bluuebunny/crossref_metadata_2025 huggingface dataset:
The relation between net calcium, alkali cation and chloride movements in red cells exposed to salicylate.
Authors: Bürgin H , Schatzmann H J
Published: December 2014

1. From a 150 mM‐NH4 salicylate medium salicylate enters human red cells with a rate constant of 1.9 min‐1 at 0 degrees C. 2. Salicylate increases the red cell permeability for Ca2+ (and Mg2+). There is no saturation of the Ca2+ transfer with respect to salicylate up to 150 mM and with respect to external Ca2+ up to 30 mM. 3. Ca2+ entering from salicylate media activates the Ca‐sensitive K channel present in human but not in adult ruminant red cells. 4. The increase in K permeability which ensues hyperpolarizes the membrane in Na salicylate media, accelerating further Ca2+ entry and Mg2+ entry and favouring Cl‐ loss (see Fig. 8). The Ca2+ inward movement is in agreement with the constant field equation if the membrane potential is assumed to equal the K equilibrium potential and if two charges are attributed to the mobile species. 5. The effect of salicylate on Ca2+ permeability and hence its sequelae are reversible upon washing the cells. 6. 3‐OH‐benzoic acid and 4‐OH‐benzoic acid do not exert the effect salicylate has on Ca2+ permeability. 7. In 150 mM‐Na salicylate media the Cl‐‐salicylate exchange is virtually nil at 0 degrees C. The exchange seen at 19 degrees C is obviously not across the anion exchange mechanism and proceeds at a rate comparable to that for Cl‐ movement in the nonexchange‐restricted mode given by Hunter (1971, 1977) for cells in a normal medium. 8. Ca2+ seems to increase the Cl‐ permeability seen under these conditions. 9. The possibility that salicylate acts as an ionophore for Ca2+ is discussed.
The heat sensitization of polymodal nociceptors in the rabbit and its independence of the local blood flow.
Authors: Lynn B
Published: December 2014

1. The firing frequency of polymodal nociceptor units with C‐fibre axons was found to increase exponentially with skin temperature as the latter was raised linearly at 1 degree C/sec. Q10 values ranged from 3.6 to 120. 2. Following skin heating to 54‐‐64 degrees C, average firing thresholds fell substantially. This sensitization was accompanied by a 46% increase in interval by interval variability of firing during heat stimulation. 3. Stopping the blood flow to the saphenous area by ligaturing the femoral or saphenous arteries had no significant effect on heat thresholds, on firing patterns during heat stimulation or on variability of firing in sensitized units. There were no changes in continuous, background firing during periods of arterial ligation. 4. It is concluded that if the maintenance of nociceptor heat sensitization depends on the continuous local production of chemical substances, these substances must either be rapidly broken down locally or able to move only slowly into blood vessels.
Competitive interaction between foreign nerves innervating frog skeletal muscle.
Authors: Grinnell A D , Letinsky M S , Rheuben M B
Published: December 2014

1. Competition between two foreign nerves innervating frog skeletal muscle has been studied by using pairs of somatic motor nerves (s.m.n.s) or one s.m.n. and the preganglionic splanchnic nerve (s.p.n.) implanted into a denervated sartorius muscle that has been transplanted to the lymph sac of the back. 2. A single s.m.n. implanted into the muscle succeeded in innervating essentially every fibre within 2‐‐3 months; tetanic stimulation of the nerve elicited 9‐‐100% of the maximal direct tetanus tension. Most of the e.p.p.s were suprathreshold, since a single indirect stimulus evoked a twitch 60‐‐100% as large as that to a direct stimulus. 3. If two s.m.n.s were implanted simultaneously, tetanic stimulation of either elicited 80‐‐100% of the maximal tension to direct stimulation. If one nerve was implanted 2‐‐3 months before the other, the second, although usually less effective than the first, normally innervated 50‐‐100% of the fibres, with approximately the same time course of innervation as a single s.m.n. 4. Mutual synaptic repression was seen on examination of twitch tensions. With either simultaneous or staggered innervation, stimulation of each s.m.n. resulted in a twitch of 30‐‐50% of the total direct twitch tension, with little overlap between the fields driven by the two nerves. Intracellular recordings showed that the distribution of subthreshold and spike‐producing e.p.p.s reflected the existence of separate twitch fields. Even if one s.m.n. was implanted several months before the other and had time to establish suprathreshold junctions on most muscle fibres, an s.m.n. implanted later was able to reduce sharply the effectiveness of many junctions from the earlier nerve while itself innervating most muscle fibres. 5. The subthreshold e.p.p.s had low quantal content, typically ten or fewer quanta/e.p.p. The min e.p.p. frequency was very low, while min e.p.p. amplitude appeared to be normal. 6. In the vast majority of muscle fibres, junctions from the two nerves were not within recording distance of each other. Hence, we infer that the competitive interaction was mediated somehow via the muscle fibre. 7. The preganglionic splanchnic nerve, which also successfully reinnervated frog skeletal muscle, competed with a foreign s.m.n. in ways which differ qualitatively from the competition by a second s.m.n. In the presence of a s.m.n., synapses of the s.p.n. were almost universally subthreshold. However, if the s.p.n. was implanted 2‐‐3 months before the s.m.n., the s.m.n. was prevented for several months from innervating fibres driven by the s.p.n. This delay in s.m.n. reinnervation was greater than if the first nerve implanted was also an s.m.n. 8. After 6‐‐8 months of dual innervation by s.m.n. and s.p.n., the s.m.n. became almost totally dominant. However, if the s.m.n. was then sectioned, the s.p.n. became as effective, within approximately 1 week, as it would have been in the absence of the s.m.n.
Interpretation of light diffraction by cross‐striated muscle as Bragg reflexion of light by the lattice of contractile proteins.
Authors: Rüdel R , Zite-Ferenczy F
Published: December 2014

