bluuebunny/crossref_metadata_2025 huggingface dataset:
Water flux due to colloid osmotic pressures across the haemochorial placenta of the guinea‐pig.
Authors: Anderson D F , Faber J J
Published: December 2014

1. Experiments were performed on pregnant guinea‐pigs with gestations of about 44 days to term (65 days). Under anaesthesia, one fetus in each litter was given a volume equal to 1.31% of estimated body weight (v/w) of a 40% solution of 60k‐90k dextran in Ringer solution by I.P. injection. One control litter‐mate received the same amount of Ringer solution, but without dextran. Other litter‐mates served as non‐injected controls. 2. At 20.4 (+/‐ 4.7 S.D.) hr later, the sow was re‐anaesthetized and all fetuses were removed and weighed. They were then dried to constant weight. Wet weights and dry weights were corrected for the weights of the injected materials. 3. Wet weights were normalized by dry weights to account for differences in body size. The average normalized wet weight of the fetuses injected with the dextran solution was 10.9% greater than that of the injected controls and 16.0% greater than that of the non‐injected controls. 4. The results were not affected by the removal of all amniotic fluid at the time of the injections. 5. The results could not have been due to non‐colloid osmotic forces. The Ringer solution was slightly hypo‐osmotic compared to guinea‐pig plasma and the dextran contained negligible amounts of non‐colloids. 6. The applied colloid osmotic pressure of less than 20 torr caused the transfer of a physiologically significant volume of water in a period of 1 day.
The influence of temporal frequency and adaptation level on receptive field organization of retinal ganglion cells in cat
Authors: Derrington A. M. , Lennie P.
Published: December 2014

1. The discharges of single X and Y ganglion cells (distinguished by a test of linearity of spatial summation) were recorded in the optic tract of anaesthetized, paralysed cats.

2. Fourier techniques were used to analyse the distribution of amplitudes of several component temporal frequencies in the maintained discharge. X and Y cells were distinguished by their mean rates, but not by the amplitude or variability of other component frequencies.

3. Sensitivities to moving sinusoidal gratings were measured by an automatic procedure in which stimulus contrast was adjusted to give the smallest modulation of discharge that reliably exceeded that of the relevant component frequency in the maintained discharge.

4. Spatial contrast sensitivity curves of X cells and of on‐centre Y cells could be described by a model of the receptive field as two concentric Gaussian sensitivity profiles representing the centre and the antagonistic surround.

5. Changes in temporal frequency altered the shapes of the spatial contrast sensitivity curves of most units. For X cells sensitivity at the optimum spatial frequency was greater at a temporal frequency of 10·4 Hz than at lower or higher temporal frequencies. The relative sensitivity to low spatial frequencies improved as temporal frequency was raised from 0·16 to 20·8 Hz. The shapes of the contrast sensitivity functions of Y cells were less affected by changes in temporal frequency: at all spatial frequencies sensitivity was greater at 2·6 Hz than at lower or higher frequencies.

6. The effect of temporal frequency upon the shape of the spatial contrast sensitivity curve could be explained by assuming that the centre and surround changed their sensitivities without changing their characteristic radii. A simple model, using a temporal R—C filter in the surround pathway, predicted qualitatively similar changes in the shape of contrast sensitivity curves but failed to provide acceptable fits to the observations. A second model, which assumed that surround signals are delayed by a fixed amount before being combined with those from the centre, fitted the observations of most, but not all, X cells.

7. Dark adaptation produced changes in the shape of the spatial contrast sensitivity curve consistent with a reduction in the relative sensitivity of the surround, but did not bring about systematic changes in the space constants of the best‐fitting theoretical curves.

8. The effects of adaptation level upon contrast sensitivity were expressed as plots of increment—threshold against mean illumination. The shallowest of these curves, obtained for the optimum spatial stimulus moving at about 10 Hz, had slopes averaging 0·77. Decreases in spatial or temporal frequency increased the slopes of the curves.
Presynaptic currents in mouse motor endings
Authors: Brigant J. L. , Mallart A.
Published: December 2014

1. We used external electrodes placed under precise visual control on motor endings of the mouse to record electrical activity promoted by nerve stimulation.

2. Three types of wave form have been observed in relation to well‐defined electrode emplacements: (i) at the transition between myelinated and non‐myelinated parts of the axon, the wave form consists of two negative deflexions preceded by a small positivity (preterminal response), (ii) at the main part of the terminal branches, we obtained a two component positive wave form (terminal response) and (iii) electrode positions in a narrow area between the former and the latter yielded triphasic (positive—negative—positive) wave forms (intermediate responses).

3. Since these responses could not be readily interpreted in terms of classical description of membrane currents associated with propagating action potentials, we used specific channel blocking agents to identify wave form components.

4. Bath application of tetraethylammonium or aminopyridines, or, better, a combination of both, suppressed delayed positive deflexions of terminal and intermediate responses and the late negative component of preterminal responses. Local inophoretic drug application showed that K channels are present only at the terminal part of the endings. K+ outflux promotes a local circuit whose sink is located at the preterminal part where it generates the late negative deflexion of the preterminal response.

5. Local application of tetrodotoxin suppressed the first negative component of preterminal responses but failed to affect electrical activity at the terminal part of the endings. This indicates that Na channels, and, therefore, action potential generation, are restricted to the preterminal part.

6. Suppression of K conductance revealed a slow inward current at the terminal part of the endings which could be identified as a Ca current. Ba2+ and Sr2+ could substitute for Ca2+ as inward current carriers.

