bluuebunny/crossref_metadata_2025 huggingface dataset:
Selective synapse formation during sprouting after partial denervation of the guinea‐pig superior cervical ganglion.
Authors: Maehlen J , Njå A
Published: December 2014

1. The synaptic connexions established by sprouting of intact preganglionic sympathetic axons were examined by intracellular recording in vitro and by observing the sympathetic end organ responses to ventral root stimulation in vivo. 2. The superior cervical ganglion of the guinea‐pig was partially denervated (70‐85%) by crushing the cervical sympathetic trunk at the level of the subclavian artery, leaving the ansa subclavia intact. The intact nerve carried some preganglionic axons arising from each of the eight spinal cord segments (C8‐T7) contributing innervation to the ganglion. 3. During the first 4 weeks after the operation, there was a two‐to threefold increase in the number of steps in the synaptic response elicited in individual ganglion cells by graded stimulation of the ansa subclavia. There was also an increase in the amplitude of the synaptic potential elicited by each preganglionic axon. 4. This increase in the synaptic contribution of the intact nerve to neurones in the superior cervical ganglion after partial denervation was attributed to sprouting of residual preganglionic axons. A major contribution from collateral connexions between ganglion cells was ruled out by intracellular recording form neurones during antidromic stimulation of their axons in the inferior post‐ganglionic nerve. 5. After sprouting, the specificity of the sympathetic end organ responses elicited by stimulation of the ventral roots of spinal segments T1 and T4 in vivo was indistinguishable from normal, although the strength of these responses increased from just perceptible acutely after partial denervation to near normal 3‐6 weeks after the operation, when sprouting was largely complete. 6. These results show that intact preganglionic axons arising from different spinal levels established selective connexions with different classes of ganglion cells during sprouting.
Succinate dehydrogenase activity in fibres classified by myosin ATPase in three hind limb muscles of rat.
Authors: Nemeth P , Pette D
Published: December 2014

1. Succinate dehydrogenase (SDH) activity was assessed in situ in single fibres of cross‐sectioned extensor hallucis longus, extensor digitorum longus, and soleus muscles of rat by means of microphotometric recordings of initial maximum reaction rates. 2. Each fibre assessed for SDH activity was subjectively classified into myosin subgroups by its histochemical reaction for myofibrillar actomyosin ATPase (myosin ATPase) following preincubation at pH 4.6 according to Brooke & Kaiser (1970). 3. The majority of fibres classified into myosin types I and IIa were highly reactive for SDH, such that those myosin groups could be interchangeable with the metabolic subgroups of Peter, Barnard, Edgerton, Gillespie & Stempel (1972); myosin I = slow‐twitch oxidative, myosin IIa = fast‐twitch oxidative glycolytic. 4. The myosin type IIb fibres, however, demonstrated marked variability in activity levels of SDH. Over 40% of those fibres had high SDH activity, and thus could not be equated with the metabolic subgroup fast‐twitch glycolytic. 5. The histochemical reaction for myosin ATPase in muscle fibres therefore cannot be used as a reliable means to predict the fibres’ metabolic characteristics.
Effects of acetylcholine on respiratory neurones in the nucleus ambiguus‐retroambigualis complex of the cat.
Authors: Jordan D , Spyer K M
Published: December 2014

1. The effects of ionophoretic application of acetylcholine (ACh) and cholinergic antagonists to respiratory neurones of the nucleus ambiguus‐retroambigualis complex were studied in cats. 2. Acetylcholine was ineffective when applied to inspiratory neurones (27/31) but inhibited the spontaneous activity of a significant population of expiratory neurones (21/39). 3. The expiratory neurones inhibited by ACh included neurones with axons projecting to the vagus or spinal cord, as well as neurones not antidromically activated from either of these sites. 4. The cholinergic inhibition of expiratory neurones was blocked by atropine (6/9) but dihydro‐beta‐erythroidine was ineffective. In seven expiratory neurones, ionophoresis of atropine alone evoked firing during the normal period of silence of the neurone (inspiration). 5. It is concluded that a significant population of expiratory neurones receive an active inhibition during inspiration and this involves a cholinergic mechanism. The implications of these observations for the synaptology of central respiratory control and modifications of the vagal outflow to the heart are discussed.
Calcium current‐dependent and voltage‐dependent inactivation of calcium channels in Helix aspersa
Authors: Brown A. M. , Morimoto K. , Tsuda Y. , Wilson D. L.
Published: December 2014

1. Inactivation of the Ca channels has been examined in isolated nerve cell bodies of Helix aspersa using the suction pipette method for voltage clamp and internal perfusion.

2. Satisfactory suppression of outward currents was essential. This was achieved over most of the voltage range by substitution of Cs ion for K ion and by the use of TEA intra‐ and extracellularly and 4‐AP extracellularly. A small time‐ and voltage‐dependent non‐specific current remained at potentials above +60 mV.

3. In these solutions, Ca current approaches ECa but cannot be detected in the outward direction. The Ca channel appears to be impermeable to Cs and Tris ions.