1. The diffraction spectrum obtained by illuminating a cross‐striated muscle fibre with a narrow beam of monochromatic light generally shows asymmetry of light intensity between left and right spectral lines. 2. The asymmetry of light intensity in left and right spectral lines is reversed when the fibre is rotated by 180 degrees. This indicates that intensities of the spectral lines are determined more by Bragg reflexion than by simple diffraction as in a plane grating. Populations of myofibrils with differing tilt of lattice planes must exist in each illuminated fibre segment to account for simultaneous Bragg reflexion to the left‐ and right‐hand sides. 3. The light intensity of spectral lines shows a complicated dependence on the angle at which the incident beam is directed against the fibre. This 'intensity distribution' seems to reflect the specific myofibrillar arrangement at the site of illumination. 4. The intensity distributions of the left and right first order lines show close correlation if the deflexion of the incident beam differs by twice the Bragg angle. 5. The deflexion angle of the incident beam at which maximum intensity in spectral lines is obtained depends on sarcomere length as predicted by Bragg's formula. 6. Intensities of the first and second order lines are little correlated when recorded at the same beam deflexion, but are well correlated when recorded at beam deflexions calculated from Bragg's formula. 7. When a diffraction line is scanned perpendicularly to the meridional plane, the light intensity shows fluctuations resembling those obtained by beam deflexion within the meridional plane.
Fluid movements across rabbit ileum coupled to passive paracellular ion movements.
Authors: Holman G D , Naftalin R J
Published: December 2014

1. Theophylline (10 mM) and choleragen (1 x 10(‐6) g ml.‐1) abolish net fluid absorption by everted sacs of rabbit ileum. Triaminopyrimidine (20 mM) and ethacrynate (0.1 mM) prevent this inhibition of net fluid movement. Replacing Ringer Cl‐ with isethionate prevents the theophylline‐dependent decrease in fluid absorption also. 2. Ouabain (0.1 mM) abolishes net fluid movements in both control and theophylline‐treated tissue. 3. With ouabain present, hypertonic NaCl (200 mM) in the mucosal solution causes net fluid secretion (serosal‐mucosal flux). With theophylline added to both the mucosal and serosal solution, net fluid absorption (mucosal‐serosal flux) is observed (P less than 0.001). Triaminopyrimidine (20 mM), or ethacrynate (0.1 mM), or replacement of Ringer Na+ with choline, or Ringer Cl‐ with isethionate all prevent the theophylline‐induced reversal of osmotic flow. 4. Theophylline increases passive net flux of Na+ and Cl‐ from mucosal solution containing hypertonic (200 mM) NaCl+ ouabain (0.1 mM) across sheets of ileum into serosal solution containing mannitol Ringer + ouabain. The increased passive Na+ flux is blocked by triaminopyrimidine and the increased Na+ and Cl‐ fluxes are blocked by ethacrynate (0.1 mM). 5. The suggested route of increased NaCl leakage is via the paracellular pathway as it is inhibited by triaminopyrimidine. The increase, itself, is a consequence of the increased passive permeability of the mucosal border to Cl‐, induced by theophylline or choleragen. Water is apparently electro‐osmotically coupled to the paracellular Na+ leakage (100 mole water mole‐1 Na+), hence increased passive leakage reverses osmotic flow. In active tissue the lateral intercellular space contains hypertonic NaCl, and hence increased leakage of NaCl across the tight‐junction in theophylline or choleragen‐treated tissue gives rise to net fluid secretion.
Effects of oestrous cycle and exogenous ovarian steroids on 5‐hydroxytryptamine metabolism in rat lung.
Authors: Bakhle Y S , Ben‐Harari R R
Published: December 2014

1. The metabolism of 5‐hydroxytryptamine (5‐HT) in homogenates of lung and in perfused isolated lungs, was measured, using [14C]5‐HT, over the 4‐day oestrous cycle in rats. 2. In lung homogenates, 5‐HT metabolism (reflecting monoamine oxidase (MAO) activity) was greater during met‐oestrus than during the rest of the cycle. 3. In homogenates, the apparent Km for MAO activity was lowest during met‐oestrus whereas the, Vmax value was highest during di‐oestrus. 4. In perfused lungs, 5‐HT metabolism and uptake was greater during pro‐oestrus than during met‐oestrus. 5. In lung homogenates prepared from female rats treated with 17 beta‐oestradiol or progesterone for 8 days, the metabolism of 5‐HT was increased. 6. We conclude that although the lung is not usually considered a target organ for ovarian hormones, its metabolic activity is affected by changes in the levels of endogenous or exogenous ovarian steroids, an effect comparable with those already observed in uterus, ovary and other more commonly accepted target organs.
The regularity of muscle spindle discharge in man.
Authors: Burke D , Skuse N F , Stuart D G
Published: December 2014

