bluuebunny/crossref_metadata_2025 huggingface dataset:
Trichromatic colour opponency in ganglion cells of the rhesus monkey retina.
Authors: De Monasterio F M , Gouras P , Tolhurst D J
Published: December 2014

Two hundred and eleven colour‐opponent ganglion cells were studied in the central 10 degrees of the retina of the rhesus monkey, to determine the inputs which they were receiving from different cone mechanisms. Spectral‐sensitivity measurements in the presence of neutral and coloured back‐grounds showed that 24% of these cells appeared to receive input from all three cone mechanisms. 2. In 3% of the cells, the red‐sensitive cone mechanism opposed the blue‐ and green‐sensitive ones. In 18% of the cells, the blue‐sensitive cone mechanism opposed the green‐ and red‐sensitive ones. In 3% of the cells, the green‐sensitive cone mechanism opposed the blue‐ and red‐sensitive ones. 3. In 12% of the cells receiving opponent green‐ and red‐sensitive cone inputs, responses from the beta‐band of the red‐sensitive cone mechanism could be detected and distinguished from blue‐sensitive cone input. 4. All cells receiving blue‐sensitive cone input appeared to be trichromatic. The retinal distribution of cells with trichromatic input and that of cells with beta‐band responses seemed to parallel the availability of blue‐sensitive cones in the retinal area being considered. 5. The results indicate that trichromatic interactions in the macaque visual system begin in the retina.
Synaptic transfer at a vertebrate central nervous system synapse.
Authors: Martin A R , Ringham G L
Published: December 2014

1. The relation between presynaptic depolarization and transmitter release was examined at a synapse between a Müller axon and a lateral interneurone in the spinal cord of the lamprey. Two micro‐electrodes, one for passing current and the other for recording the resulting voltage change, were placed in the presynaptic axon; a single electrode for recording the post‐synaptic potential produced by release of transmitter was placed in the post‐synaptic cell. 2. When action potentials were blocked with tetrodotoxin, brief depolarizing pulses in the presynaptic fibre were as effective as the action potential had been in producing transmitter release. 3. The release process had an apparent threshold depolarization of 40‐50 mV and saturated at presynaptic depolarizations of the order of 100 mV. Increasing the duration of the presynaptic pulse increased the maximum level of release. 4. Displacing the presynaptic voltage recording electrode from the position of synaptic contact toward the current passing electrode increased the apparent depolarization required to produce a given level of transmitter release. This shift in the input‐output relation was consistent in magnitude with the voltage attenuation between the presynaptic recording electrode and the synapse expected from the space constant of the fibre. 5. The effect of conditioning hyperpolarization and depolarization of the presynaptic fibre on subsequent transmitter release by brief depolarizing pulses was examined. No effect was observed when the presynaptic recording electrode was in the region of synaptic contact. When the presynaptic electrode was not so positioned, conditioning effects were observed which depended on electode position and could be attributed to changes in the space constant of the presynaptic fibre. No conditioning effects were observed on transmitter release by the action potential.
Influence of activity on the passive electrical properties of denervated soleus muscle fibres in the rat.
Authors: Westgaard R H
Published: December 2014

The technique of direct electrical stimulation of denervated muscle was used to study the role of muscle activity per se in controlling the passive electrical properties of muscle fibres. 2. Specific membrane resistance and capacitance of the denervated and the denervated‐stimulated muscle fibres were measured by a sinewave technique at frequencies between 5 and 240 Hz. The parameter values were constant at low frequencies up to a variable transition frequency and declined rapidly at higher frequencies. 3. Following denervation the low‐frequency value of specific membrane resistance increased (2291 omega cm2 for 19‐day denervated fibres vs. 766 omega cm2 for innervated fibres), the specific membrane capacitance declined (2‐7 muF/cm2 vs. 3‐6 muF/cm2) and the transition frequency shifted towards lower frequencies. The specific internal resistance was higher in denervated fibres (301 omega cm for 19‐day denervated fibres vs. 240 omega cm in innervated fibres) apart from a transient decline after 5 days of denervation (164 omega cm). 4. Direct electrical stimulation for 2 weeks beginning on the 5th day after denervation restored all parameters listed above to their original values before denervation. 5. Stimulation arrested in most cases further atrophy from the time of stimulation but did not restore normal fibre size.
Effects of external ions on the synaptic transmission from photorecptors to horizontal cells in the carp retina.
Authors: Kaneko A , Shimazaki H
Published: December 2014

1. Intracellular recordings were made from cones and horizontal cells of the isolated carp retina and the mechanisms of synaptic transmission from cones of horizontal cells were studied by changing the ionic composition of the external medium. 2. Cones were depolarized and their light responses enhanced in low Ca high‐Mg medium. In the same medium, in which chemical transmission is suposed to be blocked, horizontal cells were hyperpolarized and their light responses disappeared. 3. When the synaptic input was removed, the membrane potential of horizontal cells agreed well with Ek. 4. In Na‐free medium both cones and horizontal cells were hyperpolarized and response disappeared. On reaplication of normal Ringer, horizontal cells showed a trenaient membrane potential reversal (inside positive), indicating that the horizontal cell has a high Na permeability under the influence of the endogenous transmitter. 5. Application of La produced little change in cones, while it strongly depolarized horizontal cells...
Axoplasm architecture and physical properties as seen in the Myxicola giant axon.
Authors: Gilbert D S
Published: December 2014

