the rate of the beating atria due to excitation of the carotid and aortic body chemoreceptors. This response can be over‐ridden by an inflation reflex arising from the lungs.

7. It is concluded that the cardiovascular responses observed in apnoeic asphyxia are due, at least in part, to primary reflexes from the carotid and aortic body chemoreceptors engendered by arterial hypoxia and hypercapnia. The appearance of these responses is, however, dependent upon there being no excitation of a pulmonary (inflation) vagal reflex.
The slowing of gastric emptying by nine acids
Authors: Hunt J. N. , Knox M. T.
Published: December 2014

1. Test meals containing a range of concentrations of nine different acids were given to twenty healthy subjects. The acids used were hydrochloric, acetic, lactic, tartaric, phosphoric, citric, propionic, butyric and hexanoic.

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

3. A rectilinear relationship between the mean concentrations of acid (m‐equiv/l.) required to give a recovery of 450 ml. and the molecular weights of the acids used was found. The acids with high molecular weights were less effective than those with low molecular weights.

4. The results indicate that the molecular weights of the anions play the dominant part in determining the effectiveness of the various acids. Slowing of gastric emptying by acids does not seem to be dependent upon their pK values provided they are less than 5. The oil/water partition coefficients are also apparently irrelevant to effectiveness.

5. These findings are considered to be consistent with the view that a barrier to movement of the anions in an aqueous system limits the access of the hydrogen ions to duodenal receptors, which activate the mechanism slowing gastric emptying.
The role of the vagus nerves in the respiratory and circulatory reactions to anaphylaxis in rabbits
Authors: Karczewski W. , Widdicombe J. G.
Published: December 2014

1. Rabbits, previously sensitized to egg albumen, were anaesthetized and then rendered anaphylactic by a further injection of egg albumen; total lung conductance of flow, lung compliance, breathing rate, tidal volume, end‐tidal CO2%, systemic arterial and right atrial blood pressures and heart rate were measured. Before induction of anaphylaxis, some rabbits were vagotomized, some had their vagi cooled to block differential conduction, and others were paralysed and artificially ventilated to minimize secondary changes in afferent activity from the lungs and in blood gas tensions.

2. Lung conductance was reduced by anaphylaxis in spontaneously breathing and in artificially ventilated rabbits, and the effect was lessened by vagal cooling and greatly reduced by vagotomy; the hyperventilation of anaphylaxis took the form of an increase in tidal volume rather than in respiratory frequency during vagal cooling, and all changes in ventilation were abolished by vagotomy. These effects are therefore dependent on the integrity of vagal nervous pathways.

3. Lung compliance was reduced by anaphylaxis to a similar degree in all groups of rabbits; all groups showed similar falls in end‐tidal CO2%. These effects are therefore not dependent on the integrity of vagal conduction.

4. Anaphylaxis reduced systemic arterial blood pressure, the response being smaller when the vagi were cooled or cut.

5. It is concluded that anaphylaxis has direct actions on the pulmonary vascular bed, the distal airways or the alveoli. However, the changes in breathing, blood pressure and large airway calibre are mainly dependent on vagal reflex activity. By analogy with responses to injections of histamine and phenyl diguanide (Karczewski & Widdicombe, 1969b) it is concluded that anaphylaxis stimulates lung deflation and irritant receptors which mediate much of the reflex responses.
Functional consequences of tenotomy in hind limb muscles of the cat
Authors: Nelson P. G.
Published: December 2014

1. The chronic EMG activity and the contractile properties of normal, denervated or tenotomized cat triceps surae muscles were measured.

2. Following Achilles tenotomy no measurable change in EMG activity occurred in either the soleus or medial gastrocnemius muscles.

3. No change in the twitch time or tetanus‐twitch ratio was seen following tenotomy in these muscles despite marked atrophy of the muscle. Measurements were made 3‐10 weeks following the tenotomy procedures.

4. Denervation results in some prolongation of the gastrocnemius twitch.

5. The relationship between the contractile properties of a given muscle and the aggregate amount of activity imposed on that muscle by its innervation is discussed.
The secretion of electrolytes and enzymes by the pancreas of the anaesthetized cat
Authors: Case R. M. , Harper A. A. , Scratcherd T.
Published: December 2014

1. The bicarbonate concentration in cat pancreatic juice falls and the chloride concentration increases at slow secretory rates. The concentration of sodium and potassium remain constant at all secretory rates.

2. Acetazolamide reduces the maximal rate of secretion markedly, and the maximal bicarbonate concentration slightly, but does not alter the reciprocal relationship between bicarbonate and chloride at slow rates of flow.

3. By perfusion of the main duct it has been shown that there is a loss of bicarbonate and a gain of chloride across the duct wall due to a passive process of exchange diffusion. It is suggested that this may account for a substantial part of the flow‐dependent changes in bicarbonate and chloride concentrations in the intact gland.

