bluuebunny/crossref_metadata_2025 huggingface dataset:
Acetylcholine receptors: topographic distribution and pharmacological properties of two receptor types on a single molluscan neurone
Authors: Levitan Herbert , Tauc Ladislav
Published: December 2014

1. The iontophoretic application of acetylcholine (ACh) on to identified neurones in the buccal ganglion of the mollusc Navanax produced a biphasic or monophasic membrane potential change which was a function of the current intensity and site of ACh application.

2. Low iontophoretic currents, 200 msec in duration, applied to the somatic surface facing the neuropile, caused a monophasic potential change of 6–10 sec duration, which had a reversal potential of about − 50 mV, varied with changes in the [Cl]o of the bathing medium, and was not blocked by the cholinolytics tested.

3. ACh applied more distal to the soma, in the neuropile, produced a 1‐3 sec monophasic response whose reversal potential was more positive than − 30 mV, varied in amplitude with changes in the [Na]o of the medium, and was blocked by cholinolytics such as tubocurarine, hexamethonium and atropine.

4. With larger iontophoretic currents a biphasic response could be obtained, depolarization followed by hyperpolarization, which represented a superposition of the above monophasic potentials.

5. The cholinomimetics propionylcholine and butyrylcholine caused a biphasic response like that to ACh. Carbamylcholine and tetramethylammonium also produced a biphasic response but with a more prominent Cl component than that to ACh. Acetyl‐β‐methylcholine, oxytremorine and pilocarpine only produced a response comparable to the chloride phase of the ACh response.

6. Anticholinesterases prolonged both phases of the ACh response.

7. It was concluded that each of the identified neurones possess two types of cholinoceptive sites, which are pharmacologically distinct, produced different changes in membrane permeability and are distributed differently over the axo‐somatic membrane complex.
A quantitative description of end‐plate currents
Authors: Magleby K. L. , Stevens C. F.
Published: December 2014

1. End‐plate currents have been studied in glycerol‐treated frog sartorius nerve—muscle preparations with the voltage clamp technique.

2. The effects of temperature on the decay rate of end‐plate currents were investigated over a temperature range from 10 to 30·5° C. The Q10 for the decay constant of end‐plate currents depends somewhat on membrane potential; at — 100 mV the decay constant has a Q10 of 2·7.

3. Peak end‐plate current depends non‐linearly on membrane potential with a decreasing slope conductance associated with hyperpolarization.

4. The ‘instantaneous’ voltage—current relationship for end‐plate channels was determined by causing step changes in membrane potential during end‐plate current flow. This relationship appears to be linear.

5. The interaction of acetylcholine with its receptor is viewed as being analogous to the first step in enzymic catalysis. On this view, acetylcholine binds to its receptor and induces a conformational change which is responsible for opening end‐plate channels. By analogy to the first steps in the catalytic sequence of enzymes, the binding step is very rapid, almost diffusion‐limited, and the conformational change is rate‐limiting.

6. Equations describing this process have been derived. Expressions for the rate constants have also been derived by considering changing dipole moments of the transmitter‐receptor complex associated with the conformational change. As the transmitter‐receptor complex is in the membrane field, different conformational states have different energies, and the rate of conformational change thus depends on membrane potential. The equations thus derived are shown to account adequately for the time course of end‐plate conductance change.
Foetal placental blood flow in the lamb
Authors: Faber J. Job , Green Thomas J.
Published: December 2014

1. Fifteen sheep foetuses of 1·5–5·2 kg body weight were prepared with indwelling arterial and venous catheters for experimentation one to six days later.

2. Unanaesthetized foetuses were found to have mean arterial and central venous blood pressures of 40 ± 1·5 (
S.E. of mean) and 2·0 ± 0·3 (
S.E. of mean) mm Hg respectively, compared to intra‐uterine pressure. Intra‐uterine pressure was 16 ± 0·8 (
S.E. of mean) mm Hg with respect to atmospheric pressure at mid‐uterine level.

3. Mean placental blood flow of the foetuses was 199 ± 20 (
S.E. of mean) ml./(min.kg body wt.). Mean cardiac output in eleven of the foetuses was 658 ± 102 (
S.E. of mean) ml./(min.kg).

4. Mean foetal and maternal colloid osmotic pressures were 17·5 ± 0·7 (
S.E. of mean) and 20·5 ± 0·6 (
S.E. of mean) mm Hg respectively at 38° C.

5. Intravenous infusions into six ewes of 1·8 mole of mannitol and 0·4 mole of NaCl resulted in significant increases in foetal plasma osmolarity, sodium, potassium, and haemoglobin concentrations, without detectable transfer of mannitol to the foetal circulation.

6. In the sheep placenta there is osmotic and hydrostatic equilibration of water. As a consequence, there should be an interaction between foetal placental blood flow and foetal water exchange with the maternal circulation. It was concluded that this interaction tends to stabilize foetal placental blood flow.
Dogfish ganglion cell discharge resulting from extrinsic polarization of the horizontal cells
Authors: Naka Ken-Ichi , Witkovsky Paul
Published: December 2014

1. Ganglion cell discharges were evoked by extrinsic polarization of the horizontal cells in the retina of the smooth dogfish (Mustelus canis). Depolarization of the horizontal cell gave rise to a discharge similar to that evoked by a spot of light (centre type response) and hyperpolarization of the horizontal cell, a discharge similar to that by an annulus (surround type response).