A technique is described for extracting axoplasm from the giant axon of a marine worm, Myxicola infundibulum. The operation can be completed in 10 sec. 2. Axoplasm is pulled from the axon of a living worm as a long, clear cylinder, up to 35 cm long and 70 mg wet weight. The worm regenerates a new giant axon in about 4 months. 3. Myxicola axoplasm is a gel, 87% water, held together by protein neurofilaments. It contains small amounts of mitochondria and vesicles, but no detectable microtubules. 4. The internal structure of the gel is superficially similar to that of yarn. Closer inspection with light and electron microscopy, and X‐ray diffraction, show it to be organized in a hierarchy of helical forms. Squid giant axons have a similar structure. 5. Initial estimates of the bulk physical properties of extracted Myxicola axoplasm give: breaking strength, 1400 g/cm2; specific gravity, 1‐05 g/cm3; birefringence, 1‐6 X 10(‐4); index of refraction, 1‐351; resistivity, 57 omega cm. These average values are shown to be compatible with the observed structure and composition. 6. Despite its mechanical strength, the axoplasm gel is so hydrated that Na+, K+ and homarine diffuse through it at rates approaching those in free solution. Fewer than about 5% of each of these ions are tightly bound to the gel. 7. It is argued that (a) the structure and physical properties of Myxicola axoplasm are representative of those in other axons, (b) the compound helix architecture results from twist of parallel, cross‐linked fibrous proteins, and (c) this sturcture serves as a flexible internal skeleton for nerve cell processes.
A dissociation between fever and prostaglandin concentration in cerebrospinal fluid.
Authors: Cranston W I , Hellon R F , Mitchell D
Published: December 2014

1. Sustained fever has been induced in conscious rabbits by I.V. injection and infusion of endogenous pyrogen. 2. Cerebrospinal fluid (e.s.f.) was sampled from the cisterna magna at hourly intervals. The concentration of prostaglandin increased in parallel with rectal temperature. The prostaglandin was identified as one of the E series. 3. When sodium salicylate (1‐5 m‐mole followed by a continuous infusion of 9 mumole/min) was started 1 hr before endogenous pyrogen, the febrile response to the pyrogen was not significantly diminished but no rise of prostaglandin concentration was detected in c.s.f. 4. This dissociation between fever and prostaglandin concentration means that changes in cisternal prostaglandin concentration cannot be accepted as evidence that prostaglandin mediates the febrile response.
An analysis of the action of cations of the lanthanide series on the mechanical responses of guinea‐pig ileal longitudinal muscle.
Authors: Triggle C R , Triggle D J
Published: December 2014

1. The inhibitory effects of lanthanide cations (Ln3+) on mechanical responses and 45Ca uptake in guinea‐pig ileal longitudinal smooth muscle were studied. 2. Ln3+ strongly inhibited the phasic and tonic component of the response to the muscarinic agonist cis‐2‐methyl‐4‐dimethylaminomethyl‐1,3‐dioxolane methiodide (CD) the two components being affected to the same extent. Inhibition was also obtained for the responses evoked by high K+ but here the effect was mainly on the phasic response, the tonic component was merely delayed. 3. Other members of the Ln3+ series, with the exception of cerium, were found to be more effective than lanthanum in their ability to inhibit the CD response. Thulium, Tm3+, the thirteenth member of the series was the most effective cation. 4. Analysis of 170Tm uptake revealed at least two components. The concentration‐dependence of one component, saturating at 2‐5 x 10(‐6) Tm, corresponded closely to that of the inhibitory effect of Tm3+ on contraction. 5. 170Tm uptake as a function of time showed a secondary rise after 30 min of exposure to the lanthanide. 6. Although 2‐5 x 10(‐6) M‐Tm3+ produced 90% inhibition of the CD and the high K+ induced responses significant reduction of 45Ca uptake by the muscle was only detected when much higher Tm3+ concentrations (greater than or equal 10(‐3) M‐Tm3+) were used. 7. It is concluded that Ln3+ combine with membrane sites specifically involved in Ca2+ translocation during excitation‐contraction coupling.
A voltage‐sensitive persistent calcium conductance in neuronal somata of Helix.
Authors: Eckert R , Lux H D
Published: December 2014