7. Activation of spatially separated Na channels, on one side, and of K and Ca channels, on the other, generated ionic currents and separated local circuit currents which flow between preterminal and terminal parts (and vice versa). Thus, the signals recorded at each point of motor endings correspond to the sum of ionic and passive currents entering (or leaving) the membrane at that point.

8. The present results represent a further example of heterogeneity of axonal membrane.
Inhibition of gastric secretion by fat and hypertonic glucose in the dog: role of gastric inhibitory peptide.
Authors: Creutzfeldt W , Ebert R , Finke U , Konturek S J , Kwiecień N , Radecki T
Published: December 2014

1. The gastric and intestinal phases of gastric secretion were selectively evoked by ‘meals’ of 5% liver extract or saline in five dogs provided with a special cannula that allowed complete separation of the stomach from the duodenum. 2. The gastric phase in response to liver extract administered into the stomach amounted to an increase in acid output equivalent to about 70% of the maximum output in response to histamine. There was also a significant rise in the concentration of gastrin but not of gastric inhibitory peptide (GIP) in the serum. 3. The addition of fat (2 or 4% corn oil) or glucose (20%) to this liver extract meal inhibited secretion of gastric acid by 50 and 30%, respectively, without affecting the concentration of gastrin or GIP in the serum. 4. The 5% liver extract in the duodenum stimulated an increase in gastric acid output amounting to about 40% of the maximum response to histamine. Serum gastrin and GIP levels were not affected. Additional fat (0.5‐4.0%) or glucose (10‐20%) reduced acid secretion under these conditions by between 50 and 80% without affecting serum gastrin concentrations. Significant increases in the concentration of GIP in the serum occurred in response to intraduodenal glucose (5%), and to fat at the highest dose used (4%). 5. Intraduodenal infusions of glucose (5‐20%) significantly increased serum GIP levels. Gastric secretion in response to 5% liver extract in the stomach was significantly inhibited at the highest dose (10 or 20%) although gastrin release was unaffected. 6. These results show that intraduodenal fat and glucose both exhibit potent inhibitory effects on post‐prandial gastric acid secretion but that there is no correlation between the changes in serum GIP concentration and the inhibition of gastric secretion under these conditions. 7. We conclude that GIP is unlikely to mediate fat‐induced inhibition of gastric secretion, but it is still possible that it might be involved in the inhibition that occurs during intestinal perfusion with hypertonic glucose solutions.
Insulin response to secretogogues in sheep exposed to cold.
Authors: Sasaki Y , Takahashi H
Published: December 2014

1. The effects of cold exposure on insulin secretion in response to intravenous injections of glucose, butyrate, arginine, glucagon and tolbutamide were examined in ten sheep exposed to a temperature of 0 degree C for 4‐13 days. 2. Cold exposure produced a marked decrease in insulin responses to glucose and butyrate to a level similar to that caused by arginine administration. Cold exposure brought about a significant but only slight decrease in the insulin response to arginine. 3. Glucagon injection resulted in a markedly lower secretion of insulin in the cold than in the warm environment. 4. In the warm environment tolbutamide caused a significant increase in insulin secretion, but in the cold environment did not produce any statistically significant increase in plasma insulin. 5. It is concluded that cold exposure decreases insulin secretion in response to a variety of stimuli.
A reclassification of B and C neurones in the ninth and tenth paravertebral sympathetic ganglia of the bullfrog.
Authors: Dodd J , Horn J P
Published: December 2014

1. The cellular organization of the ninth and tenth paravertebral sympathetic ganglia in the bullfrog was studied with intracellular and extracellular recording methods. An isolated preparation was used in which anatomical details of individual cells could be resolved while making physiological measurements. This permitted the characterization of neurones in terms of their size, the segmental origin of their cholinergic innervation, and their orthodromic and antidromic conduction velocities. With these criteria, three classes of sympathetic neurones were identified. 2. As in previous studies, C cells were distinguished from B cells by the origin of their innervation. C cells are innervated by slowly conducting axons (0.4 m/sec) from spinal nerves 7 and 8 and B cells are innervated by rapidly conducting axons (2.4 m/sec) from the sympathetic chain above ganglion 7. 3. In earlier work it has been suggested that the conduction velocity of a preganglionic axon generally matches that of its target neurone. In this study we have characterized a large group of B cells for which this is not true. The axons of B cells fall into a rapidly conducting group (2.0 m/sec) and a slowly conducting group (0.6 m/sec). In contrast, C neurones, like their preganglionic inputs, have only slowly conducting axons (0.3 m/sec). Consequently, neurones have been classified as C type, fast B type, and slow B type. Fifty‐nine percent of the B cells that we studied were slow B cells. These findings were corroborated by measurements of compound extracellular responses in post‐ganglionic nerves. 4. Some neurones can be identified also by the size of their cell bodies. C cells are about 30 microns in diameter while B cells are about 50 microns in diameter. In our sample, 96% of the cells with radius less than 16 microns were C cells and 94% of the cells with radius greater than 21 microns were B cells. However, fast B cells could not be distinguished from slow B cells by size.
Muscarinic inhibition of sympathetic C neurones in the bullfrog.
Authors: Dodd J , Horn J P
Published: December 2014

