bluuebunny/crossref_metadata_2025 huggingface dataset:
Calcium and potassium systems of a giant barnacle muscle fibre under membrane potential control
Authors: Keynes R. D. , Rojas E. , Taylor R. E. , Vergara J.
Published: December 2014

1. Single barnacle muscle fibres from Megabalanus psittacus (Darwin) were internally perfused and the effects of various internal and external solutions on voltage clamp currents were examined.

2. The usual internal solution was 180 m
M‐K+ aspartate (osmotic pressure adjusted to 1000 m‐osmole by adding sucrose). Fibres perfused with this solution gave an average resting potential of −55 ± 5 mV (all potentials are referred to the external solutions as ground). Further increase in internal K concentration depolarized the fibres.

3. With membrane current control the total capacitance, referred to apparent membrane surface area, was 21·2 ± 2·4 μF/cm2.

4. Under normal conditions, with demonstrably good longitudinal space clamp control, voltage clamp currents associated with certain depolarizing pulses showed oscillations. These oscillations were reduced in frequency and magnitude by lowering the temperature from 20 to 10° C, by eliminating the inward currents with external Ca‐free saline or by reducing the outward currents with internal tetraethylammonium (TEA) or replacement of internal K by Cs.

5. With a Na‐ and Ca‐free, 60 m
M‐MgCl2 solution outside depolarizing voltage clamp pulses produced only outward currents. On repolarization the current tail reversed direction at about −70 mV for pulses of less than 50 msec duration. For longer pulses this reversal potential was less negative, suggesting an accumulation of external, or depletion of internal K.

6. Both the size of the outward currents and the rate at which they reached their maximum value increased with temperature. The activation energy for the rate constant was about 63 kJ/mole.

7. Fibres bathed in Na‐ and Mg‐free, 60 m
M‐CaCl2 saline were excitable. After replacement of the internal K+ with Cs+ or adding 60 m
M‐TEA to the internal solution only sustained inward currents were recorded with depolarization.

8. Sustained inward currents could be reduced by external application of 5 m
M‐LaCl3. Tetrodotoxin was not effective even at a concentration of 1000 n
M.

9. The rate at which these inward currents reached a maximum value increased with increase in temperature of the bathing solution with an activation energy of the order of 42 kJ/mole.

10. The reversal potential of the inward currents changed with the level of internal Ca ions. For a fibre perfused without ethyleneglycol‐bis (β‐aminoethyl ether) N,N′‐tetraacetic acid (EGTA) this reversal potential was 175 mV (internal free Ca 5 × 10−7
M), and was 196 mV for a fibre perfused with 20 m
M‐Tris EGTA (internal free Ca 0·26 × 10−8
M).

11. We propose an electrical equivalent circuit to account for most of the observed electrical properties of barnacle muscle fibres. In this model the Ca and the K system are located at different anatomical places and they interact through a series resistance.
Studies on micellar fatty acid uptake by rat intestine in vitro with reference to the role of bile
Authors: Rampone Alfred J.
Published: December 2014

1. The uptake and esterification to trigylceride of oleic acid in micellar form was studied in rat intestine in vitro. Sacs of the upper half of the everted intestine taken from bile fistula rats were incubated in a buffered solution containing mono‐olein, 14C‐labelled oleic acid and bile salt (sodium taurocholate (NaTch) in concentrations exceeding the critical micellar concentration).

2. At 37° C incubation temperature increasing the NaTch concentration enhanced both uptake and esterification. Adding whole rat bile caused uptake to decrease at all NaTch concentrations but had only a slight and variable effect on esterification.

3. Lowering the incubation temperature to 0° C suppressed esterification but had no effect on uptake.

4. At 0° incubation temperature adding whole bile still decreased fatty acid uptake but had no effect on esterification.

5. It is concluded that intestinal fatty acid uptake from micelles is a non‐energy requiring process and that a non‐bile salt component in bile exists which can suppress this process.

6. It is suggested that lecithin may be the non‐bile salt component and that it suppressed uptake by interacting either with the micelles or with the epithelial membrane to reduce fatty acid permeability.
DNP‐induced dissipation of ATP in anoxic ventricular muscle
Authors: McDonald Terence F. , MacLeod Don P.
Published: December 2014

1. During aerobic incubation in 5 mM glucose medium, 10−5 M‐DNP reduced the action potential duration and amplitude and the developed tension of guinea‐pig ventricular muscle more rapidly and to a greater extent than anoxia.

2. The DNP effect on electrical and mechanical activity was even more pronounced following prolonged anoxic incubation. Since the action potential duration and developed tension of anoxic ventricular muscle have previously been shown to be dependent on glycolytic ATP, and since the effects of DNP could not be duplicated with NaCN, it was concluded that DNP was exerting an effect in addition to its uncoupling of oxidative phosphorylation.

3. Anoxic muscle was incubated with 10−4 M‐IAA or with 10−4 M‐IAA + 10−4 M‐DNP. The ATP content of IAA‐treated muscle was significantly lower than control but in the presence of both IAA and DNP there was a further reduction in ATP and an increased lactate production.

4. Sodium azide (10−2 M), a potent inhibitor of mitochondrial ATPase, did not prevent the reduction of ATP in DNP‐treated anoxic muscle.

5. Ouabain (10−7 M) partially prevented the rapid decline of action potential duration and developed tension of DNP‐treated anoxic muscle. In addition, the glycoside partially blocked the DNP‐induced break‐down of ATP and stimulation of lactate production.

