bluuebunny/crossref_metadata_2025 huggingface dataset:
The relation between carotid body chemoreceptor discharge, carotid sinus pressure and carotid body venous flow
Authors: Biscoe T. J. , Bradley G. W. , Purves M. J.
Published: December 2014

1. Activity in forty‐two single chemoreceptor afferent fibres from the carotid body in thirty‐nine cats was measured when the carotid body was naturally and artificially perfused. In nine of these cats, carotid body venous flow was also measured.

2. When pressure within the carotid sinus segment was suddenly raised or lowered, chemoreceptor activity changed in the opposite direction within the first 5‐10 sec by an amount which was significantly greater than the variation of activity in the control period. Thereafter activity stabilized at a level which was not different from control.

3. Whether the carotid body was naturally or artificially perfused, carotid body chemoreceptor activity, following this initial transient change, was unaffected in eight out of twelve fibres by alterations in carotid sinus pressure within the range 60–160 mm Hg and carotid body venous flow 10–60 μl./min, blood gas tensions and pH being maintained constant. In the four remaining fibres, chemoreceptor activity increased slightly but significantly as pressure was lowered in this range. Chemoreceptor activity increased in all fibres tested when pressure was lowered below 50–60 mm Hg.

4. Chemoreceptor response curves to changes in Pa,O2 (30–450 mm Hg), Pa,CO2 (27–62 mm Hg) or [H+]a (3–7 × 10−5 m‐equiv/l.) were not significantly different whether the carotid body was perfused (a) naturally at the prevalent systemic pressure, (b) artificially at the same pressure, or (c) artificially at one higher pressure, 130 or 140 mm Hg.

5. These results indicate that the carotid body chemoreceptors are relatively unaffected by sustained changes in arterial pressure or in total carotid body flow within the physiological range.
The effect of adenosine triphosphate on the transmural potential in rat small intestine
Authors: Kohn P. G. , Newey H. , Smyth D. H.
Published: December 2014

1. ATP either in the mucosal or serosal fluid caused a transient increase in the potential difference and short‐circuit current across the wall of rat jejunum in vitro, the serosal solution becoming more positive.

2. Similar responses were observed in the ileum and colon, and in in vivo preparations of small intestine.

3. The response is relatively specific for ATP.

4. The transient nature of the response is not due to rapid hydrolysis of extracellular ATP.

5. High concentrations of K+ in the mucosal medium, serosal ouabain or mucosal 2,4‐dinitrophenol all inhibit the response without altering the time course.

6. Significant inhibition was not observed in the presence of ADP or in Mg2+‐free salines.

7. The results are consistent with an intracellular action of ATP in the epithelium to stimulate net ion transport. The results do not demonstrate whether or not extracellular ATP can act as an energy donor for an electrogenic ion pump.

8. Theophylline prolongs the time course of the response, and the involvement of the adenyl cyclase system cannot be excluded as an explanation for the findings.
The half‐life of exogenous gastrin in the circulation
Authors: Blair E. L. , Farra Yvonne , Richardson Diana D. , Steinbok P.
Published: December 2014

1. A method of gastrin bio‐assay is described which can be used on as little as 30 ng synthetic human gastrin I at a minimum concentration of 2·5 ng/ml.

2. Pentagastrin or synthetic human gastrin I added to cat plasma can be stored on ice or at 4° C, for periods up to 27 hr without apparent loss of gastrin activity.

3. Between 1½ and 13 min after the rapid
I.V. injection of pentagastrin in the anaesthetized cat and between 1½ and 15 min after the injection of synthetic human gastrin I, there is a rapid reduction of the gastrin concentration in the arterial plasma. The data relating log10 gastrin concentration in arterial plasma with time can be fitted by a single term.

4. Studies in vitro show that over the periods of time involved in the in vivo studies, both pentagastrin and synthetic human gastrin I are stable in cat plasma at 37° C in concentrations which occurred in the circulating plasma.

5. The half‐life of pentagastrin in the circulating arterial plasma of the anaesthetized cat is 1·50 min (
S.E. ± 0·08) and the half‐life of synthetic human gastrin I is 2·65 min (
S.E. ± 0·09).
Intracellular hydrolysis of short chain glycerides by rat small intestine in vitro and transfer of glycerol
Authors: Howard J. , Jackson M. J. , Smyth D. H.
Published: December 2014

1. When triacetin, tripropionin and tributyrin are incubated with sacs of rat everted intestine, they enter the epithelial cells and are completely hydrolysed to free fatty acids and glycerol.

2. The distribution between the mucosal and serosal fluids of the glycerol released is very different from that of the fatty acid. Although both hydrolytic products are accumulated in the serosal fluid, a much higher fraction of the fatty acid appears in this compartment.

3. When glycerol is initially present in the mucosal fluid there is no evidence of its movement against a concentration gradient.

4. The results confirm the existence of a transport mechanism for fatty acids released intracellularly but do not require the hypothesis of a special mechanism for glycerol transfer.
Cervico‐lumbar reflex interactions involving a proprioceptive receiving area of the cerebral cortex
Authors: Abrahams V. C.
Published: December 2014

1. In the decerebrate cat descending cervico‐lumbar reflex interactions from neck muscle nerves are absent, and those from forepaw nerves are reduced or absent.

