bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pancreatic acinar cells: membrane potential and resistance change evoked by acetylcholine
Authors: Nishiyama A. , Petersen O. H. 
Published: December 2014

1. Membrane potential and input resistance measurements were made on segments of pancreas from mice or rats, whereas potential measurements alone were made on pancreas from cats or rabbits placed in a tissue bath which was perfused with a Krebs—Henseleit solution.2. The acinar cell membrane potential was about −40 mV and the input resistance 4–8 MΩ. Spontaneous miniature depolarization potentials were occasionally observed superimposed upon the resting potential. In these cases synchronous reductions in input resistance were observed.3. The immediate effect of stimulation with ACh was always a depolarization and a concomitant reduction in input resistance and time constant. In some cases a secondary depolarization was observed accompanied by an increase in input resistance. The time constant, however, remained as short as in the first phase of depolarization.4. In the rabbit pancreas ACh evoked biphasic potential changes: depolarization followed by hyperpolarization. A similar pattern could sometimes also be observed in the mouse pancreas following a brief pulse of ACh addition. In these cases the depolarization was followed by a small but relatively long lasting hyperpolarization. The depolarization was accompanied by a reduction in input resistance.5. Pancreozymin caused depolarization of the acinar cell membrane and a marked reduction in input resistance and time constant.6. In the presence of atropine (1·4 × 10−6
M) depolarization of the acinar cell membrane by an elevated K concentration (50 m
M) in the bathing fluid did not reduce the input resistance.7. It is concluded that the two physiological stimulants of pancreatic protein secretion, ACh and pancreozymin, act on the acinar cells by increasing the permeability of the plasma membrane.
The importance of central adrenergic neurones in renal hypertension in rabbits
Authors: Chalmers J. P. , Dollery C. T. , Lewis P. J. , Reid J. L. 
Published: December 2014

1. Central nervous system adrenergic neurones were partially destroyed by injection of 6‐hydroxydopamine (6‐OHD) into the cisterna magna of normal rabbits and of rabbits with renal hypertension produced by bilateral wrapping of the kidneys with cellophane.2. Six weeks after renal manipulation, the mean arterial pressure of control animals was 122·1 ± 2·4 mmHg while the pressure of rabbits which had been pre‐treated with intracisternal 6‐OHD was only 100·0 ± 4·3 mmHg.3. Partial destruction of central adrenergic neurones by injection of 6‐OHD into the cisterna magna produced a sustained lowering of arterial pressure in rabbits with established renal hypertension, whether this hypertension had been short (6 weeks) or of long duration (18 weeks).4. Adrenergic neurones in the central nervous system play a role in the development and maintenance of the raised arterial pressure in rabbits with renal hypertension.
The ultrastructure of the carotid body in chronically hypoxic rabbits
Authors: Møller M. , Møllgård K. , Sørensen S. C. 
Published: December 2014

1. The ultrastructure of the carotid body in the rabbit has been examined by electron microscopy.2. A comparison was made between the ultrastructure of the carotid bodies in sea level rabbits, in rabbits which had been exposed to hypoxia equivalent to an altitude of 6000 m for 7 days and in rabbits which always had lived at an altitude of 4000–4300 m.3. We could not detect any difference in the ultrastructure between the two groups of hypoxic rabbits.4. When the hypoxic rabbits were compared with sea level rabbits there was a marked increase in the number of dense cored vesicles and mitochondria in the type I cells in the hypoxic rabbits. The Golgi region also appeared to be enlarged in the type I cells in the hypoxic rabbits.5. The finding suggests that in the rabbit the production of amines, probably dopamine, within the type I cells is increased during prolonged hypoxia which might explain the lowered ventilatory response to hypoxia observed in human high altitude residents.6. If the carotid bodies are organs of internal secretion the finding is compatible with an increased production of a hormone produced within the type I cells.
Extracellular space in some isolated tissues
Authors: McIver D. J. L. , Macknight A. D. C. 
Published: December 2014

