bluuebunny/crossref_metadata_2025_split huggingface dataset:
Angiotensin II‐like activity in circulating arterial blood in immature and adult rabbits
Authors: Pipkin Fiona Broughton , Mott Joan C. , Roberton N. R. C. 
Published: December 2014

1. Angiotensin II‐like activity was estimated from the contraction of the rat ascending colon superfused with arterial blood in an extracorporeal circuit. The colon was calibrated by infusion of synthetic angiotensin II amide (Hypertensin, CIBA Ltd).2. Resting levels of angiotensin II‐like activity were obtained by comparison of the length of a rat colon preparation superfused alternately with blood from an intact and from a nephrectomized rabbit.3. The resting levels of angiotensin II‐like activity reached a maximum value of about 1·6 ng/ml. at 10–14 days of age, and thereafter declined to the adult value of 0·23 ng/ml. Rabbits of less than 100 g body weight had resting levels in the same range as adults.4. Removal of 25% of the calculated blood volume induced five times greater increments in arterial angiotensin II‐like activity in immature than in adult rabbits (1·68 ± 0·26
S.E. of mean ng/ml. compared with 0·34 ± 0·08
S.E. of mean ng/ml.).5. No evidence was obtained that the high levels of angiotensin II‐like activity encountered in immature rabbits were attributable to a slower rate of inactivation of angiotensin by tissues.6. The pronounced activity of the renin‐angiotensin system demonstrated by these experiments in immature rabbits especially during haemorrhage is consistent with the suggestion that this system is of particular importance in cardiovascular control in early life.
The effects of temperature and ions on the current—voltage relation and electrical characteristics of a molluscan neurone
Authors: Marmor Michael F. 
Published: December 2014

1. Current—voltage relations were generated in the Anisodoris giant neurone (G cell) by either current pulses or slow biphasic current ramps.2. Inward‐going rectification occurred during hyperpolarization at warm temperatures (10–15° C), but not at cold temperatures (0–5° C) or in the absence of external K.3. Replacing external K with Rb eliminated inward‐going rectification in the warm, but produced it in the cold. The removal of external Na, Cl or Ca had no effect upon inward‐going rectification.4. At cold temperatures the I—V relation was linear when generated by current pulses, but was non‐linear in accordance with the constant field hypothesis when generated by current ramps.5. A high conductance state developed when the membrane was hyperpolarized beyond a critical potential (approximately — 130 mV in the cold, and — 110 mV in the warm) which was dependent upon external Ca, but not upon K, Na or Cl.6. Hysteresis was observed in the ramp‐generated I—V relation whenever the cell was polarized into the high conductance state.7. Rectification and the high conductance state appear to involve different mechanisms within the membrane. However, both are dependent upon absolute membrane potential and not the resting potential.8. The axonal‐somatic conductance ratio for the G cell was calculated to be between 2 and 10.9. The membrane time constant (200–100 msec) and specific resistance (0·1–1·5 × 106 Ω cm2) varied with temperature, membrane potential, and external ions in a manner that correlated with changes in the shape of the I—V relation. In addition, the resistance was dependent upon external Ca.10. The K permeability (PK), measured during inhibition of inwardgoing rectification, was independent of temperature and membrane potential. However, PNa increased with warming.11. The specific capacitance was calculated to be 0·5–1·0 μF/cm2. The capacitance increased slightly with warming, but was independent of membrane potential and unaffected by reductions in external K or Na.
On the direct and crossed components of reflex responses to unilateral stimulation of the carotid body chemoreceptors in the dog
Authors: McQueen D. S. , Ungar A. 
Published: December 2014

1. In dogs under chloralose‐urethane anaesthesia the chemoreceptors of the two carotid bodies were separately stimulated.2. The distribution of three primary reflex responses to carotid body stimulation was studied: parasympathetic bradycardia, sympathetic vasoconstriction, and increase in somatic phrenic nerve activity.3. The reflex bradycardia evoked by either carotid body was mediated by both vagus nerves, but when either vagus was blocked a greater response could be obtained from the contralateral than from the ipsilateral carotid body.4. The reflex vasoconstriction evoked by either carotid body was seen in both hind limbs, with no predominance in either limb.5. The reflex increase in phrenic nerve activity evoked by either carotid body was seen in both phrenic nerves, with no predominance in either nerve.
Permeability of lung capillaries and alveoli to non‐electrolytes in the foetal lamb. With an Appendix
Authors: Normand I. C. S. , Olver R. E. , Reynolds E. O. R. , Strang L. B. , Welch Keasley 
Published: December 2014