2. Procion dye injection established that the current‐passing electrode was sometimes located in the external horizontal cell. Other possibilities, such as middle and internal horizontal cells, were neither confirmed nor excluded.

3. Activation of ganglion cells by current was possible under completely dark‐adapted conditions and for several log units above this level.

4. Depolarizing current enhanced the ganglion cell response evoked by a light spot in the centre of its receptive field; hyperpolarizing current antagonized the response to the same flash.

5. The results are consistent with the supposition that a potential change in the horizontal cell, irrespective of its polarity, or whether produced by light or current, spreads within a laminar layer (the S‐space). The effect of the potential change is to modulate the response of bipolar cells and their input into the ganglion cell.
The role of the solitary and paramedian reticular nuclei in mediating cardiovascular reflex responses from carotid baro‐ and chemoreceptors
Authors: Miura Mitsuhiko , Reis Donald J.
Published: December 2014

1. With dye‐filled micro‐electrodes single neurones in the medulla of anaesthetized paralysed cats were identified which: (a) fired rhythmically in synchrony with or were modulated by the cardiac cycle, and which ceased firing with occlusion of the ipsilateral common carotid artery (carotid sinus baroreceptor neurones); (b) were excited by stimulation of carotid body chemoreceptors by close intra‐arterial injection of lobeline into the thyroid artery (carotid body chemoreceptor neurones).

2. Twelve carotid baroreceptor neurones were identified, in thirty‐three cats, nine of which were localized in the intermediate area of the nucleus of the solitary tract (NTS) within 1 mm ahead of or behind the obex; three units were located either in the parahypoglossal area or the dorsal portion of the paramedian reticular nucleus (PRN).

3. Of the twenty‐one carotid chemoreceptor neurones which were identified, thirteen were localized in the NTS, three in the parahypoglossal area and four in the dorsal PRN.

4. Bilateral lesions of the paramedian reticular area of medulla destroying the PRN, abolished or reversed the depressor response to electrical stimulation of myelinated fibres of the carotid sinus nerve (CSN), attenuated the depressor response to carotid sinus stretch and augmented the pressor response to chemoreceptor stimulation by lobeline. Such lesions did not significantly alter the reflex heart rate responses.

5. Small lesions of the NTS within an area 1 mm rostral to the obex abolished all reflex blood pressure and heart rate responses to electrical stimulation of the CSN or natural stimulation of carotid baro‐ or chemoreceptors.

6. Baroreceptors and chemoreceptors of the CSN project both to the intermediate zone of the NTS and to more medial areas of the medulla, particularly the dorsal PRN and parahypoglossal area.

7. The PRN serves to mediate the reflex depressor, but not cardio‐vagal, response from myelinated baroreceptors and buffers the pressor responses from chemoreceptors; it may serve as an important area integrating cardiovascular activity descending from forebrain, brain stem and cerebellum with baroreceptor reflexes.

8. Cardiovascular reflex responses arising from non‐myelinated baroreceptors and all chemoreceptors are mediated by neurones in the intermediate area of the NTS.
Permeability of urinary bladder of Rana cancrivora to urea in the presence of oxytocin
Authors: Chew Miow‐Miow , Elliott Annie B. , Wong H. Y.
Published: December 2014

1. When Rana cancrivora collected from fresh water had been exposed for 3 days to saline solutions having osmolalities from 280 to 690 m‐osmole/kg, urea concentrations in plasma and urine appeared to come into equilibrium, and were from 70 to 200 m‐mole/l.

2. Plasma urea level of fresh water R. cancrivora (48 m‐mole/l.) was doubled (82 m‐mole/l.) after 8 hr of exposure to 270 m‐osmolal saline. It continued the same after 24 hr of exposure.

3. When isolated urinary bladders of R. cancrivora were exposed to Ringer on the serosal aspect and one‐fifth Ringer on the mucosal aspect, then in response to this osmotic difference of 190 m‐osmole/kg, the rate of fluid movement (mucosa to serosa), which was 10·3(±2) μl./cm2.hr, was not significantly altered when up to 60% of the NaCl of the Ringer solution was substituted by urea.

4. Under the same circumstances, when oxytocin (50 m‐u./ml.) was present in the serosal solution, the rate of fluid movement (mucosa to serosa) was 133·2(±7·9) μl./cm2.hr in the absence of urea; it was progressively decreased by the presence of urea until, when 80% of the NaCl had been substituted by urea, the rate of fluid movement was reduced to 14·5(±4·0) μl./cm2.hr.

5. The diminished rate of fluid movement under the above circumstances could not be correlated with serosal urea concentration, with serosal availability of Na+, nor with Na+ concentration difference across the bladder wall. It appeared to be directly related to the ‘non‐urea osmotic difference’ across the bladder wall provided by solutes other than urea.

6. When isolated bladders were exposed to an osmotic difference of 190 m‐osmole/kg, but having 25 m
M urea present in the mucosal solution, then fluid moved from mucosa to serosa at a rate of 10·4(±1·3) μl./cm2.hr in the absence of oxytocin and 124(±9) μl./cm2.hr when oxytocin (50 m‐u./ml.) was present. In the former case no urea passed across the bladder wall, but in the latter case urea passed from mucosa to serosa at a rate of 3·16(±0·3) μmole/cm2.hr. The fluid moving from mucosa to serosa thus contained urea 25·5 m‐mole/l.