4. Inactivation of Ca currents occurs as a bi‐exponential process. The faster rate is 10‐20 times the slower rate and is about one twentieth the rate of activation. The development of inactivation during a single voltage‐clamp step and the onset of inactivation produced by prepulses followed after brief intervals by a test pulse, have roughly similar time courses.

5. The rates of inactivation increase monotonically at potentials more positive than about ‐25 mV. The amount of steady‐state inactivation increases with membrane depolarizations to potentials of about +50 mV. At more positive potentials, steady‐state inactivation is reduced.

6. Intracellular EGTA slows the faster rate of inactivation of ICa and reduces the amount of steady‐state inactivation measured with a standard two pulse protocol. The effect is specifically related to Ca chelation and hydrogen ions are not involved. This component of inactivation is referred to as Ca current‐dependent inactivation and is consistent with observations that increased Cai inactivates the Ca channel. The process does not depend upon current flow alone since Ba currents of comparable or greater magnitude have smaller initial rates of inactivation. Furthermore, application of Ba ion intracellularly in large concentrations has no effect on steady‐state inactivation.

7. The bi‐exponential inactivation process that persists in the presence of EGTAi is similar to that occurring when extracellular Ba ion carries current through the Ca channel. Steady‐state inactivation also persists and is similar in the two cases. Therefore it is concluded that inactivation is voltage‐dependent as well as Ca current‐dependent.

8. Diffusion models that included reasonable values for the effect of binding on diffusion, even when combined with declining influxes, did not account for this ‘mixed’ form of calcium‐ and voltage‐dependent inactivation. A compartmental model in which the particular kinetic model of voltage‐dependent inactivation was not critical described the Ca current‐dependent inactivation.
Ouabain and regulation of cellular volume in slices of mammalian renal cortex
Authors: Cooke K. R.
Published: December 2014

1. The effect of ouabain on cellular volume recovery in rabbit, guinea‐pig and rat renal cortical slices was studied. A concentration of ouabain that is maximally effective in inhibiting slice potassium accumulation was determined for each species. Slices from each species were either freshly prepared and then incubated, or leached and then incubated, or preincubated in oxygenated ordinary medium (equilibrated), leached and then reincubated in media with and without this concentration of ouabain. All incubations were at 25 °C.

2. Potassium loss produced by ouabain was greater in rabbit and guinea‐pig slices than in rat slices.

3. With slices that were freshly prepared and then incubated, and with slices that were leached and then incubated, cellular volume recovery was inhibited by ouabain in rabbit and guinea‐pig slices, but not in rat slices.

4. After equilibration, swelling during leaching was less, especially in rabbit and guinea‐pig slices. However, on subsequent reincubation, significant differences in tissue water and cation contents that were consistent with inhibition of cellular volume recovery by ouabain, were seen in slices from these two species, but not in rat slices.

5. Slices from all three species, when incubated with concentrations of ouabain that were maximally effective in inhibiting potassium accumulation, appeared to approach a steady‐state tissue potassium content that was greatest in rat slices and least in rabbit slices. Rat slices, previously depleted of potassium, reaccumulated potassium in the presence of 10 m
m‐ouabain to reach this steady‐state potassium content.

6. Despite superficial appearance to the contrary (especially in the case of rat slices) these results are consistent with a major role for the conventional pump in controlling cortical cell volume. They do not provide evidence for the postulate that renal cortical cells possess a separate, ouabain‐insensitive mechanism regulating cell volume.
Stromal lactate accumulation can account for corneal oedema osmotically following epithelial hypoxia in the rabbit.
Authors: Klyce S D
Published: December 2014

1. The mechanism underlying stromal oedema subsequent to epithelial hypoxia was investigated in isolated rabbit corneas. 2. Stromas swelled about 20 micrometer following a 1 hr period of tear side hypoxia in both whole corneal isolates and in preparations in which fluid movement across the endothelium was blocked with silicone oil. In the experiments using whole corneas, stromal thickness was independent of tear side oxygen tension as long as aqueous humour PO2 was greater than 40 mmHg. 3. Neither epithelial thickness nor epithelial electrical resistance, a measure of total ion permeability, was significantly affected by blocking respiration. 4. A 10 degrees C reduction in corneal temperature markedly reduced the rate of hypoxic swelling, suggesting the involvement of a metabolism‐dependent hydrating process and implicating the stromal accumulation of a catabolyte. 5. When CN‐ was used to mimic the hypoxic effect in isolated whole corneas, the passive 36Cl unidirectional flux was unaffected, but lactate production rate and stromal [lactate] more than doubled. 6. These measurements were used with a mathematical model for corneal hydration dynamics to examine the causes of hypoxic oedema. The principal conclusions were: epithelial hypoxia enhances epithelial lactate production and release to the stroma; this process causes an increase in stromal lactate concentration and a decrease in stromal NaCl concentration (primarily through dilution); stromal lactate accumulation exceeds in osmotic load and dilutional effect on [NaCl], producing stromal oedema. Whereas hypoxia produces corneal metabolic acidosis, effects on endothelial permeability of HCO3‐ transport need not be postulated to explain the stromal oedema that results from hypoxia.
The components of synaptic potentials evoked in cat spinal motoneurones by impulses in single group Ia afferents.
Authors: Jack J J , Redman S J , Wong K
Published: December 2014