1. Two sets of experiments were performed on intact foetal lambs exteriorized at Caesarean section; in one set radioactively labelled test substances (inulin, sucrose, mannitol, erythritol, urea) were injected
I.V. either singly or in pairs and then followed in plasma, lung lymph and alveolar liquid; in the other set labelled test substances (inulin, sucrose, mannitol, erythritol,
D‐serine,
L‐serine,
D‐α‐alanine, urea, water, thiourea, N‐ethylthiourea) were introduced singly, in pairs, or sequentially into alveolar liquid and their concentration followed in alveolar liquid and plasma.2. Inulin was found to cross lung capillary walls but not alveolar walls. Measurements of its concentration following injection into alveolar liquid were used to determine the volume of foetal alveolar liquid (mean = 30 ml./kg) and its rate of formation (mean = 0·036 ml./min.kg). The volume of the lung interstitial space was determined from previous experiments in which [125I]PVP had been injected
I.V. then measured after 2 hr in lung tissue and lung lymph (mean = 10·4% foetal lung weight after withdrawal of liquid; ≈ 20% wet lung tissue weight).3. Transfer constants (min−1) for lung capillaries (KC) and alveoli (K0) were obtained from the experimental results by compartmental analysis. Permeability constants (PC and PO, cm/sec) were derived from them using estimates for capillary and alveolar areas. For lipid insoluble molecules PC and PO both increased with decreasing molecular radius, the effect being much greater for PO than PC. PO was also shown to increase with lipid solubility of the test molecule even though molecular size increased with lipid solubility in the series tested (urea, thiourea, N‐ethylthiourea).4. Analysis of the results for the lipid insoluble substances in terms of pore theory gave a value of pore radius for lung capillaries of 150 Å and for alveolar walls of 5·5 Å. The smallness of the pores in alveolar walls is thought to prevent proteins and other plasma solutes from penetrating alveoli, and to determine the forces which operate in the osmotic flow of water across alveolar walls.
Kininogenase of the guinea‐pig's coagulating gland and the release of bradykinin
Authors: Moriwaki C. , Schachter M. 
Published: December 2014

A kininogenase (CGK) in the coagulating gland of the guinea‐pig was partially purified, characterized and separated from a kininase also present in the gland. This kininogenase is not inhibited by the usual kininogenase and protease inhibitors. Our results indicate that it is identical with the esterolytic enzyme in the gland which hydrolyses the synthetic ester TAME.The kinin released by CGK from dog's crude pseudoglobulin was purified more than 1500 times and identified as bradykinin by chromatography on paper, on carboxymethyl‐cellulose columns, and on silica gel.
Observations on the control of stepping and hopping movements in man
Authors: Jones G. Melvill , Watt D. G. D. 
Published: December 2014

1. The presence of a form of stretch reflex, previously described in the arm by other authors, has been confirmed in the gastrocnemius muscle of the human leg. The electromyographic (e.m.g.) manifestation of this reflex occurred 120 msec (
S.E. of mean = 3·5 msec) following a sharply applied, and maintained, dorsiflexing force to the foot. This form of response is referred to in this article as the Functional Stretch Reflex (FSR).2. To determine the contribution of the FSR to the control of normal leg movement, the e.m.g. activity in the above muscle was monitored during single downward steps of 12·7, 25·4 and 38·1 cm and during repetitive, rhythmic, hopping movements on one foot.3. It was found that e.m.g. activity associated with steps to the ground began 141 msec (
S.E. of mean = 8·5 msec) before contact with the ground and ended 131 msec (
S.E. of mean = 7·6 msec) after contact, when the e.m.g. usually became temporarily inactive.4. It is inferred from these results that the muscular deceleration associated with landing was brought about by the release of a pre‐programmed pattern of neuromuscular activity which was inaccessible to reflex activity resulting from the mechanical event of landing, rather than by a stretch reflex.5. It was found that subjects chose their preferred frequency of hopping with great accuracy and consistency. The mean value obtained was 2·06 Hz (
S.E. of mean = 0·02 Hz).6. At the preferred frequency, e.m.g. activity began 84 msec (
S.E. of mean = 9·6 msec) before and terminated 263 msec (
S.E. of mean = 10 msec) after contact with the ground.7. It is inferred that in rhythmical hopping and perhaps also in running, each landing is effected, as in single steps, by a predetermined pattern of neuromuscular activity. However, when hopping at the preferred frequency, the take‐off phase of muscular activity is timed to make maximal use of the FSR, i.e. between 120 and 260 msec after initial contact.8. The results emphasize the importance of pre‐programming complex muscular contractions suitable for opposing sudden passive stretching forces, and of initiating them prior to the onset of these forces.
Muscular control of landing from unexpected falls in man
Authors: Jones G. Melvill , Watt D. G. D. 
Published: December 2014

