bluuebunny/crossref_metadata_2025_split huggingface dataset:
Further studies of the mechanism of passive sensitization
Authors: Mongar J. L. , Winne D. 
Published: December 2014

1. The mechanism of passive sensitization of chopped guinea‐pig lung when incubated with rabbit antiserum alone and in the presence of non‐antibody γ‐globulin has been investigated.2. The effect of concentrations of antibody on the fraction of receptors occupied by molecules attached at one, two or three points has been calculated assuming mass action relations. If a single attachment is sufficient for sensitization the predicted log concentration—effect curve is S‐shaped; if two or more attachments are needed the curve is bell‐shaped. The effect of inhibiting non‐antibody γ‐globulin on the shape and position of the curves has also been calculated.3. The effect of incubating with a wide range of concentrations of antibody on the subsequent histamine release with antigen has been determined. Bell‐shaped curves were obtained. Their shape and position were altered by inhibiting non‐antibody in a manner predicted by the two‐point attachment hypothesis.4. The first affinity constants for antibody and non‐antibody γ‐globulin have been calculated from the experimental concentration—effect curves. They are similar and have a value of about 107 l./mole. Approximate values for the second affinity constants and for the fraction of receptors effectively occupied at maximum sensitization have also been estimated.
A study of the increased sensitivity of denervated and re‐innervated muscle to depolarizing drugs
Authors: Maclagan Jennifer , Vrbová Gerta 
Published: December 2014

1. The response of re‐innervated muscles to depolarizing blocking drugs was studied.2. During the early stages of re‐innervation the ‘new’ neuromuscular junctions are more sensitive to decamethonium and suxamethonium. The recovery from the block and the repolarization of the end‐plate are markedly slowed.3. This increased sensitivity does not appear to be characteristic of all newly formed neuromuscular junctions. It was found that in new‐born kittens the muscles are very insensitive to neuromuscular blocking drugs.4. It is concluded that the increased sensitivity of re‐innervated muscles to depolarizing blocking drugs and the slow repolarization are due to a persistence of changes which developed during denervation.
Activity of neurones in the paraventricular nucleus of the hypothalamus and its control
Authors: Brooks C. McC. , Ishikawa T. , Koizumi Kiyomi , Lu H-H. 
Published: December 2014

1. Activity of the paraventricular nucleus neurones was recorded by micro‐electrodes during resting conditions and while various osmotic, chemical, direct and indirect neural stimuli were applied. This activity was correlated with evidence of oxytocin release by recording milk ejection responses.2. Seventy‐four per cent of all paraventricular nucleus neurones were osmosensitive in that firing was augmented following close arterial injection of hypertonic solutions (1 ml. 1
M‐NaCl in 10‐15 sec). A very few neurones showed decreased activity and in twenty‐two per cent no change at all occurred following injection. Evidence indicated that the observed depressions of cellular firing rate were due to other than osmotic stimulation.3. In post‐partum cats an osmotically‐induced neurone discharge increase was accompanied by a milk ejection response equivalent to that produced by 2‐3 m‐u. of oxytocin.4. Paraventricular neurones were also sensitive to acetylcholine. Intracarotid injections of 40‐80 μg of acetylcholine greatly increased discharge rates and caused a very definite milk ejection response.5. Stimulation of the nipples by gentle suction, but not by electrical shock, and distension of the uterus in post‐partum cats increased unit discharge in the paraventricular nucleus and evoked a milk ejection response.6. Neurones of the paraventricular nucleus, unlike those of the supraoptic nucleus, did not appear to be specifically responsive to electrical stimulation of skin and muscle afferent or of central nervous structures. Such stimuli did cause slight augmentations or depressions in firing rates of cells within and adjacent to the paraventricular nuclei, but many neurones were unaffected. Stimuli such as those applied appeared to have a general central effect involving paraventricular as well as many other neurones.7. Direct electrical excitation of the pituitary stalk produced a milk ejection response in post‐partum cats. Electrical pulses applied to the paraventricular nuclei were less effective for reasons discussed.
Action of choline on frog sartorius muscle
Authors: Ochs S. 
Published: December 2014