1. Excitatory post‐synaptic potentials (e.p.s.p.s) were evoked in cat spinal motoneurones by impulses in single group Ia afferent fibres. The probability density of the fluctuations in peak amplitude of each e.p.s.p. was calculated from the recorded peak amplitude and the probability density of the recording noise. 2. Most e.p.s.p.s fluctuated between different components (i.e. individual e.p.s.p.s of a particular discrete amplitude) with peak amplitudes which were integer multiples of the increment between successive components. The average peak amplitude of this incremental e.p.s.p. was about 90 microV for e.p.s.p.s generated at or near the soma. 3. In general, the probability density of the peak amplitude could not be described using Poisson or binomial distributions. 4. For many e.p.s.p.s the complete time course of each component could be calculated. There was no variability in the amplitude of these components nor in their latency of onset. For some e.p.s.p.s there were differences in the latency and time course of the components. 5. The increments between successive components of e.p.s.p. generated proximally were no larger (at the soma) than the corresponding increments for e.p.s.p.s generated at more distal dendritic sites. 6. These results and those from subsequent papers (Jack, Redman & Wong, 1981; Hirst, Redman & Wong, 1981) reinforce earlier suggestions that each bouton behaves in an all‐or‐nothing manner with respect to post‐synaptic effect, and the probability of failure varies at different boutons arising from the same afferent.
Modifications to synaptic transmission at group Ia synapses on cat spinal motoneurones by 4‐aminopyridine.
Authors: Jack J J , Redman S J , Wong K
Published: December 2014

1. The average amplitude of e.p.s.p.s evoked in cat spinal motoneurones by impulses in single group Ia afferents usually increased following the intravenous injection of 4‐aminopyridine (4‐AP). Most of this increase occurred over the first 30 min following injection of 4‐AP. 2. The increase in the average amplitude following 4‐AP occurred by a reduction in the probability of occurrence of component e.p.s.p.s with smaller peak amplitudes, and an increase in the probability of occurrence of component e.p.s.p.s with larger peak amplitudes. There was no evidence that the discrete amplitudes of components after 4‐AP were a result of graded increases of the discrete amplitudes before 4‐AP. 3. The interpretation suggested for these results is that each component e.p.s.p. is generated by transmission at a different combination of boutons. At each of these boutons sufficient transmitter is released to saturate all available receptors. The effect of 4‐AP is to decrease the probability of failure to release transmitter at each bouton, including some boutons which, before 4‐AP, did not release transmitter.
Mechanics and energetics of contraction in striated muscle of the sea scallop, Placopecten magellanicus.
Authors: Rall J A
Published: December 2014

1. Mechanics and energetics of contraction in the striated adductor muscle of the sea scallop, Placopecten magellanicus, were determined and compared to a more conventional muscle preparation, the semitendinosus muscle of the frog, Rana pipiens. Experiments were conducted at 10 degrees C. 2. Scallop and frog striated muscle exhibited similar isometric twitch kinetics, heat coefficients (ratio of force produced to energy liberated), and twitch to tetanus ratios. 3. There were significant differences between scallop and frog muscle in that scallop muscle demonstrated a 30% lower isometric force, an inability to maintain force during a tetanus, and a transient decrease in economy of force development in a twitch after a tetanus, i.e. a decrease in the isometric heat coefficient.
Effects of intestinal secretagogues and distension on small bowel myoelectric activity in fasted and fed conscious dogs
Authors: da Cunha Melo J. , Summers R. W. , Thompson H. H. , Wingate D. L. , Yanda R.
Published: December 2014

1. Defined jejunal segments were perfused with solutions of bile salts and of ricinoleic acid during fasting and after feeding in two groups of conscious dogs, one with the segment in continuity, and the other with a Thirty‐Vella loop. Myoelectric activity was recorded from chronically implanted electrodes on the jejunal segment and also from the proximal and distal in situ bowel.

2. The results in both groups were identical. During fasting, migrating complexes were present in the segment, but were replaced by intermittent spike activity during chenodeoxycholate without and with ricinoleic acid perfusion. After food, when migrating complexes were replaced by intermittent spike activity, none of the solutions produced any consistent effect.

3. In fasted animals, low levels of distension (15 mmHg) interrupted the migrating complexes in the segment and induced intermittent spike activity which was similar to that seen with the secretagogues. The migrating complexes in the main bowel continued during distension. In fed animals, spike activity increased in the segment during distension at 25 mmHg and decreased in the main bowel. In both groups, distension of the segment to pressures between 37.5 and 50 mmHg abolished spike activity both in the distended segment and the main bowel in fasted and fed states, and, in fasted dogs, migrating complexes were also abolished.