1. An intracellular voltage clamp in conjunction with a patch pipette utilizing feed‐back to monitor local current from the soma membrane were used to analyse transient and stationary currents in bursting pacemaker neurones in Helix pomatia and H. levantina. 2. A weak, net inward current flows during small (less than or equal 20 mV) depolarizations. This current exhibits slow activation kinetics, persistence during prolonged depolarization, and slow turning off at end of depolarization. Consequently, the steady‐state current‐voltage curve exhibits a region of negative resistance from about ‐55 to ‐35 mV. 3. The slow inward current and the negative resistance characteristic are rapidly and completely abolished by substitution of Co2+ or La3+ for Ca2+ and are partially blocked by the Ca‐blocking drug D‐600. Substitution of Tris or glucose for Na+ significantly reduces the inward current only after 15‐20 min exposure, recovery being equally slow. 4. The inward current and the negative resistance characteristic of the I‐V curve are greatly enhanced by Ba2+ substitution for Ca2+. This is ascribed in part to Ba2+ carrying current through the slow inward current channels and in part to a suppression of the late K+ current by Ba2+. 5. The inward current is also present in many non‐bursting neurones but fails to appear as a net inward current due to short circuiting by a leakage current or by the delayed potassium current. In these cells the slow inward current contributes to inward going rectification. Replacement of Ca2+ with Ba2+ enhances the current so as to produce a net inward current during small depolarizations in these neurones. 6. It is concluded that the slow inward current is carried primarily by Ca2+ in the soma membrane of bursting pace‐maker neurones and a number of non‐bursting cells examined in the parietal ganglion of Helix. 7. The sensitivity to small depolarizations and persistence during prolonged depolarization suggests two roles for the Ca system in the generation of slow pace‐maker oscillations. In this model the Ca system contributes to the slow depolarization which constitutes the onset of the pace‐maker wave, and also contributes to the increment in [Ca] in which activates the Ca‐sensitive K+ conductance responsible for repolarization. The inhibition of spontaneous bursting by Ca‐blocking agents supports this model.
Cancellation of rod signals by cones, and cone signals by rods in the cat retina.
Authors: Rodieck R W , Rushton W A
Published: December 2014

1. The interaction of rod and cone signals at the level of cat retinal ganglion cells was studied by a method of light exchange. Two spectrally distinct lights were exchanged in such a manner that the rate of photon catch by rods increased in a stepwise manner at the same moment that the cone rate decreased in the same manner, and vice versa. 2. Under any conditions of adaptation, where both rods and cones contributed to the ganglion‐cell discharge, it was always possible to adjust the ratio of the magnitudes of the rod and cone stimuli so that no change in ganglion‐cell discharge could be detected by listening to the recorded activity via a loudspeaker. We term this condition a silent exchange. 3. On the face of it, the condition of silent exchange arises when rod and cone signals are able to cancel one another, when made opposite in phase by the exchange situation. But was this silence due to a true cancellation of the signals from one photoreceptor type by those of the other type, or was it due to our failure to stimulate the photoreceptors adequately? In order to test whether rod signals can cancel those of cones we bleached both visual pigments and set our exchange apparatus to stimulate the two photoreceptors in the antagonistic manner described above. At first no response could be heard on exchange, for the thresholds of both rods and cones lay above that of our apparatus. But the cones soon recovered and a strong response was heard on exchange. With no change in our stimulating situation, this response diminished with time and silence was again restored. This restoration of silence could not be due to the cones alone, for with time their sensitivity could only further increase. It could only be the increasing sensitivity of the rods that quietened the cone signals. In agreement with this conculsion, the dark‐adaptation curve of the rods showed that they became sensitive to our stimulus at the time that the cones began to be silenced. 4. By means of coloured backgrounds we have also shown the converse, namely that rods signals can be cancelled by those of cones.
Directional differences of impulse spread in trabecular muscle from mammalian heart.
Authors: Clerc L
Published: December 2014

Trabecular bundles from the right ventricle of calf hearts were used. Electrical properties measured by the application of longitudinal current were compared to those measured by the application of transverse current. 2. The following data were obtained on the basis of classical cable analysis: (i) a ratio of 3‐0 for longitudinal to transverse conduction velocity, (ii) a ratio of 3‐6 for intra‐ to extracellular longitudinal resistance, (iii) a ratio of 12‐6 for intra‐ to extracellular transverse resistance, (iv) a ratio of 9‐4 for intracellular transverse to intracellular longitudinal resistance, (v) a ratio of 2‐7 for the extracellular transverse to the extracellular longitudinal resistance. 3. The disparity in conduction velocity could be explained on the sole grounds of differences in the resistivity of the intracellular and extracellular paths for current flow in the two directions, confirming theoretical predictions. 4. The value of the transverse internal resistance can be accounted for on the ground of frequent branching in a three‐dimensional network. There is no need to make the additional assumption of current flow through lateral low resistance pathways between parallel fibres.
Facilitated transport of prostaglandins across the blood—cerebrospinal fluid and blood—brain barriers
Authors: Bito L. Z. , Davson H. , Hollingsworth Jillian R.
Published: December 2014

1. Ventriculo‐cisternal perfusions were performed on rabbits with artificial cerebrospinal fluid containing blue dextran and tritium‐labelled prostaglandin F2α ([3H]PGF2α). In order to study the nature of prostaglandin (PG) transfer across the blood—brain barrier, high concentrations of PGF2α or potential PG transport inhibitors were added to the perfusion fluid after the normal rate of [3H]PGF2α clearance was established.

2. The [3H]PGF2α clearance was inhibited by 10−6 to 10−3
M PGF2α, PGF2β, probenecid, iodipamide or bromcresol green but not by perchlorate.

3. The 3H content of the brain, relative to the 3H‐activity in the ventricular system, was also increased by high concentrations of PGF2α, iodipamide or bromcresol green.