1. The muscarinic inhibitory post‐synaptic potential (i.p.s.p.) in sympathetic C neurones has been characterized in an isolated preparation of bullfrog paravertebral chain ganglia. Interactions between the i.p.s.p. and two other synaptic potentials have also been examined. 2. A single presynaptic stimulus to a C cell produces a nicotinic excitatory post‐synaptic potential (e.p.s.p.) followed by a muscarine i.p.s.p. The latency of the i.p.s.p. is 50 msec or longer and the response lasts for seconds. C cells receive multiple cholinergic innervation but the thresholds for activation of the e.p.s.p. and i.p.s.p. are inseparable. Trains of 50 or more presynaptic stimuli produce a non‐cholinergic e.p.s.p. which follows the nicotinic e.p.s.p. and i.p.s.p. and which lasts for tens of seconds. 3. The i.p.s.p. produced by a single presynaptic stimulus can be 30 mV in amplitude. However, in most cells, a short train of stimuli applied at an optimal frequency of 10 Hz is required to produce a large i.p.s.p. 4. The i.p.s.p. is blocked by atropine but is not affected by catecholamine antagonists. 5. Ionophoretically applied acetylcholine (ACh) mimics the i.p.s.p. in its latency, time course and amplitude. In addition, the i.p.s.p. and the muscarinic response to ACh reverse polarity at the same membrane potential: ‐102 mV in normal Ringer solution. The i.p.s.p. reversal potential shifts by 55 mV/decade change in extracellular K+ concentration and is insensitive to the Cl‐ gradient. 300 microM‐Ba2+ totally blocks the muscarinically activated conductance in a reversible manner. 6. Action potentials, when initiated by a supramaximal nicotinic e.p.s.p. or by an antidromic impulse, are not blocked by the i.p.s.p. 7. Near resting potential (‐50 to ‐60 mV), C cells can fire repetitively. The non‐cholinergic slow e.p.s.p. is often accompanied by oscillations in membrane potential and firing of action potentials. This repetitive firing of C cells, which appears to be enhanced by the non‐cholinergic e.p.s.p., is strongly inhibited by the i.p.s.p. The inhibition can be mimicked by injection of very small hyperpolarizing currents (e.g. 25 pA). Interactions between the i.p.s.p. and the non‐cholinergic e.p.s.p. can generate phasic bursting patterns in C cells. 8. The mechanism underlying the i.p.s.p. and the consequences of these findings for ganglionic integration are discussed.
Renal function during lactation in the rat.
Authors: Arthur S K , Green R
Published: December 2014

1. Glomerular filtration rate (g.f.r.), renal plasma flow (r.p.f.), salt and water reabsorption and plasma concentrations of progresterone and prolactin were measured in virgins, 19 day pregnant and lactating rats. 2. G.f.r. was raised by about 40% in animals at 6‐7 days of lactation when compared with virgins but towards the end of lactation returned to virgin levels. Salt and water reabsorption followed a similar pattern. 3. At the time of maximum change of g.f.r. during lactation r.p.f. was raised by about 30% and so filtration fraction rose by about 10% when compared with virgins. 4. Plasma prolactin and progesterone concentrations rose early in lactation but remained elevated when the renal changes had returned to normal. 5. Factors other than changes in prolactin and progesterone concentrations must be implicated in the changes in renal function that occur during lactation.
Responses of abdominal vascular resistance and capacitance to stimulation of carotid chemoreceptors in anaesthetized dogs.
Authors: Hainsworth R , Karim F , McGregor K H , Wood L M
Published: December 2014

1. In anaesthetized dogs the regions of the carotid bifurcations were isolated vascularly and perfused at constant non‐pulsatile pressures. The abdominal circulation was isolated vascularly, perfused at constant flow and drained through the inferior vena cava at constant pressure. Vascular resistance and capacitance responses were determined from the changes in perfusion pressure and changes in venous outflow. 2. Stimulation of carotid chemoreceptors with venous blood resulted in an increase in arterial perfusion pressure of 38% (S.E. +/‐ 4.6) and a decrease in vascular capacitance of 24.4 +/‐ 2.5 ml. (1.05 +/‐ 0.24 ml. kg‐1). 3. When carotid perfusion pressure was higher than 17 kPa, stimulation of chemoreceptors resulted in significantly (P less than 0.05) smaller resistance responses but significantly (P less than 0.05) greater capacitance responses than those obtained at lower carotid pressures. 4. These results show that abdominal resistance and capacitance vessels constrict in response to stimulation of carotid chemoreceptors. We suggest that the larger responses of capacitance and the smaller responses of resistance obtained at higher carotid sinus pressures may be due to different sensitivities of resistance and capacitance vessels to efferent sympathetic nerve activity.
Electrical properties of the costo‐uterine muscle of the guinea‐pig.
Authors: Parkington H C
Published: December 2014

The spontaneous electrical and mechanical activity of the costo‐uterine muscle of the guinea‐pig are described. The spontaneous electrical activity, recorded intracellularly, is similar to that observed previously in longitudinal myometrium of rat (Marshall, 1959) and ionic substitution suggests that, though calcium may be the predominant ion carrying the current during the upstroke of the action potential, some influence of sodium cannot be ruled out. During dioestrus, when circulating progesterone levels are high, there is an increase in the resting membrane potential and a decrease in the frequency of electrical and mechanical activity. There is a two‐fold decrease in the space constant (lambda) during dioestrus. At this time the membrane time constant (tau m) is also decreased. The diameter and length of the smooth muscle cells are smaller during dioestrus. However, the differences in cell diameter do not explain all of the differences observed in lambda at this time and it is suggested that there may be an increase in the resistance to current flow between cells. It is concluded that high circulating progesterone may bring about quiescence of target smooth muscle in two ways: by stabilizing the cell membrane and by restricting the spread of activity.
Sites of action of procaine at the motor end‐plate.
Authors: Gage P W , Hamill O P , Wachtel R E
Published: December 2014