4. These results demonstrate that the inhibitory intestino‐intestinal reflex is mediated through extrinsic nerves and does not require an intact myenteric plexus, whereas the altered myoelectric activity induced by secretagogues is a local effect and does not spread to adjacent bowel through either intrinsic or extrinsic neural pathways. It seems likely that the local motor effect of secretagogues is a result of net secretion, producing distension to pressures below the threshold required to activate the intestino‐intestinal reflex.
Properties of high Q10 units in the conscious duck's hypothalamus responsive to changes of core temperature
Authors: Lin M. T. , Simon E.
Published: December 2014

1. Five Pekin ducks were chronically implanted with a device allowing thermal stimulation of the hypothalamus and simultaneous recording of hypothalamic single unit activity on the conscious animals in repeated experiments. In addition, the core temperature of the animals could be lowered by means of a thermode tube which was placed in the colon and was perfused by a cold solution. Hypothalamic temperature was measured in the centre of the hypothalamic thermode array; core temperature was measured in the axillary pit.

2. Each unit was tested in two periods of hypothalamic ramp cooling, one was performed at normal core temperature, and the other at a lowered core temperature during sustained intestinal cooling.

3. Among forty‐six neurones exhibiting a local Q10 > 2 of their discharge rate, intestinal cooling was found to activate 26% (fall feed‐back units), to inhibit 44% (rise feed‐back units), and not to affect 30% (non‐reactive units). The local Q10 values of the fall feed‐back units were, on average, significantly higher than those of the rise feed‐back units.

4. By multiple linear regression analysis the thermal coefficients (impulses/sec. °C) relating unit discharge to hypothalamic (local) and to core (remote) temperature changes were evaluated. The fall feed‐back units exhibited average local temperature coefficients of 0·79±0·11 and remote coefficients of ‐2·75±0·56 (means±
s.e. of mean); the corresponding coefficients of the rise feed‐back units were determined as 0·44±0·08 and +2·33±0·41.

5. The results of this study support the hypothesis that the activity of hypothalamic neurones conveying extrahypothalamic cold signals is depressed more by hypothalamic cooling than that of the neurons conveying extrahypothalamic warm signals. This would explain the paradoxical effects of hypothalamic cooling on thermoregulatory effector activity in birds.
Extracellular versus intracellular digoxin action on bovine myocardium, using a digoxin antibody and intracellular glycoside application.
Authors: Hess P , Müller P
Published: December 2014

1. The actions of externally and internally applied digoxin in heart ventricular muscle have been compared. 2. External application of digoxin (5 x 10(‐8)‐‐10(‐7) M) had an inotropic effect, a steady level of twitch tension being reached at the end of about 3 hr. 3. Addition of an anti‐digoxin antibody to the bathing solution prevented or reversed the digoxin effect, depending on the time of application. 4. The efflux of the antibody‐[3H]digoxin‐complex could be fitted by a single exponential with a half‐time of 18 min. 5. In the absence of antibody, [3H]digoxin washout was two‐compartmental with half‐times of 4 and 72 min respectively. It is thought that the fast process signifies efflux from the extracellular space while the slow process reflects the washout of initially membrane bound glycoside. 6. When digoxin was applied by a cut end method, there was no effect on contractile strength. 7. The profile of radioactivity several hours following exposure to [3H]digoxin clearly indicated movement from cell to cell, the concentration of [3H]digoxin being above 10(‐7) M in half the preparation at the end of 6 hr. Longitudinal diffusivity averaged 8.6 x 10(‐8) cm‐2 sec‐1. 8. We conclude that digoxin has an inotropic effect when reaching the surface membrane of cardiac cells from the outside but is ineffective when applied from the inside.
Analysis of reflex responses in preganglionic parasympathetic fibres innervating submandibular glands of rabbits.
Authors: Kawamura Y , Matsuo R , Yamamoto T
Published: December 2014

1. The volume of submandibular salivary secretion and electrical activities in preganglionic parasympathetic fibres innervating the submandibular gland were recorded in rabbits, anaesthetized with chloralose‐urethane, to evaluate the neural control mechanisms subserving reflex salivary secretion. 2. Single, paired or repetitive electrical shocks were applied to the various parts of the oral region in sympathetically decentralized animals. A copious salivary secretion was induced when the repetitive electrical stimulation was applied to anterior ipsilateral parts of the oral region, especially the upper lip. The optimum frequency of stimulation was 10‐‐20 Hz. 3. About 90% of the preganglionic parasympathetic fibres responded to single electrical shock applied to a respective confined area of the oral region with a mean latency of 10.8 msec. The remainder responded to wider areas of the oral region with a mean latency of 31.5 msec. 4. Preganglionic fibres were classified into three types (E‐type, N‐type and I‐type) in accordance with the mode of impulse discharges. Spontaneous discharges of E‐type fibres (41%) were increased, while those of N‐type fibres (36%) were unchanged and those of I‐type fibres (23%) were decreased by repetitive stimulation at over 10 Hz. Most dominant responses in E‐type fibres were induced by electrical shocks with a frequency of 10‐‐20 Hz. 5. When paired shocks with varying intershock intervals were applied, excitability of E‐type fibres was enhanced for about 20 msec, and then inhibited for about 100 msec, while that of N‐type was inhibited for 150‐‐200 msec, and I‐type was inhibited for 500‐‐700 msec after onset of the first shock. 6. The volume of reflex submandibular salivation evoked by varying frequencies of electrical shocks applied to the oral region correlated statistically significantly with the magnitude of responses in E‐type fibres. This result strongly suggests that E‐type fibres are secretory fibres. The functional significance of N‐type and I‐type fibres is discussed.
Calcium‐independent release of GABA from isolated horizontal cells of the toad retina.
Authors: Schwartz E A
Published: December 2014