1. The variability of discharge of thirty‐nine muscle spindle afferents from the pretibial muscles of normal human subjects was determined for spike train sequences recorded with the ankle joint fixed in 25 degrees plantar flexion, during further stretch and during graded voluntary contractions of the receptor‐bearing muscle. 2. In non‐contracting muscles with the ankle joint in 25 degrees plantar flexion, a sustained discharge was maintained by twenty‐four of the thirty‐nine endings. The mean discharge frequency for the active endings was 11.1 Hz (range 4.8‐‐22.1 Hz), the mean coefficient of variation 0.073 (range 0.021‐‐0.183). With further stretch, the discharge of endings maintaining frequencies below 10‐‐12 Hz became more regular. For endings maintaining higher frequencies, changes in the coefficient of variation were small and occurred in either direction. All secondary endings maintained a highly regular discharge, but, at these frequencies, there was no statistically significant difference in the variability of primary and secondary endings. 3. It is considered that these findings are comparable to those of Matthews & Stein (1969) for de‐efferented feline spindle endings, and support the view that there is no functionally effective background fusimotor drive to non‐contracting muscles of normal human subjects. 4. A voluntary contraction sufficient to accelerate a spindle ending invariably decreased the regularity of its afferent discharge. During voluntary contractions, coefficients of variation up to 0.345 were recorded. However, coefficients as low as 0.1 were not uncommon, and thus the absence of fusimotor drive cannot necessarily be inferred from a regular afferent discharge pattern. 5. With contractions of different strength, the increase in the coefficient of variation did not parallel the increase in discharge frequency. It is concluded that not all fusimotor influences acting on a spindle ending are translated into variability, and that measurements of the variability of discharge do not accurately reflect the level of fusimotor drive. 6. The discharge frequency of some spindle endings decreased slightly in some contractions and this was accompanied by an increase in the variability of discharge. It is suggested that contracting extrafusal muscle fibres can modulate the discharge pattern of spindle endings and contribute to the variability of discharge during a voluntary contraction. 7. In contracting muscles the irregular fusimotor‐driven spindle discharge contained a ‘hidden’ periodicity, but this was not as extensive as has been reported for the cat. No such periodicity could be demonstrated for spindle endings in non‐contracting human muscles.
Assessment of the pulmonary origin of bronchoconstrictor vagal tone
Authors: Jammes Y. , Mei N.
Published: December 2014

1. In anaesthetized spontaneously breathing cats, the sensory component of the vagal nerves was sectioned at the level of nodose ganglion, using a method described previously (Mei, 1966; Mei & Dussardier, 1966).

2. The strength of the Hering—Breuer reflex (inhibitory ratio, i.e. T1/T0) provided a test for effectiveness of section of vagal afferents, particularly respiratory afferents. On the other hand, by studying the cardiac and bronchomotor effects induced by electrical stimulation of the supranodose portion of the vagal nerve, it was possible to test the integrity of the efferent vagal component.

3. Unilateral right sensory vagotomy was followed by a 29% reduction in total pulmonary resistance.

4. Section of the contralateral sensory vagal component (sensory bivagotomy), produced a weak supplementary effect (total decrease of total pulmonary resistance: 31%).

5. No additive bronchomotor effect could be observed after the bilateral section of efferent vagal fibres (total bivagotomy).

6. In intact cats, blockade of the two vagal nerves by procaine induced a decrease in pulmonary resistance similar to those produced by the sensory bivagotomy (23%). This bronchodilatator effect was concomitant with a complete disappearance of the C wave of the compound vagal potential.

7. Intravenous injection of phenyl diguanide, immediately after the blockade of the C vagal fibres by procaine did not modify bronchomotor tone. This result confirms that the C pulmonary afferents, which are activated by phenyl diguanide, are mainly involved in this mechanism.

8. The pulmonary irritant receptors seem to play a minor role. In fact, the
I.V. administration of histamine under the same conditions, provides evidence that the corresponding neurones (small sized myelinated fibres) are potent during the procaine application.

9. From these results, it appears that bronchoconstrictor vagal tone has an exclusive peripheral origin and that pulmonary endings, in particular those connected with non‐medullated fibres, are probably involved in this mechanism.
Secretion and metabolism of cortisol and aldosterone during controlled hyperthermia.
Authors: Collins K J , Few J D
Published: December 2014

1. The rates of secretion and metabolic clearance of cortisol and aldosterone in response to passive heating have been investigated in fifteen young men by the controlled hyperthermia technique combined with continuous I.V. infusion of [14C]cortisol and [3H]aldosterone. 2. During a 1 hr period of elevation of deep body temperature to 38.0 degrees C mean hepatic blood flow measured by indocyanine green clearance decreased by more than 25% compared with normothermic condition. 3. The pattern of response in hyperthermia involved decreasing plasma specific activities indicating increased adrenal secretion of both cortisol and aldosterone. 4. Aldosterone metabolic clearance rate usually decreased in hyperthermia when there was little change in the clearance rate of cortisol, but an increased aldosterone clearance rate was observed when there were significant increases in the clearance rate of cortisol. A contributing factor to elevation of plasma aldosterone concentration in the heat is the reduction in hepatic blood flow which reduces aldosterone metabolic clearance rate. 5. Suppression of the thermally induced rise in plasma cortisol concentration by dexamethasone was associated with a decrease in aldosterone clearance rate which may reflect increased availability of aldosterone‐binding plasma protein. 6. Marked rises in plasma cortisol were always accompanied by simultaneous rises in aldosterone, but rises in aldosterone sometimes occurred in the absence of a rise in cortisol. We therefore suggest that ACTH stimulation plays an important, but not exclusive, role in the stimulation of aldosterone secretion during hyperthermia.
The recovery heat production in non‐myelinated garfish olfactory nerve fibres.
Authors: Howarth J V , Ritchie J M
Published: December 2014

