bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of the conductance of the sodium channel from current fluctuations at the node of Ranvier.
Authors: Conti F , Hille B , Neumcke B , Nonner W , Stämpfli R
Published: December 2014

Single myelinated nerve fibres of Rana esculenta were investigated under voltage clamp conditions at 13 degrees C. Fluctuations of steady‐state membrane current were measured during the last 152 msec of 190‐225 msec pulses depolarizing the membrane by 8‐48 mV. Noise power spectral densities were calculated in the frequency range of 6‐6‐6757 Hz. 2. External application of 150 nM tetrodotoxin (TTX) and/or 10 mM tetraethylammonium (TEA) ion reduced the current fluctuations. The difference of current noise spectra measured in the presence and absence of TTX (TEA) was not changed by the presence of TEA (TTX) during both measurements, and was taken as the spectrum of the Na (K) current fluctuations. 3. Residual current noise during application of both TTX and TEA was, except for some excess noise at the low and high frequency ends of the spectrum, similar to the noise measured from a passive nerve model and could be understood in terms of Nyquist noise of the known resistances and the amplifier noise. 4. Na current fluctuation spectra were interpreted as the sum N/f+SNa(f) where SNa(F) represents the spectrum expected for a set of equal, independent Na channels with only two conductance states (open or closed) which follow Hodgkin‐Huxley kinetics. With values of hinfinity, tauh and minfinity measured from macroscopic Na currents, the measured spectra were fitted well by optimizing N, SNa(0) and taum. Values of taum obtained by this method were in fair agreement with values found from macroscopic currents. 5. The 1/f component of Na current noise was roughly proportional to the square of the steady‐state Na current, I2. The mean value of N/I2 was (1‐1 +/‐ 0‐3) X 10(‐4). 6. The current carried by a single Na channel was calculated from fitted spectra and steady‐state Na currents measured simultaneously with the current fluctuations. The single channel conductance gamma normalized to zero absolute membrane potential was calculated. The average gamma from twelve measurements at depolarizations of 8‐40 mV was 7‐9 +/‐ 0‐9 pS (S.E. of mean). The apparent value of gamma was smallest with small depolarizations. Variations of the assumed kinetic properties of the model did not drastically affect the single channel conductance. 7. External application of 0‐1 mM‐Ni ion lengthened taum in the macroscopic currents and in the fluctuation spectra and enhanced both the steady‐state Na current and the current fluctuations. In Ni‐treated nodes gamma was smaller than in normal nodes.
Conductance of the sodium channel in myelinated nerve fibres with modified sodium inactivation.
Authors: Conti F , Hille B , Neumcke B , Nonner W , Stämpfli R
Published: December 2014

1. Na current fluctuations in nodes of Ranvier were measured under voltage clamp conditions as described in the preceding paper (Conti, Hille, Neumcke, Nonner & Stämpfli, 1976) and analysed in terms of power spectral density calculated for frequencies between 30 Hz and 5 kHz. 2. External (10(‐5) g/ml.) Leiurus scorpion venom or Anemonia Toxin II (3 X 10(‐5) g/ml.) or internal 20 mM iodate were applied in order to remove or slow down inactivation in part of the Na channels. The treatment increased the steady‐state Na current during the noise measurement one‐to eight fold over that in normal fibres. 3. Noise spectra were interpreted as the sum of 1/f noise and noise SNa(f) due to all‐or‐none, open‐close transitions of single Na channels. The drug effects on the inactivation could be accounted for either by assuming two populations of channels, one with and one without inactivation, or by postulating a single population with modified inactivation characteristics. 4. Except for an increase in amplitude, the fluctuation spectra SNa(f) were similar to the ones in normal nodes. Again, the time constants taum obtained from the fit of the spectra agreed within a factor of 2 with the values of taum found in the macroscopic Na currents. 5. From the fluctuation spectra, single Na channel conductances gamma of 5‐4 +/‐ 0‐4 pS (iodate), 6‐7 +/‐ 0‐5 pS (Leiurus) and 7‐0 +/‐ 0‐6 pS (Anemonia) were calculated. The value of gamma was not significantly voltage dependent. 6. Our observations indicate that inactivation of Na channels can be modified with at most small effects on the microscopic properties of the activation process and on the conductance of the open channel. They suggest that the h mechanism normally produces all‐or‐none, open‐close changes of conductance.
Influence of the sodium pump on intercellular communication in heart fibres: effect of intracellular injection of sodium ion on electrical coupling.
Authors: De Mello W C
Published: December 2014

1. The effect of intracellular sodium injection on the electrical coupling between cardiac Purkinje cells was investigated. 2. It was found that an increase in the intracellular sodium concentration produces uncoupling in about 500 sec and increases the input resistance of the injected cell. Both effects were completely reversible. 3. Inhibition of the sodium pump by ouabain (6‐8 x 10(7) M) also causes electrical uncoupling. 4. The decoupling of heart cells achieved by sodium injection was considerably accelerated in fibres treated with ouabain. 5. The influence of sodium injection on cell communication seems to be related to the intracellular calcium concentration 6. The above results indicate that the maintenance of a low intracellular sodium concentration by the sodium pump is essential for the preservation of a high junctional conductance in cardiac fibres.
The effects of bilateral adrenalectomy or hypophysectomy of the foetal lamb in utero.
Authors: Barnes R J , Comline R S , Silver M
Published: December 2014