1. When toad retinae were incubated first with veratrine, then with antibodies that reacted with the outer segments of photoreceptors, and finally with complement, horizontal cells survived and most other neurones died. This preparation of ‘isolated’ horizontal cells accumulated radioactive GABA from the incubation medium. The subsequent release of radioactive GABA could then be measured. 2. The efflux of GABA was increased by exposure to an elevated potassium concentration or added glutamate. Both procedures are known to depolarize horizontal cells. 3. GABA in the external medium also increased the efflux of GABA. 4. The increase in GABA efflux produced by an elevated potassium concentration was unaffected with calcium in the external medium was replaced with cobalt and when sodium was replaced with choline or lithium. 5. The increase in GABA efflux produced by glutamate was unaffected when calcium was replaced with cobalt and when sodium was replaced with lithium, but was inhibited when sodium was replaced with choline. 6. The increase in GABA efflux produced by external GABA was unaffected when calcium was replaced with cobalt but required sodium. Neither choline nor lithium would substitute for sodium. 7. An increase in GABA efflux was accompanied by an increase in sodium efflux. 8. After a high concentration of GABA (2‐20 mM) had produced a maximal increase in GABA efflux, the addition of glutamate produced no further effect. Conversely, after a high concentration of glutamate (2‐20 mM) had produced a maximal increase in efflux, the addition of external GABA produced only a small further increase. These and the preceding results could occur if GABA release were mediated by a carrier system which could be activated by either depolarization or homoexchange.
On the calcium receptor activating exocytosis: inhibitory effects of calmodulin‐interacting drugs on rat mast cells.
Authors: Douglas W W , Nemeth E F
Published: December 2014

1. A series of neuroleptic drugs (five phenothiazines, imipramine, and pimozide) and the smooth muscle relaxant W‐7, which all inhibit calcium‐calmodulin‐activated processes inhibited rat mast cell secretion elicited by antigen, by 48/80, and by the calcium ionophore A23187. 2. Neither the phenothiazines nor W‐7 reduced 45Ca uptake in response to A23187. The drugs thus exert an inhibitory action distal to the rise in intracellular Ca ions that activates exocytosis. 3. Chlorpromazine sulphoxide, which shares several membrane‐perturbing actions of the phenothiazines but is a weak inhibitor of calmodulin, did not inhibit secretion. Moreover, the inhibitory effects of the phenothiazines were not overcome by a 5‐ or 10‐fold increase in the concentration of calcium, which should counter unspecific membrane effects. 4. The inhibitory effects of the various neuroleptic drugs appeared to be related to their ability to inhibit calmodulin because the individual potencies of these compounds on secretion evoked by 48/80 or A23187 correlated significantly with their reported potencies in inhibiting calmodulin‐activated processes. (The greater potency and different rank order of these compounds on secretion evoked by antigen suggests an additional inhibitory action, perhaps involving Ca entry.) 5. These results, which parallel those obtained with drugs of this sort in smooth muscle where calmodulin seemingly functions as the Ca receptor activating contraction, strengthen the view that calmodulin, or some calmodulin‐like protein, is the Ca receptor activating exocytosis.
The effect of captopril (SQ14,225) upon mother and fetus in the chronically cannulated ewe and in the pregnant rabbit.
Authors: Broughton Pipkin F , Symonds E M , Turner S R
Published: December 2014

1. An inhibitor of angiotensin‐I‐converting enzyme activity (D‐3‐mercapto‐2‐methylpropanoyl‐L‐proline, Captopril) was given to five chronically cannulated pregnant ewes and eleven rabbits in late pregnancy. 2. Within 2 min of administration to the sheep, Captopril had blocked the maternal conversion of angiotensin I to II, as assessed by the pressor response evoked by the i.v. administration of angiotensin I. Maternal and fetal basal systemic blood pressures had fallen within 10 min of administration. Although maternal systemic blood pressure returned to basal levels within 2 hr, fetal pressures remained low for up to 2 days. 3. All ewes went into spontaneous labour at or near term. One lamb was live‐born but very weak and failed to establish suckling. The remaining seven lambs were fresh still‐births. 4. Gestation length was significantly prolonged in the treated rabbits by comparison with ten controls. The still‐birth rate was 37% in the treated animals and 6% in the controls (P less than 0.001). 5. It is concluded that the administration of Captopril to the two species studied is harmful to the fetus. The observations suggest that the drug rapidly crosses the placenta, and may cross the blood‐brain barrier to exert a central effect. It may also interfere with the normal initiation of parturition.
Remote pattern reversal reduces the proximal negative response of the goldfish retina.
Authors: Olsen B T , Seim T , Valberg A
Published: December 2014