1. The spaces occupied by isotopically labelled inulin, polyethylene glycol, mol. wt. 4000 (PEG 4000), polyethylene glycol, mol. wt. 1000 (PEG 1000) and sucrose in metabolizing mammalian kidney and liver slices and in toad bladder epithelial cell preparations incubated in vitro have been examined.2. In slices of mammalian tissue, and in homogenized liver, it proved impossible to extract inulin completely from tissue which had been dried. However, inulin was recovered as completely from both dried and undried toad bladder epithelial cells scraped from hemibladders incubated in vitro.3. PEG 4000 occupied a space in all preparations similar to that from which inulin was extracted in dried tissue.4. PEG 1000 and sucrose entered cellular water in mammalian slices, but PEG 1000 occupied a similar space to inulin in toad bladder epithelial cell preparations.6. It is concluded that inulin enters cellular water in mammalian slices from which after drying of the slices it cannot be extracted. It thus rather fortuitously provides a measure of extracellular water under these conditions. In preparations of toad bladder epithelial cells inulin seems to be a satisfactory extracellular marker. PEG 4000, which did not appear to enter cellular water also allows a reasonable estimate of extracellular water. PEG 1000 is a suitable extracellular marker for toad bladder epithelial cell preparations but not for mammalian slices. Sucrose entered cellular water in both slices and toad bladder epithelial cells and is not a satisfactory extracellular marker in these tissues.
Kinetic analysis of the delayed outward currents in frog atrium. Existence of two types of preparation
Authors: Ojeda Carlos , Rougier Oger 
Published: December 2014

1. The outward currents underlying delayed rectification have been studied in frog auricular trabeculae with the double sucrose gap method.2. The results obtained in our experimental conditions allow us to discard the hypothesis of an accumulation of ions during the flow of the outward current.3. In most of the cases the delayed current is composed of two components similar to those previously described by Noble & Tsien (1969a, b).4. The first component I1 is activated with a time constant of about 0·3 sec at the resting potential (E = − 70 mV) and of about 0·75 sec at E = − 5 mV. The steady‐state value of the degree of activation (x1)∞ varies from 0 at E = − 90 mV to 1 at E = + 20 mV. The reversal potential is near E = − 80 mV; this current seems to be mainly carried by potassium ions.5. The second component I2 is very slowly activated, with a time constant of 3·5 sec at E = − 70 mV and of 5 sec at E = − 5 mV. The steady‐state value of the degree of activation (x2)∞ varies from 0 at E = −40 mV to 1 at E = + 25 mV. The reversal potential is near E = −60 mV; this current is less specific than the first component.6. In some preparations the delayed current is composed of only one component. This current is activated with a time constant of 0·6 sec at the resting potential and of 1·5 sec at E = −5 mV. The steady‐state value of the degree of activation is 0 at E = −90 mV and 1 at E = + 30 mV. The reversal potential is between E = −70 and E = −60 mV.7. The role of these currents in the processes of repolarization of normal and prolonged action potentials, and in the pace‐making activity is discussed.
Correlation of the directly observed responses of mesenteric vessels of the rat to nerve stimulation and noradrenaline with the distribution of adrenergic nerves
Authors: Furness J. B. , Marshall Janice M. 
Published: December 2014

1. The effects of nerve stimulation and of the topical application of noradrenaline on arteries, capillaries and veins of the mesentery of the anaesthetized rat were examined by direct observation under a microscope. The distribution of adrenergic nerves to the vessels of the mesentery was studied using the fluorescence histochemical method.2. Principal arteries, small arteries and terminal arterioles were all innervated by a network of adrenergic fibres and they all constricted in response to the stimulation of paravascular nerves and to exogenous noradrenaline. Few adrenergic fibres accompanied the smaller, precapillary arterioles; these vessels did not respond to nerve stimulation, although they were constricted by concentrations of noradrenaline as low as 10−10 g/ml.3. The capillaries did not respond to nerve stimulation or to applied noradrenaline. All veins were constricted by noradrenaline, but only those veins greater than about 30 μm in internal diameter responded to nerve stimulation.4. At stimulus frequencies greater than 4 Hz the flow of blood through the microvasculature usually ceased, although there was never complete closure of these vessels. The maximum constriction observed in principal arteries was usually between 50 and 70% of the control internal diameter, and in small arteries and terminal arterioles was between 40 and 65% of the control internal diameter.5. It is concluded that the principal arteries and small arteries of the mesenteric vasculature are important in the control of blood flow through this vascular bed during sympathetic stimulation and following topical application of noradrenaline, and that the precapillary arterioles are important vessels determining the rate of blood flow through the capillary bed under resting conditions.
Effects of dopamine on the superior cervical ganglion of the rabbit
Authors: Dun N. , Nishi S. 
Published: December 2014