7. Vasotocin (10−9
M), which is equipotent with oxytocin (50 m‐u./ml.) in affecting permeability of the isolated urinary bladder to water, was also equipotent in producing a reduced rate of water fluid movement in the presence of 40% urea (vasotocin, 63 μl./cm2.hr; oxytocin, 59 μl./cm2.hr).

8. When groups of frogs were cystectomized, and other groups of frogs were sham‐operated, then after 48 hr of exposure to fresh water or to 300 m‐osmolal saline the sham‐operated frogs had plasma urea level raised from 20 m‐mole/l. (fresh water) to 42 m‐mole/l. (saline), while the cystectomized frogs had 20 m‐mole/l. (fresh water) and 26 m‐mole/l. (saline).

9. The hypothesis is presented that hormone‐induced permeability of the urinary bladder to urea contributes to the immediate adjustment of plasma urea level by which R. cancrivora survives when exposed to high environmental salinity.
Reflex effects of laryngeal irritation on the pattern of breathing and total lung resistance
Authors: Boushey H. A. , Richardson P. S. , Widdicombe J. G.
Published: December 2014

1. The reflex responses to chemical and mechanical irritation of the laryngeal mucosa have been studied by applying stimuli to the open larynx of tracheostomized cats while monitoring ventilatory and circulatory variables. The responses were studied before and after vagotomy and before and after denervation of the larynx by transection of the superior and recurrent laryngeal nerves.

2. The immediate response to laryngeal irritation was not consistent. The most frequent responses were coughing, and slowing and deepening of breathing without coughing. Less common were expiratory apnoea and sustained, simultaneous inspiratory and expiratory activity.

3. A consistent late change in the pattern of breathing occurred. Slower, deeper breathing with increased total lung resistance (bronchoconstriction) was seen after the immediate response abated.

4. The slowing of breathing was due to prolongation of both the time for inspiration and the time for expiration. The rate of increase in phrenic nerve activity was also slowed.

5. Vagotomy did not alter qualitatively the reflex changes in the pattern of breathing, although bronchoconstriction no longer occurred.

6. The responses were abolished by denervation of the larynx.
Three acetylcholine receptors in Aplysia neurones
Authors: Kehoe Jacsue
Published: December 2014

1. In the pleural ganglion of Aplysia californica, groups of cells were identified that respond differently to an iontophoretic injection of ACh. The anterior neurones are excited by ACh, whereas the medial cells are inhibited. The inhibitory response is biphasic, consisting of a short‐latency, rapid component and a longer‐latency, slow component. Homologous responses (e.p.s.p.s in the anterior cells and a two‐component inhibitory response in the medial cells) are evoked in these same cell groups by stimulation of an identifiable presynaptic neurone.

2. The e.p.s.p. and the corresponding ACh potential are completely eliminated by hexamethonium which has no effect on either of the inhibitory potentials. Both the e.p.s.p. and the rapid i.p.s.p. (and the corresponding ACh potentials) are blocked by tubocurarine, dihydro‐β‐erythroidine, strychnine and brucine. These drugs have no effect on the slow inhibitory potential, whether elicited synaptically or by ACh injection. The slow response can be selectively blocked by methylxylocholine, tetraethylammonium (TEA), and phenyltrimethylammonium (PTMA). Since the three types of potentials were found to be differentially affected by ACh antagonists, it was concluded that the various responses are due to activation of three different ACh receptors.

3. Of the cholinomimetics tested, only carbamylcholine imitates all three actions of ACh. Nicotinic agents, which were shown to activate the two curare‐sensitive receptors, have no stimulating effect on the curare‐insensitive receptor. This latter receptor can be selectively stimulated by arecoline. The cholinomimetics were shown to have a secondary blocking effect on the receptor(s) they stimulate.

4. Muscarine, even at high doses, is ineffective as either a stimulating or a blocking agent on any of the three receptor types. The muscarinelike drugs oxotremorine, methacholine, and pilocarpine have only weak and non‐specific cholinomimetic action on these receptors. Their blocking effects are likewise negligible.

5. The two curare‐sensitive receptors, which are presumably the same as those described by Tauc & Gerschenfeld (1962), respond like vertebrate nicotinic receptors to both cholinomimetics and cholinolytics. The third receptor type, on the other hand, has a unique pharmacological profile. It is unaffected by both nicotine and muscarine, and is blocked neither by curare nor by atropine. Knowing that it can be stimulated by arecoline and blocked by methylxylocholine, TEA and PTMA does not facilitate its incorporation into the classical scheme of cholinergic receptors.
The physiological role of three acetylcholine receptors in synaptic transmission in Aplysia
Authors: Kehoe Jacsue
Published: December 2014

1. It is shown that a single presumably cholinergic presynaptic neurone can mediate, monosynaptically, multicomponent responses in a given cell and different responses in different cells.

2. Complex responses (whether evoked synaptically or by ACh injection) are shown to be the result of the coexistence on a given post‐synaptic neurone of more than one of three cholinergic receptor types previously described. Likewise, different responses in different cells are due to the fact that different post‐synaptic neurones bear different combinations of these three receptors.

3. Pharmacological analysis shows that the multicomponent nature of many of the responses is not always evident: what appears, under normal conditions, to be a single‐component excitatory potential can be shown often to be a complex response consisting of superimposed e.p.s.p.s and rapid i.p.s.p.s which are sometimes, though not always, accompanied by a slow i.p.s.p.