4. The enzyme content of pancreatic juice is made up of a small continuous basal output, to which may be added a much larger secretion in response to hormonal stimulation.

5. From analysis of successive small samples of juice it has been found that the response to single injections of pancreozymin lasts a very short time, during which the secretory cells release enzymes in a small volume of chloride‐containing fluid.

6. It is concluded that in the cat pancreatic secretion consists of an isosmolar primary secretion mostly of sodium bicarbonate, to which is added small amounts of a chloride‐containing enzyme secretion. This fluid is modified, particularly at slow flow rates, by transductal exchange of chloride and bicarbonate which, at least in the main duct, is passive in nature.
A lesion of the transverse tubules of skeletal muscle
Authors: Howell J. N.
Published: December 2014

1. A method is described by which a selective lesion can be made in vitro in the transverse tubules of frog skeletal muscle.

2. The method consists of exposing the muscle for 1 hr or more to a buffered salt solution made hypertonic by the inclusion of 400 m
M glycerol and then returning the muscle to an isotonic salt solution. The lesion is induced during the washout of the glycerol.

3. Electron micrographs reveal that the lesion consists of a rearrangement of the T‐system membranes in such a way that the continuity of the tubules is lost. The membranes appear to coalesce into large vesicles scattered irregularly throughout the sarcoplasm.

4. The glycerol treatment results in a depression of the resting potential of up to 30 mV. The treated fibres are depolarized by high concentrations of K as are normal muscle fibres.

5. T‐tubule lesioned fibres are unable to respond mechanically either to electrical stimulation or to elevated K but they do contract in the presence of caffeine and relax when the caffeine is removed.

6. Problems concerning the variability of the procedure are presented and certain considerations concerning the mechanism of the effect are discussed.
Hypoxia and pulmonary arterial pressure in the rabbit
Authors: Owen-Thomas J. B. , Reeves J. T.
Published: December 2014

1. The effect of hypoxia on pulmonary arterial pressure was studied in young and adult rabbits.

2. In isolated perfused lungs, hypoxia caused no rise in pulmonary arterial pressure in rabbits on the day of birth. The size of the hypoxic response increased progressively until 9–11 days of age, when the adult response of a 20% rise of pulmonary arterial pressure at constant flow was attained.

3. The intact adult rabbit responded to hypoxia with a 14–30% rise in pulmonary arterial pressure, attributed to vasoconstriction and independent of frequency or tidal volume during positive pressure ventilation.
Transmission from preganglionic fibres in the hypogastric nerve to peripheral ganglia of male guinea‐pigs
Authors: Blackman J. G. , Crowcroft P. J. , Devine C. E. , Holman Mollie E. , Yonemura K.
Published: December 2014

1. Intracellular records were obtained from ganglion cells of the pelvic plexus of male guinea‐pigs.

2. The input resistance of cells which responded to intracellular stimulation varied from 40 to 150 MΩ. Slope resistance decreased when the membrane was hyperpolarized. Time constants varied from 5 to 200 msec. Resting membrane potentials ranged from 40 to 70 mV.

3. Action potentials in response to direct stimulation were followed by a prolonged phase of after‐hyperpolarization.

4. A second type of cell was also impaled which did not respond to electrical stimulation. These cells had resting membrane potentials in the range 60–70 mV, input resistances of less than 20 MΩ and time constants of less than 3 msec.

5. In most ganglion cells, stimulation of the hypogastric nerve evoked action potentials which were often followed by a secondary phase of depolarization indicating continuing transmitter action.

6. Orthodromic responses were generally ‘all‐or‐nothing’ and could not be graded with changes in stimulus strength. The latency of orthodromic responses indicated that ganglion cells were innervated by both B and C fibres in the hypogastric nerve.

7. Orthodromic responses were blocked by tubocurarine, 5 × 10−5 g/ml., and dihydro‐β‐erythroidine, 10−5 g/ml.

8. Spontaneous, excitatory post‐synaptic potentials of up to 4·8 mV in amplitude were observed. The frequency of their discharge was greatly increased by repetitive stimulation of the hypogastric nerve.

9. The ultrastructure of the pelvic ganglia was studied by electronmicroscopy. Two types of ganglion cell process were observed, fine (0·1 μ) branching tufts thrown up from the soma within the surrounding capsule and longer, thicker (1 μ) extracapsular processes. Synapses were found to occur most frequently between the varicose terminal segments of preganglionic axons and the small intracapsular processes.