The effects of procaine at pH 7.4 and 9.9 were studied by examining the decay phase of spontaneous miniature end‐plate currents (m.e.p.c.s) recorded from toad sartorius muscle fibres. Following exposure to procaine (0.05‐0.1 mM) at pH 7.4, the decay of m.e.p.c.s rapidly became biphasic, and could be described as the sum of two exponential components. When the same concentrations of procaine were applied at pH 9.9, the development of biphasic m.e.p.c.s took much longer. Reversal of the effect upon washing out the procaine was much slower at pH 9.9 than at pH 7.4. A rapid change in pH from 7.4 to 9.9 during exposure to a constant concentration of procaine quickly reduced the effect of procaine on m.e.p.c.s. The effect gradually returned after prolonged exposure to procaine at pH 9.9. These results suggest that procaine applied at high pH, where it is predominantly in uncharged form, may be diffusing to a site of action which is not directly accessible from the external surface of the membrane. The voltage‐dependence of procaine action was similar whether it was applied at pH 7.4 or 9.9. Intracellular injection of procaine rapidly produced biphasic m.e.p.c.s, whether the extracellular pH was 7.4 or 9.9. The effect of membrane potential on these m.e.p.c.s was similar to that seen for biphasic m.e.p.c.s produced by extracellular application of procaine. The results indicate that procaine can affect end‐plate channels when applied to either surface of the muscle membrane, and that the voltage‐dependence of procaine action does not arise from the influence of membrane field on the movement of charged procaine molecules into open channels.
Recurrent actions on gamma‐motoneurones mediated via large and small ventral root fibres in the cat.
Authors: Appelberg B , Hulliger M , Johansson H , Sojka P
Published: December 2014

Effects on single lumbar gamma‐motoneurones, mediated via fibres running in the ventral roots, were studied by micro‐electrode recording in cats anaesthetized with chloralose. Graded electrical stimulation of ventral roots or of peripheral nerves was used. The cells were identified as gamma‐motoneurones by antidromic stimulation and by measurement of their axonal conduction velocity. Some of the cells were classified as static or dynamic. The findings confirm the previously demonstrated existence of low‐threshold, presumed recurrent, inhibition of both static and dynamic gamma‐motoneurones. Strong evidence for the occurrence of high‐threshold recurrent inhibition of gamma‐motoneurones is also presented. In addition, excitatory effects on gamma‐cells, also mediated via fibres in the ventral roots, are described. The low‐threshold effects from ventral root fibres are attributed to recurrent alpha‐collateral activity and the high‐threshold effects to gamma‐collateral activity. The significance of recurrent inhibition of gamma‐motoneurones is discussed in relation to the ‘gain regulator’ concept proposed by Hultborn, Lindström & Wigström (1979).
Lack of segmental selectivity in elimination of synapses from soleus muscle of new‐born rats.
Authors: Thompson W J
Published: December 2014

The elimination of polyneuronal innervation from neonatal rat soleus muscle was studied by comparing the extent of synapse loss by motor neurones emerging through each of the two spinal nerves (L4 and L5) supplying the muscle. The fraction of muscle fibres receiving innervation from the L4 spinal nerve declined from an average of 75% in 6‐day‐old animals (when all fibres are polyneuronally innervated) to 18% in animals older than 16 days (when almost all muscle fibres are singly innervated). By comparison innervation by the L5 spinal nerve declined from 99% of the fibres at 6 days to 83% of the fibres after 16 days. As a result of synapse elimination there is a greater reduction in the innervation of the muscle by the L4 nerve. The difference in loss of muscle fibres innervated by L4 vs. L5 was not, however, due to a greater degree of synapse elimination of L4 motor nerve terminals. As shown by measurements of the sizes of motor units, both L4 and L5 have units which on average are about four to five times larger at 6 days than at the conclusion of synapse elimination. Thus L4 and L5 motor neurones undergo approximately the same degree of size reduction. The apparently disproportionate loss of muscle innervation by the L4 nerve is explained by the fact that L4 usually contains only a small portion of the total of soleus motor neurones. I therefore conclude that there is no selective loss of synapses based on spinal origin of motor neurones.
A study of the mechanisms by which potassium moves through brain tissue in the rat.
Authors: Gardner‐Medwin A R
Published: December 2014

The flux of K+ produced by electric current across the pia‐arachnoid surface of the neocortex of anaesthetized rats has been studied with K+‐selective electrodes in a cup at the surface and with flame photometry. The potential differences developed across three regions of the rat brain (neocortex, cerebellum, hippocampus) have been measured as [K+] was altered in fluid at the surface. The experimental results have been related to those that would be expected (i) if K+ moved principally by diffusion in extracellular space and (ii) if current flow through cells makes a significant contribution to K+ transfer. K movement produced by current across the neocortical surface accounted for 0.06 of the transfer of electric charge with small currents in either direction (ca. 5 microA mm‐2) and with larger currents out of the tissue. Large currents (ca. 20 microA mm‐2) into the tissue produced less K+ movement, but still more than the fraction 0.012 expected for purely extracellular flux. Alternating current pulses (5 Hz) with zero net transfer of charge produced no flux of K+ across the surface, while alternation with unequal durations produced the same effects as the equivalent steady charge transfer. The K+ flux lagged behind the onset and cessation of current with a time constant ca. 45 sec, approximately as expected from calculations with a model of the tissue. A surface‐negative potential shift averaging 2 mV was observed when [K+ ]at the brain surface was increased from 3 to 12 mM. The time for development of half of the full potential change was 20 sec, with the solution changes complete in less than 4 sec. These results are inconsistent with the hypothesis that K+ movement through brain tissue occurs principally through intercellular clefts, except where these movements involve very localized gradients. They are consistent with the conclusion that ca. 5 times as much K+ flux passes through cells (probably largely glial cells) as through extracellular space, with fluxes driven by either extracellular voltage or concentration gradients.
Changes of extracellular potassium activity induced by electric current through brain tissue in the rat.
Authors: Gardner‐Medwin A R , Nicholson C
Published: December 2014