4. Although which and how many of the three receptor types is the major factor contributing to the type of response observed, in the case of some of the synaptic potentials certain other factors were found to contribute to the final response form. First, in the large cells of the visceral ganglion, as well as in the left giant cell of the pleural ganglion, there is a marked ‘electrical separation’ between the region in which the synaptic currents are generated and the point of recording. This ‘electrical distance’ often altered the inversion potential, and sometimes the form of the responses. Secondly, in some visceral neurones, activation of the cholinergic presynaptic neurone L10 causes (either directly or indirectly) a potential change which cannot be accounted for in terms of the activation of cholinergic receptors. This ‘non‐cholinergic’ response (not imitated by an ionophoretic injection of ACh) is unmasked by the blocking of all three cholinergic receptors. It contributes differentially in different cells to the total response pattern produced by L10 under normal conditions, but its contribution is often characterized by a late hyperpolarizing phase which appears to be impossible to invert. This phase has been shown, however, to be dependent upon the potassium concentration in the extracellular space surrounding the synapse.

4. It is tentatively suggested that this residual, non‐cholinergic element of the synaptic response in some visceral cells be the result of the activation of an electrical synapse.
Some quantitative observations upon the responses of neuroglial cells which follow axotomy of adjacent neurones
Authors: Watson W. E.
Published: December 2014

1. The dry mass and nucleic acid content of freshly isolated neuroglial cells and of their nucleoli were measured by interference microscopy and ultraviolet absorption microspectrography. The incorporation of tritiated nucleosides and of an amino acid was followed autoradiographically.

2. After hypoglossal axotomy in the adult rat hypertrophy of astrocytes of the hypoglossal nucleus occurred in a biphasic manner. The first phase lasted from days 1–10 and was accompanied by a small degree of astrocytic hyperplasia, and the second from days 20–80. Hypertrophy of oligodendrocytes accompanied the second phase of the astrocytic response.

3. When severed axons failed to reinnervate denervated muscle, the second phase of the astrocytic response was markedly reduced and the hypertrophy of oligodendrocytes did not occur.

4. If the severed axons re‐innervated denervated muscle after a controlled delay, the second phase of the astrocytic response and the oligodendroglial hypertrophy was also delayed.

5. Injection of botulinum toxin into the tongue caused changes in astrocytes and oligondendrocytes closely resembling those found after axotomy.

6. Transient astrocytic hypertrophy occurred in the uninjured right hypoglossal nucleus, and had a different time course to the changes occurring on the injured side.

7. The results are discussed in relation to changes in the metabolism and to alterations in the dendritic fields of injured neurones, previously measured in these circumstances.
Uptake of [3H]ouabain and Na pump turnover rates in cells cultured in ouabain
Authors: Boardman Lesley J. , Lamb J. F. , McCall D.
Published: December 2014

1. The binding of [3H]ouabain to fresh Girardi and Hela cells and to those cultured in low concentrations of ouabain for 24 hr has been measured.

2. Fresh cells bind 1·6–2·2 × 106 molecules of ouabain* per cell from K‐free Krebs, but less than 0·3 × 106 molecules from 15 m
M‐[K]o Krebs. The ouabain* binds with a t½ of about 8 min from K‐free 2 × 10−7
M ouabain* and is released with a t½ of about 20 hr. Cells in a poor condition probably exchange ouabain more quickly.

3. Cells incubated in ouabain* for 24 hr bind ouabain in amounts dependent on the [ouabain] and the external [K]. At the highest [ouabain] used the total amount bound exceeds that bound by fresh cells. Lowering [K]o in the medium increases the maximum ouabain which is bound.

4. Cells incubated in ouabain* for 24 hr bind an additional amount of ouabain when exposed to 2 × 10−7
M ouabain* in K‐free Krebs.

5. There is a close relationship between the% of the total ouabain bound in 24 hr and the% inhibition of the Na efflux suggesting that this ouabain is bound to the Na pumps.

6. Radiochromatography of the counts recovered from the cells showed that it migrated to the same place as the applied [3H]ouabain. The wash‐off rate of ouabain bound to cells during incubation is similar to that from fresh cells, both tests suggesting that the ouabain exists in the same state in the cells.

7. The number of Na ions extruded per pump is constant at about 60 sec−1 in fresh cells and those pre‐incubated in ouabain.

8. The total ouabain bound by the cells is closely related to the [Na]i in cells pre‐incubated in ouabain but is unaffected by it in fresh cells where [Na]i is raised acutely.

9. These results are compatible with the hypothesis that partial blocking of Na pumps leads to the production of more pumping sites by the cell.
Miniature end‐plate currents and potentials generated by quanta of acetylcholine in glycerol‐treated toad sartorius fibres
Authors: Gage Peter W. , McBurney Robert N.
Published: December 2014

1. Part of the end‐plate region of glycerol‐treated toad sartorius muscle fibres in a hypertonic solution was voltage‐clamped using two microelectrodes. The control was adequate for recording miniature end‐plate currents (m.e.p.c.s) in the vicinity of the electrodes only, at clamp potentials from — 20 to — 100 mV. At any potential, the peak amplitude of m.e.p.c.s varied widely but their mean amplitude was linearly related to clamp potential. The equilibrium potential, obtained by extrapolation, was more positive than in normal fibres.