2. Lesions restricted to the anterior pole of the suprasylvian gyrus regularly abolish descending cervico‐lumbar reflex interactions from neck muscle nerves. The same lesions may reduce or abolish descending cervico‐lumbar reflex interactions from forepaw nerves.

3. The ascending cortical looping pathway utilized in descending cervico‐lumbar reflex interactions is crossed, and the descending pathway from the cerebral cortex is bilateral.
Mesopic increment threshold spectral sensitivity of single optic tract fibres in the cat: cone—rod interaction
Authors: Andrews D. P. , Hammond P.
Published: December 2014

1. Mesopic increment threshold spectral sensitivities of sixty‐six on‐centre and twenty‐five off‐centre ganglion cells in the cat were determined by recording from single fibres of the left optic tract at a level posterior to the optic chiasma.

2. All units were monocularly driven; receptive fields were located almost exclusively in the right visual half‐fields within 30° of the area centralis, but with slight overlap across each retinal mid line to the left half‐fields. The extent of field spread to the right temporal hemi‐retina was significantly larger than that to the left nasal hemi‐retina. Field centre diameters ranged from less than 0·25° for central units to 2° for more peripheral units.

3. At high mesopic adaptation of 1 log cd/m2 all responsive units (forty‐four fibres) received mixed cone—rod input. Threshold curves could always be fitted by the absorption spectra of visual pigment 556 together with varying contributions from visual pigment 507, each derived from the Dartnall nomogram.

4. Of forty‐seven fibres analysed under low mesopic background (0 log cd/m2) 92% received similar cone—rod input, being fitted predominantly by visual pigment 507 with slight cone contamination. The remaining 8% received pure rod input and could be matched by visual pigment 507 alone.

5. In conclusion, the cat retina presumably contains a single class of cones with absorption maxima at 556 nm, and a single class of rods. Discrepancy between the presumed rod absorption maximum (502 nm) and the low‐mesopic sensitivity maxima of tract fibres (507 nm) is considered in terms of tapetal reflectivity, and absorption by ocular media. Both mechanisms input to the great majority of retinal ganglion cells. At high mesopic levels the cone mechanism predominates. At low mesopic levels the rod mechanism predominates. A small proportion of ganglion cells within the central 30° of the retina receive input only from rods, and in these the rod mechanism saturates completely below 1 log cd/m2.
On the relationships between membrane potential, calcium transient and tension in single barnacle muscle fibres
Authors: Ashley C. C. , Ridgway E. B.
Published: December 2014

1. The calcium‐sensitive photoprotein aequorin has been used to follow the rapid changes in intracellular calcium concentration that occur during the contraction of single muscle fibres from the barnacle Balanus nubilus, Darwin.

2. The transient change in calcium‐mediated light emission (calcium transient) and the changes in membrane potential and tension were recorded simultaneously, thus permitting an examination of the relationships between the chemical, electrical, and mechanical events of excitation—contraction coupling.

3. With short‐duration stimuli (< 200 msec), the calcium transient shows an S‐shaped rising phase reaching a maximum soon after the cessation of the stimulus pulse. During membrane repolarization the calcium transient begins an exponential falling phase which has a time constant of 50–80 msec at 11–12° C.

4. The shape of the calcium transient resembles the first derivative of the rising phase of the isometric tension response, thus suggesting that calcium controls the rate of tension development.

5. There is no detectable increase of the light emission above resting values, during the falling phase of isometric tension.

6. A plot of the calcium transient area (lumen × sec) versus peak isometric force (g. cm−2) is linear over, at least, a range of forces from ca. 50–400 g. cm−2.

7. When the fibre is capable of producing an active membrane response following the intracellular injection of potassium citrate, the onset and cessation of the calcium transient follow closely the onset and cessation of the active membrane response. Tension responses under these conditions are much suppressed, suggesting that excitation—contraction coupling may be partially blocked between calcium release and the development of tension.

8. Hypertonic salines (1
M sucrose or 1
M glycerol) cause little change in the membrane response, but greatly suppress the calcium transient and completely abolish the tension responses. These effects are readily reversible when normal saline is reintroduced, suggesting that excitation—contraction coupling may be temporarily blocked between the membrane response and calcium release.

9. If the stimulus is prolonged (> 250–300 msec), the calcium transient falls slowly from its maximum value despite continued membrane depolarization, suggesting a time‐dependent change in the ratio of the rate of release of calcium to the rate of calcium binding. The results from brief tetanic stimulation also support this suggestion.
Miniature potentials in denervated slow muscle fibres of the frog
Authors: Miledi R. , Stefani E.
Published: December 2014

1. Pyriformis and iliofibularis muscles of the frog were studied with micro‐electrodes. Both muscles contain a mixture of fast and slow muscle fibres, which can be distinguished by differences in their miniature end‐plate potentials (min.e.p.p.s).

2. In addition, the membrane time constant of fast fibres is < 20 msec, while that of slow fibres is > 200 msec.

3. The characteristic difference in time constant persisted after denervation and allowed the identification of fibre type.

4. Denervated slow fibres had min.e.p.p.s of variable time courses and skew amplitude distributions. Their frequency was lower than in normally innervated fibres, and could be increased by hypotonic solutions.