6. Oligomycin (10 μg/ml.) partially prevented the reduction in action potential duration and developed tension of DNP‐treated anoxic muscle.

7. It was concluded that DNP induces an ‘energy leak’ by actively promoting the hydrolysis of an high energy glycolytic intermediate at least one step beyond the sites of ATPase inhibition by ouabain and oligomycin.
Pre‐ and post‐ junctional effects of 1‐fluoro‐2,4‐dinitrobenzene at the frog neuromuscular junction
Authors: Edelson Alan M. , Nastuk William L.
Published: December 2014

1. FDNB increased by 60–90% the depolarization of the end‐plate produced by applied carbachol in frog sciatic nerve‐sartorius muscle preparations.

2. In partially curarized preparations, FDNB (0·4 mM) increased the amplitude of the end‐plate potential by a factor of 1·8.

3. The quantal content of end‐plate potentials was increased by FDNB (2 mM) as determined by the method of failures.

4. After approximately 25–35 min, neuromuscular transmission was blocked by 0·4 mM‐FDNB, as evidenced by abolition of neurally elicited end‐plate potentials. At this stage miniature end‐plate potentials could still be recorded, which indicates that the neuromuscular block was presynaptic.

5. FDNB (0·4 mM) increased miniature end‐plate potential frequency several hundred‐fold when the Ringer solution contained normal calcium concentration (1·8 mM) or 0·45 mM calcium and 5·4 mM magnesium.

6. During the first 60 min of exposure to 0·4 mM‐FDNB there was a slight drop (4–6 mV) in resting potentials of muscle fibres. During this period directly initiated action potentials showed a marked decrease in the rate of repolarization and a small decrease in the amplitude and rate of rise.

7. Using the technique of point voltage clamping in tetrodotoxin‐treated muscles, it has been found that FDNB almost completely abolished the active increase in gK during stepwise depolarization of the nonjunctional muscle fibre membrane from −90 to 0 mV. The passive outward leakage current appeared unaffected by FDNB.
Electrophysiological identification of cell bodies of the tubero‐infundibular neurones in the rat
Authors: Sawaki Yukiko , Yagi K.
Published: December 2014

1. Electrical stimulation of the median eminence induced unit responses in the suprachiasmatic, the ventromedial and the arcuate nuclei of the hypothalamus in the female rat anaesthetized with urethane.

2. Arcuate units with constant latency responded in one to one fashion to repetitive stimuli up to 286 Hz.

3. A conditioning stimulus just above threshold increased the threshold and latency for responses produced by a test stimulus given within 6 msec after the conditioning stimulus. Absolute refractory period was 1·4–2·0msec.

4. A conditioning stimulus just below threshold did not alter the threshold and latency of the responses to test stimuli at any interval.

5. A stimulus given within a time period following a spontaneously occurring spike failed to induce a unit response.

6. It is concluded that the arcuate nucleus of the hypothalamus includes cell bodies of origin of the tubero‐infundibular axons in the rat.
The inotropic effect on the heart of stimulating the vagus in the dog, duck and toad
Authors: Furnival C. M. , Linden R. J. , Snow H. M.
Published: December 2014

1. The chronotropic and inotropic effects of stimulating the vagus on the hearts of the dog, duck and toad were studied.

2. The maximum rate of rise of pressure in the left ventricle (dP/dt max) measured at a constant heart rate and mean aortic pressure was used as an index of the inotropic changes.

3. The sensitivity of dP/dt max as an index of inotropic changes brought about by stimulating the vagus was established in the toad where a 49% reduction in heart rate was associated with a 30% reduction in dP/dt max.

4. In the dog stimulation of the vagus resulted in a reduction in heart rate of 38% and only a small reduction in dP/dt max of 6%.

5. Results similar to those found in the dog were obtained in the duck where the reduction in heart rate of 44% was associated with reduction in dP/dt max of only 3%.

6. It is concluded that the vagus has only a small and negligible negative inotropic effect on the ventricles of the dog and duck.
Changes in firing rate of human motor units during linearly changing voluntary contractions
Authors: Milner‐Brown H. S. , Stein R. B. , Yemm R.
Published: December 2014

1. Human subjects generated approximately linearly increasing or decreasing voluntary, isometric contractions using the first dorsal interosseus muscle of the hand.

2. Single motor units began firing at 8·4±1·3 impulses/sec (mean ±
S.D. of an observation) and increased their firing rate 1·4±0·6 impulses/sec for each change of 100 g in voluntary force. These values were independent of the threshold force for recruiting motor units.

3. At intermediate rates of increasing and decreasing voluntary force (one complete cycle every 10 sec) the firing rate of single motor units varied linearly with force over the entire range of forces studied. However, during slow increases in voluntary force, the firing rate tended to reach a plateau, while during rapid increases an initial train of impulses at a roughly constant rate was observed.

4. The relative importance of recruitment and increased firing rate, as mechanisms for increasing the force of voluntary contraction, was determined. Only at low levels of force is recuitment the major mechanism. Increased firing rate becomes the more important mechanism at intermediate force levels and contributes the large majority of force if the entire physiological range is considered.
Influence of chronic neostigmine treatment on the number of acetylcholine receptors and the release of acetylcholine from the rat diaphragm
Authors: Chang C. C. , Chen T. F. , Chuang Sing‐Tai
Published: December 2014

1. Rats were treated twice daily for 7 days with neostigmine and the diaphragm was isolated for study of its acetylcholine content, release upon nerve stimulation and the number of receptors in the end‐plate.