1. Foetal hypophysectomy or bilateral adrenalectomy, carried out in utero at about 100 or 125 days gestation respectively, increased the length of gestation in sheep. It was confirmed that pregnancy was not prolonged significantly if hypophysectomy or adrenalectomy was carried out on one of a pair of twins. The hypophysectomized foetus was, however, smaller and the adrenalectomized foetus larger, than the unoperated twin. 2. In about half of the previously operated foetuses intravascular catheters were inserted into both mother and foetus, either at about 125 days, for a comparison with normal catheterized foetuses, or during the post‐mature period. Both adrenalectomized and hypophysectomized foetuses appeared to have little resistance to stress or infection and the majority survived only 1‐2 weeks after the insertion of catheters. 3. Maternal peripheral plasma oestrogen, progesterone and corticosteroid concentrations did not appear to be altered by either foetal hypophysectomy or adrenalectomy and were maintained in the normal range during prolonged gestation. 4. Foetal plasma oestrogen concentrations were significantly lower after hypophysectomy or adrenalectomy than values found in control lambs. Plasma progesterone values were low in all three groups of foetuses. 5. Plasma corticosteroid concentrations after foetal hypophysectomy (12‐6 ng/ml.) or adrenalectomy (14‐7 ng/ml.) were in the same range as the values for control lambs before the pre‐partum rise (14‐6 ng/ml.). However, there was a small but significant maternal‐to‐foetal plasma corticosteroid gradient in the two operated groups whereas this difference was not found in the control animals. 6. Tissue glycogen concentrations were measured in non‐catheterized adrenalectomized and hypophysectomized foetuses. In these two groups, whether examined before 149 days or after prolonged gestation, liver glycogen concentrations were 30‐40% of those in non‐catheterized control foetuses at term. In other respects there was little apparent difference between adrenalectomized and control foetuses. 7. Hypophysectomized foetuses had significantly higher glycogen concentrations in heart, skeletal muscle and lung compared with control or adrenalectomized lambs. Plasma glucose and fructose values were also low in this group compared with control foetuses.
Specific innervation of guinea‐pig superior cervical ganglion cells by preganglionic fibres arising from different levels of the spinal cord.
Authors: Njå A , Purves D
Published: December 2014

1. The synaptic contribution of preganglionic nerve fibres arising from the last cervical (C8) and the first seven thoracic spinal cord segments (T1‐T7) to neurones of the guinea‐pig superior cervical ganglion has been studied by means of intracellular recording during ventral root stimulation in vitro. 2. The majority of neurones received innervation from the middle segments (T2 and T3) of the length of spinal cord from which preganglionic fibres derive; an intermediate number of ganglion cells were innervated by fibres from the segments adjacent to these (T1, T4, and T5), and relatively few neurones by fibres from the most rostral and caudal segments supplying innervation to the ganglion (C8, T6 and T7). 3. Each neurone received preganglionic terminals from multiple thoracic segments (range 1‐7, mean = 4‐0). The estimated minimum number of preganglionic fibres contacting each neurone was 10, on average. 4. As a rule, the spinal segments innervating a neurone were contiguous. Thus we rarely encountered neurones innervated by segments located both rostrally and caudally to a segment which failed to provide innervation. 5. Neurones tended to be innervated predominantly by axons arising from a single spinal segment, with adjacent segments contributing a synaptic influence that diminished as a function of their distance from the dominant segment. All segments provided dominant innervation to at least some neurones. 6. Stimulating the ventral roots of C8‐T7 in vivo showed that the axons arising from each segment produced a characteristic pattern of peripheral effects. Thus different populations of neurones in the superior cervical ganglion of the guinea‐pig are innervated by preganglionic axons from different levels of the spinal cord, as originally suggested by Langley (1892) for the cat, dog, and rabbit. 7. On the basis of our in vitro studies we conclude that underlying the specificity of innervation of neurones of the superior cervical ganglion that can be inferred from in vivo experiments is a tendency for individual neurones to be innervated in a systematically graded fashion by a contiguous subset of the eight spinal segments which provide innervation to the ganglion.
Rat adrenocortical dynamics.
Authors: Papaikonomou E
Published: December 2014

1. The dynamics of the adrenocortical response to adrenocorticotrophic hormone (ACTH) was studied in anaesthetized, acutely hypophysectomized male rats. 2. ACTH test‐signals were applied either in a jugular vein ('intact infused preparation') or in the aorta through the coeliac artery with the aorta ligated below this artery ('isolated in situ perfused preparation'). The adrenocortical responses were measured directly in samples serially taken from the left adrenal vein. 3. Tested ACTH signals were either impulses (injections of 0‐05‐‐1‐2 mu. ACTH) or step functions (constant infusions of 0‐025‐‐1‐6 mu. ACTH/min). 4. All responses showed a 3‐6 min delay, larger delays corresponding to smaller input signals. The step responses reached steady‐state level without overshoot. 5. The impulse responses of the isolated perfused and of the intact infused glands, as well as their step responses, were similar as to dynamic form. 6. It is concluded that there is an inherent delay in the responses of both the isolated perfused and of the intact infused rat adrenal gland. Further, unlike what has been reported for the canine adrenal gland, the intact rat adrenal gland does not appear to be appreciably 'faster' in its response than the isolated gland. Finally, the amplification factor from ACTH to corticosterone could be estimated for both preparations in the case of ACTH injections; a value of 1‐3 X 10(6) (one ACTH molecule activates synthesis and release of 1‐3 million corticosterone molecules) was found.
Reaction of intact spinal motoneurones to partial denervation of the muscle.
Authors: Huizar P , Kuno M , Kudo N , Miyata Y
Published: December 2014