5. In analogy with similar observations made previously in fast muscle fibres, it is suggested that after nerve degeneration the Schwann cells of small motor nerve fibres release packages of transmitter which give rise to min.e.p.p.s.
The effect of the tetraethylammonium ion on the delayed currents of frog skeletal muscle
Authors: Stanfield P. R.
Published: December 2014

1. A method which permitted control of the membrane potential near the end of a muscle fibre and measurement of an approximation of the membrane current was used to investigate the effects of the tetraethylammonium (TEA) ion on the delayed outward potassium current obtained on depolarizing.

2. Assuming Ri to be 250 Ω cm and a fibre diameter of 80 μ, the mean value for the maximum potassium conductance (ḡK) was 23·2 ± 3·2 mmho.cm−2.

3. 58 m
M‐TEA, in two series of experiments, reduced ḡK by about 90%. A concentration—effect relation for TEA in its action on the delayed rectifier could be fitted by a curve for a drug‐receptor complex assuming one molecule of TEA to combine reversibly with one receptor, and a dissociation constant of 8 × 10−3
M.

4. TEA tended to shift the threshold for delayed rectification to slightly more negative membrane potentials. TEA caused a similar shift in the relation between n∞ and membrane potential, but did not much alter the form of the relation.

5. The relation between n∞ and membrane potential and between τn−1 and membrane potential were well fitted by the model of Adrian, Chandler & Hodgkin (1970a) assuming that the Q10 was 2·5.

6. TEA slowed the rate of onset of the delayed potassium currents, decreasing τn−1 (the reciprocal of the time constant of the fourth power function which described the current's development) by about 80%.

7. The inactivation of the delayed current with time was shown to follow a complex time course. A fast phase decays with a time constant of 270 msec and a slow phase with a time constant of 2·3 sec at a membrane potential of + 10 mV.

8. The fast phase of the delayed current is much more susceptible to the action of TEA than the slow phase, and these are interpreted in terms of different potassium channels. TEA has little effect on the time constant with which either the fast current or the slow current inactivates.
Characteristics of neural transmission from the semicircular canal to the vestibular nuclei of cats
Authors: Jones G. Melvill , Milsum J. H.
Published: December 2014

1. The characteristics of the dynamic response of specifically canal‐dependent neural units in cat vestibular nuclei have been examined during sinusoidal rotation of the head in decerebrate cats over the narrow frequency range 0·–1·7 Hz.

2. Unit action potential frequencies were averaged on line from extracellular steel micro‐electrodes stereotaxically located in the vestibular nuclei through the intact cerebellum.

3. Action potential frequency was approximately in phase with stimulus angular velocity, the mean phase for forty‐six units being + 11·°
S.E. of the mean ± 2·2°). Correction for a form of dynamic asymmetry reduced this value almost to zero.

4. The mean gain of thirty‐nine single unit responses was 0·76
S.E. ± 0·08) AP/sec per °/sec. The gain varied as the (−0·28) power of stimulus angular velocity, for the five cells appropriately tested.

5. A method was evolved for computing the spontaneous condition of cells, in terms of an equivalent spontaneous firing frequency, fsp irrespective of whether they were spontaneously active or silent. This fsp value was normally distributed about a mean value of 11·2 AP/sec (range + 70 to − 40 AP/sec).

6. Directionality was examined in 116 units, of which 62% were ipsilateral (e.g. cells on left side excited by left‐going rotational velocity) and 38% contralateral. Ipsilateral units proved easier to isolate and retain than contralateral ones.

7. No significant differences in mean phase or gain were found in the sub‐sets of spontaneously active/inactive cells and ipsilateral/contralateral cells.

8. It is inferred that the cell population examined was a functionally homogeneous one in which the neural signal was closely tied to the angular velocity of canal rotation for the narrow band of sinusoidal rotational stimuli here employed. It is suggested that this signal is probably retained essentially intact in the ensemble neural message fed forwards from this region.
Field potentials evoked in the brain stem of the cat by stimulation of the carotid sinus, glossopharyngeal, aortic and superior laryngeal nerves
Authors: Biscoe T. J. , Sampson S. R.
Published: December 2014

1. In a primarily topographical study, the field potentials evoked in the brain stem of the cat by stimulation of the sinus, glossopharyngeal (IX), aortic and superior laryngeal (SLN) nerves have been recorded with glass micro‐electrodes.

2. Extracellular negative potentials were evoked in the region of the nucleus of the tractus solitarius and in the lateral reticular formation (LRF) by electrical stimulation of all four nerves. There were differences in the form of these potentials amongst the nerves, particularly between sinus‐IX and aortic‐SLN. The potentials were identified as post‐synaptic with early and late components and were sometimes preceded by an afferent volley.

3. Extracellular positive potentials were evoked in the subnucleus reticularis medialis medullae oblongatae and the nucleus reticularis gigantocellularis. Intracellularly recorded hyperpolarizations recorded from six cells had the same time course as the extracellular positivity. Spontaneously active cells encountered in these regions were sometimes depressed for the duration of the positivity.

4. Each of the above field potentials was maximal in the region of Horsley—Clarke A. P. co‐ordinates −10 to −13 mm.

5. At A.P. co‐ordinates of −15 to −17 mm negativity showing post‐tetanic potentiation was evoked, at latencies similar to the negativity in the LRF, in the commissural nucleus of Cajal, the dorsolateral reticular formation and the medial reticulo‐spinal tract.