1. The recovery heat production of the non‐myelinated fibres of garfish olfactory nerve has been measured. 2. At about 20 degrees C the total recovery heat was 381 +/‐ 26 microcal g‐1 impulse‐1 at a stimulation frequency of 2 sec‐1. 3. The time constant of decay of the recovery heat production after a brief period of stimulation was 78.7 +/‐ 3.1 sec at about 20 degrees C. 4. Changing the temperature (by +/‐ 5 degress C) had little effect on the total recovery heat produced. 5. However, lowering the temperature reduced both the rate of rise, and the maximum rate of recovery heat production whereas the time constant of decay was increased. Raising the temperature produced corresponding changes in the opposite direction. 6. the recovery heat production measured in the present experiments is consistent with the previously measured oxygen consumption in the same preparation.
Responses in the diagonal band of Broca evoked by stimulation of the fornix in the cat.
Authors: Hubbard J I , Mills R G , Sirett N E
Published: December 2014

1. Field potentials were recorded within the boundaries of the septal component of the diagonal band of Broca following stimulation of the fornix. The position of the recording electrode was marked by pressure injection of Alcian blue dye. 2. Stimulation of the medial aspect of the ipsilateral fornix produced a simple field caudally consisting of a short duration, short latency negative wave (N1) and a later small prolonged positive wave (P1). It is suggested that N1 is due to antidromic activation of the cells and P1 to their recurrent inhibition. 3. In the rostral part of the septal component of the diagonal band of Broca the field pattern was more complex, containing, in addition to N1 and P1, further negative waves, N2 and N3. N2 was compounded of antidromically and synaptically evoked components and N3 was associated with monosynaptic excitation of the cells. 4. Stimulation of the lateral margin of the fornix was shown to excite antidromically and synaptically the same cells as were excited by stimulation of the medial aspect of the fornix. 5. Stimulation of the medial and lateral aspects of contralateral fornix generated positive waves of similar character to P1. 6. Intracarotid injection of hyperosmotic saline solution caused behavioural signs of arousal and inhibition of spontaneous discharge in a third of the units tested. Spontaneously discharging units (mean frequency +/‐ S.E. of mean, 13.4 +/‐ 1.8, n = 55) were inhibited by stimulation of the medial and lateral ipsilateral and contralateral fornix. It is suggested that inhibitory interneurones receive contra‐ and ipsilateral input. Units with these characteristics were found. 7. The septal component of the diagonal band of Broca was compared with other septal nuclei and found to resemble them in its rostral portion in that it has a reciprocal relationship with ventral and dorsal hippocampus. The caudal portion is unique in the cells project to dorsal and ventral hippocampus but there is no reciprocal projection.
Plasma volume shifts during moderate exercise in splenectomized greyhounds.
Authors: Sarelius I H
Published: December 2014

1. Plasma volume was measured in splenectomized greyhounds, using T‐1824, and sequential changes in plasma volume were measured using two independent methods, based on T‐1824 plasma decay characteristics and on changes in haematocrit. 2. There were no significant differences between estimates of plasma volume made by the two methods in resting or exercising dogs. Therefore it was concluded that the characteristics of the decay of dye concentration in plasma were not affected by exercise and that sequential determinations of plasma volume from a single dye injection provide a valid determination of plasma volume during exercise in dogs. 3. During submaximal exercise, the plasma volume increased by 0‐11.8% of its initial value. In no case did plasma volume decrease significantly. 4. An increase in plasma volume during excercise was also seen in animals previously made acutely hypervolemic or hypovolemic. 5. It is suggested that the increase in plasma volume constitutes part of a mechanism maintaining oxygen delivery to tissues during exercise.
Sodium, potassium and water metabolism in the rabbit: the effect of sodium depletion and repletion.
Authors: Grace S A , Munday K A , Noble A R
Published: December 2014

1. Dietary sodium depletion and subsequent repletion was studied in rabbits. Potassium intake was maintained constant. 2. during sodium depletion and repletion blood pressure, packed cell volume, food consumption and body weight remained at control values. 3. Decreased sodium excretion was observed in both urine and faeces during sodium depletion and the physiological control of these changes is discussed in relation to the renin‐angiotensin‐aldosterone system. 4. Potassium excretion during sodium depletion initially fell as a result of reduced urine volume and gradually returned to normal. Urine potassium concentration remained constant. 5. Faecal excretion of potassium rose by 63% during sodium depletion and there was a rise from a control value of 17‐25% in the proportion of total potassium excretion accounted for by the faecal component. 6. Water consumption and urine volume both decreased in the initial phase of sodium depletion and then returned to control levels. 7. It is important to consider both urinary and faecal excretion of sodium and potassium when calculating balance status for either ion. Faecal excretion, as well as kidney function, shows important physiological adaptations.
Subject instruction and long latency reflex responses to muscle stretch.
Authors: Colebatch J G , Gandevia S C , McCloskey D I , Potter E K
Published: December 2014