1. It was previously shown that the controlled landing from single steps to the ground is typically brought about by accurately timed motor activity, commencing before the actual landing, and completed before time would permit the participation of a useful stretch reflex response.2. To investigate further the validity of this conclusion, subjects were dropped from an electromagnetic suspension at unexpected moments. Their gastrocnemius electromyographic (e.m.g.) responses and the forces applied to their feet were recorded throughout.3. No useful contribution of a stretch reflex response was detected. Indeed, it was shown that a functionally effective reflex resulting from the mechanical event of landing would occur far too late to contribute to the muscular deceleration of the fall.4. It was also found that a consistent muscular response occurred, commencing 74·2 msec (
S.E. of mean = 1·4 msec) after starting the fall, independent of height.5. It is suggested that this response in the leg musculature is a reflex originating in the otolith apparatus. In addition, a possible mechanism for the control of repetitive hopping, and perhaps running, movements, involving the above reflex, is suggested.
The fine structural localization of cholinesterases in the carotid body of the cat
Authors: Ballard Kathleen J. , Jones J. V. 
Published: December 2014

1. The distribution of cholinesterases in the carotid body of the cat has been investigated with the electron microscope to obtain a clearer picture of the localization of the enzyme. This is of relevance to the possible role of acetylcholine as a transmitter in the carotid body.2. Tissues were fixed for short periods and incubated by the method of Karnovsky for the fine localization of cholinesterases.3. The enzyme was found in two main sites. Butyrylcholinesterase was present on the type II cell membrane while acetylcholinesterase was found in groups of peripheral axons. No intracellular enzyme was found.4. It is concluded that acetylcholine may be a transmitter in the carotid body and that it may be partly destroyed by enzymic hydrolysis. A possible explanation for some of the anomalous pharmacological findings is suggested.
Measurements of small variations in ‘absolute’ pitch
Authors: Wynn V. T. 
Published: December 2014

1. Longitudinal studies on absolute pitch estimates have been observed in one male and two female subjects.2. The female subjects underwent rhythmic variations in their estimates that were related to their menstrual cycles. One female subject, the more intensively studied of the two, also showed variations in her pitch estimates that were related to illness.3. Relevant correlations between the menstrual cycle and known biochemical parameters are mentioned which suggest that the fluctuations in the female estimates are governed by changes in the electrical activity of the auditory nervous system.4. The male subject showed similar fluctuations in his pitch estimates. A rhythm of approximately 20 days was observed.5. A connexion between the fluctuations in the pitch estimates and the sex hormones in both the female and the male subjects is suggested as a possible explanation of the difference between two different types of absolute pitch.6. The hypothesis is extended to show how the adrenal corticosteroids could account for the changes in the pitch estimates that occurred with illness.
Reflex respiratory and cardiovascular effects of stimulation of receptors in the nose of the dog
Authors: James Jennifer E. Angell , Daly M. de Burgh 
Published: December 2014