6. Negative potentials were evoked in the contralateral LRF.
Monosynaptic chemical and electrical connexions between sensory and motor cells in the central nervous system of the leech
Authors: Nicholls J. G. , Purves D.
Published: December 2014

The synaptic connexions that underlie three different segmental shortening reflexes have been traced by recording intracellularly from individual sensory and motor nerve cells in the
C.N.S. of the leech. The fourteen sensory cells involved in these reflexes respond specifically to one of three modalities: touch, pressure, or noxious stimuli applied to the skin. All three types of sensory neurone give rise to excitatory synaptic potentials in two large motoneurones. Each of these motor cells provides excitatory innervation to the longitudinal muscle fibres of the opposite side of the segment. The mechanism of synaptic transmission is, however, different for each type of sensory cell.

1. An impulse in a sensory cell that responds to touch gives rise to a short‐latency depolarizing potential in the large longitudinal motoneurones by way of an electrical synapse. This junction rectifies so that excitation can spread in only one direction (from the sensory to the motor cell), whereas a hyperpolarizing potential can pass only in the opposite direction.

2. The synaptic potential evoked in the motoneurone by an action potential in a sensory cell responding to noxious stimuli can be attributed to the action of a chemical transmitter agent and has different properties: the post‐synaptic potential arises after a delay of about 2‐4 msec, is abolished by high concentrations of Mg, and enhanced by high concentrations of Ca. Several lines of evidence show that this connexion is monosynaptic.

3. The synaptic potential following an impulse in a pressure cell is produced by both chemical and electrical synaptic mechanisms. Rectification, similar to that described for the touch cell, also occurs at this electrical synapse.

4. One or more impulses in any one of the fourteen mechanoreceptor cells in the ganglion can initiate impulses in the large longitudinal motoneurones to produce a shortening of the segment. The contraction is abolished by blocking impulse initiation in the motoneurones.

5. The arborizations of the sensory cells and the motoneurone within the neuropile have been studied histologically after injecting a fluorescent dye. Their processes are intertwined in a highly complex manner so that the sites of the synaptic junctions cannot be determined with the resolutions so far achieved. Nevertheless, taken together the histological and the electrical results support the idea that individual cells are connected in a stereotyped pattern and operate by distinctive mechanisms.

6. These findings provide a basis for studying the functional role of chemical and electrical synaptic mechanisms in these pathways.
Adrenaline in bird brain
Authors: Juorio A. V. , Vogt Marthe
Published: December 2014

1. Catecholamine estimations were made on the whole diencephalon and on the hypothalamus of pigeons and fowls using fluorimetry of the acetylated amines as one, and bio‐assay after chromatographic separation of the amines as a second method.

2. There was no significant difference between the results obtained by the two methods; for pigeons mean percentage methylation was 10% with one and 12% with the other technique, and in the Rhode Island Red breed of fowls the corresponding figures were 28 and 31%.

3. The percentage methylation for the hypothalamus of another breed of fowls (Plymouth Rock) was the same as in Rhode Island Red, but it was significantly lower in White Leghorn birds.

4. Between the ages of 3·5 weeks and maturity the percent methylation remained unchanged.

5. There is no evidence to suggest that bio‐assay of adrenaline as used in this and previous work lacks specificity, but differences between avian breeds exist and have to be reckoned with.
The effect of hypercapnia on myocardial blood flow and metabolism
Authors: Ledingham I. McA. , McBride T. I. , Parratt J. R. , Vance J. P.
Published: December 2014

1. In closed‐chest dogs anaesthetized with trichlorethylene, the inhalation of carbon dioxide sufficient to increase the arterial PCO2 from 40 to about 100 mm Hg, increased myocardial blood flow (measured using a 133Xe clearance technique) and right atrial pressure. There were no consistent changes in mean arterial blood pressure, heart rate or cardiac output.

2. The effect of hypercapnia on myocardial blood flow was not influenced by the previous administration of atropine and propranolol or of bretylium. It can be concluded, therefore, that the elevated arterial PCO2 has a direct vasodilator effect on the myocardial microcirculation.

3. During hypercapnia the coronary sinus PO2 was increased and the coronary arteriovenous oxygen content difference, and calculated myocardial oxygen consumption, reduced. It is suggested that this latter effect may be the result of myocardial depression produced by the decrease in arterial blood pH.

4. There was no evidence of myocardial glucose uptake either before or during hypercapnia. The myocardial extraction of lactate and pyruvate at rest varied between 0 and 55%. During acute hypercapnia the extraction of lactate usually fell.

5. When the arterial PCO2 was maintained at 100 mm Hg for a period of 1 hr the effects on myocardial blood flow and on oxygen consumption were not sustained.

6. Stepwise increments and decrements in arterial PCO2 of 10–20 mm Hg produced corresponding increases and decreases in myocardial blood flow and demonstrated that changes in arterial PCO2 of 20–30 mm Hg can markedly affect blood flow in the myocardium.
Haemodynamic and other studies on the renoprival hypertensive rat
Authors: Ledingham J. M. , Pelling D.
Published: December 2014

1. The optimal conditions for the development of hypertension after total nephrectomy were defined in the rat. Under these conditions, haemodynamic changes were then studied before and for 3 days after total nephrectomy in the unanaesthetized animal and compared with mock‐nephrectomized controls.

2. Changes in cardiac output were followed with an electromagnetic flowmeter chronically implanted on the ascending aorta, and mean arterial pressure with an indwelling aortic cannula.