1. The properties of soleus motoneurones of the cat were examined with intracellular electrodes about 3 weeks after partial denervation of the soleus muscle. Soleus motoneurones whose axons had been left intact were distinguished from those whose axons had been sectioned by the presence or absence of muscle contraction in response to intracellular stimulation of each motoneurone. 2. The average twitch tension of motor units evoked by intracellular stimulation of intact soleus motoneurones after partial denervation of the muscle was not significantly different from that observed in control, unoperated cats. Therefore, it was assumed that the majority of intact motoneurones had not been subject to injuries in their axons upon partial denervation. 3. Soleus motoneurones whose axons had been sectioned showed a significant increase in overshoot of action potentials and a significant decrease in resting membrane potential, in axonal conduction velocity and in the duration of after‐hyperpolarization. 4. Soleus motoneurones whose axons had been left intact also showed a significantly shorter after‐hyperpolarization than that seen in control, unoperated cats. Other electrophysiological properties of the intact soleus motoneurones were indistinguishable from those observed in unoperated animals. 5. The decrease of the duration of after‐hyperpolarization in intact soleus motoneurones was greater in highly denervated preparations than in moderately denervated preparations. 6. The decrease of the duration of after‐hyperpolarization in intact soleus motoneurones was associated with a decrease in contraction times of the innervated muscle fibres, the former preceding the latter by one to two weeks. 7. It is concluded that motoneurone properties can be modified without injury to their axons and that alterations in the properties of intact motoneurones depend upon the degree of partial denervation of the muscle. The possible signal for alterations of motoneurone properties is discussed. 8. It is also concluded that the contractile properties of muscle fibres can be modified without cross‐union of the nerves. It is suggested that the contractile properties of muscle fibres may be linked to the duration of after‐hyperpolarization or to some mechanism related to this factor in the innervating motoneurones.
Fractionation studies on the absorption of labelled immunoglobulin G by the gut of young rats.
Authors: Morris B , Morris R
Published: December 2014

1. Centrifugation in density gradients was used to study the fragments produced during intraluminal and intracellular digestion, after the injection of 125I‐labelled immunoglobulin G (IgG) into different regions of the small intestine of 14 to 15‐day‐old (pre‐closure) and 24‐day‐old (post‐closure/ rats. 2. After injection into the proximal small intestine and into the ileum of pre‐closure animals, the bulk of the radioactivity recorded for gut washes and gut homogenates was located at 4S‐7S. The serum from animals which had received injections into the proximal small intestine had high radioactivity and one peak at 7S; the serum from animals which had received injections into the ileum had low radioactivity and no activity in the 7S region. 3. After injection into the proximal small intestine of post‐closure animals, the bulk of the radioactivity recorded for gut wash samples was located at 3‐5S‐‐5S. Gut homogenates had peak activity at 2‐5S‐‐4S. Thus large molecular weight products can be absorbed by the proximal enterocytes of post‐closure rats and degraded. The sera of these animals had low radioactivity. 4. After injection into the distal small intestine of post‐closure animals, the bulk of the radioactivity recorded for gut wash and gut homogenate samples was located at 4S‐7S and in this respect the radioactivity plots resembled those for (2) above. Serum radioactivity was low. 5. The effect of precipitation with trichloroacetic acid and incubation with specific antiserum upon the radioactivity of gut washes, gut homogenates and serum samples was recorded. 6. The relevance of these findings to studies on the transmission of protein by the rat small intestine is discussed.
A physiological and behavioural study in cats of the effect of early visual experience with contours of a single orientation.
Authors: Blasdel G G , Mitchell D E , Muir D W , Pettigrew J D
Published: December 2014

1. Three kittens were reared in visual environments that consisted of stripes at one of three orientations ‐ horizontal, right oblique, or left oblique. Two additional cats were reared as controls. One of these matured viewing right and left oblique stripes on alternate days. The other experienced a normal visual environment. 2. Following the completion of rearing, and after several weeks of normal visual experience, behavioural testing of the stripe‐reared animals demonstrated a deficit in visual acuity for orientations which were not present in the early visual environment. No comparable deficit emerged for either of the control cats. 3. Following 1‐3 years of further, normal, visual experience, each of the cats was shipped separately to California where single units were recorded from area 17 of the visual cortex and an effort made to guess the early visual history of each animal which was unknown to the experimenters. Cell samples from each experimental cat and the normal control cat allowed the physiologist to guess their early visual experience correctly. The control cat which matured viewing orthogonal sets of oblique stripes on alternate days demonstrated a bias for horizontal contours in his cell sample. In contrast to units recorded from normal cats, about 80% of which are binocular, only about 30% of the cells recorded from the stripe‐reared animals could be influenced by both eyes.
The development of some metabolic responses to hypoxia in the foetal sheep.
Authors: Jones C T
Published: December 2014