1. External and micro‐electrode measurements were made of fibre membrane potentials taken at intervals along the length of frog sartorius muscle fibres before and after adding choline. In ‘cold‐treated’ Rana pipiens which had been kept at 1‐3° C for at least 5 days, 10−3 w/v choline caused a long‐lasting depolarization of approximately 3 hr. Depolarization occurred first at the end‐plate region and spread more slowly to the end‐plate free region. The potential became equalized along the muscles during recovery.2. R. pipiens kept at room temperature showed a faster repolarization in the choline solution, within approximately 1 hr. R. temporaria showed a similar recovery time in muscles from ‘cold‐treated’ animals. In R. temporaria kept at room temperature the duration was shorter, approximately 20‐30 min. The apparently generalized depolarization of the muscle seen in ‘cold‐treated’ R. pipiens appears to be due to the spreading effect of a long‐maintained depolarization at the end‐plates. A similar far‐spread of depolarization was seen following crush of fibres.3. Length‐constants of muscle fibres determined with pulses were found to be within the normal range in muscles from ‘cold‐treated’ R. pipiens and slightly reduced after adding choline.
Membrane capacity of the cardiac Purkinje fibre
Authors: Fozzard H. A. 
Published: December 2014

1. The basis for the relatively high membrane capacitance of the cardiac Purkinje fibre has been investigated.2. The capacitance measured by analysis of the cable response to a current step (square wave) was compared in the same fibres to the capacitance calculated from the foot of the propagated action potential. The square wave value for capacitance was 12·8 ± 1·3 μF/cm2 and that from the foot of the action potential, 2·4 ± 0·5 μF/cm2.3. The capacitative filling at the beginning of a voltage clamp in short Purkinje fibres was measured. The current‐time course deviated from that predicted by a model membrane containing resistance and capacitance in parallel.4. The results obtained by both methods are consistent with two components to the membrane capacitance, with part in parallel with the membrane resistance (2·4 μF/cm2) and part (7 μF/cm2) in series with a resistor (300 Ω cm2).5. The value of the series resistor could be increased by decreasing the conductivity of the extracellular fluid.6. The possible anatomical basis for these findings is discussed.7. Implications of this model on the shape of the Purkinje fibre action potential and on the electrical triggering of contraction are considered.
The excitatory synaptic action of climbing fibres on the Purkinje cells of the cerebellum
Authors: Eccles J. C. , Llinás R. , Sasaki K. 
Published: December 2014

1. A single climbing fibre makes an extraordinarily extensive synaptic contact with the dendrites of a Purkinje cell. Investigation of this synaptic mechanism in the cerebellum of the cat has been based on the discovery by Szentagothai & Rajkovits (1959) that the climbing fibres have their cells of origin in the contralateral inferior olive.2. Stimulation in the accessory olive selectively excites fibres that have a powerful synaptic excitatory action on Purkinje cells in the contralateral vermis, evoking a repetitive spike discharge of 5‐7 msec duration. Almost invariably this response had an all‐or‐nothing character. In every respect it corresponds with the synaptic action that is to be expected from climbing fibres.3. Intracellular recording from Purkinje cells reveals that this climbing fibre stimulation evokes a large unitary depolarization with an initial spike and later partial spike responses superimposed on a sustained depolarization.4. Typical climbing fibre responses can be excited, but in a much less selective manner, by stimulation of the olive‐cerebellar pathway in the region of the fastigial nucleus, there being often a preceding antidromic spike potential of the Purkinje cell under observation.5. Impaled Purkinje cells rapidly deteriorate with loss of all spike discharge, the climbing fibre response being then reduced to an excitatory post‐synaptic potential. This potential shows that stimulation of the inferior olive may evoke two or more discharges at about 2 msec intervals in the same climbing fibre. The complexity of neuronal connexions in the inferior olive is also indicated by the considerable latency range in responses.6. A further complication is that, with stimulation in the region of the fastigial nucleus, the initial direct climbing fibre response is often followed by a reflex discharge, presumably from the inferior olive, which resembles the responses produced by inferior olive stimulation in being often repetitive.7. Typical climbing fibre responses have been evoked by peripheral nerve stimulation and frequently occur spontaneously.8. An account is given of the way in which the responses evoked by climbing fibres in the individual Purkinje cells can account for the potential fields that an inferior olive stimulus evokes on the surface and through the depth of the cerebellar cortex.9. By the application of currents through the recording intracellular electrode it has been possible to effect large changes in the excitatory post‐synaptic potential produced by a climbing fibre, it being diminished and even reversed with depolarizing currents and greatly increased by hyperpolarizing currents.
Comparison of the reflex responses elicited by stimulation of the separately perfused carotid and aortic body chemoreceptors in the dog
Authors: Daly M. de Burgh , Ungar A. 
Published: December 2014