10. Similarities between the properties of the pelvic ganglia innervated by the hypogastric nerve and those of the parasympathetic division of the autonomic nervous system are discussed.
Chicken cerebrospinal fluid: normal composition and response to insulin administration
Authors: Anderson D. K. , Hazelwood R. L.
Published: December 2014

1. With the exception of Na, K and Cl clear cerebrospinal fluid (c.s.f.) obtained from chickens varying in age from 6 weeks to 2 years did not reveal significant alterations in composition as could be related to age per se.

2. Considerably higher levels of total protein and glucose are found in chicken c.s.f. than are found in mammalian fluid; slightly more chloride is found in chicken than most mammalian c.s.f.'s.

3. Intravenous beef insulin depressed chicken cerebrospinal fluid glucose levels; insulin placed intracisternally had no effect on the avian glycogen body glycogen content indicating that c.s.f. glucose constancy, with or without glycogen body assistance, is not responsible for the resistance of the chicken to pharmacological doses of insulin.

4. Bovine insulin injected into the cisterna magna of chickens depresses plasma glucose partially by acting over vagal pathways to release endogenous insulin and partially by diffusion across the c.s.f.—blood barrier to exert a peripheral effect.
Osmotic responses demonstrating the extracellular character of the sarcoplasmic reticulum
Authors: Birks R. I. , Davey D. F.
Published: December 2014

1. Changes in the dimensions of the sarcoplasmic reticulum in frog sartorius muscles exposed to hypertonic and hypotonic solutions have been studied with the electron microscope.

2. The volume of the sarcoplasmic reticulum has been found to be linearly related with a negative slope to the reciprocal of the osmotic pressure. Over the range 0·75 to 3·5 × normal osmotic pressure the reticulum volume has been calculated to change from 11·5 to 18·5% of normal cell volume.

3. These changes in sarcoplasmic reticulum volume correspond to the calculated changes in the volume of the intra‐fibre sucrose compartment, postulated by earlier workers on the basis of studies on changes in cell volume with changes in osmotic pressure in living muscles.

4. To explain these and other related findings on the distribution of electrolytes in muscle, it is proposed that the sarcoplasmic reticulum of skeletal muscle is an extracellular compartment.

5. The significance of this hypothesis for the mechanism of excitation‐contraction coupling is discussed.
Respiratory responses to electrical stimulation of the cervical sympathetic nerves in decerebrate, unanaesthetized cats
Authors: Mills E. , Sampson S. R.
Published: December 2014

1. The effects of respiration of electrical stimulation of the peripheral cut end of the cervical sympathetic nerve were studied in seventeen decerebrate, unanaesthetized cats.

2. The tidal volume increased and the end‐tidal CO2 fell within 2‐3 breaths after the onset of stimulation in fourteen cats.

3. In three experiments tidal volume and respiratory rate fell during stimulation and increased above the control when the stimulus was interrupted.

4. All respiratory responses to sympathetic stimulation were abolished after cutting the carotid sinus nerves and are attributed to activation of chemo‐ and baroreceptor afferents.

5. With the carotid sinus nerves intact, respiratory responses could be eliminated completely only by cutting the post‐ganglionic sympathetics that pass directly to the carotid body and the post‐ganglionic sympathetics that join the glossopharyngeal nerves to course with the sinus nerves to the carotid bifurcation.

6. Pentobarbitone (10 mg/kg) or chloralose (40 mg/kg) given intravenously depressed spontaneous ventilation and responses to sympathetic nerve stimulation.

7. Stimulation changed blood pressure slightly in fourteen experiments; in ten it fell and in four it increased 10 mm Hg or less. After pentobarbitone or chloralose, stimulation elicited a pronounced pressor response.

8. The results of the study indicate that activation of sympathetic pathways to the carotid body constitutes an effective stimulus to ventilation.
Quantum efficiency and false positive rate
Authors: Hallett P. E.
Published: December 2014

1. This paper presents an analysis of the efficiency of performance at the absolute threshold of human vision. The data are from the same series as the previous papers (Hallett, 1969b, c) and consist of frequency‐of‐seeing curves, thresholds, false positive rates and equivalent background measurements, accumulated as small samples over a number of days.

2. Quantum efficiency is defined here as the ratio of the thresholds of an ideal and a real detector performing the same task with the same sampling error. This avoids the problem as to whether the frequency‐of‐seeing curve of the real detector is exactly a Poisson sum or not.

3. The long‐term quantum efficiency can be low (about 0·04) as a result of drifts in the mean threshold.

4. The average short‐term quantum efficiency is in the region of 0·1, which is roughly the physiological limit set by Rushton's (1956b) measurements of rhodopsin density in the living rods. If this is correct, then the absorption of a quantum, and not the bleaching of a rhodopsin molecule, is sufficient for the generation of a neural event.

5. Application of a simple signal/noise theory to the data gives solutions close to those suggested by Barlow (1956) and shows that false positives almost invariably arise from errors subsequent to the signal/noise decision process.