1. The effects of dopamine on isolated rabbit superior cervical ganglion were investigated with intracellular recording techniques.2. Dopamine (10−5‐10−3
M) depressed the amplitude of the excitatory post‐synaptic potential (e.p.s.p.) and blocked impulse transmission.3. Dopamine (10−4
M) induced a slight (2–5 mV) post‐synaptic hyperpolarization without altering membrane conductance.4. The post‐synaptic membrane sensitivity to acetylcholine (ACh) applied iontophoretically was not affected by dopamine.5. Dopamine decreased the frequency of miniature excitatory post‐synaptic potentials (m.e.p.s.p.s) in a high K+ solution, with no change in the amplitude of m.e.p.s.p.s.6. Dopamine reduced the quantal content of the e.p.s.p. in a low Ca2+ and high Mg2+ solution, but had no effect on the quantal size.7. The ganglionic blocking effect of dopamine was antagonized by phenoxybenzamine, but not by propranolol.8. The results show that the ganglionic depressant effect of dopamine is exerted primarily through an alpha‐adrenoceptive site at the presynaptic nerve terminal.
Stimulation electrically and by acetylcholine of the rat hypothalamus in vitro
Authors: Bradbury M. W. B. , Burden Janet , Hillhouse E. W. , Jones M. T. 
Published: December 2014

1. The hypophysiotrophic area of the rat hypothalamus was studied in vitro. The preparation remained viable for at least 3 hr and showed oxygen consumption varying between 68·9–120 μmole/g.hr. The tissue potassium ion content (per unit wet weight) fell to about 50% of the in vivo concentration during this time compared with 15% in the presence of ouabain (10−4 M). Histological examination of tissue incubated for 3 hr showed variable perineuronal oedema but the nuclei were of normal appearance and none showed the pyknotic changes that would be associated with cell degeneration.2. Corticotrophin releasing hormone (CRH) in the medium pooled from five to twenty hypothalami was assayed in five to twelve rats which were median‐eminence lesioned 48 hr earlier. In vitro corticosterone production of quartered adrenals was used as the end point of the assay. Regression lines of the dose—response curves for ACTH, crude CRH and different volumes of medium from electrically stimulated hypothalami were parallel. CRH output was maximal at 75 Hz and 100 μA when the square‐wave pulses lasted for 1 msec. No CRH activity was found on stimulation of cerebral cortex or thalamic tissue pieces of equivalent size.3. Hypothalami taken from rats, adrenalectomized 7–14 days previously, released several‐fold more CRH into the medium during electrical stimulation than the initial content of the tissue, showing that the tissue was capable of synthesizing CRH in vitro. The hypothalami taken from intact rats released considerably less CRH into the medium than tissue taken from 12 to 14 day adrenalectomized rats. The hyper‐secretion of CRH observed in hypothalami taken from adrenalectomized rats was abolished by pre‐treatment with 5 mg/100 g s.c. of corticosterone 24 hr before removal of the tissue. It is therefore proposed that the delayed negative feed‐back action of corticosterone at the hypothalamic level is by the suppression of CRH synthesis and that the effect of secretion is secondary to the effect on synthesis.4. The presence of Ca2+ in the medium was essential for the release of CRH.5. CRH secretion increases linearly with doses of acetylcholine from 5·5 × 10−15‐5·5 × 10−14 M. Cerebral cortex incubated with acetylcholine showed no CRH activity. The effect of acetylcholine was reduced by atropine (3·5 × 10−13 M). Median eminence‐pituitary stalk fragments (which contain mainly terminal axons of neurones) incubated with acetylcholine showed no CRH stimulation in the doses that activate the release of CRH using the hypophysiotrophic hypothalamus. Acetylcholine may act as a neurotransmitter at the dendritic level in the CRH neurone.
Afferent fibres from pulmonary arterial baroreceptors in the left cardiac sympathetic nerve of the cat
Authors: Nishi K. , Sakanashi M. , Takenaka F. 
Published: December 2014