1. Using the eyecup preparation, proximal negative responses (PNR) to small test spots of different irradiance were recorded with (a) a stationary peripheral black and white grating surrounding the test spot, and (b) with contrast reversal of the same grating. In the latter case, the PNR‐amplitude was reduced by a magnitude that was dependent on the frequency of contrast reversal. The reduction was maximum (approximately 50%) for a frequency of 8‐10 Hz. 2. The attenuation was constant for PNR‐amplitudes greater than half the maximum value, but increased for smaller responses. The fact that the intensity‐response curve was not merely shifted towards higher values on the log intensity axis, indicates that the suppression was an effect neither of stray light nor of adaptive processes in the distal retina. 3. The effect of a single shift of the grating (by half a cycle) on the PNR was studied at different delays between grating shift and test spot presentation. Strong suppression of the PNR was found for delays between 100 ms (shift preceding test spot) and ‐50 ms (test spot preceding grating shift), with a maximum at about 30 ms. 4. This long‐range effect of peripheral transient stimulation is of inhibitory nature, and probably related to Werblin's windmill effect.
The role of the pituitary‐adrenocortical axis in reflex responses of the adrenal medulla of the dog.
Authors: Critchley J A , Ellis P , Henderson C G , Ungar A
Published: December 2014

1. The release of catecholamines from the adrenal medulla, in response to carotid body hypoxia, may outlast the stimulus by more than 30 min. 2. After denervation of the adrenal gland the immediate release of catecholamines in response to carotid hypoxia is abolished, but the prolonged release remains. 3. The prolonged release of catecholamines is abolished by cycloheximide. 4. Both corticotrophin in vivo and hydrocortisone in the isolated perfused adrenal gland release adrenomedullary catecholamines. 5. It is concluded that a component of the response of the adrenal medulla to carotid body hypoxia is mediated by corticotrophin and corticosteroid release.
Octopamine mediated relaxation of maintained and catch tension in locust skeletal muscle.
Authors: Evans P D , Siegler M V
Published: December 2014

1. The modulatory actions of an identified octopaminergic neurone (DUMETi) that projects to the extensor‐tibiae muscle of the locust hind leg depend upon the frequency of stimulation of the slow motoneurone (SETi) to this muscle. 2. At low frequencies of SETi stimulation (1Hz and below) the predominant modulatory effects are increases in the amplitude and relaxation rate of twitch tension. At higher frequencies, where twitches summate but tetanus is incomplete (up to 20 Hz), the reduction of maintained tension becomes considerably more important. 3. Both octopamine application and DUMETi stimulation reduce the amount of catch tension displayed by the extensor muscle when SETi is fired in a variety of different stimulus patterns. The extensor‐tibiae muscle is itself ‘pattern sensitive’ since is shows a ‘positive spacing effect’ when SETi is stimulated at an average frequency of 1 Hz. 4. It is suggested that a primary function of DUMETi is to change the response of the muscle from one that favours maintenance of posture to one that favours rapid changes in joint position or force, such as might occur during locomotion.
Acetylcholine‐induced membrane depolarization and potential fluctuations in the rat adrenal chromaffin cell
Authors: Kidokoro Y. , Miyazaki S. , Ozawa S.
Published: December 2014

1. The effect of acetylcholine (ACh) on the rat adrenal chromaffin cell membrane was examined in culture by using an intracellular recording technique. ACh was applied with gas pressure through a pipette which had an internal tip diameter of about 3 μm.

2. Upon application of ACh the chromaffin cell membrane depolarized with superimposed potential fluctuations. Occasionally repetitive spikes were observed during the entire period of ACh application up to 30 sec. In some cells a hyperpolarization with a slow time course followed the initial depolarization.

3. The depolarization was detectable with 0·1 μ
m‐ACh; the amplitude increased with higher concentrations of ACh and saturated at 100 μ
m. The half‐maximal concentration was approximately 10 μ
m.

4. The amplitude of the ACh depolarization increased when the membrane was hyperpolarized by passing current through the recording electrode, and decreased upon depolarization. This technique gave an apparent reversal potential of ‐24±4 mV (mean±S.D., n = 6).

5. When the mean amplitude of the ACh depolarizations and the variance of the potential fluctuations in a given cell were plotted, a linear relation was found. The slope was 0·23±0·06 mV (n = 9) at the average membrane potential level of ‐60 mV. With a few assumptions this value approximates the amplitude of an elementary potential change.

6. Temporal characteristics of the potential fluctuations were obtained by calculating an auto‐correlation function. The averaged auto‐correlation function in a given cell declined exponentially with time. The mean time constant at 31 °C was found to be 40±19 msec (n = 9) at the average membrane potential level of ‐60 mV. With a few assumptions this value provides an estimate of the mean duration of an elementary potential change.

7. The ionic mechanism of the ACh depolarization was examined by changing the ion composition of the external solution. Na, K and Ca ions appear to be the current carriers during the ACh depolarization; Cl ions do not contribute.

8. Various ACh receptor agonists and antagonists were applied to determine the pharmacological properties of these ACh receptors. The receptors were found to be nicotinic.