1. Foetal and maternal plasma metabolite and catecholamine concentrations have been measured in chronically catheterized sheep, 95‐145 days pregnant. 2. With increasing gestational age there was rise in foetal plasma lactate, free fatty acid and ketone body concentration and in maternal plasma in free fatty acid and ketone body concentration. With the exception of alpha‐amino nitrogen none of the plasma metabolites showed any correlation with foetal blood gas or pH values; alpha‐amino N was inversely related to foetal blood pH. 3. Hypoxia in the foetuses was induced by causing the ewe to breathe 9% O2 with 3% CO2 in N2. This had a small effect on plasma metabolites in the ewe, mainly producing an increase in free fatty acid and ketone body concentration. 4. In the foetus hypoxia was associated with a large rise in plasma lactate and a small rise in alpha‐amino N, the magnitudes of which did not change over the gestational range studied. Consistent and large increases in foetal plasma glucose, free fatty acid and ketone body concentration in response to hypoxia were seen only between 130 and 145 days. 5. In foetuses of 130‐145 days the magnitude of the hypoxia‐induced rise in plasma glucose and free fatty acid concentration was proportional to the plasma catecholamine concentration. 6. The concentration of acetate in foetal plasma was lower than and proportional to that in the maternal plasma. Neither concentration changed significantly during hypoxia. 7. The results are discussed in relation to the ability of the foetal sheep independently to control the concentration of its plasma metabolites and to mobilize its carbon stores at times of need. They indicate that in the sheep plasma catecholamines are important regulators of plasma glucose and free fatty acid concentrations late in foetal life.
The influence of the autonomic nervous system in the control of erythropoietin secretion in the hypoxic rat.
Authors: Beynon G
Published: December 2014

1. Erythropoietin has been measured in the serum of hypoxic rats that have been exposed to 6 hr of hypoxia, by use of a biological assay. 2. The effects of section of splanchnic, renal and sinus nerves on the concentration of Erythropoietin present in the serum ofthe hypoxic animals has been investigated. 3. Serum levels of Erythropoietin were reduced in the hypoxic animals immediately after cutting the splanchnic nerves, but unaltered one week after the operation. 4. The concentration of Erythropoietin in the serum of hypoxic rats was increased by the secretion of the renal nerves. Section of the sinus nerves abolished the effect. 5. Elevated levels of Erythropoietin were present in the sera of hypoxic rats immediately after section of the sinus nerves. The effect was still obtained when the animals were exposed to hypoxia 1 week after cutting the nerves, though in attenuated form. 6. The rise in the concentration of the hormone after chronic section of the sinus nerves was estimated as as 261% (fiducial limits 167‐513, P = 0‐05), by parallel line bio‐assay. 7. The concentration of Erythropoietin in the serum of hypoxic rats was progressively elevated as the arterial PO2 of the animals was reduced. Section of the sinus nerves did not alter the secretion of Erythropoietin in these experiments.
Microiontophoretic studies of the effects of cyclic nucleotides on excitability of neurones in the rat cerebral cortex
Authors: Stone T. W. , Taylor D. A.
Published: December 2014

1. Responses of cerebral cortical neurones to the microiontophoretic application of acetylcholine, noradrenaline, cyclic adenosine 3′,5′‐monophosphate (cyclic AMP) and cyclic guanosine 3′,5′‐monophosphate (cyclic GMP) were examined.

2. The application of acetylcholine and cyclic GMP to identified pyramidal tract neurones resulted in an increased frequency of firing in a large number of cells. Upon application of both substances to cells which could not be identified as pyramidal tract cells, a reduction in the frequency of spontaneous firing was sometimes observed.

3. Careful current controls had no effect on the cells discussed here, indicating that the observed responses were not due to the iontophoretic currents. Also, the electro‐osmotic ejection of cyclic GMP (outward current) produced similar changes of cell firing to those which followed iontophoretic application (inward current).

4. The microiontophoretic application of atropine resulted in a blockade of acetylcholine responses while leaving responses to cyclic GMP unaffected. This suggests that cyclic GMP was not acting indirectly by releasing acetylcholine from presynaptic endings.

5. Ejection of cyclic GMP from solutions containing calcium ions produced responses comparable to those produced by cyclic GMP alone. It is unlikely therefore that cyclic GMP was causing excitation by chelating calcium.

6. Applications of noradrenaline and cyclic AMP produced a reduction in the spontaneous discharge rate of most neurones tested.

7. Phosphodiesterase inhibitors such as ICI 63,197 caused a potentiation of the noradrenaline responses of pyramidal tract neurones.

8. 5′‐adenosine monophosphate produced a powerful depression of all cells to which it was applied. This action was blocked by aminophylline, suggesting the effect was mediated through an adenosine receptor. Responses to cyclic AMP were usually not abolished, but were reduced by about 50% in amplitude.