3. Haematocrit fell in animals developing hypertension, due to plasma volume expansion. Restriction of administered saline did not reduce the fall in haematocrit without also preventing development of the hypertension.

4. Cardiac output and stroke volume increased significantly on the second and third days after nephrectomy. Peripheral resistance remained unchanged and pulse rate tended to fall.

5. The increase in cardiac output appeared to be more than could be accounted for by anaemia alone, and it is suggested that plasma volume expansion was partly responsible.

6. In another group of rats developing renoprival hypertension a correlation was found between changes in plasma volume and arterial pressure over the three days.

7. Renoprival hypertension was accompanied by a slight but significant reduction in oxygen consumption in comparison with the controls.

8. No relationship was found between the changes in blood pressure, and plasma sodium and potassium levels.

9. It is concluded that the observed rise in cardiac output associated with renoprival hypertension as induced in this study was not attributable to anaemia nor to a rise in metabolic rate. The implications of this situation are discussed in relation to a theory of the pathogenesis of hypertension and the findings of other workers.
Kinetics of pentose permeation in the perfused rat heart
Authors: Fisher R. B. , Gilbert J. C.
Published: December 2014

1. The fractional permeation of heart cell water by
L‐arabinose and
D‐xylose after a standard period of perfusion is less the higher the extracellular pentose concentration.

2. At any given pentose concentration the kinetics of permeation are consistent with passive diffusion through the cytoplasm or with transport across the cell membrane by a saturable carrier.

3. The concentration dependence of permeation is inconsistent with passive diffusion.

4. The kinetics of
L‐arabinose permeation are consistent with a carrier having Vmax = 2·2 m‐mole/l. extracellular water per min and a half‐saturation concentration [K] of 0·5 × 10−4
M. The corresponding figures for
D‐xylose are Vmax = 1·4, [K] = 1·6 × 10−4
M.
Autoradiographic demonstration of inhomogeneous distribution of sodium in single oocytes of Bufo bufo
Authors: Dick D. A. T. , Fry D. J. , John P. N. , Rogers A. W.
Published: December 2014

1. Autoradiography of frozen cells labelled with 22Na has been used to locate a sequestered fraction of internal Na in the oocyte which exchanges very slowly or not at all with external Li.

2. Relative grain density in nucleus and cytoplasm, measured photometrically, was used as an indication of 22Na distribution within the oocyte. In test experiments grain density fell to 50% within 19 μm of the edge of the section. Owing to the large diameter of the oocyte (> 600 μm) and its nucleus (> 200 μm), this resolution was adequate to determine cytoplasmic/nuclear (C/N) ratios of grain density.

3. In oocytes fully loaded with 22Na, the mean C/N ratio was 0·92 ± 0·03 (n = 11). After 5 hr exchange in Li‐substituted Na‐free Ringer solution, the mean C/N ratio was 2·18 ± 0·04 (n = 11). After 5 hr exchange in Ringer solution as a control, the mean C/N ratio was 1·39 ± 0·18 (n = 7). The cytoplasm thus contained a fraction of 22Na inexchangeable with Li, and more slowly exchangeable with Na than that in the nucleus.

4. The non‐Li‐exchangeable fraction of internal Na thus revealed appeared to be quantitatively similar to that already demonstrated by studies of 22Na fluxes and of internal Na activity by means of Na‐sensitive micro‐electrodes.
The penetration of inulin, sucrose, mannitol and tritiated water from the interstitial space in muscle into the vascular system
Authors: Crone Christian , Garlick David
Published: December 2014

1. An isolated gastrocnemius muscle from cat was perfused with a modified Ringer fluid containing the extracellular tracers mannitol, sucrose and inulin and in some cases tritiated water (HTO). When equilibration of the tracers between the perfusate and the tissue was obtained, perfusion with tracer‐free fluid was started.

2. The fractional rate of escape, Φ (t), of the tracers was followed. For all tracers it declined steadily with time. The rate of decline was faster for the smaller extracellular molecules when any combination of two extracellular tracers was studied.

3. Arrest of flow for 1–2 min lead to an increase in Φ (t) for the extracellular tracers when flow was resumed. There was little or no effect upon Φ (t) for HTO.

4. Doubling the rate of flow had no effect upon Φ (t) for the extracellular tracers, while that of HTO increased.

5. We conclude that the cause of the decline in Φ (t) for the extracellular tracers is concentration gradients in the interstitial space. The findings raise problems in methods for studying capillary permeability by means of the fractional rate of escape of tracers from the interstitial space into the vascular system.
Response of semicircular canal dependent units in vestibular nuclei to rotation of a linear acceleration vector without angular acceleration
Authors: Benson A. J. , Guedry F. E. , Jones G. Melvill
Published: December 2014

1. Recent experiments have shown that rotation of a linear acceleration vector round the head can generate involuntary ocular nystagmus in the absence of angular acceleration. The present experiments examine the suggestion that adequate stimulation of the semicircular canals may contribute to this response.

2. Decerebrate cats were located in a stereotaxic device on a platform, slung from four parallel cables, which could be driven smoothly round a circular orbit without inducing significant angular movement of the platform. This Parallel Swing Rotation (PSR) generated a centripetal acceleration of 4·4 m/sec2 which rotated round the head at 0·52 rev/sec.

3. The discharge frequency of specifically lateral canal‐dependent neural units in the vestibular nuclei of cats was recorded during PSR to right and left, and in the absence of motion. The dynamic responses to purely angular motion were also examined on a servo‐driven turntable.