1. Surface electromyographic recordings were made in eight normal subjects from the isometrically contracting elbow flexors before and during forcible extension of the elbow through 7 degrees in 50‐150 msec. 2. Weh the subjects were instructed prior (2‐5 sec) to a forthcoming stretch to ‘resist’ or to ‘let go', they could reliably enhance or suppress e.m.g. activity occurring between 40 and 70 msec from commencement of the stretch. Such e.m.g. activity represents a ‘long‐latency’ (or ‘M2') reflex response: it occurs with a latency longer than the spinal segmental monosynaptic reflex, but shorter than a voluntary reaction time. When the subjects were given their instructions (by means of a light) at the moment the stretch commenced, however, none of them could adjust the long‐latency reflex appropriately. 3. It is concluded that central, evaluative processes commencing at the time of a perturbation cannot influence long‐latency reflex responses to that perturbation.
Mono‐and multi‐synaptic origin of the early surface‐negative wave recorded from guinea‐pig olfactory cortex in vitro.
Authors: Gilbey M P , Wooster M J
Published: December 2014

1. Silices of guinea‐pig olfactory cortex were cut at 550 micrometer nominal thickness and preincubated at 24 +/‐ 0.5 degrees C for than 2 1/2 hr. They were then stimulated via the lateral olfactory tract, and field potential recordings were made from all regions of the slice. 2. Potentials recorded resembled those described previously, but it was noticed the early N‐wave had two distinct components, which we designated the N'a' wave (earlier) and N'b' wave (later). Evidence was obtained that this was not a consequence of the division of a single population e.p.s.p. (N‐wave) into two by a P notch (synchronous discharge of post‐synaptic action potentials). 3. In some slices the N'a' wave and N'b' wave had similar thresholds, and in others the N'a' wave had the slightly lower threshold. 4. The N'b' wave was best developed at low frequencies of stimulation (less than 0.1 Hz), and considerably depressed with stimulation above 1 Hz. This was most evident with submaximal stimulation. 5. Exploration of the distribution of peak amplitudes and latencies of the N'a' and N'b' waves showed that the N'a' wave could have been directly initiated by lateral olfactory tract action potentials, while the N'B' wave could not. The N'b' wave amplitude was relatively larger towards the periphery of the slices, away from the tract. In a few cases, an N'b' wave could be recorded in the absence of an N'a' wave at that site. 6. Depth studies showed that the origin of the N'b' wave lay deeper in the slice than that of the N'a' wave. 7. The effect of conditioning stimulation on the N'a' and N'b' waves was examined. The N'b' wave was more depressed at short conditioning intervals than the N'a' wave, and showed less later potentiation. The recovery of the N'b' wave from conditioning was much slowed with submaximal stimulation, and when trials were repeated at low frequency. 8. The N'a' and N'b' components persisted when the slice was warmed to near‐physiological temperatures, and showed a similar pattern of response to conditioning stimulation as had been found at lower temperatures. 9. N'a' and N'b' waves could still be recorded when slices were incubated in a medium containing 1.2 mM‐Mg2+ and 1.2 mM‐Ca2+. These physiological concentrations were about half those routinely employed. There was little or no depression of the N'b' component by conditioning stimulation in this medium. 10. The N'a' wave is probably a result of e.p.s.p.s in apical dendrites of superficial pyramidal cells, initiated by transmitter release from lateral olfactory tract axon collaterals. The N'b' wave may reflect e.p.s.p.s in the apical dendrites of deeper pyramidal cell elicited by firing in recurrent collaterals from superficial pyramidal cell axons.
Changes in motoneurone electrical properties following axotomy.
Authors: Gustafsson B
Published: December 2014

1. Passive electrical properties, afterpotential properties and the pattern of repetitive discharge induced by constant current injection were studied in axotomized lumbar motoneurones. 2. Following axotomy, the motoneurones showed a larger input resistance and membrane time constant, but had a normal electrotonic length. 3. Duration and peak amplitude of the afterhyperpolarization (ahp) were on average unchanged following axotomy. There was, however, a significant reduction in the conductance underlying the ahp. The distribution of values for ahp duration was also narrower following axotomy, with an absence of long and short values. 4. As in normal motoneurones, the ahp conductance, calculated from the voltage, decayed in an approximately exponential manner with a phase of slower decay corresponding to the hyperpolarizing phase of the ahp. The phase of slower decay was, however, less accentuated and several axotomized motoneurones showed an exponential decay of the ahp conductance. 5. The frequency‐‐current (f‐‐I) curves for the first interspike intervals were, as in normal motoneurones, non‐linear, deviating upwards at higher frequencies. The steady‐state f‐‐I relations were, however, linear in most of the axotomized neurones. The slopes of the f‐‐I curves were steeper following axotomy. These steeper slopes were well correlated with the decreased ahp conductance. 6. The interspike voltage trajectories were similar to those in normal motoneurones, i.e. concave at low current strength and changing to a convex shape with increasing current injection. The changes in the trajectory shape were not correlated with the changes in the slope of the f‐‐I curves. 7. It is concluded that the afterhyperpolarization conductance is the major factor in the regulation of repetitive firing in axotomized motoneurones.
Thickness and volume constants and ultrastructural organization of basement membrane (lens capsule).
Authors: Fisher R F , Hayes B P
Published: December 2014