9. The nature of the ACh‐induced membrane potential fluctuations is discussed.
Intracellular recordings from the stellate ganglion of the cat.
Authors: Bosnjak Z J , Kampine J P
Published: December 2014

1. Intracellular recordings were made, in vitro, and in situ, from neurones of the cat stellate ganglion. 2. Preganglionic stimulation, in vitro, via the T3 ramus or post‐ganglionic stimulation via the ventral ansa, dorsal ansa or stellate cardiac nerve evoked graded synaptic responses which led to the discharge of one or more action potentials. Since the conduction velocities of fibres converging onto a single cell may vary, their convergence may mean that there is an interaction in the stellate ganglion between functionally different pathways. 3. Most neurones in the stellate ganglion receive synaptic input from fibres of both central and peripheral origin. 4. Intracellular recordings were made, in situ, from neurones of the cat stellate ganglion attached via the stellate cardiac nerve to the rest of the animal. When peripheral sympathetic afferent input to the stellate ganglion was increased by occluding the descending aorta, some of the neurones exhibited an increase in excitatory post‐synaptic potentials (e.p.s.p.s) and/or action potentials. Most of the synaptic input recorded from the ganglion cells in situ had a close relationship with the cardiac cycle and/or respiration. 5. These data and our previous studies support the contention that sympathetic efferent nerve activity can be modified by peripheral excitatory inputs and that these neural connexions may function as pathways for a peripheral reflex at the level of the paravertebral ganglion.
Synaptic organization of sensory and motor neurones innervating triceps brachii muscles in the bullfrog
Authors: Frank Eric , Westerfield Monte
Published: December 2014

1. The anatomy and physiology of sensory‐motor pathways were studied in the brachial spinal cord of adult bullfrogs to characterize the properties and specificity of these connexions.

2. Motoneurones innervating a given forelimb muscle are located in discrete and reproducible regions of the lateral motor column. Yet only a fraction of the motoneurones in a particular region innervates any one muscle.

3. The central projections of sensory afferent axons from the triceps muscles extend throughout the rostro‐caudal length of the brachial spinal cord. Within this region these projections terminate in an area containing many motoneuronal dendrites.

4. Within the triceps motor pool sensory neurones from the triceps muscles produce monosynaptic potentials only in triceps motoneurones even though these motoneurones are mingled with motoneurones innervating other muscles.

5. Motoneurones innervating each of the three heads of the triceps muscles, medial, internal and external, receive monosynaptic input from their own, homonymous muscle head. Sensory fibres from the medial head also innervate 98% of the heteronymous motoneurones projecting to the internal or external heads, and nearly 90% of the medial triceps motoneurones are innervated by sensory axons from the other two heads.

6. Similarly, other brachial motoneurones receive monosynaptic input from sensory axons in their own muscle nerves. However, most of the synaptic potentials evoked in triceps motoneurones by stimulation of muscle nerves other than triceps are of longer latency and probably involve polysynaptic pathways.

7. Thus, the pattern of synaptic connexions between muscle sensory afferents and motoneurones in the frog's spinal cord is specific. Furthermore, comparison with homologous pathways in the cat's spinal cord suggests that the strength and pattern of these connexions are similar.
Fluoride blocks an inactivation step of transduction in a locust photoreceptor
Authors: Payne Richard
Published: December 2014

1. Photoreceptors in a superfused retina of a locust compound eye are treated with saline containing 10 mM‐NaF, while their intracellular resting potential and responses are recorded using glass micropipettes.

2. Treatment for two minutes with 10 mM‐NaF, followed by a series of brief, bright flashes of light, results in an irreversible, noisy depolarization of approximately 10 mV. The final, stable level of depolarization is reached through the summed effect of each of the noisy, depolarizing afterpotentials that follow every response of the cell to a light flash. If kept in darkness after treatment with NaF, the noisy depolarization still develops, but more gradually, over a period of 5 min.

3. The voltage noise induced by NaF mimics light‐induced voltage noise when the two are compared at mean depolarizations of more than 15 mV. At very small depolarizations, however, fluoride‐induced noise cannot be resolved into the large discrete events (bumps) that are typical of the response of a dark‐adapted photoreceptor to a single photon.

4. The complete replacement of the superfusate sodium by choline reversibly reduces the fluoride‐induced noise and depolarization to the same extent as it does the light‐induced noise and depolarization of an illuminated cell.

5. Increasing the superfusate calcium concentration from 0·5 to 10 mM also reversibly reduces fluoride‐induced noise and depolarization to the same extent as it does light‐induced noise and depolarization. This action of calcium is accompanied by an increase in a cell's input resistance which opposes the reduction caused by light or fluoride treatment.

6. The results confirm the proposal (Payne, 1981) that anionic metabolic inhibitors cause spontaneous activity in sodium channels that are normally opened by light. A model is proposed in which fluoride acts by blocking the inactivation of a late stage in the transduction mechanism.
Ions and energy metabolism in duck salt‐gland: possible role of furosemide‐sensitive co‐transport of sodium and chloride
Authors: Ernst S. A. , van Rossum G. D. V.
Published: December 2014

1. The effects of methacholine on net ionic movements and energy metabolism of the avian salt‐gland have been studied, using slices of glands taken from salt‐adapted Pekin ducks. The slices were equilibrated with media and drugs for 120 min at 1 °C before the experimental incubation at 38 °C.