9. These results are consistent with the hypothesis that cyclic AMP may mediate some neuronal effects of noradrenaline and cyclic GMP may mediate some effects of acetylcholine. The results are also consistent with the suggestion that the two nucleotides may sometimes mediate opposite cellular responses to humoral stimuli.
Effects of steady‐state plasma vasopressin levels on the distribution of intrarenal blood flow on electrolyte excretion.
Authors: Akatsuka N , Moran W H , Morgan M L , Wilson M F
Published: December 2014

1. In order to evaluate the effects of arginine vasopressin (AVP) on the distribution of intrarenal blood flow and on electrolyte excretion, steady‐state plasma AVP levels (4‐8, 19‐1, 44‐3, and 100‐6 micro u./ml.) were produced in anaesthetized dogs, which were hydrated to minimize endogenous anti‐diuretic hormone (ADH) release. 2. The urinary excretion of sodium and potassium increased without change in their filtered loads during AVP infusion. 3. Measurement by the 133xenon washout method revealed diphasic blood flow shifts, as a function of the plasma AVP level, between compartment 1 (outer cortex) and compartment 2 (inner cortex and outer medulla) without change in compartment 3 (inner medulla). 4. In a separate study, the radioactive microsphere (15 micronm) method was used with a plasma AVP levels of 19‐8 micronu./ml. Blood flow (expressed as % flow/g tissue) decreased in the outer cortex and increased in the inner cortex. 5. Total renal blood flow did not change during infusion of AVP. However, the values measured by 133xenon were lower than those measured by the microsphere method. 6. There was agreement between these two independent methods that blood flow shifted from outer to inner cortex, with no change in total renal flow, at similar plasma AVP levels (19‐1 and 19‐8 micronu./ml.). The relationship of these intrarenal circulatory changes to the increased electrolyte excretion is discussed.
Electrical responses of rods in the retina of Bufo marinus
Authors: Cervetto L. , Pasino E. , Torre V.
Published: December 2014

1. Intracellular responses to flashes and steps of light have been recorded from the outer segment and the cell body of rods in the retina of the Bufo marinus. The identification of the origin of recorded responses has been confirmed by intracellular marking.

2. Responses to flashes delivered in darkness or superimposed on a background were analysed. Responses recorded from outer segments conform to the principle of ‘spectral univariance’. The shape of the response is not affected by enlarging the spot diameter from 150 to 1000 μm.

3. The membrane potential measured in darkness at the outer segments varied from ‐15 to ‐25 mV. Injection of steady hyperpolarizing currents increases the size of the response to light; depolarizing currents reduce the response. The mean value of the input resistance is 97 ± 30 MΩ in darkness and increases by 20‐30% during illumination.

4. The responses obtained from the cell body of rods have the same shape, time course and spectral sensitivity of those recorded at the outer segment. Injection of steady current at the cell body produces different effects than at the outer segment: hyperpolarizing currents reduce the amplitude of the response to light; depolarizing currents increase the response.

5. The experimental data are fitted according to a model similar to that used to describe the responses of turtle cones (Baylor & Hodgkin, 1974; Baylor, Hodgkin & Lamb, 1974a, b).

6. The model reproduces the electrical responses of the rod outer segment to a variety of stimuli: (a) brief flashes and steps of light in dark adapted conditions; (b) bright flashes superimposed on background illuminations; (c) pairs of flashes delivered at different time intervals. Responses to hyperpolarizing steps of current are also reproduced by the model.
The distribution of α‐bungarotoxin binding sites on mammalian skeletal muscle developing in vivo
Authors: Bevan Stuart , Steinbach Joe Henry
Published: December 2014

1. The distribution of α‐bungarotoxin binding sites on embryonic and neonatal rat skeletal muscle fibres was determined by autoradiography. Most of the bungarotoxin binding could be inhibited by curare. This observation, together with the spatial distribution of toxin‐binding sites, indicates that the distribution of bound toxin reflects that of acetylcholine (ACh) receptors on these developing muscle cells.

2. At 15 days of embryogenesis, muscle fibres showed an essentially uniform distribution of receptors. By 16 days, many fibres showed an accumulation of receptors in their mid‐region. This accumulation was at the same location as histochemically demonstrated cholinesterase activity.

3. At 16 days ACh receptors were distributed over the entire length of the fibres, with a gradient of increasing density as the accumulation was appoached. The density of toxin binding sites in the accumulation was greater than the general level on 15 day cells, suggesting that the high junctional density does not develop solely by the loss of extrajunctional receptors.

4. The accumulations of ACh receptors became more pronounced and circumscribed with embryonic development, and after birth the extent of the localizations appeared to follow the size of the neuromuscular junction. The extrajunctional receptor density decreased with development, and by 1 week after birth was undetectable by the methods used.