1. Afferent discharges were recorded from the left cardiac sympathetic nerve or the third sympathetic ramus communicans of anaesthetized cats. Twenty‐one single units with baroreceptor activity were obtained.2. The receptors of each unit were localized to the extrapulmonary part of the pulmonary artery, determined by direct mechanical probing of the wall of the pulmonary artery after death of the animals. Conduction velocity of the fibres ranged from 2·5 to 15·7 m/sec.3. Afferent discharges occurred irregularly under artificial ventilation. The impulse activity was increased when pulmonary arterial pressure was raised by an intravenous infusion of Locke solution, or by occlusion of lung roots, and decreased by bleeding the animal from the femoral artery.4. Above a threshold pressure, discharges occurred synchronously with the systolic pressure pulse in the pulmonary artery. A progressive further rise in pressure did not produce an increase in the number of impulses per heart beat. Occlusion of lung roots initially elicited a burst of discharges but the number of impulses for each cardiac cycle gradually decreased.5. The receptors responded to repetitive mechanical stimuli up to a frequency of 10/sec, but failed to respond to stimuli delivered at 20/sec.6. The results provide further evidence for the presence of afferent fibres in the cardiac sympathetic nerve. These afferent fibres are likely to provide the spinal cord with specific information only on transient changes in pulmonary arterial pressure.
The binding of tetrodotoxin and α‐bungarotoxin to normal and denervated mammalian muscle
Authors: Colquhoun D. , Rang H. P. , Ritchie J. M. 
Published: December 2014

1. The binding of [3H]tetrodotoxin and [125I]iodo‐α‐bungarotoxin to innervated and denervated rat diaphragm muscle has been measured.2. A saturable component of tetrodotoxin binding, which was inhibited by saxitoxin, was detected in addition to considerable non‐saturable binding. The saturable component had an equilibrium constant of K = 6·1 n
M (limits 4·7–7·8 n
M) and binding capacity M = 2·5 f‐mole/mg wet wt. (limits 2·1–2·8 f‐mole/mg).3. If the saturable component consisted of one‐to‐one binding of tetrodotoxin to sodium channels, the density of sodium channels would be about 21/μm2 of surface membrane, a figure similar to that found in other excitable membranes.4. After denervation the specific tetrodotoxin binding, as measured by the ratio M/K, fell by a factor of 2·8. This change appeared to be due to a fall in binding capacity rather than a decrease in affinity.5. After denervation the maximum rate of rise of the action potential fell by 27% and became partially resistant to tetrodotoxin. The maximum rate of rise was at first reduced by tetrodotoxin in similar concentrations to those affecting normal muscle, but even large concentrations which completely blocked normal muscle only reduced the maximum rate of rise by a factor of about 2.6. Detubulation with glycerol did not appreciably affect the tetrodotoxin sensitivity of normal or denervated muscle.7. Tetrodotoxin resistance was not observed after denervation of the frog sartorius muscle.8. [125I]iodo‐α‐bungarotoxin binding amounted to 3·8 ± 0·7 f‐mole/mg in innervated muscle and 44·5 ± 2·1 f‐mole/mg in denervated muscle. Most of the uptake was inhibitable by (+)‐tubocurarine.9. The increase in the labelled bungarotoxin binding is much larger than the specific tetrodotoxin binding of innervated muscle, which renders implausible the possibility that the acetylcholine receptors which appear after denervation are related to the tetrodotoxin resistant‐sodium channels.
Brisk and sluggish concentrically organized ganglion cells in the cat's retina
Authors: Cleland B. G. , Levick W. R. 
Published: December 2014