4. Without exception all proven canal‐dependent cells examined (twenty‐nine cells in nine cats) were more active during PSR in the direction of endolymph circulation assessed to be excitatory to the unit, than during PSR in the opposite direction.

5. The observed changes in discharge frequency are assessed to have been of a magnitude appropriate for the generation of the involuntary oculomotor response induced by the same stimulus in the intact animal.

6. The findings suggest that a linear acceleration vector which rotates in the plane of the lateral semicircular canals can be an adequate stimulus to ampullary receptors, though an explanation which invokes the modulation of canal cells by a signal dependent upon the sequential activation of macular receptors cannot be positively excluded.
Non‐cholinergic transmission by post‐ganglionic motor neurones in the mammalian bladder
Authors: Ambache N. , Zar M. Aboo
Published: December 2014

1. In mucosa‐free preparations of the detrusor muscle electrical stimulation with 0·1 msec pulses has been utilized to reveal the non‐cholinergic nature of most, if not all, of the post‐ganglionic motor neurones in the guinea‐pig bladder.

2. The twitches elicited by 0·1 msec pulses were abolished by tetrodotoxin, but were not reduced by dimethyltubocurarine or by hexamethonium. Hexamethonium was nevertheless present in all the experiments in order to restrict acetylcholine action to ‘muscarinic’ receptors in the muscle fibres.

3. There was little or no diminution in the twitches after prolonged exposure to atropine, 10−8‐10−5 g/ml., although the twitch‐matching dose of acetylcholine was raised 1000–2500 times. Hence, there was no anomalous refractoriness to atropine in these ‘muscarinic’ receptors.

4. Despite massive atropinization, the recruitment of unoccupied transmitter‐receptors by means of extra pulses remained unaffected.

5. Eserine failed to potentiate the atropine‐resistant twitches.

6. The twitches were not depressed by morphine.

7. Noradrenaline produced relaxation and twitch reduction. The twitches persisted after α + β adrenoceptor blockade with phentolamine + pronethalol and were unaffected by the monoamine oxidase and catecholamine‐O‐methyl transferase inhibitors, tranylcypromine and pyrogallol.

8. Rapid contractions were elicited by 5‐HT and by histamine but the twitches remained unaltered after antagonism of 5‐HT by methysergide and of histamine by mepyramine.

9. The twitches could be mimicked by injections of ATP, but after desensitization of the preparation to ATP the response to electrical stimulation remained unaltered.

10. Prostaglandins E2 and F2α, only in large doses, produced delayed, sluggish contractions which persisted after the wash; these contractions were quite different from the responses to electrical stimulation, which were immediate, sharp and brief.

11. The non‐cholinergic nature of the post‐ganglionic motor neurones was confirmed in the bladder of two other species, the cat and the rabbit.
The electrical activity of the digestive tract of the sheep as an indication of the mechanical events in various regions
Authors: Ruckebusch Y.
Published: December 2014

1. A method is described in the conscious sheep for recording oscillographically the electrical potentials led from enamelled stainless‐steel wires implanted in the wall of the stomach and intestine.

2. Slow waves characterized by cyclically recurring and rhythmic fluctuation in voltage have been recorded, together with the superimposed fast activity or burst of spikes when the muscle is contracting. The whole activity comprised a distinguishable pattern of grouped discharge which is synchronous with mechanical events within different regions of the alimentary tract.

3. Grouped discharge occurs at a regular frequency of 7/min in the pyloric part of the abomasum and 18/min from the intestine, but 13/min from the middle duodenum and proximal ileum. Only the major grouped discharges of the fore‐stomach is correlated with the orderly sequential movements of the reticulum and rumen.

4. The relationship between electrical and mechanical activity of the reticulo‐rumenal movements was examined at rest, and during feeding and ruminating.

5. Electrical correlates of motor activity in the small bowel were investigated under different dietary regimens.
Electrical constants of trabecular muscle from mammalian heart
Authors: Weidmann Silvio
Published: December 2014

1. The passive electrical properties of muscle bundles obtained from the right ventricle of sheep or calf hearts were determined. Preparations were kept in silicon oil; through extracellular electrodes constant current pulses were made to flow between the ends of the bundles.

2. Using micro‐electrodes for potential recording, the following data were obtained: (i) a space constant of 880 μ; (ii) a membrane time constant of 4·4 msec; (iii) a ratio of intra‐to‐extracellular longitudinal resistance of 3·5: 1; (iv) a conduction velocity of 0·75 m/sec.

3. The intracellular specific resistance (Ri) in the longitudinal direction was 470Ω cm, corresponding to 3 times Ri of Purkinje fibres or 9 times the specific resistance of Tyrode solution.

4. A calculation of specific membrane resistance (Rm) and capacity (Cm) was up against uncertainties in estimating the surface area. Taking morphological data as obtained by light microscopy, Rm works out at 9100Ω cm2, Cm 0·81 μF/cm2. Electron micrographs suggest that the true surface membrane might be either larger (T‐tubules) or smaller (tight junctions between parallel fibres) than the surface area as seen by the light microscope.

