bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of the nasal mucosa and the carotid rete upon hypothalamic temperature in sheep
Authors: Baker Mary Ann , Hayward James N. 
Published: December 2014

1. In chronically‐prepared sheep, intracranial temperatures were measured in the cavernous sinus among the vessels of the carotid rete and at the circle of Willis extravascularly, and in the preoptic area and in other brain stem regions. Extracranial temperatures were measured intravascularly in the carotid or internal maxillary arteries and on the nasal mucosa and the skin of the ear.2. At 20° C ambient temperature, shifts in temperature of the hypothalamus and of other brain sites paralleled temperature shifts in the cerebral arterial blood which was cooler than central arterial blood. During periods of arousal and of paradoxical sleep, vasoconstriction of the nasal mucosa and the ear skin occurred and temperatures at the cerebral arteries and in the brain rose without a comparable rise in central arterial blood temperature.3. Anaesthetic doses of barbiturate abolished the temperature oscillations in the cerebral arterial blood and the brain. When air was blown rapidly over the nasal mucosa in anaesthetized animals, temperatures dropped precipitously in the cavernous sinus, at the cerebral arteries, and in the brain, while central arterial temperature fell only slightly. Injections of latex into the facial venous system demonstrated a venous pathway from the nasal mucosa to the cavernous sinus.4. When sheep were exposed to 45‐50° C ambient temperature, respiratory rate increased 5‐10 times and the temperature gradient between central and cerebral arterial blood widened.5. It is concluded that venous blood returning from the nasal mucosa and the skin of the head to the cavernous sinus cools the central arterial blood in the carotid rete. This is an important factor in the maintenance of hypothalamic temperature in the wool‐covered, long‐nosed, panting sheep and undoubtedly affects hypothalamic thermoreceptors and temperature regulation in artiodactyls.
The components of the sodium efflux in frog muscle
Authors: Keynes R. D. , Steinhardt R. A. 
Published: December 2014

1. In normal Ringer solution containing 2·5 m
M‐K only 37% of the efflux of labelled sodium from a freshly dissected frog muscle is blocked by treatment with ouabain; in sodium‐loaded muscles the ouabain‐sensitive fraction of the efflux increases to 75%.2. Under all conditions, the ouabain‐insensitive component of the sodium efflux is markedly reduced if the sodium in the external medium is replaced by lithium; at least in sodium‐loaded muscles, the ouabain‐sensitive component is increased in lithium Ringer.3. Only the ouabain‐sensitive component of the efflux is affected by the external potassium concentration.4. In the presence of 2·5 m
M‐K the sodium influx in a freshly dissected muscle is not significantly altered by ouabain, but in a K‐free medium the influx and the efflux are both reduced by nearly 20%.5. The sodium efflux can therefore be regarded as consisting of (1) a sodium‐potassium coupled component that is blocked by ouabain and involves a sodium‐sodium exchange in the absence of external potassium, and (2) a potassium‐insensitive component that is unaffected by ouabain and tends to reach saturation at relatively lower internal sodium concentrations.6. The evidence is considered for attributing component (1) to an efflux of sodium from the sarcoplasm proper, and component (2) to an efflux from the sarcoplasmic reticulum. Although such an interpretation is consistent with many of the observations, a definite identification of the possible sodium compartments in frog muscle cannot yet be made.
Active transport of l‐glucose by isolated small intestine of the dietary‐restricted rat
Authors: Neale R. J. , Wiseman G. 
Published: December 2014

1. The effect of semistarvation and complete starvation (sufficient to produce a loss of about 32 and 25% respectively of initial body weight) on the active transport of
L‐glucose has been studied by the use of sacs of everted mid‐small intestine of rats. The animals were allowed free access to water.2. Sacs from animals on a restricted diet transported
L‐glucose against its concentration gradient, but sacs from fully fed rats did not. Even when sacs from fully fed rats were distended sufficiently to cause them to lose serosal volume, the
L‐glucose concentration in the final serosal fluid was never greater than that in the final mucosal fluid.3. The
L‐glucose active transport was independent of net water movement, needed oxygen, was not demonstrable at 27° C, and required Na ions at a concentration of 83 m
M or greater. It could be completely inhibited by 10−6
M phlorrhizin, or 10 m
M L‐histidine, or 1·39 m
M D‐glucose. Phlorrhizin at a concentration of 10−8
M reduced, but did not prevent,
L‐glucose active transport.4. It seems probable that
L‐glucose active transport is mediated by the mechanism that actively transports
D‐glucose.5. Un‐incubated mid‐small intestine of fully fed rats contained 37·8 mg
D‐glucose/100 g wet wt. of tissue, whereas semistarved intestine had only 10·8 mg
D‐glucose/100 g. The lack of demonstrable active transport of
L‐glucose by normal intestine may possibly have been caused, at least in part, by inhibition of the process by endogenous
D‐glucose.6. There appeared to be no metabolism of
L‐glucose by rat intestine, nor conversion to the
D‐form.7. The hypothesis that sugars require the
D‐pyranose ring structure for active absorption is no longer tenable.
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.