1. In forty‐one out of forty‐seven dogs under chloralose—urethane or Nembutal anaesthesia, mechanical stimulation of the nasal mucous membrane caused a reduction or inhibition of respiration, bradycardia, variable changes of arterial blood pressure, and a small rise in venous pressure.2. Simultaneous measurements of arterial and venous pressures, and also of blood flow in various arteries by means of an electromagnetic flowmeter indicate that the calculated vascular resistance increases in the intact limb, muscle, and skin, and the vascular beds of the vertebral, superior mesenteric, renal and splenic arteries. No changes in vascular resistance occur in the common carotid circulation.3. Evidence is presented that the increase in vascular resistance is due to vasoconstriction, and occurs in the absence of changes in pulmonary ventilation.4. Stimulation of the nasal mucous membrane causes a reduction in volume of the spleen.5. The respiratory and cardiovascular responses are reflex in nature, being abolished by the application of a local anaesthetic to the nose or by combined division of the maxillary and ethmoidal branches of the trigeminal nerves. The cardiac response is mediated largely by the vagus nerves, and the vascular responses by sympathetic adrenergic fibres.6. Cessation of the stimulus to the nose not infrequently results in the following temporary after‐effects: hyperventilation, tachycardia, hypertension, and vasodilatation in the intact limb and in muscle.
The hyperglycaemic response to stimulation of the hepatic sympathetic innervation in adrenalectomized cats and dogs
Authors: Edwards A. V. 
Published: December 2014

1. The extent to which the hyperglaemic and glycogenolytic responses to splanchnic nerve stimulation depend upon the integrity of the hepatic innervation has been investigated in adrenalectomized dogs and cats.2. In both species maximal stimulation of the hepatic nerves (20 c/s) produced changes in plasma glucose concentration comparable to those which have been found to occur in response to bilateral splanchnic nerve stimulation at the same frequency. Furthermore, the hyperglycaemic response to splanchnic nerve stimulation was very substantially reduced by section of the hepatic nerves, whereas the associated changes in haematocrit and mean aortic blood pressure were not significantly altered.3. Comparison of the changes in plasma glucose concentration in response to splanchnic or hepatic nerve stimulation at relatively low frequencies (1·0–2·0 c/s) showed that stimulation of either nerve produced closely similar responses in adrenalectomized animals of both species.4. In adrenalectomized dogs maximal stimulation of the hepatic nerves (20 c/s) for shorter periods (30 sec) caused a significant rise in plasma glucose concentration whereas total occlusion of the portal vein for the same period in the same animals produced no statistically significant hyperglycaemic effect.5. Maximal stimulation of the hepatic nerves (20 c/s) caused a rapid rise in plasma glucose concentration in hypoglycaemic adrenalectomized cats pretreated with a large dose of insulin (4 u./kg body wt.).6. It is concluded that the hyperglycaemic response to stimulation of the peripheral ends of the splanchnic nerves in adrenalectomized dogs and cats is directly dependent upon activation of sympathetic efferent fibres to the liver.
The location of the fluid pump in the cornea
Authors: Maurice D. M. 
Published: December 2014

1. Fluid transport across rabbit corneal tissue has been investigated by observing the movement of fluid interfaces under the microscope, or by mounting the tissue between two chambers and observing the displacement of menisci within capillary tubes.2. In both cases, the endothelial layer supported on a thin sheet of connective tissue is capable of pumping fluid in a direction out of the cornea, against a head of pressure. The volume of fluid moved may amount to twelve times the thickness of the endothelial cells in an hour.3. This active fluid movement accounts for the prevention of swelling of the normal corneal stroma. The hypothesis that corneal hydration is regulated by the sodium pump in the epithelial layer is not supported by these experiments.
The action of insulin on brown adipose tissue in vivo
Authors: Hardman M. J. , Hull D. 
Published: December 2014

1. The action of insulin on the net exchange of glucose, free fatty acids and glycerol by brown adipose tissue of young rabbits was investigated.2. Infusion of insulin (10,000 μu./kg.min I.V. for 10 min) caused a large increase in the uptake of glucose by brown adipose tissue of fed week‐old rabbits. The release of fatty acids fell but glycerol release was unchanged.3. The brown adipose tissue of 9‐day‐old rabbits fasted in a warm environment had a high initial rate of fatty acid and glycerol release and low rates of glucose uptake. Insulin infusions (10,000 and 100 μu./kg.min) greatly reduced fatty acid release but had little or no effect on glucose uptake.4. The brown adipose tissue of 9‐day‐old rabbits fasted in a cold environment was depleted of fat and took up free fatty acid as well as glucose from the circulation. Infusion of insulin (10,000 μu./kg.min) caused a large increase in glucose uptake accompanied by a reduction in fatty acid uptake.5. The experiments support the view that insulin has a direct effect on fatty acid transport across the cell membrane.
Influence of adaptation level on response pattern and sensitivity of ganglion cells in the cat's retina
Authors: Yoon Myonggeun 
Published: December 2014