2. During incubation at 38 °C the slices accumulated K+ and lost Na+ and Cl−. In the presence of methacholine, they retained more Na+ and Cl− and accumulated less K+, the maximal effects being given by 0·5‐1·0 mM‐methacholine. Similar results were obtained whether the medium contained 10 mM‐Tris (used in most experiments) or 25 mM‐HCO3− as the major buffer.

3. The higher final levels of cell Na+ and Cl− induced by methacholine were not seen when furosemide (1 mM) was also present. Methacholine did not induce a higher level of cell Na+ when medium Cl− was replaced by I−, NO3− or SO42-, and did not induce a higher Cl− content when medium Na+ was replaced by choline or Li+. The fall of K+ accumulation caused by methacholine was also prevented by furosemide or by replacing Cl− in the medium with other anions. The anion‐transport inhibitors, SCN− (up to 10 mM) and 4,4′‐diisothiocyano‐2,2′‐disulphonic acid stilbene (DIDS) (up to 2 mM) did not prevent the effects of methacholine.

4. Methacholine stimulated respiration and lowered the slice ATP contents, and these effects were both prevented by ouabain or furosemide. Ouabain, but not furosemide, also reduced the basal (i.e. in the absence of methacholine) rate of respiration and raised the ATP level. SCN− and DIDS had no effect on basal or stimulated respiration or on ATP contents.

5. The respiratory stimulation and fall of ATP induced by methacholine were totally prevented if medium Na+ was replaced by choline. Replacement of Na+ by Li+ caused some stimulation of basal respiration; it also permitted some loss of ATP in the presence of methacholine, but the loss was smaller than that seen in the normal Na+ medium.

6. The respiratory stimulation and fall of ATP induced by methacholine were prevented if medium Cl− was replaced by SO42-. The effects of methacholine were partially blocked when NO3− replaced Cl−.

7. The results are consistent with the stimulation by methacholine of a furosemide‐sensitive, coupled entry of Na+ and Cl− into the cells, associated with a loss of K+. This would result in a stimulation of Na+ extrusion by the ouabain‐sensitive transport system for Na+ and K+ with increased consumption of ATP.
Isometric contractions of motor units and immunohistochemistry of mouse soleus muscle.
Authors: Lewis D M , Parry D J , Rowlerson A
Published: December 2014

1. Isometric contractions of motor units, isolated functionally by ventral root splitting in vivo, were recorded from mouse soleus muscle. 2. Motor unit tensions varied over a narrow symmetrical range and averaged 4.7% of whole muscle tension, corresponding to twenty‐one motor units per muscle. 3. There was considerable variation between muscles in isometric twitch times‐to‐peak and even greater variation for the motor units. The distribution of motor unit times‐to‐peak was apparently unimodal and could be fitted by a single normal population. A slightly better fit was, however, obtained with two normal populations, as suggested by the histochemistry. 4. Twitch time‐to‐peak decreased in proportion to axonal conduction velocity in individual animals. The whole population of motor units could be fitted by a linear relation between time‐to‐peak and the reciprocal of conduction time in the motor axon. Motor unit tension was also linearly related to the reciprocal of conduction time. 5. Histochemistry showed clear division between Type I and Type IIa fibres. Type I fibres reacted strongly with antibody against slow myosin of cat soleus muscle; Type IIa gave a reaction no stronger than the background. The division was as clear as in the cat or rat.
Electrical properties of the basolateral membrane of the straight portion of the rabbit proximal renal tubule.
Authors: Bello‐Reuss E
Published: December 2014

1. Cell membrane potentials were measured with intracellular 3 M‐CKl microelectrodes in isolated, perfused segments of the straight portion of the rabbit proximal tubule. 2. Under in vitro conditions simulating the in vivo situation, the transepithelial potential difference was about 1.6 mV, lumen‐positive, and the basolateral membrane potential was 61 mV, cell negative. 3. Isomolar single ion substitutions in the bath (K+ for Na+, isethionate for Cl‐, N‐methyl‐D‐glucamine (NMDG+) for Na+, and Cl‐ for HCO3‐) resulted in significant basolateral membrane potential changes only when [K+] was increased and [HCO3‐] was reduced; in both cases the basolateral membrane depolarized. Cl‐ and Na+ substitutions with large monovalent ions did not change basolateral membrane potential. 4. Transepithelial potential changes in substitution experiments suggest that, at the paracellular pathway, PK greater than PNa greater than PNMDG, and PCl greater than Pisethionate. 5. It is concluded that the basolateral membrane of these cells is mainly K+‐conductive and that electrodiffusional PNa and PCl are undetectable by this technique. 6. Addition of 1 mM‐Ba2+ to the bath reduced basolateral membrane electro‐diffusional PK, as evidenced by depolarization and by a reduction of the magnitude of the change in membrane potential produced by increasing bath [K+]. 7. The depolarization produced by lowering bath [HCO3‐] appears to result from a reduction of electrodiffusional PK, since it is blocked by Ba2+. There is no need to postulate a conductive pathway for HCO3‐ or a related species.