2. While the content of total acetylcholine was unchanged, the release of acetylcholine on stimulation with trains of 500 pulses at 100 Hz every 20 sec was reduced by about 50%. Five days after the end of neostigmine treatment the release of acetylcholine recovered to normal.

3. The total number of acetylcholine receptors in the end‐plate as measured from the binding of N, O‐di[3H]acetyl α‐bungarotoxin was reduced from 2·1 × 107 to 1·2 × 107 per end‐plate.

4. The above‐mentioned changes are not due to acute pharmacological effects of neostigmine, nor to an immediate effect of cholinesterase inhibition but presumably due to chronic accumulation of acetylcholine at the neuromuscular junction.
Effect of previous dietary history of calcium intake on the skeleton and calcium absorption in the rat
Authors: Kemm J. R.
Published: December 2014

1. Rats were fed either a high or a low calcium diet for 6 weeks. Thereafter all were given the low calcium diet, and the time during which differences persisted between the two groups in apparent absorption of calcium and urinary excretion of calcium has been studied. The apparent absorption of calcium is the same in the two groups after 15 days but the differences in urinary excretion of calcium persist longer.

2. Faecal endogenous calcium and true absorption of calcium have been measured by an isotope dilution technique. The fall in apparent absorption of calcium seen in rats fed a high calcium diet is in part due to a fall in true absorption. Faecal endogenous calcium is also increased in these animals.

3. The amount of calcium and phosphate in the bones is increased by feeding a high calcium diet and decreased by feeding a very low phosphate diet. Femur, humerus, caudal vertebrae and calvaria are equally affected by the different diets.

4. There are strong inverse correlations between absorption of calcium and the percentage of calcium in the bones. This suggests that absorption of calcium may be regulated by the degree of bone mineralization.

5. Rats were fed diets with different calcium phosphate ratios for 6 weeks. Thereafter all were given a low calcium diet with a calcium: phosphorous ratio of 1 and absorption and urinary excretion of calcium were studied. The effects of the different diets may be explained by their effect on calcium status and bone mineralization.
The spinal origin of the motor and inhibitory innervation of the rat anococcygeus muscles
Authors: Gillespie J. S. , McGrath J. C.
Published: December 2014

1. A preparation is described whereby the responses of the two anococcygeus muscles can be recorded in vivo in the pithed rat and the autonomic outflows to the muscle selectively stimulated in the spinal canal.

2. Motor responses are obtained from stimulation at two levels; an upper extending from T 11 to L 3 and a lower from L 6 to S 2. Stimulation between these levels, i.e. between L 3 and L 6, produces no response. The response to stimulation at both upper and lower levels is abolished by phentolamine. The response to stimulation in the upper region is abolished by hexamethonium and is, therefore, presumably preganglionic; the response to stimulation at the lower level is resistant to hexamethonium and presumably post‐ganglionic. Stimulation at levels above T 11 causes contraction after a delay, by liberating catecholamines from the adrenal medulla. This effect is blocked by both phentolamine and hexamethonium.

3. If the adrenergic motor nerves are blocked and the muscle tone raised by a combination of guanethidine and tyramine, stimulation between L 5 and S 2 produces inhibition. The inhibitory outflow, therefore, overlaps the motor outflow but extends one segment more rostral (L 5). Stimulation restricted to this L 5 segment even in the presence of a normal unblocked motor innervation causes inhibition. The inhibitory response is blocked by hexamethonium or mecamylamine but desensitization and ‘escape’ occurs. This desensitization is less than that observed in the vas deferens when its motor nerves are similarly stimulated in the spinal cord.

4. It is concluded that inhibitory fibres to the anococcygeus arise in the spinal cord and are organized in the pattern of the autonomic nervous system with a peripheral synapse. The site of origin of these inhibitory fibres is different from the motor adrenergic fibres to the muscle.
Maintenance of normal corneal thickness in the cold in vivo (hibernation) as opposed to in vitro
Authors: Bito L. Z. , Roberts Jane C. , Saraf S.
Published: December 2014

1. Corneal thickness was measured in vivo in normothermic and hibernating (body temperature = 7–10° C) woodchucks and the [Na+], [K+], [Mg2+] and water content of woodchuck and rabbit corneas were determined on freshly isolated tissues.

2. Woodchuck eyes from both normothermic and hibernating animals were incubated in moist chambers at 5 or 11° C and the corneal thickness was measured periodically.

3. Woodchuck corneas undergo continuous swelling when kept in vitro in a moist chamber at either 5 or 11° C. The rate of this swelling was the same for eyes from active and hibernating animals; it was almost completely reversible upon rewarming at 35° C.

4. In the hibernating woodchuck the corneal thickness did not increase measurably, even after several days of hibernation, although the mean corneal temperature was 9·4° C.

5. At 7° C, the lactate production of corneas from both hibernating and normothermic woodchucks was reduced to about one fifth its levels measured at 37° C. Oxygen consumption was also greatly reduced in the cold although the endothelial O2 consumption of corneas from hibernating woodchucks appears to be relatively insensitive to cold.

6. It is concluded that removal of the eye and/or the in vitro conditions per se render the cornea more vulnerable to the effects of cold, possibly as a result of the elimination of the influences of orbital tissues and/or secretions or as a result of changes in some intrinsic properties of the cornea due to the elimination of neurohumoural factors or the release of autocoids.