1. The basement membrane of the crystalline lens of the rat has been found to have the following elastic constants: a Young's Modulus of elasticity of 0.56 +/‐ 0.38 x 10(6) Nm‐2 at low stress and 11.3 +/‐ 1.9 x 10(6) Nm‐2 at rupture, an ultimate stress of 28.8 +/‐ 4.5 x 10(5) Nm‐2, and a maximum percentage elongation of 41.3 +/‐ 5.8. 2. The ratio of initial thickness of the membrane to the thickness at the point of rupture is 0.271 +/‐ 0.02 while the similar ratio for volume is 0.461 +/‐ 0.031. 3. Electron microscopic observations of ultrasonicated fragments of the entire membrane show long filaments in parallel arrays and sheets. The filaments show a periodicity of 3.7 nm and a spacing of 3.5 nm. 4. Electron microscopic observations of collagenase‐treated membrane show a poorly staining matrix associated with separate short straight non‐periodic filaments some 2.5 nm in diameter. In addition strands project from the ends of the filaments with a diameter of between 0.5 and 1.0 nm. 5. A model is proposed which consists of these filaments, composed of between three and five parallel strands, some 0.8 nm in diameter, wound in a superhelix. 6. The model predicts satisfactorily thickness and volume changes in the membrane when subjected to stress, and also indicates that the filaments would have a similar Young's Modulus of elasticity and ultimate stress to those of collagen. 7. If the basement membrane of the smallest retinal capillaries is subjected to a change of pressure of only 5 mmHg within the vessel lumen, then the membrane is likely to undergo some 30% reduction in thickness.
The effects of hypercapnia, hypoxia, exercise and anxiety on the pattern of breathing in man.
Authors: Bechbache R R , Chow H H , Duffin J , Orsini E C
Published: December 2014

1. The pattern of breathing, defined as the relations between tidal volume and inspiratory and expiratory times, was measured during the stimulation of breathing by carbon dioxide (hyperoxic rebreathing at rest) in twenty‐seven healthy, young volunteers. 2. Most of the patterns (twenty) were divisible into two parts, for low (range 1) and high (range 2) tidal volumes. The relations were curved, inverse proportionalities for both inspiration and expiration in range 2, and for expiration in range 1. The relations for inspiration in range 1 were evenly divided between those with constant inspiratory times (type 1) and those with curved, inverse proportionalities (type 2). 3. In four volunteers, direct proportionalities predominated and the patterns were scattered (type 3). 4. Eight of the volunteers (four type 1, two type 2 and two type 3 patterns) repeated the measurements and one changed from a type 1 to a type 2 pattern. 5. Nine of the volunteers also rebreathed during resting hypoxia. Two altered their patterns, and the others had patterns which were superimposed upon those measured during hyperoxic rebreathing at rest. 6. Eighteen of the volunteers also rebreathed (hyperoxic) during light exercise (25 W). Five entrained their breathing frequency to the exercise rhythm and showed exercise patterns with constant inspiratory and expiratory times. The others had patterns which were extensions of those measured during hyperoxic rebreathing at rest. 7. The pattern of breathing in range 1 was measured by steady‐state methods in a further ten volunteers at rest with their eyes closed and open, and during mental arithmetic. The pooled average pattern showed that the stress of mental arithmetic shortened both inspiratory and expiratory times, and changed a type 2 pattern into a type 1 pattern.
A voltage‐dependent gate in series with the inwardly rectifying potassium channel in frog striated muscle.
Authors: Mancinelli E , Peres A
Published: December 2014

1. The degree of tubular potassium depletion and the decrease of potassium conductance due to hyperpolarizing pulses in striated muscular fibres have been examined with the three micro‐electrode voltage‐clamp technique. 2. The conductance of the fibre membrane has been measured in different extracellular K+ concentrations from 1 to 10 mM. 3. Comparison of the two sets of measurements shows that changes in tubular K+ concentration are not sufficient to account for the conductance decrease associated with hyperpolarization. 4. The presence of a voltage‐dependent gate in series with the inwardly rectifying channel for K+ ions, suggested by Almers (1972a, b), is thus confirmed.
Intersarcomere dynamics during fixed‐end tetanic contractions of frog muscle fibres.
Authors: Julian F J , Morgan D L
Published: December 2014

1. The stability of sarcomere lengths along single twitch fibres from frog muscles was examined during fixed‐end tetani, using a spot follower apparatus to monitor the length of a central segment. 2. Internal movement, with most of the fibre lengthening and small regions at the ends shortening as the contraction proceeded, was always seen at fibre lengths beyond those corresponding to a sarcomere length of 2.3 micrometer. 3. The rate of lengthening of the central region was fastest during the slow phase of tension rise (creep) but continued at a slower rate throughout the tetanus. These observations are in accord with the idea that progressive development of sarcomere non‐uniformity is responsible for the creep phase. 4. Observations at various muscle lengths of the rate of decay of tension and the duration of the slow phase of relaxation suggest that movement during relaxation is due to sarcomere length non‐uniformities and variations of decay rate with sarcomere length. 5. The rate of tension fall after stimulation ceases in an isometric sarcomere, and the factors which determine that rate, are discussed in view of evidence from fixed‐end and length‐clamped tetani, and recently reported experiments using aequorin.
Differential conduction block in branches of a bifurcating axon.
Authors: Grossman Y , Parnas I , Spira M E
Published: December 2014