Ion‐selective micro‐electrodes have been used to measure K+ and Ca2+ activity changes in extracellular space beneath the surface of the neocortex and cerebellar cortex during current flow across the tissue surface in anaesthetized rats. Inward currents produced decreases of [K+]o and outward currents produced increases, with insignificant changes in [Ca2+]o. Changes of [K+]o were largest just under the surface of the tissue, but were detectable down to depths of ca. 1 mm. With appropriate sitting of electrodes in the cerebellar cortex, currents of 22 microA mm‐2 for 400 sec produced changes averaging ‐42% for inward current and +66% for outward current. The [K+]o changes near the surface were most rapid immediately after the onset of current and more gradual after some tens of seconds. Deeper within the tissue the rate of change was more uniform and after the end of stimulation the return to base line was slower. The amplitude, depth dependence and time course of the [K+]o changes were in reasonable agreement with the results calculated for a model in which K+ moves partly through extracellular space but primarily through membranes and cytoplasm within the tissue. The [K+]o changes were not attributable to variations in neuronal activity, although unit activity could be modified by current, since alternating currents failed to produce [K+]o changes and neither 0.1 mM‐tetrodotoxin nor 5 mM‐Mn2+ abolished the changes. The [K+]o changes were not abolished by topically applied ouabain (4 X 10(‐4) M), 2,4‐dinitrophenol (20 mM) or iodoacetate (10 mM), or by asphyxiation. Consequently the [K+]o changes are not dependent on metabolism. The data suggest that there is a selective mechanism for passive K+ transport in an electrochemical gradient within brain tissue that results in higher K+ fluxes than could be supported by ionic mobility in the extracellular fluid. This mechanism exists not only at the surface but within the brain parenchyma and may involve current flow through glial cells.
Reinnervation of skeletal muscles by vagal sensory fibres in the sheep, cat and rabbit.
Authors: Falempin M , Rousseau J P
Published: December 2014

Fibres of the sterno‐cleido‐mastoid (s.c.m.) muscle normally innervated by the accessory nerve have been reinnervated by afferent fibres of the vagus nerve after supranodose vagal‐accessory nerve anastomoses or direct implantation of the vagus nerve into the s.c.m. in cats, rabbits and sheep. The afferent fibres contributing to this reinnervation were confirmed to be cholinergic as transmission was blocked by gallamine, and histochemical evidence obtained of cholinergic motor end‐plates. The association of the axons of cells of the nodose ganglion and s.c.m. muscle fibres was further demonstrated when horseradish peroxidase injected into the s.c.m. was detected in somata of nodose ganglia cells. The largest number of reinnervated motor units, fifty, identified by electromyographic recording from the s.c.m. muscle, represents a small proportion of the afferent fibres in the vagus. Factors contributing to this degree of reinnervation are discussed. Conduction velocities in afferent fibres involved in the reinnervation were in the range less than 2.5 to greater than 35 m/s with 36% being 6‐12 m/s. Between 40 and 98.5% of the myelinated fibres of the accessory nerve replaced by vagal afferent fibres were less than 6 microns in diameter. The afferent nerve fibres involved in the reinnervation were associated with larynx, respiratory tract, oesophagus and stomach. Afferent discharges recorded as bursts of electromyographic potentials in the s.c.m. occurred during spontaneous movements of these structures and on their mechanical stimulation.
Reinnervation of striated muscle by peripheral vagal fibres cut above or below the nodose ganglion in the cat and rabbit.
Authors: Coget J , Rousseau J P
Published: December 2014

In cats and rabbits, the peripheral stump of the vagus nerve cut above the nodose ganglion (supranodose anastomoses: s.n.) or below this ganglion (infranodose anastomoses: i.n.) was either sutured with epineurial sutures to the peripheral stump of the branch of the spinal accessory motor nerve innervating the sterno‐cleido‐mastoid (s.c.m.) muscle, or directly implanted in this muscle after resection of its motor nerve. After about six months, reinnervation of this muscle by vagal fibres was studied. By electromyographic recording during electrical stimulation of the cervical vagus nerve, it was shown that the vagal reinnervation of the s.c.m. muscle was established in 65% of the cats studied (57% s.n., 69% i.n.) and 33% of rabbits (37% s.n. and 31% i.n.). The average number of distinct potentials recorded in the reinnervated muscle, following vagal stimulation, was twenty‐two in s.n. cats, thirteen in i.n. cats, eleven in s.n. rabbits and twelve in i.n. rabbits. Recorded potentials were monophasic (8%), biphasic (22.5%), triphasic (11.5%) or polyphasic (58%). These potentials were abolished by curare and alpha‐bungarotoxin. The use of retrograde axonal transport of horseradish peroxidase showed labelled cells in the nodose ganglion, the cervical vagus and cranial thoracic vagus, and in the stellate ganglia. It is concluded that cholinergic vagal afferents reinnervated the s.c.m. muscle. Involvement of the sympathetic system is discussed.
Stimulation and inhibition by ATP and orthophosphate of the potassium‐potassium exchange in resealed red cell ghosts.
Authors: Eisner D A , Richards D E
Published: December 2014