7. The finding that normal corneal thickness can be maintained under conditions where the environment is maintained essentially constant for days strongly argues against the validity of the recently proposed nonsteady‐state theory of corneal thickness control.
Isometric contractions of motor units in a fast twitch muscle of the cat
Authors: Bagust J. , Knott Sarah , Lewis D. M. , Luck J. C. , Westerman R. A.
Published: December 2014

1. Isosmetric contractions of cat flexor digitorum longus whole muscles and of functionally isolated motor units have been measured under conditions similar to those used by Buller & Lewis (1965a).

2. Motor unit twitch time to peak was inversely related to axonal conduction velocity. The logarithm of tetanic tension was directly related to conduction velocity. These relationships suggest that each motoneurone has an influence on the muscle fibres which it innervates.

3. The ratio of twitch to tetanic tension was directly related to the time to peak of the motor unit. This fact might be explained by variation between motor units of the duration of ‘active state’.

4. The muscle length at which tension was maximal varied between motor units and the optima were found over the range of muscle lengths which could occur in the body. Slow motor units had longer optimal lengths.

5. The sample of motor units was considered to be unbiased because the distribution of axon conduction velocities was compatible with reported motor fibre diameter spectra of the muscle nerve. The mean motor unit tetanic tension gave a reasonable estimate of the number of α‐motor axons in the muscle nerve. Twitch tensions gave a value that was 40% higher.

6. Motor unit and whole muscle data were in good agreement for length‐tetanus tension curves, for times to peak and for twitch‐tetanus ratios at long muscle lengths.
The asymmetry of the facilitated transfer system for hexoses in human red cells and the simple kinetics of a two component model
Authors: Baker G. F. , Widdas W. F.
Published: December 2014

1. 4, 6‐O‐Ethylidene‐α‐
D‐glucopyranose (ethylidene glucose) has been used to study the competitive inhibition of glucose exchange fluxes when the reagent was (i) inside the cells and (ii) on the outside.

2. 50% inhibition of glucose exchange at 20 m
M and 16° C required 200 m
M ethylidene glucose when on the inside in contrast to 25–30 m
M when on the outside.

3. The inhibitions at different inhibitor/glucose concentration ratios were measured and analysis of the data suggested that the half‐saturation constant for ethylidene glucose was 6 times that for glucose inside the cell as against 1·5 outside. The analysis, however, suggested an asymmetry in respect to the affinities for glucose of approximately ten‐fold and this would make the asymmetry towards ethylidene glucose forty‐fold.

4. Such asymmetries make it necessary to consider a transfer mechanism for sugars with different components on the outer and inner membrane interfaces and simple kinetics for a two component system have been developed and used for analysing the experimental data quantitatively.

5. The kinetic similarities to and difference from the kinetics of a simple mobile carrier and those of some more recent models are briefly discussed.
The effects of temperature and metabolic inhibitors on the spontaneous relaxation of the potassium contracture of the heart of the frog Rana pipiens
Authors: Chapman R. A.
Published: December 2014

1. The spontaneous relaxation of the potassium contracture and the relaxation induced by the removal of extracellular calcium or the restoration of the original potassium concentration, in the frog heart, show a strong dependence on temperature.

2. The energy of activation of the later exponential phase of the spontaneous relaxation is 10·43 kcal mole−1, a value close to that reported for the binding of calcium ions by isolated sarcoplasmic reticulum, but larger than that for the calcium efflux from mammalian heart.

3. The use of metabolic inhibitors shows that relaxation can be sustained when glycolysis is poisoned, but the disruption of oxidative phosphorylation slows relaxation.

4. Poisoning of both glycolysis and oxidative phosphorylation blocks all but the small initial part of the spontaneous relaxation of the potassium contracture and also interferes with relaxation induced by other means.

5. The results are considered to favour the existence, in frog heart, of an active intracellular relaxing system which uses ATP as its substrate to lower the sarcoplasmic calcium concentration. This system is likely to be the sarcoplasmic reticulum but the mitochondria could also be involved.
Pancreatic acinar cells: ionic dependence of the membrane potential and acetylcholine‐induced depolarization
Authors: Matthews E. K. , Petersen O. H.
Published: December 2014

1. Intracellular recordings of membrane potentials have been made in vitro from the exocrine acinar cells of the mouse pancreas using glass micro‐electrodes.

2. The mean membrane potential of the acinar cells during superfusion with Krebs‐Henseleit solution was −39·2 mV. Increasing [K]o tenfold decreased the membrane potential by 28 mV when [K]o was above 10 m
M. This depolarization was not affected by atropine (1·4 × 10−6
M). Strophanthin‐G (10−3
M) slowly depolarized the cells at about 10 mV hr−1.

3. Brief exposure to acetylcholine (ACh), 5·5 × 10−5
M, or pancreozymin resulted in a short lasting depolarization of the acinar cells. Atropine (1·4 × 10−6
M) blocked the depolarizing action of ACh but not that of pancreozymin. Adrenaline (5·5 × 10−5
M) or cyclic AMP (10−3‐10−4
M) did not influence the membrane potential.

4. The amplitude of the ACh‐induced depolarization was not dependent on the presence of CO2/HCO3 in the bathing fluid, but it was closely dependent on the extracellular Na concentration. However, ACh was still able to evoke a small depolarization even after prolonged exposure of the tissue to a Na‐free solution.

5. During exposure of the tissue to a Ca‐free solution the resting membrane potential was decreased and the ACh‐induced depolarization was significantly reduced. Some substances which are known in other tissues to inhibit membrane Ca2+ currents, i.e. La3+, D‐600 and tetracaine, were able to reduce, but never abolish, the ACh‐induced depolarization.