5. The results suggest that the high junctional receptor density found on adult, innervated skeletal muscle fibres develops after the formation of the neuromuscular junction.
On the question of body fluid volume or sodium status influencing renin release.
Authors: Blair-West J R , Brook A H , Simpson P A
Published: December 2014

1. The extent to which renin release is affected by simultaneous changes in body Na and body fluid volume was studied in six sheep. 2. The animals' water intake was restricted for 10‐17 days after which they were offered solutions containing varying amounts of NaCl. 3. Plasma renin concentration (PRC) of water restricted sheep was 2‐3 times normal. 4. The changes in PRC following drinking were inversely related to the amount of sodium consumed, Na excretion and plasma Na concentration. There was no correlation between the changes of PRC and of plasma volume in so far as the latter is reflected by alterations in plasma protein concentration. 5. We conclude that changes in renin release were related to the animals' handling of NA, and not to alterations in body fluid volume. 6. These findings are compatible with the proposition that renin release was mediated by a macula densa mechanism.
The pupillary, the intraocular pressure and the vasomotor responses to noradrenaline in rabbits.
Authors: Langham M E , Palewicz K
Published: December 2014

1. A study has been made of the cause of the temporal disparity between the pupillary and intraocular pressure responses to noradrenaline applied topically. 2. Over a 5‐day experimental period, the quantitative characteristics of the pupillary response to noradrenaline applied either once or several times daily remained essentially unchanged. In the same rabbits the delay in pressure response to noradrenaline on the first day was increased by a second application and, on subsequent days, multiple applications of noradrenaline induced a biphasic pressure response. 3. Intravenous phenoxybenzamine inhibited both the pupillary and the biphasic pressure responses to noradrenaline. Phenoxybenzamine applied topically inhibited the ocular hypertensive but not the hypotensive and pupillary responses. 4. Analysis of aqueous humour dynamics by manometric procedures showed that the hyper‐ and hypotensive responses were associated with increase and decrease, respectively, of the resistance to outflow of the aqueous humour.
A mathematical model for counter‐current multiplications in the swim‐bladder.
Authors: Sund T
Published: December 2014

1. A computer model for swim‐bladder gas filling has been developed. Phenomenological descriptions of the Root effect (pH‐dependent O2 capacity of fish haemoglobin), of the lactic acid production in the gas gland and of the geometry of the rete mirabile are incorporated in the general counter‐current equations to give a comprehensive model of gas filling. 2. It is known that pH along the rete is not constant, as supposed in an earlier gas‐filling model. It is also known that the Root shift reaction has a different half‐time model. It is also known that the Root shift reaction has a different half‐time depending on whether the haemoglobin absorbs or releases O2. These particular effects are accounted for in the present model. 3. The model gives gas filling rate and maximum swim‐bladder pressure for CO2, O2 and N2. The partial pressure of these gases as well as the concentration of lactic acid and the pH along the rete are also calculated. 4. The model reproduces quite accurately experimental values for gas‐filling rate in eel, together with lactic acid, CO2 and O2 concentrations measured at the rete end‐points. There is also good correlation between maximum predicted stable swim‐bladder pressure and maximum recorded depth for four fishes investigated (r=0‐937; P=0‐06). 5. The model predicts an enhancement of O2 filling rate and maximum swim‐bladder pressure of at least 4 when the reaction rates of the Root shift in eel haemoglobin are 0‐2 sec (Root‐off) and 10 sec (Root‐on), as compared to an instantaneous Root shift. 6. With a swim‐bladder pressure of 1 atm and Root‐shift reaction rates of equal magnitude, the po2‐profile along the rete is nearly linear. When the reaction rates are such as found experimentally in eel haemoglobin, the po2 along the rete is non‐linear, with a maximum of approximately 2 atm near the bladder pole of the rete. An experimental verification of this maximum will constitute a crucial test of the model. 7. The calculations show that blood flow through rete can regulate both gas‐filling rate and stable swim‐bladder pressure. At high pressure, the main factor limiting gas filling is loss of gas through back diffusion along the rete. 8. Maximum po2 in the swim‐bladder is highly dependent upon the Root effect. If the Root effect persists up to about 100 atm, as seems to be the case blue hake, maximum po2 is more than 200 atm. When the Root effect is abolished at 10 atm, as is expected in eel, the maximum po2 drops to about 30 atm. 9. The pN2 in the bladder can reach 10‐15 atm depending on blood flow, whereas PCO2 will not exceed 1 atm.
Spectral and orientation specificity of single cells in foveal striate cortex of the vervet monkey, Cercopithecus aethiops
Authors: Bertulis Algis , Guld Christian , Lennox-Buchthal Margaret A.
Published: December 2014

1. The spectral sensitivity, orientation specificity and inhibitory surround of seventy‐three cells were studied in the vervet monkey. The eye was in the dark or illuminated with steady white or spectral light. The cells were in the striate cortex corresponding to the foveal representation. Nearly all the cells gave on‐ or on/off‐responses.

2. More than a third of the cells (41%) responded over a narrow spectral band, in the blue, green, yellow or red section. Three quarters of them were orientation specific with flanking inhibitory surround and half of these were of the ‘stopped‐end’ variety as well. The effect of the wave‐length of the background indicated that only a half were activated by such excitatory—inhibitory colour pairs as have been described in the geniculate nucleus.

3. A third of the cells (36%) responded to most colours but with the greatest response to green, yellow or red. Less than half were orientation specific. Unlike the narrowband cells, the response decreased with the intensity of the light. Two thirds were activated by the excitatory‐inhibitory colour pairs that have been described in the geniculate nucleus.

4. In both groups of cells the wave‐length of the spectral peak could be different when the stimuli were weak compared with when they were strong.

5. One quarter of the cells (23%) gave on/off‐responses to all spectral flashes; half were not orientation specific. The difference in orientation specificity between narrow‐ and broadband cells is significant (P < 0·01).
Movements of radioactive potassium in isolated rat ganglia
Authors: Scholfield C. N.
Published: December 2014

1. Isolated rat superior cervical ganglia were continuously superfused with 42K (or 86Rb) solution and the amount of radioactivity taken up was monitored using scintillation counting.