1. In dogs under chloralose and urethane anaesthesia, the carotid and aortic bodies were isolated from the circulation and separately perfused with blood, the composition of which could be controlled at will. The remainder of the systemic circulation was perfused at constant blood flow, thereby enabling the reflex vascular responses to be determined. The systemic venous blood was oxygenated in the isolated perfused lungs of a second dog and the PO2 and PCO2 of the systemic arterial blood was maintained constant.2. Using hypoxic hypercapnic blood to stimulate the arterial chemoreceptors, carotid body excitation in spontaneously breathing animals caused an increase in respiratory minute volume approximately seven times larger than that evoked by stimulation of the aortic bodies. Whereas the hyperpnoea of carotid body origin is due to an increase in rate and depth of breathing, that from the aortic bodies is due predominantly to an increase in respiratory frequency.3. Stimulation of the carotid bodies in spontaneously breathing animals caused small variable changes in systemic vascular resistance, whereas stimulation of the aortic bodies invariably increased the vascular resistance.4. When pulmonary ventilation was maintained constant, the vascular response to stimulation of the carotid bodies was considerably modified in that constriction invariably occurred; that from the aortic bodies, however, was little affected. There was now no significant difference in the size of responses from the two groups of chemoreceptors. These constrictor responses represent the primary vascular effects.5. A similar modification of the carotid body vascular response occurred in the spontaneously breathing animal after denervation of the lungs, and is due to abolition of a lung‐inflation vasodilator reflex.6. The size of the primary vasoconstrictor responses from the carotid and aortic bodies is reduced by lowering the arterial blood PCO2.7. The results indicate that there is a fundamental difference in the functions of the carotid and aortic bodies. They exert a quantitatively similar primary control of the ‘vasomotor centre’ which is in striking contrast to the relatively more powerful influence on respiration by the carotid bodies. In the spontaneously breathing animal, however, the primary vasoconstrictor response from the carotid bodies is offset to a varying degree by the lung‐inflation vasodilator reflex initiated by the concomitant hyperpnoea. This is not evident with the aortic bodies because of the relatively weaker respiratory response they evoke.
The oxygen consumption of the placenta and foetal membranes in the sheep
Authors: Campbell A. G. M. , Dawes G. S. , Fishman A. P. , Hyman A. I. , James G. B. 
Published: December 2014

1. In anaesthetized sheep near term the O2 uptake of the foetus from the placenta was reduced to zero either by replacing the foetus with a mechanical pump, or by ventilation of the foetus after delivery or in utero. When umbilical arterial and venous PO2 were made equal, they were much less than maternal arterial PO2.2. This difference in PO2 was attributed to O2 consumption both within the placental cotyledons and the extra‐cotyledonary foetal membranes.3. The foetal membranes and cord in the sheep are supplied by branches of umbilical blood vessels and constitute an oxygen‐consuming by‐pass on the foetal side of the placenta.4. The O2 consumption of individual placental cotyledons was measured in vivo.5. The combined O2 consumption of the whole placenta and foetal membranes in vivo was a considerable fraction of foetal O2 consumption.6. The consequences of these observations are discussed in relation to O2 transfer across the placenta.
The distribution of calcium—47 in the rat
Authors: Anderson J. , Tomlinson R. W. S. 
Published: December 2014