6. These results suggest that the effect of ACh on the pancreatic acinar cell is to increase the permeability of the membrane to commonly occurring ions with a consequent Na‐influx and a small Ca‐influx.
Effects of membrane depolarization on light scattering by cerebral cortical slices
Authors: Lipton Peter
Published: December 2014

1. A system is described for simultaneously measuring the respiration and the reflectance of a tissue slice and is applied to a study of guinea‐pig cerebral cortical slices.

2. Reducing bathing medium osmolarity led to a reversible decrease in reflectance of these slices (as well as slices from liver and kidney cortex). In half isotonic solutions reflectance was reduced by 31%.

3. Anoxia led to a decreased reflectance which was eliminated if all the Cl was substituted by the larger glucuronate anion.

4. It is concluded that slice reflectance is lowered when cellular volumes are increased by water or isotonic solution influx.

5. Membrane depolarization effected by ouabain, high (60 m
M) K bathing medium, veratridine or repeated electrical pulses led to rapid decreases in reflectance of 25, 27, 31 and 7·5% respectively. Turning off the electrical pulses caused reflectance to return to control values. Reversibility of the chemical effectors was not tested.

6. Substitution of Cl by glucuronate abolished the reflectance changes, although it did not inhibit the increased respiration induced by the depolarizing stimuli.

7. Tetrodotoxin abolished both the respiratory and reflectance effects of veratridine and electrical pulses but had no effect upon those of high K or ouabain.

8. The decrease in reflectance began about 1 sec after initiation of the pulses and was half maximal by 8 sec.

9. Titrating reflectance against [K] showed that an increase of 5 m
M‐K led to a 4% decrease in reflectance and that reflectance became minimal between 60 and 80 m
M‐K+.

10. It is concluded that membrane depolarization in excitable cells of the cerebral cortex (and also, possibly, in the glia) causes rapid increases in cell volume due to influx of isotonic solution.

11. The results indicate, more specifically, that changes in intercellular K concentrations of size and duration thought to occur following nervous activity in the
C.N.S. cause cell volume changes large enough to drastically reduce the intercellular volumes and so, transiently, increase extracellular molecular and ionic concentrations. Increases of extracellular [K] and [Ca] have significant effects upon synaptic transmission and upon spontaneous nervous activity. It is suggested that nervous activity in one cell (or portion of it) might, in this way, strongly influence function in neighbouring elements.
Effects of potassium cyanide, strophanthin or sodium‐free perfusion fluid on the electrical potential difference across the guinea‐pig placenta perfused in situ
Authors: Štulc J. , Švihovec J.
Published: December 2014

1. The possible role of active transport of Na in generating the transplacental potential difference (p.d.) was studied in the guinea‐pig placenta perfused in situ by testing the effects of strophanthin or KCN added to the perfusate or of Na‐free perfusion fluid.

2. The p.d. across the perfused placenta was about −20 mV, and was relatively steady during perfusion.

3. Strophanthin (10−5
M) slightly increased the p.d. In a concentration of 2 × 10−6
M strophanthin was without significant effect.

4. KCN (10−3
M) decreased the p.d. When KCN was removed after a 30 min treatment the p.d. increased significantly exceeding the initial level. KCN (10−4
M) slightly increased the p.d.

5. Perfusion with Na‐free fluid decreased the p.d. to a steady level of about 50–60% of the control values.

6. Perfusion with Na‐free fluid containing KCN (10−3
M) for 30 min decreased the p.d. However, the effect did not seem different from the effect of KCN (10−3
M) or Na‐free fluid alone. When KCN was removed the p.d. significantly increased in spite of continued perfusion with Na‐free fluid.

7. Excepting the effect of KCN (10−4
M), which could not be explained, the observations were found to be consistent with active transport of Na from foetal to maternal side of the placenta as a source of the p.d. The Na transport could account for about 40–50% of the p.d.
Intracellular recording from the myenteric plexus of the guinea‐pig ileum
Authors: Nishi S. , North R. A.
Published: December 2014

1. Ganglion cells of the myenteric plexus of the guinea‐pig ileum have been studied with intracellular micro‐electrodes.

2. Three types of cell were distinguished. Type 1 cells had a high resistance (58 MΩ) and had properties similar to guinea‐pig sympathetic ganglion cells. Type 2 cells were also excitable but had a lower resistance (21 MΩ) and showed accommodation to depolarizing current pulses. Type 3 cells were inexcitable.

3. Point stimulation within 150 μm excited neurones either antidromically or orthodromically, sometimes both.

4. Antidromic responses had a small all‐or‐nothing component which was subthreshold for the soma spike. Two or more such components sometimes occurred, and were probably due to stimulation of two or more cell processes.

5. Excitatory post‐synaptic potentials (e.p.s.p.s) were blocked by hexamethonium (400 μ
M). They progressively declined in amplitude when elicited at frequencies of 0·05 Hz or more, and this is discussed in relation to studies on acetylcholine (ACh) output.

6. Many cells often showed a slow after‐hyperpolarization following a direct or antidromic spike. Its mechanism and significance are discussed.