1. Nine hundred and sixty cat retinal ganglion cells were evaluated with respect to receptive‐field organization and latency to antidromic activation of their axons from optic‐tract and mid‐brain positions.2. The vast majority (92%) had the familiar concentric centre/surround organization. As in earlier work these could be classed as sustained or transient, independently of the centre type. About 13% of the concentric cells were characterized by relatively sluggish responses to conventional visual stimuli which yielded brisk responses from the others. The sluggish cells constituted a previously unspecified class of concentric receptive fields.3. The responses of brisk and sluggish cells to a variety of stimuli were described with a view to developing procedures for distinguishing them on functional grounds.4. Measurements of latency to antidromic activation of retinal axons confirmed earlier work in showing that cells classed as brisk‐transient had the shortest conduction times from the optic tract. Cells classed as brisk‐sustained had intermediate conduction times and from earlier work would constitute an important input to the lateral geniculate nucleus. A proportion of the brisk‐sustained axons reached the pretectal region (especially on‐centre types) and a small minority reached the superior colliculus (especially off‐centre types).5. Sluggish cells had generally slower antidromic conduction times; despite some overlap with the brisk‐sustained class, the slower conduction provided independent support for the functional differentiation. Sluggish axons reached the pretectal region and superior colliculus.6. The brisk‐sustained cells constituted the majority of the recordings in the area centralis.7. A comparison with the morphological data of Boycott & Wässle is made which suggests that the brisk‐transient units corresponded with α cells, the brisk‐sustained with β cells, and the sluggish units were included amongst the γ cells.
The entry of labelled calcium into the innervated region of the mouse diaphragm muscle
Authors: Evans R. H. 
Published: December 2014

1. A method is described for measuring the distribution of 45Ca between the junctional and non‐junctional regions of the mouse diaphragm muscle.2. Muscles which were incubated in Ringer solution containing labelled calcium accumulated the tracer at the junctional region when acetylcholine or carbachol was present. Denervation did not prevent this accumulation at the normally innervated region.3. Histochemical evidence indicated that, in the presence of acetylcholine or carbachol, calcium entered diaphragm muscle fibres at the junctional region.4. Accumulation of calcium occurred at all regions of muscle fibres depolarized by potassium. In the presence of acetylcholine or carbachol, accumulation occurred at the junctional region in the absence of muscle fibre post‐junctional membrane depolarization.5. It is suggested that the desensitized muscle fibre post‐junctional membrane has an increased calcium permeability.
The circadian rhythms of human subjects without timepieces or indication of the alternation of day and night
Authors: Mills J. N. , Minors D. S. , Waterhouse J. M. 
Published: December 2014

1. Seven solitary subjects, and two groups of four, spent from 5 to 13 days in an isolation unit without knowledge of time. Three solitary subjects and one group of four adopted fairly regular activity habits with a period of 25–27 h; one subject adopted a period of 30 h, and one of 27 h initially, decreasing to 24–25 h after a few days. One group of four awoke roughly every 24 h, after a sleep which was alternately about 8 h, or about 4 h and believed by the subjects to be an afternoon siesta. Two solitary subjects alternated sleeps of about 8 or 16 h, separated by 24 h of activity.2. Deep temperature in all subjects oscillated with a period of 24–26 h, which was thus commonly distinct from their activity habits.3. Urinary potassium followed a rhythm whose period, though usually close to, was sometimes distinct from, that of temperature. A secondary period corresponding to that of activity was also sometimes present.4. Urinary sodium and chloride usually gave evidence of two periodic components, one corresponding to activity and the other to the rhythm of either temperature or of urinary potassium.5. Urinary creatinine and phosphate usually followed the subject's routine of activity.6. Plasma samples were collected on a few occasions and analysed for phosphate and 11–hydroxycorticosteroids. Changes in plasma phosphate were usually, but not always, associated with similar changes in urinary phosphate, and changes in plasma corticosteroids were often, but not always, associated with similar changes in urinary potassium shortly afterwards.7. Observations are recorded on a subject alone in a cave for 127 days. His activity habits, though wildly variable, gave evidence of a period of 25·1 h and his urinary electrolyte excretion indicated a shorter period, of 24·6 h. During the following 3 days, when he remained in the cave but was visited frequently, his plasma corticosteroids and urinary potassium oscillated with a period of 16 h.8. The possible mechanisms controlling these rhythms are discussed.