2. The growth phase of m.e.p.c.s was linear and rapid (< 0·7 msec). The decay phase was exponential. The time constant of decay of m.e.p.c.s was affected by temperature, and increased as the membrane potential was increased. At 20° C, the time constant of decay ranged from 0·8 to 3·8 msec at membrane potentials from — 20 to — 100 mV.

3. The mean conductance change caused by a quantum of acetylcholine was 5·5 × 10−8 mho.

4. Voltage responses to rectangular current injections through one electrode were recorded with three other electrodes in the end‐plate region of glycerol‐treated fibres. Miniature end‐plate potentials (m.e.p.p.s) were also recorded with the same four electrodes.

5. The decrement of both DC voltage responses and m.e.p.p.s along a fibre was exponential but the m.e.p.p. ‘space constant’ was significantly shorter than the DC space constant.
Acetylcholine and lobster sensory neurones
Authors: Barker David L. , Herbert Edward , Hildebrand John G. , Kravitz Edward A.
Published: December 2014

Experiments are presented in support of the hypothesis that acetylcholine functions as a sensory transmitter in the lobster nervous system.

1. Several different peripheral sensory structures incorporate radioactive choline into acetylcholine. The preparation most enriched in sensory as opposed to other nervous elements (the antennular sense organs of the distal outer flagellum) does not incorporate significant amounts of glutamate, tyrosine or tryptophan into any of the other major transmitter candidates.

2. There is a parallel between the distribution of the enzyme choline acetyltransferase and the proportion of sensory fibres in nervous tissue from many parts of the lobster nervous system.

3. Isolated sensory axons contain at least 500 times as much choline acetyltransferase per cm of axon as do efferent excitatory and inhibitory fibres.

4. Abdominal ganglia and root stumps show a decline in the rate of incorporation of choline into acetylcholine 2 to 8 weeks after severing the first and second roots bilaterally (leaving the connectives and third roots intact). Extracts of the root stumps exhibit a significantly lower level of choline acetyltransferase 2 weeks after this operation.

5. Curare and atropine partially block an identified sensory synapse in the lobster abdominal ganglion.
After‐images on backgrounds of different luminance: a new phenomenon and a hypothesis
Authors: Carpenter R. H. S.
Published: December 2014

1. After‐images may be caused to vanish suddenly and reversibly by viewing them against a background of suitable luminance Ie.

2. The value of Ie at any moment is not related to any parameter (intensity, colour, duration, time) describing the stimulus that caused the after‐image.

3. On the other hand, Ie is very closely related to the immediate adaptational history of the eye, so that viewing a dark background for a few seconds lowers, and a light one raises, the value of Ie.

4. It is suggested that the signal conveying sensations of relative brightness in this situation is related to the rate of change of concentration of an intermediate photo‐product decaying spontaneously with a time constant of some 14 sec.
A second neural mechanism of binocular depth discrimination
Authors: Blakemore Colin , Fiorentini Adriana , Maffei Lamberto
Published: December 2014

1. Rotation of an object about its horizontal axis, towards or away from the viewer's eyes, usually causes the images of its contours to have slightly different orientations on the two retinae.

2. We recorded action potentials from binocular neurones in the cat's visual cortex and measured their orientation‐selectivity carefully in both eyes.

3. The optimal orientation for a single cell is not necessarily identical on both retinae. For a large sample of cells there is a range of more than + 15° (
S.D. about 6–9°) in the difference of preferred orientation in the two eyes. These interocular differences in receptive field properties cannot be attributed to rotation of the eyes or to the errors of measurement.

4. During simultaneous binocular stimulation the images must not only lie in the correct place on both retinae but also have exactly the right orientation for both receptive fields in order to elicit the maximum response from a neurone.

5. Therefore certain binocular cells respond specifically to objects tilted in three‐dimensional space towards the cat, or away from it.
The effects of calcium and magnesium on statistical release parameters at the crayfish neuromuscular junction
Authors: Wernig A.
Published: December 2014

1. Transmitter release at excitatory neuromuscular junctions of crayfish muscle was studied at low temperature by recording synaptic potentials with extracellular micro‐electrodes.

2. Increasing the Ca concentration in the bathing solution produced an increase in the average number of quanta released per nerve stimulus (m). Increasing the Mg concentration resulted in a decrease in m.

3. Statistical analysis of fluctuations in the quantal release from trial to trial, assuming binomial statistics, indicated that both the changes in m were due to changes in the average quantal release probability (p).
Renal handling of phenol red. I. A comparative study on the accumulation of phenol red and p‐aminohippurate in rabbit kidney tubules in vitro
Authors: Sheikh M. Iqbal
Published: December 2014

1. The characteristics of renal accumulation of phenol red and p‐aminohippurate (PAH) by slices of rabbit kidney cortex suspended in an electrolyte medium have been compared.

2. It has been found that at low medium concentrations the accumulation of phenol red is about 4–5 times as high as that of PAH. Furthermore, phenol red is accumulated by the renal tissue under anaerobic conditions, in contrast to PAH.

3. Experiments involving incubation of slices at low temperatures and addition of various metabolic inhibitors to the medium, indicate that the anaerobic accumulation of phenol red is due to binding to cellular constituents. This conclusion is corroborated by studies on renal homogenates from which it appears that phenol red is bound predominantly to the microsomal and mitochondrial fraction.