4. It is concluded that the removal of PGs from the extracellular fluids of the brain is mediated by saturable, facilitated transport processes across both the choroidal and extrachoroidal regions of the blood—brain barrier system. In the case of the mammalian brain, such facilitated PG transport appears to be the primary mechanism for the termination of the action of these potent, endogenously produced autacoids.
Genetic dissection of the photoreceptor system in the compound eye of Drosophila melanogaster
Authors: Stark William S. , Walker John A. , Harris William A.
Published: December 2014

1. Three mutations which eliminate specific types of photoreceptors in Drosophila were characterized.

2. Of the eight photoreceptors in each facet, two mutations delete the outer six (R 1‐6). The third eliminates R 7, one of the two central photoreceptors. Double mutants can be constructed in which only photoreceptor R 8 is present.

3. The spectral sensitivities, photopigments, and behavioural properties of these mutants were investigated.

4. R 1‐6 have two sensitivity peaks, near 350 and 470 nm. These receptors contain a rhodopsin with these absorption peaks. It interconverts with a metarhodopsin that absorbs around 570 nm.

5. R 7 is a U.V.‐receptor, containing rhodopsin that absorbs around 370 nm and interconverts with a metarhodopsin which absorbs around 470 nm.

6. R 8 is a non‐adapting blue‐receptor with a third type of rhodopsin.

7. The properties of these photopigments explain the different sensitivities and spectral adaptation phenomena of the various photoreceptors.

8. All the photoreceptors have input into phototaxis. Spectral analysis of this behaviour provides evidence for integration of the input from the different photoreceptors.
Binocular visual mechanisms in cortical areas I and II of the sheep.
Authors: Clarke P G , Donaldson I M , Whitteridge D
Published: December 2014

1. Units were recorded in the primary and secondary visual areas (V1 and V2) of the sheep. They were stimulated binocularly, using an adjustable prism to vary the disparity. 2. Cells in V1 responded optimally to stimuli with very small or zero disparities, but cells in V2 frequently preferred disparities of several degrees crossed or uncrossed. Many cells in V2 were particularly selective to disparity, often giving no response to a monocular stimulus. 3. Cells preferring the same disparity occur in discrete columns, about 400 muM wide. Changes between columns result from a step displacement of the receptive field of one eye. The disparities encoded in successive columns seem to follow a regular sequence: crossed, zero, uncrossed, zero, etc. 4. In both V1 and V2, cells are clustered, perhaps in columns, according to their orientation preference and ocular dominance. In V2, the constant disparity columns appear to be independent of the orientation clusters.
Cholinergic motor neurones in the stomatogastric system of the lobster.
Authors: Marder E
Published: December 2014

1. A study of the neurotransmitters used by each of the eleven types of excitatory motor neurones (identified according to the muscle innervated) of the lobster stomatogastric ganglion was undertaken. 2. The dorsal dilator muscle is innervated by the two motor neurones designated 'PD'. Bath and iontophoretic applications of acetylcholine (ACh) produce contractures and depolarizations respectively in the dorsal dilator muscle. 3. Pharmacological experiments support the cholinergic nature of the excitatory junctional potentials (e.j.p.s) recorded in the dorsal dilator muscle when the PD motor nerve is stimulated. 4. The apparent reversal potentials for the e.j.p.s and the iontophoretic ACh response in the dorsal dilator muscle are the same. 5. On the basis of choline acetyltransferase assays on identified stomatogastric ganglion motor neurone somata and tension measurements on the muscles innervated by each type of stomatogastric ganglion motor neurone, a transmitter candidate was established for each type of motor neurone. Motor neurones named VD, LPG, GM, MG, LG, and DG are putatively cholinergic. L‐Glutamate is a transmitter candidate for the motor neurones called LP, PY, IC, and AM. 6. Potential correlations between the distribution of putatively cholinergic and glutaminergic motor neurones and the electrical coupling among the stomatogastric ganglion motor neurones are discussed.
The distribution of blood flow between individual muscles and non‐muscular tissues in the hind limb of the young ox (Bos taurus): values at thermoneurality and during exposuer to cold.
Authors: Bell A W , Hilditch T E , Horton P W , Thompson G E
Published: December 2014

1. The radioactive microspheres method was used to measure the distribution of blood flow in the hind leg in conscious young steers exposed to thermoneutral and moderately cold environments. Simultaneous measurement of total leg blood flow allowed calculation of blood flow (ml. 100 g tissue‐1 min‐1) to individual muscles and the major non‐muscular tissues in the leg. 2. In the thermoneutral environment, leg blood flow was distributed approximately according to tissue weight, so that about 65% went to muscle and the remainder to bone, skin, connective tissue and fat; 1‐7‐11‐5% of the injected dose of microspheres was found in the lungs, indicating the presence of functioning arteriovenous anastomoses in the leg. 3. During cold exposure leg blood flow increased two‐and‐a‐half fold and 91% of this increase was due to increased blood flow in muscle. This was accompanied by substantial decreases in both total and capillary blood flow in leg skin in three of the four animals. 4. Values for resting tissue blood flow to the six largest individual leg muscles were compared, as well as that for tissue blood flow to the remaining leg muscle. Blood flow in the three large upper thigh muscles (biceps femoris, semimembranosus and semitendinosus) was about half that in muscles in the rest of the leg. 5. Cold exposure caused a threefold increase in total leg muscle blood flow, but the only individual muscles to respond substantially in all four animals were the vastus lateralis and the rectus femoris. Comparison of results from individual animals suggested a relation between total leg blood flow and the number of muscles (apart from vastus lateralis and rectus femoris) involved in shivering. Leg adipose tissue blood flow also increased significantly in the cold.
Mechanisms underlying recurrent inhibition in the sacral parasympathetic outflow to the urinary bladder.
Authors: de Groat W C
Published: December 2014