The potassium:potassium (K‐K) exchange through the sodium pump has been measured as the ouabain‐sensitive 86Rb uptake by Na‐free ghosts resealed to contain various concentrations of ATP, orthophosphate and K. The exchange is activated by increasing either internal or external K+ (Rb+) ion concentration. The activation curves can be described by simple Michaelis kinetics as: exchange = Vmax [K]/(Kapp + [K]). Increasing ATP concentration increases the apparent affinity for external K ions but decreases the apparent affinity for internal K (Ki+). Increasing [ATP] from 1 microM to 1 mM typically increases the Kapp for Ki+ from less than 1 mM to about 30 mM. Increasing ATP first activates the exchange but, after an optimal concentration is reached, further increase of ATP inhibits. The value of ATP concentration which gives the maximum flux depends on the internal and external K+ concentrations. The higher [Ki], the greater the optimal ATP concentration. Increasing external K (Rb) decreases the optimal ATP concentration. Increasing the concentration of orthophosphate (Pi) activates the exchange at high ATP but inhibits at low ATP concentration. A concentration of Pi which stimulates the exchange at high external K (Rb) can inhibit at low external K (Rb). These findings are in agreement with a consecutive or ping‐pong model of the K‐K exchange. We suggest that previous experiments have not shown the inhibitory effects of ATP and Pi because of the particular range of concentrations investigated.
Classical tritanopia
Authors: Alpern M. , Kitahara K. , Krantz D. H.
Published: December 2014

1. A subject who has suffered from central serous chorio‐retinopathy in his left eye noticed differences in the colour of a given light as perceived by each eye alone. Standard screening tests (colour order and colour matching) indicated a tritan defect in the left eye; the right eye was normal on these tests.

2. The subject was dichromatic in his left eye, trichromatic in his right. The left‐eye distimulus colour‐matching functions, spectral luminosity, and wave‐length discrimination functions were indistinguishable from corresponding data for congenital tritanopia. Comparable right‐eye data were normal.

3. Spectral dichromatic colour matches were invariant under changes of intensity and under addition of a common light to both halves of the field. (Grassmann's laws of linearity are satisfied.)

4. Increment threshold versus intensity (t.v.i.) curves for a blue (481·9 nm) test on a yellow background yielded the normal three branches (for Π4(μ), Π1(μ) and Π3(μ) respectively) in the trichromatic eye. In the dichromatic eye a single mechanism was found. It had the field sensitivity of Π4(μ) whether measured with the blue, or with a violet (429·5 nm) test. No trace of Π3(μ) or Π1(μ) was ever discovered in the tritanopic eye. Both are normal in the trichromatic eye.

5. The field sensitivities of Π4, Π5 and Π3 of the normal eye are well fitted by linear combinations of the spectral colour‐matching functions of the trichromatic eye. Π4 and Π5 of the dichromatic eye are well fitted by linear combinations of the tritanopic matching functions.

6. Colour matches made by the trichromatic eye do not match when viewed by the tritanopic eye, almost certainly because the ocular media of the two eyes have wave‐length‐dependent differences in absorption. For the largest difference (430 nm) the trichromatic eye transmits about 2·2 times more light than its fellow. When allowance is made for these differences, the field sensitivities of Π4 and Π5 of the two eyes do not differ. The field sensitivities of Π4 and Π5 of the normal eye, on the other hand, differ significantly from those of the average spectra obtained on four normal trichromats by Stiles, in a way that cannot be attributed to differences in transmittance of ocular media.

7. It is concluded that classical (or acquired) tritanopia is not distinguishable in its manifestations from congenital tritanopia; furthermore, tritanopia can be regarded as a reduced form of normal trichromacy, once allowances are made for absorption of the ocular media and for variations among normal trichromats.

8. Despite extensive search no evidence could be uncovered which might exclude the hypothesis that the colour vision in tritanopia depends exclusively upon absorption in only two foveal cone pigments, one long‐wave‐absorbing and one medium‐wave‐absorbing.
Volumes of distribution of sodium and albumin in the sheep placenta.
Authors: Boyd R D , Canning J F , Stacey T E , Ward R H , Weedon A P
Published: December 2014