1. Plasma specific activities were measured at various times after the intravenous injection of calcium‐47 in four different age groups of rats.2. The data may be represented as two power functions. The change in power function occurs at a set time which is significantly different in three of the age groups.3. Various bones, muscle and skin all show different uptakes of the calcium‐47 and the change in the power function of the plasma data probably represents an equilibrium of the soft tissue calcium.
The increased extensibility of pregnant myometrium
Authors: Schofield Brenda M. 
Published: December 2014

1. Experiments were carried out on isolated strips of uterine muscle to determine the extensibility of the myometrium at different stages of pregnancy and post‐partum.2. Results showed that the extensibility increases significantly after mating and remains fairly constant from days 7 to 27 of pregnancy. Thereafter there is a further significant increase in extensibility which lasts until delivery. During the first 24 hr post‐partum the extensibility decreases rapidly.3. In unilateral pregnancy there appeared to be no difference in extensibility between the two horns.4. The extensibility found in the myometrium of oestrous females could be reproduced in ovariectomized rabbits treated with oestrogen. When progesterone was injected in addition to oestrogen, the extensibility was significantly increased but not to the same extent as in mid‐pregnancy.5. The extra increase in extensibility found at the end of pregnancy was not reproduced in ovariectomized rabbits after long‐term injections of oestrogen and progesterone followed by additional relaxin or diminished progesterone therapy or relaxin and diminished progesterone therapy.6. It is suggested that the changes in extensibility of the myometrium associated with pregnancy are hormone‐based, that the main hormone is progesterone and that perhaps equivalent changes can only be reproduced in the ovariectomized rabbit by critical doses of oestrogen and progesterone.
Potentiometric measurement of membrane action potentials in frog muscle fibres
Authors: Frankenhaeuser B. , Lindley B. D. , Smith R. S. 
Published: December 2014

1. A potentiometric method for recording membrane action potentials from small segments of isolated skeletal muscle fibres has been described.2. The value of the method in muscle physiology has been appraised by recording from fast and slow skeletal muscle fibres of the frog under a variety of conditions.3. Artifacts associated with this method have been described and their sources investigated.
Observations on the histamine forming capacity of mouse tissues and of its potentiation after adrenaline
Authors: Pearlman D. S. , Waton N. G. 
Published: December 2014

1. The histamine forming capacity (h.f.c.) was determined in minced or homogenized skin, lung, skeletal muscle or stomach of mice weighing 18‐20 g using radioactive 14C histidine as substrate and determining the radioactive 14C histamine formed by conversion to its dibenzenesulphonyl derivative.2. The optimal pH for the formation of histamine was 7·0‐7·5 for lung and skin, 6·5‐7·5 for skeletal muscle. For stomach a more acid pH was optimal and depended on substrate concentration.3. The formation of histamine increased with an increase of the substrate histidine.4. The formation of histamine was not affected by the presence in the incubation mixture of chlorpromazine, pyridoxal‐5‐phosphate, non‐radioactive histamine or benzene. The addition of aminoguanidine slightly increased the formation in skin, lung and skeletal muscle but not in stomach. The formation was unchanged when incubation was in an atmosphere of nitrogen instead of air.5. H.f.c. for stomach of normally fed mice varied 170‐fold. For stomachs of mice unfed for 16 hr, h.f.c. was much lower and it varied only sevenfold.6. Injection of adrenaline into mice increased h.f.c. of the skin, lung and skeletal muscle. With skin tissue a linear log. dose log. response relation was demonstrated. The injection of adrenaline caused however either no or only a slight increase in the h.f.c. of stomach tissue.7. The effect of adrenaline on h.f.c. in skin, lung and skeletal muscle was not abolished by α‐ or β‐adrenergic blocking agents either injected separately or together before the injection of adrenaline.
Micro‐electrophoretic studies of neurones in the cat hippocampus
Authors: Biscoe T. J. , Straughan D. W. 
Published: December 2014