2. Entry of 42K into the ganglia could be resolved into two components, one amounting to 83% of the total 42K uptake, with a rate constant of 0·015 min−1, and the other of 17% of the total, with a rate constant of 0·15 min−1.

3. With 6 m
M‐K in the bathing solution, the equilibrium uptake of 42K after 4 hr corresponded to an intracellular concentration of 147 m
M‐K. Changes in the K concentration of the bathing solution (0·5‐20 m
M) had little effect on this value.

4. Carbachol or nicotine caused a rapid net loss of 42K. 42K was recaptured on washing out the depolarizing agents, with a rate constant of about 0·3 min−1. This recapture rate was slowed by ouabain, dinitrophenol, cyanide, mersalyl and by reducing the K concentration in the bathing solution.

5. Efflux of 42K from preloaded ganglia occurred with a rate constant of 0·017 min−1. This rate was increased about sixfold by 180 μ
M carbachol in 6 m
M‐K but not in 150 m
M‐K suggesting that the increase in efflux was mainly a consequence of the depolarization caused by carbachol.

6. 86Rb fluxes and the effects of carbachol thereon were similar.
Sodium currents in mammalian muscle
Authors: Adrian R. H. , Marshall M. W.
Published: December 2014

1. A method is described which allows the approximate computation of membrane current from measurements with three electrodes in the mid‐region of a muscle fibre.

2. Measurements of inward sodium current in frog muscle are compared with the results of previous clamping studies to test the validity of the new method.

3. Sodium current in rat muscle (extensor digitorum longus) is in general similar to sodium current in frog muscle. Two differences in detail have been found between sodium current in rat and frog muscle: (a) at the same temperature (in the range 0‐20° C) inactivation is slower in the rat than in the frog; (b) in rat the steady‐state activation is shifted negatively on the voltage axis by some 10‐15 mV.

4. Delayed outward current and charge movement (Schneider & Chandler, 1973) are present in rat muscle.

5. Rat muscle fibres are more resistant than frog muscle fibres to the action of tetrodotoxin. Inward current is still detectable in rat muscle at 100 n
M tetrodotoxin. We found no evidence to suggest the existence in rat muscle of two kinds of sodium channel, one sensitive and one less sensitive to tetrodotoxin.
Laminar differences in receptive field properties of cells in cat primary visual cortex
Authors: Gilbert Charles D.
Published: December 2014

1. Cells in area 17 of the cat visual cortex were studied with a view towards correlating receptive field properties with layering. A number of receptive field parameters were measured for all units, and nearly every unit was marked with a microlesion to determine accurately the layer in which it was found.

2. Cells were defined as simple or complex by mapping with stationary stimuli, using the criteria of Hubel & Wiesel (1962). Complex cells fell into two groups: those that showed summation for increased slit length (standard complex) and those that did not (special complex).

3. The simple cells were located in the deep part of layer 3, in layer 4, and in layer 6. This corresponds to the distribution of afferents from the dorsal layers of the lateral geniculate nucleus. In these cortical layers the simple cells differed primarily with respect to their receptive field size, cells in layer 4 having the smallest, layer 3 intermediate, and layer 6 the largest fields. Layer 4 was the only layer in which simple cells showed end‐inhibition (a reduction in response to slits extending beyond the excitatory portion of the receptive field).

4. The standard complex cells were found in all layers, but were quite scarce in layer 4. As with the simple cells, field size varied with layer: in layer 2+3 they had small to intermediate field sizes, in layer 5 intermediate, and in layer 6 very large. Layer 6 cells showed summation for slits of increased length up to very large values, and responded best when the slits were centred in the receptive field.

The only standard complex cells that showed end‐inhibition were those in layer 2+3, and these were similar to the layer 4 simple cells in terms of proportion of end‐inhibited units and degree of end‐inhibition.

5. The special complex cells, originally described by Palmer & Rosenquist (1974), were found in two tiers: the upper one at the layer 3/layer 4 border and the lower one in layer 5. They were different from the standard complex cells in having a high spontaneous activity, high velocity preference, and large fields which were similar in size (at a given eccentricity) from one cell to the next. Many showed reduced response to slits of increasing length, even for slits that did not extend beyond the borders of the responsive region.

6. Cells in layer 6 (the origin of the corticogeniculate projection) were antidromically activated from the lateral geniculate nucleus. The antidromically activated units included both simple and complex cells, and they had the long receptive fields characteristic of the overall population of cells in layer 6.

7. The results showed that there are different types of simple and complex cells, and that cells in different layers have different properties. Taken together with their differences in site of projection, this demonstrates that the anatomical lamination pattern is reflected in functional differences between cells in different layers.
Properties of vestibular neurones projecting to neck segments of the cat spinal cord*
Authors: Rapoport S. , Susswein A. , Uchino Y. , Wilson V. J.
Published: December 2014

1. Vestibular neurones projecting to the upper cervical grey matter (vestibulocollic neurones) were identified by localized microstimulation in the C3 segment of the cat spinal cord.