7. Spontaneous e.p.s.p.s and spikes were occasionally seen.

8. Intracellular injection of a fluorescent dye reveals that the neurones have one to seven processes, which usually arise from the poles of the oval soma.
Effect of insulin upon the sodium pump in frog skeletal muscle
Authors: Moore Richard D.
Published: December 2014

1. Insulin increased the rate of net Na extrusion from Na‐loaded frog skeletal muscle into glucose‐free Na‐Ringer. After a 90 min period of efflux, the insulin‐treated muscles contained approximately 11% less intracellular water than did their controls. This decrease in intracellular water resulted in an increase in the concentration of intracellular K, [K+]i, even though there was no definite effect upon net K flux. In spite of the decrease in intracellular water, [Na+]i was lower in those muscles treated with 500 m‐u. insulin/ml. than in the controls.

2. Insulin consistently increased 22Na efflux into Na‐Ringer containing either 10 or 2·5 m
M‐K+. This effect was reversible and was not produced by other proteins.

3. Acetylstrophanthidin (5 × 10−6
M) blocked all or nearly all net Na efflux even in the presence of insulin. The presence of this concentration of acetylstrophanthidin or of K‐free Na‐Ringer inhibited the effect of insulin upon 22Na efflux from Na‐loaded muscles.

4. All of the above results indicate that insulin in some way increases the activity of the Na pump. The inhibition by K‐free Na‐Ringer also suggests that this is not due to production of additional pump sites.

5. Insulin also increased 22Na efflux and net sodium efflux into Li‐Ringer. When the new steady‐state was reached after addition of insulin, the 22Na kinetics still obeyed a power relation to intracellular 22Na. However, in every single case, insulin resulted in a decrease of approximately 18% in the exponent, n.

6. Curve‐fitting of the kinetic data to equations based upon a three‐site model of the Na pump suggests that insulin increases the affinity of the sites toward Na+. In terms of Eisenman's theory of ion selectivity, this would indicate an increase in the anionic field strength of the Na‐carrying sites and also predict that the increase in affinity for H+ would be greater than that for Na+. This latter prediction is entirely consistent with the observed decrease in n.

7. The results suggest that insulin may be increasing H+ efflux as well as Na+ efflux and thereby may be increasing intracellular pH. It is suggested that some of the intracellular effects of insulin might be mediated by such an effect.
Effects of tubocurarine and eserine on the axon‐Schwann cell relationship in the squid nerve fibre
Authors: Villegas Jorge
Published: December 2014

The effects of eserine and
D‐tubocurarine on the axon and Schwann cell membrane potentials have been studied in the giant nerve fibre of the squid.

1. The addition of eserine at concentrations of up to 10−4
M to the external sea‐water medium has no appreciable effects on either the Schwann cell electrical potential of unstimulated nerve fibres or on the resting and action potentials of the axon.

2. However, eserine at a concentration of 10−9
M prolongs the long‐lasting Schwann cell hyperpolarizations which follow the conduction of impulse trains by the axon.

3. Higher concentrations of eserine (10−7, 10−4
M) decrease and block the long‐lasting effects of nerve impulse train conduction.

4.
D‐tubocurarine at concentrations of up to 10−5
M has no appreciable effect on the resting and action potentials of the axon.

5. However,
D‐tubocurarine at a concentration of 10−9
M blocks completely the hyperpolarizing effects of nerve impulse trains on the Schwann cell electrical potential.

6. In addition to its blocking action,
D‐tubocurarine induces transient hyperpolarizations in the Schwann cells of unstimulated nerve fibres both in intact fibres and in slitted preparations.

7. These findings suggest that a cholinergic system, which may be located at the axon‐Schwann cell boundary, is involved in the genesis of the long‐lasting Schwann cell hyperpolarization caused by the conduction of nerve impulse trains by the axon.
The role of the liver in non‐shivering thermogenesis in the rat
Authors: Stoner H. B.
Published: December 2014

1. The temperatures of the liver and afferent aortic and portal blood were measured in 20° C acclimated rats at different environmental temperatures (Ta) between 20 and 37° C. The heated‐thermocouple technique was used to measure the metabolic heat production of the liver, its blood flow, and to correct the temperature difference between it and the reference junction for blood flow.

2. The temperature of the liver was higher than that of the afferent blood. On raising Ta from 20 to 30° C the liver temperature fell and the temperature difference between the liver and the aortic blood was reduced despite the decrease in the thermal gradient between the liver and the exterior and a small reduction in hepatic blood flow. A further rise in Ta to 37° C led to an increase in the liver and blood temperatures. The same pattern was seen when the temperature differences were corrected for blood flow.

3. Metabolic heat production in the liver decreased when Ta was raised from 20 to 30° C.

4. In a 20° C environment inhibition of non‐shivering thermogenesis with propranolol HCl (10 mg/kg body wt.
I.V.) led to a fall in the temperature of the liver and its metabolic heat production towards levels found in untreated rats at Ta = 30° C. Consequently, in treated rats the change in metabolic heat production on raising Ta to 30° C was less than in untreated ones.

5. These results are interpreted as evidence for the participation of the liver in thermoregulatory non‐shivering thermogenesis.
Stimulus—response functions of rapidly adapting mechanoreceptors in the human glabrous skin area
Authors: Knibestöl M.
Published: December 2014

1. Single unit impulses were recorded from the ulnar and median nerves of awake human subjects with tungsten electrodes inserted percutaneously in the upper arm.

2. Forty‐nine rapidly adapting mechanoreceptors with receptive fields in the glabrous skin area were studied. Thirty‐nine units had small receptive fields with distinct borders (RA‐receptors) while ten units had large fields with indistinct borders (PC‐receptors).

3. The afferent response to stimuli of varying indentation amplitude and velocity of indentation, was analysed.

4. Amplitude thresholds varied from 0·05 to 1·65 mm for the RA‐receptors. For the PC‐receptors amplitude thresholds ranged from less than 0·05 to 1·95 mm.