1. Propagation of action potentials at high frequency was studied in a branching axon of the lobster by means of simultaneous intracellular recording both before and after the branch point. 2. Although the branching axon studied has a geometrical ratio close to one (perfect impedance matching) conduction across the branch point failed at stimulation frequencies above 30 Hz. 3. The block of conduction after high frequency stimulation occurred at the branch point per se. The parent axon and daughter branches continued to conduct action potentials. 4. Conduction block after high frequency stimulation appeared first in the thicker daughter branch and only later in the thin branch. 5. With high frequency stimulation there was a 10‐15% reduction in amplitude of the action potential in the parent axon, a corresponding decrease in the rate of rise of the action potential, a 25‐30% decrease in conduction velocity, marked increase in threshold and prolongation of the refractory period. In addition the membrane was depolarized by 1‐3 mV. 6. Measurements of the membrane current using the patch clamp technique showed a large decrease in the phase of inward current associated with the action potential, before the branching point. 7. The small membrane depolarization seen after high frequency stimulation is not the sole cause of the conduction block. Imposed prolonged membrane depolarization (8 mV for 120 sec) was insufficient to produce conduction block. 8. In vivo chronic extracellular recordings from the main nerve bundle (which contains the parent axon) and the large daughter branch revealed that: (a) the duration and frequency of trains of action potentials along the axons exceeded those used in the isolated nerve experiments and (b) conduction failure in the large daughter branch could be induced in the whole animal by electrical stimulation of the main branch as in the isolated preparation. 9. Possible mechanisms underlying block of conduction after high frequency stimulation in a branching axon are discussed.
The metabolic effects of sodium depletion in calves on salt appetite assessed by operant methods.
Authors: Bell F R , Sly J
Published: December 2014

1. Sodium deficiency was induced in calves by unilateral exteriorization of the parotid duct, the continual loss of alkaline saliva from the body to the environment causing negative sodium balance. 2. The metabolic effect of negative sodium balance was seen in statistically significant reduction in plasma sodium and blood bicarbonate, together with marked acidosis and reduced plasma osmolality. 3. The homoeostatic response to sodium depletion was associated with a reversal of sodium/potassium ratio in parotid saliva and a reduction of the rate of secretion. Appetite diminished. The extracellular fluid was halved as marked diuresis developed with considerable weight loss. Urinary and faecal sodium was reduced to zero. 4. On restoration of sodium balance by allowing the calves to drink sodium bicarbonate solutions the metabolic deviations were eliminated. 5. During sodium depletion the parotid gland was able to respond to transient reflex stimulation by increasing flow rate and the sodium concentration of the saliva. 6. When sodium depleted, the calves became restless and agitated and would run from the home pen to the operant procedure stand. The sodium depleted animals readily pressed a panel for sodium bicarbonate rewards in direct proportion to the degree of sodium imbalance. When the balance was restored the motivation to work for sodium bicarbonate disappeared. 7. The motivation which developed during sodium depletion was directed specifically towards the sodium ion. Lithium was an exception to this rule and sodium carbonate was aversive. 8. It is possible that in sodium depletion the glottal sodium taste receptors develop an enhanced threshold for sodium ions because of the reduced sodium content of the saliva. This effect would be abolished when the content of sodium was restored in saliva. 9. The correlation of operant reactions and sodium depletion suggests that the consequential metabolic effects activate changes in the central nervous system. 10. The metabolic changes which develop in parallel with the severity of the sodium deficit appear to be able to evoke behavioural changes with increase in salt appetite directed towards restoration of sodium balance.
Mode of stimulation by injection of cyclic AMP and external acidification of the sodium efflux in barnacle muscle fibres.
Authors: Bittar E E , Demaille J , Fischer E H , Schultz R
Published: December 2014

1. A study has been made in single barnacle muscle fibres of the effect of micro‐injected pure protein kinase inhibitor (PKI) on the response of the Na efflux to injection of cyclic AMP and external acidification. 2. (i) Injection into fibres of 1.6 x 10(‐4) M‐pure PKI is without effect on the resting Na efflux. (ii) Injection of 1.6 x 10(4) M‐pure PKI before 0.03 M‐cyclic AMP causes a marked reduction in the magnitude of the response of the Na efflux to the nucleotide. The same is true when 10(‐4) M‐cyclic AMP is injected after PKI. (iii) Injection of partially pure catalytic subunits causes a sustained stimulation of the ouabain‐insensitive Na efflux, which is almost completely reversed by injecting PKI. (iv) Injection of 100 mM‐EGTA before PKI fails to alter the lowered response of the ouabain‐insensitive Na efflux to injection of 10(‐4) M‐cyclic AMP. (v) Ouabain (10(‐4) M) when applied following the injection of 10(‐4) M‐cyclic AMP causes a drastic fall in the stimulated Na efflux. 3. (i) Injection of 1.6 x 10(‐4) M‐pure PKI before or after external acidification fails to abolish or reduce the stimulatory response to acidification. (ii) Injection of 1.6 x 10(‐4) M‐pure PKI before acidification practically abolishes the response of the ouabain‐insensitive Na efflux to 0.03 M‐cyclic AMP in the presence of acidification. (iii) Radioimmunoassay of total cyclic AMP and cyclic GMP content in single fibres before and after acidification shows no appreciable alteration in nucleotide content following acidificiation. (iv) Injection of 100 mM‐EGTA before acidification enhances the stimulatory response to acidification. (v) External application of Dantrolene (10(‐5) M) fails to alter the size of the stimulatory response to acidification. 4. (i) Prior external application of 5 x 10(‐4) M‐benzolamide results in a marked reduction in the magnitude of the response of the ouabain‐insensitive Na efflux to the injection of 3 x 10(‐4) M‐cyclic AMP. (ii) Benzolamide totally abolishes the response of the ouabain‐insensitive Na efflux to the injection of catalytic subunits. 5. The evidence brought forward is compatible with the view that (a) The mechanism by which cyclic AMP stimulates the Na efflux involves activation by cyclic AMP of the cyclic AMP‐dependent protein kinase system, and hence release of the catalytic subunit, and (b) the mechanism by which external acidification leads to stimulation of the Na efflux involves activation of a benzolamide‐sensitive system, possibly carbonic anhydrase, rather than the adenyl cyclase system. The actions of cyclic AMP and catalytic subunits on the Na efflux are closely linked to activation of the benzolamide sensitive system.
Properties of single central Ia afferent fibres projecting to motoneurones.
Authors: Munson J B , Sypert G W
Published: December 2014