1. In cats with the sacral dorsal roots cut on one side electrical stimulation (15‐40 c/s) of the central end of the transected ipsilateral pelvic nerve depressed spontaneous bladder contractions. The depression was abolished by transecting the ipsilateral sacral ventral roots. 2. Electrical stimulation of acutely or chronically transected ('deafferented') sacral ventral roots depressed spontaneous bladder contractions and the firing of sacral parasympathetic preganglionic neurones innervating the bladder. The depression of neuronal firing occurred ipsilateral and contralateral to the point of stimulation, but only occurred with stimulation of sacral roots containing preganglionic axons and only with stimulation of sacral roots containing preganglionic axons and only at intensities of stimulation (0‐7‐4V) above the threshold for activation of these axons. 3. The inhibitory responses were not abolished by strychnine administered by micro‐electrophoresis to preganglionic neurones, but were blocked by the intravenous administration of strychnine. 4. The firing of preganglionic neurones elicited by micro‐electrophoretic administration of an excitant amino acid (DL‐homocysteic acid) was not depressed by stimulation of the ventral roots. 5. It is concluded that the inhibition of the sacral outflow to the bladder by stimulation of sacral ventral roots is related to antidromic activation of vesical preganglionic axons. Collaterals of these axons must excite inhibitory interneurones which in turn depress transmission at a site on the micturition reflex pathway prior to the preganglionic neurones.
The association between acidification and electrogenic events in the rat proximal jejunum
Authors: Lucas M. L.
Published: December 2014

1. Simultaneous measurement of hydrogen ion production, transmural potential difference and intermittent short‐circuit current (SCC) was made in the rat proximal jejunum in vitro: similarly, potassium and sodium ion movements were measured to investigate the relationship of acidification to electrogenic events and associated ion movements in the jejunum.

2. Acidification correlated significantly with the short‐circuit current and both were inhibited by 10 m
M serosal ouabain or 10 m
M mucosal aminophylline. Both inhibitors had effects on net potassium movement but not on net sodium movement. Moreover, in isotope studies whereas 10 m
M serosal ouabain reduced the Jms sodium flux, 10 m
M mucosal aminophylline had no effect, i.e. aminophylline can reduce both short‐circuit current and acidification without perceptibly altering the serosally directed sodium flux.

3. In low‐sodium buffers in which acidification still occurs although reduced, transmural potential differences occur of reversed polarity that are apparently unrelated to sodium diffusion potential differences (as evidenced by isotopic sodium efflux experiments) and which could be caused by hydrogen ion production. In low sodium buffers however the inhibitors have opposing effects, ouabain causing an increase and aminophylline a decrease in the reversed potential differences.

4. A model for acidification (that of potassium rather than sodium ion exchange for the hydrogen ion and hydroxyl for chloride ion exchange) is proposed to explain the present experimental findings and other diverse observations in the literature: although either step might be the electrogenic step, acidification must be also considered as a component of the jejunal short‐circuit current.
The nature of the pi1 colour mechanism of W.S. Stiles.
Authors: Pugh E N
Published: December 2014

The ppi1 colour mechanism was isolated by means of Stile's auxiliary field technique: that it is pi1 which is isolated is proven by both test and field action spectra. 2. The fundamental mechanisms of human trichromatic colour vision must satisfy Grassman's law of additivity. The hypothesis that pi1 is one of the three fundamentals is tested by experiments in which pairs (u1, u2) of monochromatic adapting fields are mixed 3. When two fields with wave‐lengths in the neighbourhood of its primary mode (mu1, mu2 less than or equal to 500 nm) are combined, pi1 is field‐additive, consistent with the hypothesis that this portion of the pi1 action spectrum is that of the short‐wave‐length‐sensitive photoreceptors. 4. When a short‐wave‐length adaptation field (mu1 less than or equal to 500 nm) is mixed with a longer wave‐length field (mu2 greater than or equal 550 nm) i1 is strongly non‐additive. This result proves that the long‐wave‐length portion of the pi1 field spectrum is generated at least in part by a signal originating in the long‐ or middle‐wave‐length sensitive cones. 5. Analysis of the additivity failures supports a model of pi1 in which the signal to be detected is generated in the short‐wave‐length cones, and must pass serially through two gain stages: the gain in the first stage is controlled by the short‐wave‐length cones alone; the gain in the second stage is controlled by a signal originating in the middle, or long‐wave‐length cones, or both.
Identification, classification and anatomical segregation of cells with X‐like and Y‐like properties in the lateral geniculate nucleus of old‐world primates.
Authors: Dreher B , Fukada Y , Rodieck R W
Published: December 2014