2. The neurones were found in the lateral (Deiters'), medial and descending nuclei bilaterally and projected to the spinal cord in the lateral and medial vestibulospinal tracts (LVST and MVST). Ipsilateral axons of Deiters' neurones were mostly in the LVST, axons of medial and descending neurones in the MVST; a few Deiters' neurones had axons in the MVST; some descending neurones had axons in the LVST. Most axons of contralateral neurones were in the MVST.

3. The axons of 62% of ipsilateral vestibulocollic Deiters' neurones not only gave off a collateral to C3, but also extended as far as the cervical enlargement (‘branching’); some of these neurones projected as far as the upper thoracic cord, almost none to the lumbar cord. Ipsilateral descending nucleus neurones branch in the same fashion, but there is no branching in the relatively small medial nucleus population.

4. A large majority of vestibulocollic neurones receive monosynaptic excitation from the ipsilateral labyrinth and a number are inhibited by stimulation of the contralateral labyrinth (commissural inhibition). It is possible that commissural inhibition acts on a broad population of vestibular neurones involved in the control of eye, head and trunk movement.

5. Vestibulocollic neurones do not make up a homogeneous population acting only on the neck. Instead it is likely that subpopulations, for example branching and non‐branching neurones, have different functions.
The effect of internal and external 4‐aminopyridine on the potassium currents in intracellularly perfused squid giant axons
Authors: Meves H. , Pichon Y.
Published: December 2014

1. The effect of 4‐aminopyridine (4‐AP) on the K outward and inward currents in perfused giant axons of Loligo forbesi has been studied with the voltage‐clamp technique.

2. Small internal or external 4‐AP concentrations (10‐100 μ
M) considerably delay the rise of the K outward current. Repetitive pulsing with a pulse interval of 0·1‐5 sec leads to a faster rise of the K current; in 10 μ
M 4‐AP a small effect is visible even with a pulse interval of 60 sec.

3. The phenomenon has been studied quantitatively by using a prepulse of varying height and duration, followed after 5 sec by a constant test pulse. The effect of changing the holding potential has been investigated.

4. The effect of repetitive pulsing disappears in higher 4‐AP concentrations; 1‐10 m
M 4‐AP markedly reduce the size of the K outward current; the blocking effect is less pronounced for large depolarizing pulses than for small.

5. In K‐rich sea water 4‐AP reduces both the K outward current and the K inward current; the blocking effect on the K outward current is smaller than in K‐free sea water.

6. The K outward current in fibres treated with 10 μ
M 4‐AP and immersed in K‐rich sea water is increased and accelerated by repetitive depolarizing pulses. The effect of repetitive pulsing is not dependent on the size of the K outward current (which can be increased by removing K inactivation).

7. The effect of repetitive pulsing and the voltage dependence of the 4‐AP block can be explained by the hypothesis that 4‐AP molecules are displaced from their blocking sites during the pulse and slowly rebound afterwards. Removal of the 4‐AP block by a depolarizing pulse seems to be a direct effect of the potential during the pulse and not related to K current.
Further observations on an ether‐O‐oxidase, formerly called alkyl etherase, from liver tissue.
Authors: Peters R A , Shorthouse M
Published: December 2014

1. The microsomal enzyme from liver previously called an "etherase" is now described more accurately as an ether‐O‐oxidase. It has been investigated further to free it from the membranes in aqueous solution and to try to define its physiological substrate. 2. After a variety of attempts with detergents, etc., the enzyme was obtained in impure solution from precipitation with 35‐45% (NH4)2SO4 solution after a short digestion at room temperature. 3. When a suitably reinforced the enzyme in solution forms citrate from added ethyl ether, as it does in membranous form. This indicates the intermediary formation of acetyl CoA. 4. The enzyme in solution is unstable, though some activity remains after standing at 0degrees C for 2‐3 days. Activity is lost rapidly by deep freezing, exposure to 2M‐NaCl and at a pH more acid than pH 5‐0. 5. The enzyme does not appear to be a known oxidase obtainable from liver microsomes; it is not for instance part of the inducible mixed oxygenase system, nor a peroxidase or catalase. 6. Since there were some similarities in stability with enzymes dealing with protozoal plasmalogens, or with lanosterol or cholesterol, we were led to explore these substrates in detail, with negative results. But a specimen of cholesterol oxidase from the branching bacterium Nocardia gave O‐oxidation with diethylether. 7. The enzyme is present in the livers of all four animals examined, namely the rat, pig, guinea‐pig and pigeon, but not in kidney or brain. 8. The enzyme takes up O2 with some compounds containing O‐me groups. 9. The hypothesis is advanced that this normal oxidase in liver membranes exists to deal with some substances from plant sources which might prove toxic upon entering the circulation.
Direct evidence for the location of kallikrein in the striated ducts of the cat's submandibular gland by the use of specific antibody.
Authors: Hojima Y , Maranda B , Moriwaki C , Schachter M
Published: December 2014

Kallikrein was located in the apical portion of the striated duct cells of the cat's submandibular gland by an immunohistochemical technique. This portion only of these cells showed an intense band of specific fluorescence. There was no evidence of specific fluorescence in the acinar and demilune cells nor in the interstitial tissue or blood besells. In some sections the collecting ducts showed a very fine fluorescent luminal rim.