1. Electrical potentials in the cat lumbosacral spinal cord evoked by the action of single medial gastrocnemius Ia afferent fibres were recorded using low impedance, bevelled micropipette electrodes and the spike triggered averaging technique. 2. Axonal potentials from the Ia fibres recorded extracellularly appeared as brief triphasic predominantly negative potentials. 3. Terminal potentials recorded in regions of Ia afferent termination appeared as brief diphasic positive‐negative waves, often with additional wavelets. 4. Focal synaptic potentials, recorded extracellularly in regions of the medial gastrocnemius Ia afferent termination, appeared as slow (about 10 msec duration) negative potentials following terminal potentials. 5. Excitatory post‐synaptic potentials, recorded intracellularly in Ia target cells of the medial gastrocnemius, appeared as slow (about 10 msec duration) positive potentials following terminal potentials. 6. Analysis of the temporal progression of these potentials through the spinal cord allowed calculations of the Ia conduction velocity in the dorsal funiculus stem axon (50‐60 m/sec), in major collateral branches (8‐19 m/sec) and in terminal branches (0.2‐1.0 m/sec). 7. The number of major collateral branches (nine or fewer) and their spacing along the spinal cord (1071 micron mean value) were determined by analysing the extent of the triceps surae motoneurone column. 8. The structural and functional properties of medial gastrocnemius Ia afferent fibres are discussed in relation to recent single fibre anatomical data and the present single fibre electrophysiological data.
Internal effects of divalent cations on potassium permeability in molluscan neurones.
Authors: Gorman A L , Hermann A
Published: December 2014

1. Electrophoretic injection of Ca ions into Aplysia pace‐maker neurones activates an outward current, carried primarily by K ions, whose magnitude is determined by the intensity and duration of the injection current, the position of the injection electrode within the cell and the holding potential. 2. The efflux of K ions measured with an extracellular K sensitive electrode is a linear function of the Ca activated outward current and disappears at its reversal potential. 3. The outward current decays exponentially with an early and late phase. The early but not the late phase is temperature dependent with a Q10 of about 3‐5. 4. Of the divalent cations which activate the outward current, Ca is the most effective followed by Cd, Hg, Sr, Mn and Fe. Injections of Ba, Co, Cu, Mg, Ni and Zn are ineffective. 5. Low temperatures or prolonged injection of Cd or Hg, increase the amplitude of the outward current activated by Ca. 6. Prolonged injection of Ba inhibits the Ca activated outward current and reduces substantially all currents carried by K ions. 7. It is concluded that the effectiveness of a divalent cation in activating the K current is, in part, related to its ionic radius, and that the site of activation can accommodate ionic radii between about 0.76 and 1.13 A.
Arterial pressure and pulse interval responses to repetitive carotid baroreceptor stimuli in man.
Authors: Baskerville A L , Eckberg D L , Thompson M A
Published: December 2014

1. Carotid baroreceptors of eight healthy young men were stimulated with brief (0.6 sec), moderate (30 mmHg), single or repetitive (2, 3 or 5), R wave coupled neck suction during held expiration, and brachial arterial pressure and pulse interval changes were measured for 10 sec. 2. Mean systolic arterial pressure declined significantly from control levels after single or multiple baroreceptor stimuli. The reduction of systolic pressure was significant within the first sec after the onset of trains of baroreceptor stimuli; its duration was proportional to the number of stimuli. 3. The sinus node response to a single baroreceptor stimulus was biphasic: inhibition was followed by less intense, but more prolonged facilitation (cardio‐acceleration). A single baroreflex stimulus modulated sinus node function for about 7 sec. The integral of sinus node inhibition was linearly related to the number of baroreceptor stimuli. Inhibition with five repetitive stimuli peaked at about 1.5 sec after the onset of stimulation and delcined to a new steady‐state level during the period of baroreceptor stimulation. 4. Human baroreflex adjustments of arterial pressure and sinus node function occur very early after a step increase of phasic baroreceptor afferent activity. The perturbation of sinus node function is complex and probably reflects changing temporal relationships between the arterial pulse and sinus node activity, and interactions between oscillating levels of acetylcholine and sinus node responsiveness to acetylcholine.
Studies on the excitability of sinus nerve afferent terminals.
Authors: Jordan D , Spyer K M
Published: December 2014

1. The excitability of sinus nerve afferent terminals within the nucleus of the tractus solitarius has been studied in cats and rabbits using the technique of antidromic activation. 2. Conditioning stimuli to the hypothalamic defence area increased the excitability of some glossopharyngeal nerve afferents, though no such effects were observed on sinus nerve terminals. 3. Although the excitability of superior laryngeal nerve afferent terminals was observed to fluctuate in phase with the central respiratory cycle, no equivalent variation in sinus nerve terminal excitability were observed. 4. It is concluded that sinus nerve afferent terminals are not influenced by presynaptic mechanisms. Possible sites for the observed modulations of baroreceptor and chemoreceptor reflexes are discussed in the light of these results.