5. Velocity thresholds varied for the RA‐receptors from 0·4 to 39·3 mm/sec, and for the PC‐receptors from 0·5 to 19·6 mm/sec.

6. The conduction velocities of the afferents were all in the A α—β range. For the RA‐receptors the conduction velocities ranged from 26 to 91 m/sec (mean = 55·3 ± 3·4), and for PC‐receptors the range was from 34 to 61 m/sec (mean = 46·9 ± 3·6).

7. The nerve impulse frequency as a function of indentation velocity was analysed for nineteen RA‐receptors and four PC‐receptors. A hyperbolic log tangent function of the type first introduced by Naka & Rushton (1966) in studies on S‐potentials in the fish retina was found to be the best description of the stimulus—response function for sixteen RA‐receptors and two PC‐receptors. For the remaining units a pure logarithmic function was the best description. However, the logarithmic function may be, as found in the present study, a special case of the more general log tanh function.
Photoreceptors in the crayfish compound eye: electrical interactions between cells as related to polarized‐light sensitivity
Authors: Muller Kenneth J.
Published: December 2014

1. The sensitivity to plane‐polarized light and the electrical interactions of photoreceptors were examined with intracellular and extracellular micro‐electrodes in excised compound eyes of the crayfish.

2. There are two types of photoreceptor: each photoreceptor cell responds best to polarized light when the electric‐vector of the light is oriented in one of two orthogonal directions. Seven cells, representing each type, are grouped together to form ommatidia.

3. In each ommatidium, cells that are sensitive to the same orientation of the electric‐vector of polarized light are coupled electrically. Cells having orthogonal polarized‐light sensitivities are not coupled.

4. Nearly all cells studied were sensitive to orange light. A few cells of both types were found that were sensitive to blue light. Blue‐sensitive cells were not coupled to orange‐sensitive cells.

5. The photocurrents of both cell types produce negative extracellular potentials which can be greater than 10 mV when measured near the photoreceptive membranes within ommatidia. Evidence suggests that the extracellular potentials produced by one type of cell can effectively reduce the receptor potentials recorded in the other cell type. It is proposed that such a mutual non‐synaptic interaction can make a cell more sensitive to the orientation of polarized‐light than would be predicted from the cell's differential absorption of polarized light (i.e. its dichroic ratio).
Further effects of chlorpromazine on the hexose permeability of the human erythrocyte
Authors: Baker G. F. , Rogers H. J.
Published: December 2014

1. The effect of chlorpromazine on hexose transfer across the human erythrocyte membrane was investigated by optical and isotopic techniques in intact erythrocytes.

2. Chlorpromazine produces two phases of inhibition of glucose exit at 17° C in both types of experiment.

3. Glucose exchange flux shows a much smaller decrease in flux rate at the same concentrations of chlorpromazine at 17° C.

4. Sorbose and glucose entry at 36° C show a similarly complex inhibition by chlorpromazine. The inhibitor constant (Ki) for these effects with the two sugars is similar.

5. An Arrhenius plot shows that the average energy change for the reaction of the carrier with chlorpromazine is −46 kJ mole−1 and suggests that a drug‐induced conformational change in the carrier may occur.

6. These findings require models of hexose permeation to contain separate terms in their kinetics for net and exchange fluxes and the predictions of one such model have been compared with the experimental results.
Efflux of potassium from isolated rod outer segments: a photic effect
Authors: Cavaggioni A. , Sorbi R. T. , Turini S.
Published: December 2014

1. Illumination of the isolated outer segments of rod photoreceptors loaded with 42K or 86Rb reduces the efflux of these ions.

2. During the perfusion of the isolated rod outer segments with a solution containing only 2·36 m
M‐Na the effect of light is absent, and the amplitude of the photic effect is linearly related to the logarithm of the extracellular Na concentration.

3. In darkness, raising the concentration of K in the fluid of perfusion gives an increase of the efflux of 86Rb and increasing the extracellular concentration of Ca yields a retention. The efflux of 86Rb and 42K is greater in darkness when sucrose or choline substitute for Na.

4. It is suggested that in darkness the isolated outer segments are permeable both to Na and to K. Light appears to decrease the permeability for Na ions. There is no evidence that the permeability for K ions is modified by light.
The physiological role of calcitonin assessed through chronic calcitonin deficiency in rats
Authors: Kumar M. Ashwini , Sturtridge W. C.
Published: December 2014

1. An attempt was made to assess the physiological role of calcitonin by producing its prolonged deficiency in rats.

2. Three groups of young rats viz. (I) sham‐operated controls, (II) thyroidectomized with thyroxine replacement and (III) thyroidectomized with thyroxine as well as calcitonin replacement, all with parathyroid autografts, were studied for 5 weeks. Groups II and III showed impaired Ca tolerance and group II also showed significant reduction in total (organic and inorganic) mass of femora as compared to group I.

3. Three similar groups of old mature rats were studied as under (2) for 9 weeks. Groups II and III in this case showed no significant changes as compared to group I.

4. In intact mature rats, Ca tolerance is impaired, thyroid content of calcitonin is high and the hypocalcaemic action of calcitonin is much reduced as compared to intact young rats.