4. The aerobic accumulation of phenol red is less susceptible to inhibition by probenecid, 2,4‐dinitrophenol (DNP), and octanoate than is that of PAH. Besides, probenecid, DNP, and octanoate inhibit phenol red binding to the microsomal fraction, whereas mitochondrial binding of phenol red is unaffected by the presence of these substances.

5. Fumarate and succinate affect the aerobic accumulation of phenol red and PAH to the same degree. Furthermore, fumarate, succinate, and PAH do not alter anaerobic accumulation of phenol red.

6. It is concluded that probenecid, DNP, and octanoate cause more inhibition of organic anion transport than fumarate, succinate, and PAH because of lipophilic interaction with the membrane. The pronounced resistance of phenol red accumulation to inhibition by lipophilic inhibitors is probably due to the ability of the indicator dye to displace these substances from binding sites on the transporting membranes.
Bile salt and non‐bile salt components in bile affecting micellar cholesterol uptake by rat intestine in vitro
Authors: Rampone Alfred J.
Published: December 2014

1. The uptake of micellar cholesterol was measured in sacs of the upper half of everted rat intestine. Sacs of 20 cm length were incubated 1 hr in 25 ml. phosphate buffer containing fatty acid, monoglyceride and 3H‐labelled cholesterol in micellar form with the bile salt, sodium taurocholate, as the dispersing agent.

2. Sacs obtained from bile fistula rats (bile duct cannulated 48 hr previously) took up more than twice as much cholesterol as did sacs obtained from untreated control rats.

3. In experiments utilizing bile‐deficient sacs increasing the sodium taurocholate concentration caused an increase in cholesterol uptake. Conversely, adding a small amount of whole bile caused a decrease in cholesterol uptake.

4. The inhibitory effects of the bile were greatly enhanced if the bile was pre‐treated with cholestyramine to remove the bile salts.

5. It is concluded that bile has a variable effect on intestinal cholesterol absorption depending upon its relative concentration of bile salt and a non‐bile salt component having opposite actions.

6. It is suggested that the variable effect may be related to the physico‐chemical dispersion of cholesterol and that the non‐bile salt component may be lecithin.
Central projections of gastric afferent vagal inputs
Authors: Harding R. , Leek B. F.
Published: December 2014

1. The medulla oblongata of thirteen halothane‐anaesthetized, decerebellate sheep was explored systematically with recording micro‐electrodes.

2. The nervous activity recorded was designated either ‘cyclical’, if it was related to the periodic vagal outflow responsible for primary cycle movements of the reticulo‐rumen, or ‘afferent‐like’, if it was directly related to mechanical stimulation of the reticulum or the abomasum.

3. Forms of mechanical stimulation were used which were known (from earlier ‘single afferent fibre’ studies) to evoke characteristic and distinguishable responses from four receptor types, i.e. reticular tension receptors, reticular epithelial receptors, abomasal tension receptors and abomasal mucosal receptors.

4. Micro‐electrode penetrations were made within a zone 4 mm lateral to the mid line, 6 mm rostral to and 2·5 mm caudal to the obex. In certain regions, ‘afferent‐like activity’ was recorded, which corresponded to the discharge properties of one or more of the above receptor types.

5. Units were sometimes excited or inhibited by more than one kind of receptor excitation, thus demonstrating the possibilities of a convergence of afferent projections and either a direct or a reciprocal relationship between receptor activity and central nervous ‘afferent‐like activity’.

6. It is concluded that most, if not all, of the ‘afferent‐like activity’ was recorded from the vicinity of interneurones.

7. There was a partially overlapping viscerotopic organization of ‘afferent‐like activity’ derived from abomasal and from reticular receptors.

8. Regions showing ‘afferent‐like activity’ were located dorso‐laterally to regions showing ‘cyclical activity’ although there was some overlap between the two regions.

9. ‘Afferent‐like activity’ was recorded from regions which included the dorso‐lateral part of the dorsal vagal motor nucleus, the adjacent reticular formation and the nucleus of the solitary tract between transverse planes 3 mm rostral to the obex and 1 mm caudal to the obex.

10. Some of the gastric afferent vagal inputs were projected to contralateral locations via unidentified commissural connexions.
Contrasts in spatial organization of receptive fields at geniculate and retinal levels: centre surround and outer surround
Authors: Hammond P.
Published: December 2014

1. The organization of receptive fields of retinal ganglion cells and A‐laminae cells from the dorsal lateral geniculate nucleus (LGN) of the cat are compared under identical conditions. Some aspects of the geniculate data have been given elsewhere (Hammond, 1972b).

2. The receptive fields of geniculate cells consist of three zones — centre, antagonistic surround and synergistic outer surround — compared with only two for retinal cells. This result further supports the theory that the centre and surround of geniculate cell receptive fields derive from convergent, but discrete, retinal inputs.

3. The surrounds of geniculate receptive fields are known to be more powerfully antagonistic on their centres than is true of retinal cells. This relationship is re‐examined.

4. Unlike geniculate fields, the locus of maximum sensitivity for the receptive field surround of retinal cells is not invariant either to stimulus geometry or adaptational state.

5. The latter result strongly suggests that the surround mechanism for retinal cells extends through the centre of the field. It establishes unequivocally that the overlap between receptive field centre and surround mechanisms, only marginal in geniculate, is very extensive indeed in retina.
The contractile properties of human motor units during voluntary isometric contractions
Authors: Milner‐Brown H. S. , Stein R. B. , Yemm R.
Published: December 2014

1. The electrical activity of single motor units has been recorded from the first dorsal interosseus muscle of normal human subjects during voluntary, isometric contractions, together with the force generated by the muscle.