1. Drugs have been applied micro‐electrophoretically to units in the hippocampal cortex of the anaesthetized cat, and their effects on cell firing were recorded simultaneously.2.
L‐Glutamate rapidly and powerfully excited hippocampal units, an effect which was quickly reversed on stopping the expelling current. The local application of
L‐glutamate also excited a fast seizure discharge at 15‐50/sec. Both these effects of
L‐glutamate were strongly depressed by fimbrial stimulation.3. γ‐Aminobutyric acid had a strong depressant action on all the units on which it was tested; the time course of this effect was rapid.4. ACh excited half the units to which it was applied. Characteristically this excitation developed slowly over many seconds and persisted after stopping the expelling current. Most cholinoceptive units were found to be concentrated in the superficial layer of the cortex corresponding to the hippocampal pyramidal cells and their main dendritic processes.5. Atropine selectively blocked the excitation of cholinoceptive units by ACh, but not the excitation by
L‐glutamate. No cholinoceptive units were blocked by dihydro‐β‐erythroidine, though several were selectively blocked by dimethyl (+)‐tubocurarine.6. The most usual effect seen with 5‐HT was depression, though several units were found to be excited. Some of the units tested with 3‐hydroxytyramine (dopamine) or noradrenaline were found to be depressed.
The separation of cone mechanisms in dark adaptation
Authors: Du Croz J. J. , Rushton W. A. H. 
Published: December 2014

1. In dark adaptation the threshold is raised as though the bleaching of visual pigment generated an equivalent background. Now Stiles has shown that real coloured backgrounds act selectively upon the various colour mechanisms, so we ask: ‘Do equivalent backgrounds from coloured bleachings also act selectively?’2. When dark adaptation was plotted using a blue test flash (Fig. 1b) following bleaching by orange light a kinked curve was obtained. The upper branch was shown to have the same dark adapted threshold as Stiles blue (π1) mechanism and the lower branch as his green (π4) mechanism. The π4 dark adaptation curve alone (unkinked) was obtained using a white instead of an orange bleach.3. Dark adaptation curves were obtained in which the test flash was presented upon various steady backgrounds. In conditions where only π4 was involved (Fig. 3) the experimental results fitted the curves calculated on the assumption that the equivalent background of bleaching simply adds to the real background in raising the threshold—a condition already established for rods.4. In conditions where π4 and π1 were both present (blue test, yellow‐green background and white bleach) kinked dark adaptation curves were obtained (Fig. 2) where the upper branch (π4) coincided with those of Fig. 3 and the lower were due to π1.5. The blue mechanism recovers in dark adaptation at about the same rate as red and green, or slightly slower.6. Dark adaptation curves with red (π5) and green (π4) limbs can be obtained after a deep red bleach (Fig. 4) using a red test flash and a green background. The red and the green limbs were also plotted alone in their entirety by slightly changing the conditions.7. We are led to the idea of three colour mechanisms that adapt as independently one of another after bleaching as they do with backgrounds.8. Though this simple independence accounts for the wide and conspicuous range of adaptive phenomena, we have encountered some special conditions (not here described) that seem to imply a measure of interaction between the different colour mechanisms.
The continuous estimation of angiotensin formed in the circulation of the dog
Authors: Regoli D. , Vane J. R. 
Published: December 2014

1. The use of the rat colon as a blood‐bathed organ is described for detecting changes in angiotensin concentration in the circulating blood of dogs.2. Partial occlusion of the aorta by a balloon inflated above the renal arteries leads to a contraction of the blood‐bathed rat colon.3. From the experimental evidence, it is concluded that this contraction is due to an increased concentration of circulating angiotensin, brought about by the liberation of renin from the kidneys.4. The characteristics of renin release have been studied. It occurs within seconds of reducing the blood pressure to the kidneys and is proportional to the degree of reduction of blood pressure.5. With a prolonged reduction of renal blood pressure the concentration of angiotensin increases over the first 10‐12 min and then reaches a stable level.6. After a small haemorrhage angiotensin often appears in the circulation without a concomitant release of catechol amines.7. Greater haemorrhages induce the secretion of catechol amines as well as of renin. The catechol amine secretion is inhibited by ganglion block, but the renin secretion is not.8. It is concluded that the secretion of renin by the kidneys in response to a fall of renal blood pressure is a physiological response, probably of importance in homoeostasis.