5. The apparently small value of Cm seems to indicate that the flow of current between ‘outside’ and ‘inside’ is restricted to only a fraction of the fibre surface, while a considerable part of the contact area between parallel fibres is of the low‐resistance type. This would provide for functional connexions not only at the level of intercalated disks, but also along parallel‐running fibres.
Effects of calcium on the contraction of the hypodynamic frog heart
Authors: Chapman R. A. , Niedergerke R.
Published: December 2014

1. The time course of build‐up or decline of twitch tension in response to enhancement or reduction of the external calcium concentration was determined in frog heart ventricles, in the hypodynamic state as well as under non‐hypodynamic conditions.

2. The tension build‐up induced by high calcium was greatly slowed when the heart passed into the hypodynamic state, whereas the decline in low calcium was little altered by this condition.

3. The tension decline consisted of two approximately exponential phases, an initial rapid phase (t½ between 3 and 10 sec) and a later slow phase (t½ between 50 and 180 sec).

4. A similar composite time course of tension build‐up only occurred under certain conditions: (a) in ventricles in which the hypodynamic state had not developed; (b) after a conditioning period of exposure to enhanced calcium or reduced sodium concentrations.

5. The results are explained on the assumption that contraction is brought about by the co‐operative action inside heart cells of two calcium compounds whose concentrations change at different rates after variation of the external calcium concentration.

6. Formal relationships describing the dependence of twitch tension on the concentration of these two hypothetical compounds are obtained.

A tentative explanation of the development of the hypodynamic state is also proposed.
The effect of calcium ions on long chain fatty acid transport by slices of rat jejunum
Authors: Munday K. A. , Parsons B. J. , York D. A.
Published: December 2014

1. There is a large increase in palmitic acid uptake by rat jejunum slices when incubated in the presence of calcium. This effect is observed at both 37 and at 0° C.

2. The presence or absence of calcium in the incubation medium does not affect triglyceride synthesis from absorbed fatty acid.

3. The release of synthesized triglyceride from the tissue into the medium is increased by calcium.

4. The probability that calcium transport and long chain fatty acid transport may be interrelated at both the brush border and at the basal and lateral membranes of the intestinal mucosal epithelial cell is discussed.
Two classes of slowly adapting mechanoreceptor fibres in reptile cutaneous nerve
Authors: Kenton B. , Kruger L. , Woo M.
Published: December 2014

1. The myelinated fibre spectrum of the plantar nerve of reptile consists of a unimodal distribution corresponding approximately to the delta elevation in mammalian nerve and contains a variety of receptor categories similar to those of mammals except for the obvious absence of structures related to hairs.

2. The various receptor types of reptilian skin do not fall into discrete groups on the basis of conduction velocity.

3. Only a few thermoreceptor fibres were identified but a large proportion of slowly adapting mechanoreceptors responded to rapid temperature transients.

4. Two distinct categories of slowly adapting receptors whose discharge is related to the amplitude of skin displacement have been identified and studied in detail. These two receptors can be distinguished by their patterns of discharge, and display several distinctive features including differences in resting discharge, receptive field size, threshold, response to DC polarization, etc.

5. The mathematical functions describing the response to stimuli of varying magnitude for one receptor type is markedly affected by the sequence of stimulus presentation.
Determination of extracellular space and intracellular electrolytes in rat liver in vivo*
Authors: Williams J. A. , Woodbury D. M.
Published: December 2014

1. Uptake of a number of isotopically labelled extracellular tracers by rat liver in vivo was studied.

2. A residual intravascular space of 3·0–3·5% following exsanguination was measured by use of [51Cr]red cells. This space was significantly greater than that of skeletal muscle and was also greater in nephrectomized as compared to intact rats.

3. [131I]albumin and polyvinylpyrolidine (PVP) were found to distribute initially in a space of 6–7% and this was followed by a delayed rise that was greater for PVP. The extravascular portion of this space is termed the large‐molecule accessible space and is believed to correspond to the histological space of Disse.

4. [14C]sucrose and inulin initially distribute in a space of 10–12% followed by a continued late increase. This initial space is termed the small molecule accessible space and is thought to include most of interstitial space.

5. 36Cl− and stable Na+ and Cl− spaces were constant at 19–21% and can be used to put an upper limit on extracellular space.

6. Operationally, the 1 hr inulin space in the nephrectomized rat was felt to be the best indicator of extracellular space.

7. Total electrolytes were measured and intracellular values of 22, 165 and 22 m‐mole/l. cell water for Na+, K+ and Cl−, respectively, were calculated.

8. By use of [14C]DMO, an intracellular pH of 7·25 and an intracellular HCO3− of 13 m‐mole/l. cell water were calculated.
Sodium transport across the isolated epithelium of the frog skin
Authors: Aceves J. , Erlij D.
Published: December 2014

1. A method to separate the epithelium from the underlying layers of the frog skin is described. The method is based on the combined use of collagenase and hydrostatic pressures.

2. The potential difference and the short‐circuit current values of isolated epithelia and whole skins are similar. Na net flux and short‐circuit current are equivalent.

3. The time course of changes in potential following rapid changes in composition of the bathing solutions shows that the barrier to K diffusion at the internal surface of the isolated epithelium is larger than the barrier to Na diffusion at the external surface.

4. In the isolated epithelium there are 133 m‐mole K+ and 24·7 m‐mole Na/l. cellular water. The amount of extracellular water was considered to be equal to the inulin space.