1. The effect of background illumination on response pattern is correlated with its effect on visual sensitivity by analysing post‐stimulus time‐histograms obtained from single ganglion cells in the cat's retina at various levels of background illumination between zero and 2 × 106 photons (wave‐length 523 nm).sec−1.deg−2 (via 5·7 mm2 pupil).2. If background illumination did not exceed a critical value, about 103 photons (523 nm).sec−1.deg−2 (via 5·7 mm2 pupil), stimulation of the centre of a receptive field resulted in either sustained excitation (i.e. increase in discharge rate) during ‘on’ and cessation of the excitation at ‘off’ (on‐centre unit), or sustained inhibition (i.e. decrease in discharge rate) during ‘on’ and cessation of the inhibition at ‘off’ (off‐centre unit). Within this low adaptational level, a ganglion cell maintained its maximum sensitivity regardless of whether the weak background light was presented or not.3. When background level exceeded the critical value up to 2 × 106 photons (523 nm).sec−1.deg−2, however, the simple, sustained responses changed into compound responses with two transient components of opposite polarities, either excitation at ‘on’ and inhibition at ‘off’ (on‐centre unit), or inhibition at ‘on’ and excitation at ‘off’ (off‐centre unit), and also the sensitivity began to decrease as the background increased, approximately obeying Weber's law.4. It is suggested that a ganglion cell gives simple‐sustained response when its gain control mechanism remains inactive at a low background illumination below a critical level, whereas it gives compound‐transient response when its gain control mechanism becomes active as background illumination exceeds the critical value.
Differences in sensitivity to vasoconstrictor drugs within the wall of the sheep carotid artery
Authors: Graham J. M. , Keatinge W. R. 
Published: December 2014

1. Controlled heat damage was used to separate the responses of the outer innervated smooth muscle from those of the inner nerve‐free smooth muscle of the sheep carotid artery.2. Preparations of smooth muscle from the inner part of the media gave 50% maximal contractions in response to approximately 1/15 the concentration of noradrenaline needed to produce similar responses from outer smooth muscle. The difference in sensitivity was greater in the lower than the upper parts of the dose—response curves.3. Much of the difference in sensitivity was still seen in the presence of Desipramine and after chronic denervation, and so could not be attributed to uptake of noradrenaline by the nerve fibres in the outer smooth muscle; disappearance of the fibres after denervation was confirmed by fluorescence microscopy.4. Similar but generally smaller differences in sensitivity between inner and outer smooth muscle were seen with respect to histamine, angiotensin II and 5‐hydroxytryptamine.5. Sympathetic denervation 10–14 days previously increased the sensitivity of outer strips to noradrenaline; it usually also increased their sensitivity to histamine, suggesting that the change largely represented non‐specific denervation super‐sensitivity.6. The high sensitivity of the inner smooth muscle is likely to be of value in enabling it to respond to the relatively low concentration of noradrenaline reaching it in life.
The interaction at equilibrium between tetrodotoxin and mammalian non‐myelinated nerve fibres
Authors: Colquhoun D. , Ritchie J. M. 
Published: December 2014

1. As a preliminary to chemical studies an estimate has been made of the equilibrium dissociation constant (K) for the interaction of tetrodotoxin (TTX) with the non‐myelinated fibres of the rabbit desheathed vagus nerve.2. TTX causes a parallel shift to the right of the curves obtained when either the height or the conduction velocity of the compound action potential are plotted against the logarithm of the external sodium concentration.3. A model has been formulated based on the independence principle and the Hodgkin—Huxley theory, and the experimental results shown to be consistent with it. On this basis, and on the assumptions that one TTX molecule blocks one sodium channel, and that binding is Langmuir, K was estimated to be about 3‐5 n
M at about 20° C. Other simple non‐Langmuir models gave essentially similar low values for K.4. An alternative method of computing K that makes rather different assumptions gives a similar low value.5. Despite the low value for K, a TTX concentration of at least 100 n
M is needed to block conduction completely and this seems to be related to the fact that conduction is not completely blocked until the external sodium concentration falls below 7% of its value in normal Locke.6. The minimum sodium concentration needed to support conduction increased with temperature.