1. All the cells (158) that we studied in the lateral geniculate nuclei of Macaca nemestrina and Macaca irus could be distinguished as either X‐like or Y‐like on the basis of their responses to tests developed to classify cat retinal and lateral geniculate nucleus cells. These tests include responses to stationary spots, fast moving wands and moving gratings. 2. Response latencies to electrical stimulation of the optic chiasm were determined for 130 cells; no X‐like cell showed a latency shorter than 1‐7 ms, no Y‐like cell showed a latency longer than 1‐6 ms. Primate lateral geniculate nucleus cells with X‐like properties thus receive their excitatory input from retinal cells with slowly conducting axons and these most probably include the tonic ganglion cells described by Gouras (1968, 1969); Y‐like lateral geniculate nucleus cells are driven by retinal cells with faster conducting axons, most probably including the phasic ganglion cells described by Gouras. 3. Wiesel & Hubel (1966) classified monkey lateral geniculate nucleus cells into four main types based on their receptive‐field properties, as revealed by spectrally and spatially distinct stimuli. We find that all Type I and Type II cells show X‐like properties; all type IV cells show Y‐like properties. Type III consists of a subtype that show X‐like properties, here termed Type IIIx, and a subtype that show Y‐like properties, here termed Type IIIy. 4. The first cells encountered as the micro‐electrode reached the lateral geniculate nucleus were always X‐like. In some penetrations only X‐like cells were encountered as the electrode moved downward through the lateral geniculate nucleus. In the remaining penetrations, after recording X‐like cells through most of the lateral geniculate nucleus, Y‐like cells were then encountered. No X‐like cells were found below Y‐like cells. thus these two classes of cells are anatomically segregated within the primate lateral geniculate nucleus. Electrode marking showed the borger between X‐like and Y‐like cells to correspond to the border between the paro‐ and magnocellular layers of the lateral geniculate nucleus. Thus X‐like cells (i.e. Types I, II and IIIx) occur in the parvocellular layers, Y‐like cells (i.e. Types IIIy and IV)in the magnocellular layers.
Noise analysis of drug induced voltage clamp currents in denervated frog muscle fibres.
Authors: Neher E , Sakmann B
Published: December 2014

1. Voltage clamp currents were recorded during iontophoretic application of steady doses of acetylcholine (ACh), carbachol or suberyldicholine to hyperpersensitive extrasynaptic regions of chronically denervated frog muscle fibers. Autocorrelation functions of drug induced current fluctuations were calculated and estimates of conductance gamma and average open time tau of the extrasynaptic ion channels were derived. 2. The average open time of an extrajunctional channel induced by acetylcholine is tauACh = 11 +/‐ 1‐6 msec (+/‐ S.E.) at ‐80 mV and 8 degrees C. Carbachol and suberyldicholine open channels of tauCarb = 3‐9 +/‐ 0‐4 msec and tauSubCh = 19 +/‐ 2‐5 msec (+/‐ S.E.) duration under the same conditions. The average open time of the extrasynaptic channel produced by each drug is three to five times longer than the value found for junctional channels in normal fibres. 3. The average open time of the extrajunctional channel is dependent on temperature and membrane potential. Lowering the temperature or increasing the membrane potential increases the average open time of the channels induced by any one of the drugs. 4. The conductance of a single extrajunctional channel opened by the action of acetylcholine is estimated to be gammaextra = 15 +/‐ 1‐8 pmho (+/‐ S.E.). This is somewhat lower than the value of gammaep = 23 +/‐ 2 pmho (+/‐ S.E.) found for the conductance of a single open channel in the junctional membrane of normal fibres. The extrasynaptic channels opened by the action of carbachol and suberyldicholine have similar conductances to those produced by ACh. 5. The autocorrelation function of drug‐induced current fluctuations, recorded at the former end‐plate region of chronically denervated fibres often shows both a fast and a slow time constant. They correspond in value to the time constant of the autocorrelation function obtained from end‐plate currents in normal fibres and from extrasynaptic currents in denervated fibres respectively. This could indicate that two populations of channels exist at the former end‐plate region of denervated muscle fibres.
The temperature dependence of the movement of potassium and chloride ions associated with nerve impulses.
Authors: Landowne D , Scruggs V
Published: December 2014

1. The influx and efflux of radioactive potassium and chloride across the membrane of the squid giant axon were measured in resting and in stimulated nerves. The measurements were made at room temperature and at 6‐8 degrees C. 2. At room temperature all eight flux measurements were comparable to previously reported values. 3. When the axons were cooled the resting potassium influx decreased with a Q10 of 1‐9 and the resting potassium efflux decreased with a Q10 of 1‐2. 4. With cooling the resting chloride efflux decreased with a Q10 of 1‐3 and the resting chloride influx decreased with a Q10 of 2‐8. This latter value, together with anomalous flux ratios for resting chloride fluxes may indicate an active uptake of chloride ions into the axon. 5. Cooling increased the extra efflux of potassium associated with nerve impulses with a Q10 of 1/1‐5 and increased the extra influx of potassium with a Q10 of 1/3‐3. 6. No extra efflux of chloride was detected at either temperature. Cooling produced no statistically significant change in the extra chloride influx but there was considerable scatter in the data. 7. Fluxes were computed as a function of temperature for standard action potentials with a variety of temperature coefficients for the conductances and rate constants. No single curve could match either the influx or the efflux data.
Statistical fluctuations in charge transfer at Ia synapses on spinal motoneurones.
Authors: Edwards F R , Redman S J , Walmsley B
Published: December 2014