5. Arginine vasopressin (0·1 u./ml.) markedly increased short‐circuit current and potential difference in isolated epithelia. The amount of Na in the epithelium that equilibrated with Na in the external solution was not increased by the hormone.

6. Ouabain (10−4
M) reduced short circuit current and potential difference to values close to zero. The ouabain treated epithelia contained an increased amount of Na originating in the internal solution. On the other hand the amount of Na that originated from the external solution was not increased.

7. The amount of epithelial Na that equilibrated with Na in the external solution was 0·009 μ‐equiv/cm2. This figure is about ten times smaller than the values found in whole skins.
On the control of glycogenolysis in mammalian nervous tissue by calcium
Authors: Landowne D. , Ritchie J. M.
Published: December 2014

1. A study has been made of the increase in fluorescence of the desheathed cervical vagus nerve that occurs after electrical stimulation (usually 5 sec at 30/sec) of its non‐myelinated fibres.

2. At room temperature this increase in fluorescence is normally masked by the decrease in fluorescence caused by mitochondrial oxidative phosphorylation. However, at higher temperatures (30–35° C) the increasing fluorescence phase predominates and the net change on stimulation is an increase.

3. At room temperature the increase in fluorescence is seen clearly only when ATP splitting has been prevented by ouabain, by bathing the nerve in lithium‐Locke solution, or when oxidative phosphorylation has been prevented by metabolic inhibitors.

4. The increasing fluorescence response is absent when calcium is removed from the external medium; it increases with increasing calcium concentration.

5. It is argued that the increasing fluorescence response is due to an increase in glycogenolysis (leading to an increase in the reduced pyridine nucleotide concentration) brought about by the increased calcium entry during the action potential. This calcium presumably increases the activity of phosphorylates a or phosphofructokinase.

6. Calcium entry also speeds mitochondrial oxidative phosphorylation.
The release of γ‐aminobutyric acid during inhibition in the cat visual cortex
Authors: Iversen L. L. , Mitchell J. F. , Srinivasan Vasanta
Published: December 2014

1. The release of γ‐aminobutyric acid (GABA) from the surface of the posterior lateral gyrus of the cerebral cortex was measured by a sensitive enzymic fluorimetric assay procedure. Experiments were performed with anaesthetized cats during resting conditions and during cortical inhibition produced by electrical stimulation of the brain surface or of the lateral geniculate nucleus (l.g.n.).

2. The average resting release of endogenous GABA was 0·20 n‐mole/ 7 min.cm2 cortex; this was increased during stimulation of both the cortical surface (2·9 times resting release during monopolar stimulation and 7·4 times resting release during bipolar stimulation) and the l.g.n. (5·7 times resting release).

3. Removal of calcium ions from the collection fluid did not affect the resting release of endogenous GABA but prevented the increase in GABA release normally evoked by stimulation of the cortical surface.

4. The stimulus parameters used to increase the release of GABA also inhibited the glutamate‐induced firing of single cells in the visual cortex and this inhibition was abolished in the absence of calcium ions.

5. In three experiments the total amino acid content of cortical samples was examined using an amino acid analyser. With the exception of GABA, there were no significant differences between the rates of release of any other detected amino acids during periods with and without electrical stimulation of the cortex.

6. It is suggested that since the release of GABA observed during inhibitory stimulation of the cortex is calcium‐dependent and specific, it may originate from inhibitory nerve terminals in the cortex. The present findings support the view that GABA is a central inhibitory neurotransmitter.
Voltage clamp studies of a transient outward membrane current in gastropod neural somata
Authors: Connor J. A. , Stevens C. F.
Published: December 2014

1. Outward directed membrane currents have been studied in voltage clamp experiments on isolated neural somata of the marine gastropod Anisodoris.

2. Stepping the membrane potential from a hyperpolarized level to a value in the neighbourhood of resting potential (−35 to −50 mV at 5° C) results in an outward current transient, IA, which is apparently carried by potassium ions.

3. The peak amplitude of IA is dependent upon both the holding voltage level and the test step voltage while the time courses of development and decay are independent of, or only slightly dependent on, these parameters.

4. The developing and decaying phases of IA are approximated by exponentials, leading to time constants for development of 10–25 msec and for decay of 220–600 msec over the aggregate of cells studied (data at 5° C). Q10 for the processes is approximately 3.

5. It is concluded that the transport mechanism for IA is at least operationally distinct from the mechanism underlying delayed outward current, IK.
Site of adrenaline blockade in the superior cervical ganglion of the rabbit
Authors: Christ D. D. , Nishi S.
Published: December 2014

1. The blocking action of adrenaline on the superior cervical ganglion of the rabbit was investigated with intracellular recording techniques.

2. Adrenaline (10−5
M) blocked initiation of post‐synaptic action potentials and decreased the amplitude of excitatory post‐synaptic potentials (e.p.s.p.s), but did not hyperpolarize the post‐synaptic membrane.

3. The depressant action of adrenaline was antagonized by phenoxy‐benzamine and dihydroergotamine.

4. Acetylcholine depolarizations from iontophoretic ACh were not affected by adrenaline.

5. Adrenaline decreased the frequency of miniature excitatory post‐synaptic potentials (m.e.p.s.p.s) and decreased the quantal content of e.p.s.p.s in a low [Ca2+]: [Mg2+] media.

6. It was concluded that adrenaline blocks ganglionic transmission by acting at an alpha‐adrenoceptive site in the presynaptic nerve terminals.