5. It is concluded that calcitonin plays a useful but non‐essential role in Ca metabolism and bone development of young growing rats. Its function, if any, in mature rats on a normal diet remains doubtful.
Excitation‐contraction coupling in voltage clamped uterine smooth muscle
Authors: Mironneau Jean
Published: December 2014

1. The relationship between ionic currents and contraction has been investigated in uterine strips of pregnant rat by means of a double sucrose gap apparatus combined with an optical method which permits the measurement of the contraction of the small muscular bundle where potential and current are recorded.

2. Effects of duration, size and frequency of imposed potentials upon contraction have been studied. The uterine muscle shows summation and tetanus phenomena. Tension elicited by depolarizing pulses of different durations and amplitudes can be considered as made of two components.

3. The first component of the contraction evoked by short depolarizing steps (about 50 ms) depends on the slow inward current. This contraction is abolished by manganese and lanthanum ions and by compound D 600. The amplitude of the tension can be related to the external calcium concentration and consequently to the calcium influx. The slow inward current is supposed to release a part of the bound calcium without excluding, however, a direct activation of myofibrils.

4. The second component of the contraction is observed in manganese containing solution with depolarizations longer than 200 ms and without inward current. Such a component of tension suggests the possibility of release of calcium from intracellular stores which could be located in the sarcoplasmic membrane of the uterine smooth muscle.
Relationship between the velocity of rolling granulocytes and that of the blood flow in venules
Authors: Atherton Anne , Born G. V. R.
Published: December 2014

1. The mean velocities at which granulocytes roll along the walls of small venules have been related to their mean blood flow velocities in preparations of hamster cheek pouch and mouse mesentery. In animals anaesthetized with Nembutal, 30–200 μm venules were observed microscopically and the movement of rolling granulocytes quantitated on films. Apparent mean blood flow velocity was determined from films of embolizing platelet thrombi.

2. In four venules the velocity distribution of about 100 rolling cells was almost symmetrical about the mode, with a small proportion moving at up to three times the mode velocity. Therefore, the mean and mode velocities were very similar.

3. In two mesenteric and two cheek‐pouch venules, blood flow velocity was temporarily altered during and after gentle compression with a fine glass fibre; this was associated with proportional changes in mean cell velocities.

4. In four different venules of a hamster cheek pouch, the mean velocity of rolling granulocytes increased in proportion to the mean blood flow velocity (r = 0·963).

5. In thirty‐six venules of ten mouse mesenteries, the velocities were proportional (r = 0·915) between blood velocities of about 300 and 1000 μm/sec. Above this the velocity of the cells did not increase further.

6. The rolling of granulocytes is presumably governed by two forces, the shear force of the flowing blood and an adhesive force between the surfaces of granulocytes and vascular endothelium. Our results suggest that, within limits, the proportionality between the velocities of blood flow and rolling cells is due to shear force, the adhesive force being similar for all the cells. The results suggest that this adhesion force per granulocyte is of the order of 10−5 dynes.
The rate of action of tetrodotoxin on myelinated nerve fibres of Xenopus laevis and Rana esculenta
Authors: Schwarz J. R. , Ulbricht W. , Wagner H.‐H.
Published: December 2014

1. The experiments were done on single Ranvier nodes of Xenopus laevis (voltage clamp) and Rana esculenta (action potentials). Rate and size of the effect of tetrodotoxin were determined by the reversible reduction of either the sodium inward current (Xenopus) or of V̇A, the maximum rate of rise of the action potential (Rana).

2. The results of tetrodotoxin block at equilibrium could be excellently fitted by assuming a one‐to‐one reaction between toxin molecules and sodium channels of the Xenopus membrane with an equilibrium dissociation constant K = 3·60 n
M at room temperature. V̇A was not linearly related to the fraction of unblocked sodium channels and 10·9 n
M tetrodotoxin was necessary on the average to reduce V̇A to 50% in Rana motor fibres; in sensory fibres a lower concentration sufficed.

3. Onset and offset of the tetrodotoxin effect on Xenopus nodes could be quantitatively interpreted as being determined by the rates of the tetrodotoxin channel reaction. Experiments with 3·1 and 15·5 n
M tetrodotoxin at room temperature yielded an association rate constant, k1, of 2·94 × 106
M−1 sec−1 and a dissociation rate constant, k2, of 1·42 × 10−2 sec−1. In these experiments the equilibrium dissociation constant, K, was 3·31 n
M. If determined solely from the onset in the two tetrodotoxin concentrations, k1 = 3·25 × 106
M−1 sec−1 and K = k2/k1 = 4·08 n
M was calculated.

4. In Rana fibres the onset and offset of V̇A reduction by 15·5 and 31 n
M tetrodotoxin was evaluated using the equilibrium effects of intermediary tetrodotoxin concentrations for calibration. The average results at room temperature were k1 = 4 × 106
M−1 sec−1, k2 = 1·4 × 10−2 sec−1 and K = 3·4 n
M.

5. The very short latency with which V̇A started to decline when tetrodotoxin was suddenly applied proved that the toxin had ready access to the membrane.

6. The temperature dependence of k1, k2 and K in the Xenopus experiments could be described by Arrhenius plots yielding activation energies, Ea, of 9·8, 20·5 and 7·0 kcal/mole, respectively, corresponding to Q10 values of 1·82, 3·42 and 1·53 (between 12 and 22° C). For k1, determined from onset alone, Ea = 13·7 kcal/mole (Q10 = 2·25) was obtained. Although in Rana the temperature dependence of the rate constants could not be determined directly, the Q10 for k2 must have been of the order of 3.

7. The results suggest that the rate of the toxin action on the nodal membrane of Xenopus and Rana is limited by the tetrodotoxin‐sodium site reaction.