The volumes of distribution of 22Na and 24Na, 51Cr‐EDTA and albumin labelled with 131I and 125I were measured in cotyledons and skeletal muscle taken from pregnant sheep and the fetuses near term. Radiolabelled substances were injected through chronically implanted catheters 0.5‐3.2 hr before removal of tissues in ‘short‐term’ experiments and 24‐26 hr before in ‘long‐term’ experiments. Volumes of distribution were expressed as percentages of tissue weights. Cotyledonary water content was 81.5 +/‐ 0.6% (S.E. of mean) of wet weight (n = 10 sheep). Sodium content was 76.0 +/‐ 4.0 m‐mole kg‐1 wet weight (n = 4) and potassium content was 58.8 +/‐ 2.4 m‐mole kg‐1 wet weight (n = 4). In short‐term studies cotyledonary spaces following injection into the fetal circulation were: Na, 20.5 +/‐ 0.9% (n = 10 sheep); Cr‐EDTA, 19.5 +/‐ 1.2% (n = 3); and albumin, 2.8 +/‐ 0.3% (n = 11). The equivalent maternal cotyledonary spaces were: Na, 23.5 +/‐ 1.6%, or 22.1 +/‐ 1.6% when ‘corrected’ for fetal radioactivity (n = 8); and albumin, 4.7 +/‐ 0.8% (n = 8). Maternal and fetal cotyledonary sodium spaces were additive. Larger cotyledons had larger fetal sodium spaces. In long‐term studies, the value for maternal albumin spaces was considerably higher 12.3 +/‐ 3.2% (n = 3), whereas that for fetal albumin spaces was only 3.9 +/‐ 0.4% (n = 4). The higher fetal sodium space of 24.9 +/‐ 1.0% (n = 4) in the long‐term experiments was attributable to rising sodium counts in the maternal circulation. In the short‐term experiments maternal skeletal muscle spaces were Na, 13.5 +/‐ 1.3% (n = 7) and albumin, 1.7 +/‐ 0.3% (n = 7), with higher values of 22.0% (n = 2) and 3.8 +/‐ 0.2% (n = 3) respectively in long‐term experiments. In the short‐term experiments fetal skeletal muscle spaces were Na, 32.8 +/‐ 3.2% (n = 7) and albumin, 2.5 +/‐ 0.3% (n = 10), with higher values of 39.7 +/‐ 7.4% (n = 4) and 16.2 +/‐ 0.6% (n = 4) respectively in long‐term experiments.
An electrophysiological study of excitatory neuromuscular transmission in the guinea‐pig main pulmonary artery.
Authors: Suzuki H
Published: December 2014

Electrical responses of single smooth muscle cells to perivascular nerve stimulation were recorded in the guinea‐pig main pulmonary artery with a micro‐electrode, to investigate neuromuscular transmission mechanisms. Perivascular nerve stimulation produced excitatory junction potentials in the smooth muscle cells of the main pulmonary artery. When stimulation was repetitive and of high frequency, a spike was seen in the early part of these potentials. Phentolamine, prazosin, phenoxybenzamine, guanethidine or tetrodotoxin all suppressed first the spike and then the junction potential. Exogenously applied noradrenaline also produced depolarization, and in high concentrations above 10(‐6) M, spikes. Phentolamine again suppressed the spikes and then the depolarization. The results suggest that endogenous and exogenous noradrenaline act on the same type of receptor in this artery.
Two‐component desensitization at the neuromuscular junction of the frog.
Authors: Chesnut T J
Published: December 2014

Desensitization to ionophoretically applied ACh has been studied at voltage‐clamped neuromuscular junctions of Rana pipiens. The time courses of both the onset of and recovery from desensitization displayed two components. The application of metabolic inhibitors to the preparation decreased the degree of recovery and also decreased both time constants of onset. The effect on onset was more pronounced on the slow component while no effect selective for either of the two components of recovery was seen. Intracellular injection of EGTA into the muscle cell increased both time constants of desensitization onset. The effect was much more pronounced on the slow component. Increasing the dose of ACh selectively decreased the fast time constant of desensitization onset. The effect was more selective in low‐calcium than normal Ringer solution. These observations suggest that there are at least two independent mechanisms in the process of desensitization at the neuromuscular junction. These mechanisms differ in time course, degree of dependency on [Ca]i, and sensitivity to acetylcholine dose.
Lateral distribution of sodium and potassium channels in frog skeletal muscle: measurements with a patch‐clamp technique.
Authors: Almers W , Stanfield P R , Stühmer W
Published: December 2014

We describe a method for recording Na+ and K+ currents (INa and IK) from small, voltage‐clamped patches of sarcolemma by means of fire‐polished glass micropipettes of 7‐15 microns tip diameter. Recordings can be made successively from many areas of one fibre. On a given fibre, the amplitudes of INa and IK varied from point to point. Maximum Na+ current densities varied up to three‐fold over distances of 10‐30 microns, typically between 4 and 12 mA/cm2. K+ currents showed somewhat less lateral variation. Local densities of INa and IK showed no correlation. Apparently the density of Na+ (and, to a lesser extent, K+) channels varies laterally. A contour map of Na+ channel density is constructed for a 20 microns X 90 microns section of sarcolemma. Based on the steepness of lateral gradients in channel density and the estimated survival time of a Na+ channel, it is calculated that at least half of the Na+ channels have a lateral diffusion coefficient of less than 2 X 10(‐12) cm2/s. This is three orders of magnitudes less than expected from their molecular size, and suggests that these channels are anchored in the sarcolemma.
Effect of gamma‐aminobutyric acid agonists, glycine, taurine and neuropeptides on acetylcholine release from the rabbit retina.
Authors: Cunningham J R , Neal M J
Published: December 2014