1. Net inward charge is calculated for unitary Ia e.p.s.p.s. evoked in spinal motoneurones. Fluctuations in this charge are used to describe the fluctuations in transmission at the Ia synapse. 2. The statistical details of variation in transmission at Ia synapses are largely obscured by noise, arising from spontaneous activity and recording apparatus. 3. A computational procedure is described, which utilized the measured statistical properties of the recording noise, and the measured charge histogram of the evoked e.p.s.p. (with noise) to calculate the variations in charge due to the e.p.s.p. alone. 4. The fluctuation in charge transmission at Ia synapses are, in general, non‐quantal. Nor are they described by binomial or Poisson statistics. 5. It is suggested that the basic mode of transmission at a single terminal is all‐or‐none. The fluctuations result from the combined effect of failures at several terminals arising from a single afferent fibre. This hypothesis is supported by further analysis of these results in a subsequent paper (Edwards, Redman & Walmysley, 1976a).
Effects of botulinum toxin on neuromuscular transmission in the rat.
Authors: Cull-Candy S G , Lundh H , Thesleff S
Published: December 2014

1. Botulinum toxin (BoTx) type A partially blocks spontaneous transmitter release from nerve terminals in the rat. Minature end‐plate potentials (m.e.p.p.s) are present at all end‐plates, initially with a low frequency but increasing with time after posoning. Their amplitude distribution is at first skew with a predominace of very small m.e.p.p.s but, after a few days, larger than normal m.e.p.p.s appear. 2. Tetanic nerve stimulation, Black Widow Spider Venom, the Caionophore A 23187 or mechanical damage to nerve terminals increases the frequency of m.e.p.p.s and alters the amplitude distribution of m.e.p.p.s towards a normal Gaussian one; the m.e.p.p. size approaches that seen at normal end‐plates. This was seen at any time after poisoning. 3. Nerve stimulation gives rise to end‐plate potentials (e.p.p.s) of low amplitude and high failure rate. Statistical analysis indicates that evoked release is quantal in nature and follows Poisson statistics, quantum size being initially very small, but after a few days approaching normal size. Short‐term tetanic nerve stimulation reversibly increases the quantum content of e.p.p.s and during early stages of paralysis long‐term (2 hr) stimulation causes an apparently permanent increase in quantum size. 4. Raising the extracellular Ca concentration from 2 to 16 mM increases the frequency of m.e.p.p.s in normal muscle but not in BoTx poisoned ones. K‐free medium or ouabain, which are believed to raise the intracellular Ca concentration in nerve terminals, similarly increases m.e.p.p. frequency in normal but not in poisoned muscles. When the Ca‐ionophore A 23187 is used together with high extracellular Ca (greater than 4 mM) massive release of transmitter occurs from poisoned terminals. 5. The extracellular Ca concentration which causes a certain level of transmitter release in reponse to nerve impulses is considerably higher at BoTx poisoned end‐plates than at normal ones. The slope value for Ca dependence of transmitter release is about 1‐5 compared with about 3 at normal end‐plates. 6. Tetraethylammonium (TEA) greatly increases the amount of transmitter released by nerve impulses and restores neuromuscular transmission during all stages of poisoning, although it has not effect on spontaneous transmitter release. In the presence of TEA the power relation between Ca concentration and quantum content at the BoTx poisoned end‐plate is similar to that seen at normal end‐plates. 7. It is suggested that in BoTx poisoning the mechanism for transmitter release has a reduced sensitivity to Ca, and the level for activation by intracellular Ca is elevated. Once the intracellular concentration of Ca is raised to this level, by tetanic nerve stimulation, mechanical injury to nerve terminals, the Ca‐ionophore or the prolongation of the nerve action potential with TEA, augmented transmitter release occurs, similar to that which occurs in normal nerve terminals at a lower level of Ca.
Changes in electrical properties of rat myometrium during gestation and following hormonal treatments.
Authors: Kuriyama H , Suzuki H
Published: December 2014

1. The membrane properties of the rat myometrium, during gestation and following ovarian hormone treatment, have been investigated with the micro‐electrode technique. 2. Spontaneously generated bursts of electrical activity alternating with silent periods were recorded from non‐pregnant, pregnant and post‐partum myometria. The membrane potential was highest during the middle stage of gestation, but the spike amplitude within a burst was not uniform. In the final stage of gestation and during parturition, the membrane potential was low and the spikes within a burst were of low frequency and uniform amplitude. 3. During parturition and post‐partum, a gradual depolarization of the membrane, accompanied by an increase in membrane resistance, occurred before the generation of a burst. 4. Excitability of the membrane fluctuated from a peak just before the generation of a burst to a low after the cessation of a burst. 5. Displacement of the membrane potential by electrical current or by lowering the temperature modified the slope spontaneous depolarization, but the fluctuations of excitability persisted. The Q10 value for the frequency of spontaneous bursts, measured between 36 and 30 degrees C, was 3‐8. 6. Hyperpolarization of the membrane increased the maximum rate of rise of the spike, but beyond ‐70 mV, the rate of rise was reduced. Half‐inactivation of spike generation of spike generation occurred at a membrane potential less negative than the interburst potential, indicating that the current carrying system was not fully activated during parturition. 7. In both normal and spayed rats, oestradiol hyperpolarized the membrane and the burst of spikes was generated hyperpolarized the membrane and the burst of spikes was generated on a sustained depolarization. Progesterone slightly hyperpolarized the membrane and burst discharges occurred without a sustained depolarization. Simultaneous treatment with progesterone and oestradiol produced a plateau potential of long duration during burst discharges. 8. The thickness of the muscle layer, length constant of the tissue and time constant of the membrane were measured during gestation and from spayed rats under various hormonal conditions. The length constant of the tissue was increased by oestradiol and was further increased by simultaneous treatment withoestradiol and progesterone. The increase in tissue thickness appeared to have the most marked influence on the length constant. 9. The resting and active membrane properties of the progresterone treated myometrium were similar to those observed during the middle stages of gestation. The oestradiol‐treated myometrium did not resemble that during the last stages of gestation and parturition, which was simulated by combination of the two hormones, oestradiol preceding progesterone.
An electrophysiological study of the sacral parasympathetic pathway to the colon of the cat.
Authors: de Groat W C , Krier J
Published: December 2014