2. By averaging the force correlated with the impulses from a single motor unit, the contraction time and twitch tension generated by that motor unit could be measured. When the rate of discharge was limited, either voluntarily or by automatic selection of intervals for analysis, the time for the tension to decline to half its maximum value (half‐relaxation time) could also be measured for some motor units.

3. Under our experimental conditions the trains of impulses from different motor units in most subjects were generated quite independently as tested by (a) measuring the correlation between activity in single units and that in the whole muscle as recorded by the surface electromyogram (e.m.g.), (b) measuring the cross‐correlations between pairs of single units and (c) comparing the tension generated by stimulating single motor units with the average tension correlated in time with voluntary activity of single units in the same location.

4. In one normal subject evidence of synchronization between separate motor units was obtained. Cross‐correlation studies suggested that the cause of the synchronization was the presence of substantial common excitation received by the various motor units in the muscle.

5. The frequency response for the contractions of single motor units was well fitted by that for a linear, second‐order system with nearly critical damping. However, when stimulation of a few motor units was superimposed on a voluntary contraction, underdamped (oscillatory) responses were seen which were probably of reflex origin.

6. The significance of these results in relation to the normal postural tremor in hand muscles is discussed.
Cumulative and persistent effects of nerve terminal depolarization on transmitter release
Authors: Cooke J. D. , Quastel D. M. J.
Published: December 2014

1. Following focal depolarization of rat motor nerve terminals there could often be observed an ‘after‐discharge’ of m.e.p.p.s with transient frequencies of up to 1000/sec. This after‐discharge was graded with intensity and duration of the previous depolarization.

2. Following pulses which were relatively short (about 1 sec) and not too large (< —100 mV local extracellular potential field) the logarithm of m.e.p.p. frequency fell exponentially. With larger or longer pulses there was a tail to the after‐discharge which could persist for several minutes.

3. M.e.p.p. frequency during an after‐discharge was not inhibited appreciably by nerve terminal hyperpolarization, raised [Ca] (8 m
M) or lowered pH.

4. Measured as a multiplication of spontaneous m.e.p.p. frequency after‐discharge was depressed in solution containing no Ca2+ and added 1 m
M‐MgEDTA but equal in 0·125 m
M‐Ca2+ or 2 m
M‐Sr2+ to that in 2 m
M‐Ca2+ or 8 m
M‐Ca2+.

5. During an after‐discharge the multiplication of m.e.p.p. frequency by focal nerve terminal depolarization or raised K+ was reduced. This phenomenon was termed ‘uncoupling’.

6. It was concluded that the after‐discharge is not caused by a persistent rise of K+ concentration in the synaptic cleft, nor by a maintained nerve terminal depolarization.

7. In preparations depolarized by raised K+ m.e.p.p. frequency during a relatively small focal depolarizing pulse rose continuously, after an initial rapid rise, and after the pulse there was a tail of increased m.e.p.p. frequency. The magnitude of the rise during the pulse and the tail after it were similar on, a logarithmic basis; during both processes the logarithm of m.e.p.p. frequency usually followed (approximately) an exponential time course.

8. The relative magnitude of the slow effect of depolarization, as compared with the fast effect, was increased by lowering [Ca] or increasing [Mg], and the slow effect of depolarization in contrast to the fast effect was found to exist in the presence of Ca reduced to about 10−7
M, but only during pulses. At this [Ca] there was no rapid response to depolarization. At [Ca] about 10−10
M, there was no response at all of m.e.p.p. frequency to nerve terminal depolarization.

9. The results are discussed, and compared with similar data referring to ‘facilitation’ and ‘post‐tetanic potentiation’. It is concluded that these and the slow effect of depolarization represent the same phenomenon, a response of the transmitter release system which can be distinguished from the fast response in terms of ionic requirement as well as time course.
The responses of cells in the rat thalamus to mechanical movements of the whiskers
Authors: Waite Phil M. E.
Published: December 2014

1. The responses of single cells to mechanical movements of individual whiskers have been recorded from the ventro‐basal complex of the thalamus, in rats under urethane or barbiturate anaesthesia.

2. With ramp‐shaped displacements of a whisker above a critical velocity, the cells gave a short latency response of 1–5 impulses, while with sinusoidal movement (1–35 Hz) they usually responded with 1–2 impulses per cycle.

3. The cells did not respond to maintained deflexions of a whisker. Small static displacements did not modify the response to a superimposed movement; larger static displacements reduced or abolished the response.

4. Three‐quarters of the cells were found to be particularly sensitive to movements in one quadrant (90° or less). For any one cell, there was no obvious relationship between the most sensitive direction and the position of the whisker on the face.

5. The ramp amplitude appeared to have little effect on the response. However, increases in ramp velocity decreased the response latency and, in some cells, increased the number of impulses per ramp.

6. Other studies have shown that most afferent nerve fibres from whiskers give slowly adapting responses and the possible modification of these thalamic responses, by anaesthesia, is discussed.
Properties of sustained and transient ganglion cells in the cat retina
Authors: Cleland B. G. , Levick W. R. , Sanderson K. J.
Published: December 2014

1. The functional basis for a sustained/transient classification of cat retinal ganglion cells has been strengthened by quantitative measurements of the sizes of the centre and surround components of receptive fields. Transient cells had larger surrounds than sustained; the distributions were non‐overlapping. Although the distributions of centre sizes overlapped, the transient cells had very significantly larger centres on average.