The light‐evoked release of [3H]acetylcholine (ACh) from the rabbit retina in vivo was measured and taken as an index of cholinergic amacrine cell activity. The light‐evoked release of [3H]ACh was reduced by locally applied gamma‐aminobutyric acid (GABA), muscimol and 3‐aminopropanesulphonic acid (3‐APS). The concentrations of these drugs which reduced the light‐evoked release of [3H]ACh by 50% (EC50) were 900, 0.3 and 5 microM respectively. In contrast, (‐)‐baclofen (5 mM), but not (+)‐baclofen, significantly increased the light‐evoked release of [3H]ACh. The GABA antagonist, bicuculline increased the resting release of [3H]ACh but abolished the inhibitory action of muscimol on the light‐evoked release of [3H]ACh. Glycine and taurine also reduced the light‐evoked release of [3H]ACh from the retina, their EC50 values being 1.5 and 0.3 mM respectively. This action was blocked by strychnine, but not by bicuculline. In contrast to the GABA antagonist, strychnine did not affect the spontaneous resting release of [3H]ACh. Retinal [3H]ACh release was not affected by dopamine, 5‐hydroxytryptamine (5‐HT) morphine, substance P, somatostatin, cholecystokinin sulphate, thyrotropin releasing hormone, luteinizing hormone releasing hormone or angiotensin. Electroretinographic changes produced by amino acids and GABA agonists involved mainly the b‐wave and were not correlated with their effects on ACh release. Thus, GABA increased the b‐wave amplitude, 3‐APS had no effect, whilst muscimol, taurine and glycine either had no effect, or reduced the b‐wave amplitude. No obvious changes in the e.r.g. were produced by baclofen, dopamine, 5‐HT, morphine or any of the peptides studied with the exception of somatostatin, which reduced the amplitude of the b‐wave. It is concluded that cholinergic amacrine cell activity in the rabbit retina may be affected by inputs from other amacrines using GABA or glycine (taurine) as their transmitters, but probably not by inputs from peptidergic or dopaminergic amacrine cells. Our experiments do not provide evidence on the sites of action of GABA, glycine or taurine but the action of bicuculline on the resting release of ACh implies that the activity of the cholinergic amacrine cells is affected by a tonically active GABAergic input.
The responses of cells in macaque lateral geniculate nucleus to sinusoidal gratings.
Authors: Hicks T P , Lee B B , Vidyasagar T R
Published: December 2014

Responses of cells in the parvocellular (p.c.l.) and magnocellular (m.c.l.) layers of the macaque lateral geniculate nucleus to sine‐wave gratings were studied. Both p.c.l. and m.c.l. cells responded best at a temporal frequency (drift rate) of 10‐20 Hz. P.c.l. cells responded at temporal frequencies lower than 1 Hz; m.c.l. cells did not. With coloured‐ or white‐black luminance‐modulated gratings, responses of m.c.l. cells were weaker at low than at medium spatial frequencies. With coloured gratings, p.c.l. cell responses were not attenuated at low spatial frequencies. With white gratings a few p.c.l. cells did show such attenuation. Optimal responses from p.c.l. cells were obtained with coloured gratings; white gratings evoked weaker responses. With a grating of a colour causing suppression of a p.c.l. cell's activity, the modulation of firing was much less than with a grating of a colour excitatory for the cell. M.c.l. on‐ and off‐centre cells responded equally well to moving gratings. The ability of p.c.l. cells to resolve fine gratings was dependent on cell type as well as on the colour of grating used. The ability of m.c.l. cells to resolve fine gratings was comparable to that of p.c.l. cells. The contrast sensitivity of m.c.l. cells was much higher than that of p.c.l. cells. This may account for their ability to resolve fine gratings, despite their larger centre size. In comparison with luminance‐modulated gratings, chromatically modulated gratings could evoke larger or smaller responses, depending on p.c.l. cell type and the colours in the grating. M.c.l. cells responded poorly or not at all.
Acute and chronic effects of progesterone and prolactin on renal function in the rat.
Authors: Elkarib A O , Garland H O , Green R
Published: December 2014

The renal effects of acute and chronic progesterone and prolactin administration were investigated in rats. Acute progesterone treatment caused a reduced urinary potassium excretion compared to controls (0.80 +/‐ 0.03 vs. 1.30 +/‐ 0.04 mumole min‐1; P less than 0.01). No other renal changes were apparent. Acute prolactin administration produced no significant changes in renal function. Chronic progesterone treatment reduced urinary potassium output by increasing tubular reabsorption. Absolute reabsorption (mumole min‐1) for controls was 4.70 +/‐ 0.42 and for progesterone treatment, 6.40 +/‐ 0.57 (P less than 0.05 comparing the two). No other renal changes were apparent. Animals made pseudopregnant by chronic prolactin administration showed a significant (16%) elevation in glomerular filtration rate, similarly enhanced fluid and solute reabsorption, and a significant (16%) increase in proximal tubule length. This would imply a role for prolactin in early rat pregnancy and pseudopregnancy when similar renal changes are evident and circulating hormone levels high.
Hind‐limb vascular‐capacitance responses in anaesthetized dogs.
Authors: Hainsworth R , Karim F , McGregor K H , Wood L M
Published: December 2014

In anaesthetized dogs a hind limb was vascularly isolated, perfused through the femoral artery at either constant flow or constant pressure and drained from the femoral vein at constant pressure. Inflow and outflow were recorded. Vascular‐resistance changes were calculated from changes in pressure or flow and volume changes from the differences between inflow and outflow. During constant‐flow perfusion, both changes in carotid sinus pressure and direct stimulation of efferent sympathetic nerves resulted in large resistance responses. However, changes in carotid sinus pressure did not result in changes in limb blood volume and only small decreases were obtained in response to direct stimulation. During constant‐pressure perfusion, both reflex and direct stimulation resulted not only in significant changes in resistance but also in significant volume changes which were much larger than those obtained during constant‐flow perfusion. Similar responses were obtained when the flow rate was changed by altering the pump speed. These results indicate that changes in pressure to carotid baroreceptors do not result in active capacitance responses in the limb circulation and that only very small responses are obtained even to electrical stimulation of sympathetic nerves. The larger responses occurring during constant‐pressure perfusion are thought to be secondary to changes in blood flow.