1. Electrophysiological techniques were used to study the sacral parasympathetic pathway to the colon of the cat. 2. Electrical stimulation of the sacral ventral roots or the pelvic nerve elicited contractions of the colon and firing in nerve filaments on the serosal surface of the colon. Both responses were markedly reduced by the administration of ganglionic blocking agents. It is concluded that sacral preganglionic fibres to the colon make synaptic contacts with extramural ganglion cells. These cells were identified histologically in small ganglia on the serosal surface of the distal colon and rectum. 3. Transmission in extramural colonic ganglia was cholinergic and mediated by nicotinic receptors. Colonic ganglia did not exhibit large recruiting responses during repetitive (1‐4 c/s) preganglionic nerve stimulation or an adrenergic inhibitory mechanism, both of which have been identified in bladder parasympathetic ganglia. It is concluded that colonic ganglia unlike bladder function primarily as simple relay stations and have little potential for modulating the neral activity arising in the central nervus system. 4. The preganglionic input to colonic ganglia was mediated by C fibres with maximal conduction velocities ranging from 0‐5 to 1‐4 m/sec. Bladder ganglia, on the other hand, received a preganglionic input composed of B fibres with maximal conduction velocities ranging from 8 to 10 m/sec. The possible physiological significance of different types of preganglionic fibres in the sacral outflow is discussed.
Drug blockade of open end‐plate channels.
Authors: Adams P R
Published: December 2014

1. The actions of amylobarbitone, thiopentone, methohexitone and methyprylone at voltage‐clamped frog end‐plates were studied. 2. In the presence of barbiturates the conductance change evoked by an iontophoretic carbachol application was reduced by a prepulse of carbachol. The extra inhibition evoked by a prepulse disappeared exponentially with a time constant of 150‐200 ms. 3. Barbiturates produce an increased rate of decay of nerve evoked endplate currents. Tne concentration and voltage dependence of the barbtiruate e.p.c. decay rates tally with the hypothesis that the increased rate of decay is due to block of active receptor‐channel complexes by barbiturates with a rate constant of 10(6) M‐1S‐1. 4. Conductance changes produced by bath applied agonists were depressed by thiopentone, the effect becoming greater the higher the agonist concentration. This effect, and also the observation that the concentration of thiopentone required to depress the bath agonist response is much greater than the apparent dissociation constant for binding to active receptor‐channel complexes calculated from kinetic measurements, suggest that the selectivity for binding to open receptor‐channel complexes is very high. 5. Methyprylone, which is structurally similar to the barbiturates, is only a weak antagonist and shows no interpulse interaction. It was predicted that methyprylone should produce fast and slow components in the e.p.c. decay, and this prediction was verified. 6. In the presence of barbiturates large iontophoretic carbachol applications produce conductance changes which show fast and slow components. Under these conditions the effects of carbachol prepulses become complex. However the effects are qualitatively consistent with the notion that different components of the response are contributed by channels located at various distances from the iontophoretic pipette tip. 7. All the data agree with a model in which the channel has three stages: closed, open and blocked. Only open channels can block, and blocked channels can only open.
The effects of irritation at various levels of the airway upon tracheal mucus secretion in the cat.
Authors: Phipps R J , Richardson P S
Published: December 2014

1. Sulphated glycoprotein output from the trachea, isolated in situ, has been measured in anaesthetized cats by a radio‐isotopic method. The effects of irritation of various parts of the airway on this mucus output were studied. 2. Mechanical stimulation of the nose and nasopharynx increased tracheal mucus output by reflexes which involved parasympathetic and probably also sympathetic motor pathways. 3. Laryngeal stimulation had a similar through the same motor pathways. 4. Inhalation of ammonia vapour into the lower airways reflexly increased mucus output from the isolated trachea. The efferent pathway for this reflex was mainly or entirely parasympathetic. It is argued that the afferent pathway involved cough receptors. 5. Lung inflation, inhalation of histamine aerosol and intravenous injection of phenyl diguanide (which excite mainly lung stretch receptors, lung 'irritant' receptors and alveolar 'J‐receptors' respectively) had no consistent effect on tracheal mucus secretion. 6. The afferent and efferent pathways of these reflexes are discussed.