2. There were characteristic differences in area‐threshold and annulus‐threshold curves and shapes of responses to brief and long flashes of light, and relative differences in the nature of surround adaptation and maintained discharge rates.

3. The distinction of sustained from transient units survived over a wide range of backgrounds including the two principle reorganizations of function: relative weakening of surround components at low background; Purkinjě shift at high.

4. Sustained and transient units were differentially distributed in the retina: there was an overwhelming preponderance of sustained units in the area centralis.

5. It is proposed that the transient units are the so‐called multidendritedeep cells and the sustained units are the variously styled small ganglion cells.
Effects of electrogenic sodium pumping on the membrane potential of longitudinal smooth muscle from terminal ileum of guinea‐pig
Authors: Bolton T. B.
Published: December 2014

1. The membrane potential of the separated longitudinal muscle of the guinea‐pig terminal ileum was recorded intracellularly with glass micro‐electrodes.

2. In tissues kept at room temperature and then brought to 35° C for 15–30 min or about 1 hr, the fall in membrane potential upon changing to potassium‐free solution was 21.4 ± 3.5 mV and 13.4 ± 1.8 mV respectively. Ouabain (1.7 × 10−6
M) produced a fall in membrane potential of 8.1 ± 1.1 mV. Returning potassium to potassium‐free solution, or changing from ouabain‐containing to ouabain‐free solution, resulted in an increase in membrane potential which was greater than the initial fall.

3. Readmitting potassium to potassium‐free solution produced an increase in membrane potential which began within 10 sec and reached a maximum within 15–30 sec. This response was reduced, abolished, or converted to a depolarization by ouabain. In chloride‐deficient (13 m
M) solution in which membrane resistance was increased, the response to readmitting potassium was increased 2½‐fold so that the membrane potential sometimes exceeded −100 mV, which was probably more negative than E
K. On the basis of these results it was assumed that the response to readmitting potassium was due to the electrogenic activity of the sodium pump.

4. The response to briefly readmitting a fixed concentration of potassium increased during the first 30 min in potassium‐free solution. This increase was not due to an increase in membrane resistance as this fell with time in potassium‐free solution. It was suggested that the increase in the response resulted from the progressive rise in internal sodium concentration which is known to occur in smooth muscle in potassium‐free solution.

5. Increasing the concentration of potassium over the range ∼ 0.1–20 m
M, increased the size of the electrogenic potential observed upon readmitting potassium to potassium‐free solution. There was a fall in membrane resistance upon readmitting potassium (0.6, 5.9, or 20 m
M) which was greater the larger the concentration of potassium. When allowance was made for the fall in membrane resistance, the dependency of the electrogenic response upon the concentration of potassium over the range 0.6–20 m
M was much increased.

6. The results indicate that the rate of electrogenic sodium pumping in this tissue is increased by increasing the external potassium concentration, and probably by increasing the internal sodium concentration. It was suggested that a rise in the latter could sensitize the pump to an increase in the former.
Scotopic and photopic components of the rat electroretinogram
Authors: Green Daniel G.
Published: December 2014

1. Increment thresholds were measured on the albino rat retina using the e.r.g. as an indicator of visual sensitivity.

2. Light adaptation produces a change in b‐wave spectral sensitivity independently of whether brief or steady adapting backgrounds are used. This shows that the changed spectral sensitivity is not directly associated with the bleaching of visual pigment.

3. Light adaptation does not appear to alter the spectral sensitivity of the ordinary a‐wave. Consequently, after light adaptation a‐ and b‐waves have different spectral sensitivities.

4. B‐wave increments determined with a blue test stimulus on a red adaptive background show rod saturation. Background levels which saturate the rods cause the a‐wave mechanism to cease responding to incremental stimuli.

5. A background intense enough to saturate the rods evokes a maximum a‐wave response. If a light is sufficiently bright to saturate the rods then the isolated a‐wave fails to signal the termination of the stimulus.

6. Scotopically equated blue and orange stimuli produce equal early receptor potentials.
Failure of thermoregulation in the cold during hypoglycaemia induced by exercise and ethanol
Authors: Haight J. S. J. , Keatinge W. R.
Published: December 2014

1. After young men had exercised for approximately 2 hr at 70% maximum O2 uptake, and taken 28 ml. ethanol by mouth, their mean blood glucose fell to 2·17 m
M. It fell further to 1·77 m
M during a 30 min exposure to air at 14·5° C. Plasma lactate, glycerol, β‐hydroxybutyrate and free fatty acid concentrations increased.

2. Rectal temperature fell to reach a mean level of 34·49° C by the end of the cold exposure; oesophageal temperature fell to as low as 33·00° C in one case.

3. Virtually no increase in metabolic rate and no visible shivering occurred during the cold exposure.

4. Administration of glucose (mean 60·4 g) prevented the falls in temperature, and restored metabolic response to the cold to the size found in control experiments without exercise or ethanol.

5. Neither exercise without ethanol or ethanol without exercise significantly lowered the blood glucose or impaired the maintenance of body temperature in the cold.

6. One obese subject showed almost as great a fall in blood glucose and depression of metabolic response to cold as the thinner men, but no fall in body temperature.