bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of length and stimulus rate on tension in the isometric cat soleus muscle
Authors: Rack P. M. H. , Westbury D. R.
Published: December 2014

1. By subdividing ventral roots and supplying stimulating pulses to different groups of motor units in rotation, smooth contractions of soleus could be obtained with low rates of stimulation.

2. Isometric tension was recorded with different rates of stimulation, and at different muscle lengths.

3. Longitudinal histological sections were cut from muscles fixed at different lengths, and sarcomeres were measured. Mean sarcomere lengths in soleus could then be related to the angle at the ankle.

4. At high rates of stimulation the maximum active tension was obtained at a length corresponding to an angle of about 60° at the ankle, and a mean sarcomere length of about 2·8 μ. The isometric tension fell only slightly on shortening the muscle to a length equivalent to 100°, and a mean sarcomere length about 2·3 μ. Further shortening caused a marked fall in tension.

5. There was a reciprocal relationship between stimulus rate and muscle length; when the muscle was long low rates of stimulation gave near maximal tension, whereas at short lengths the maximum tension was reached only when the stimulus rate was very high. It is suggested that stimulating pulses activate the contractile machinery of the muscle more effectively at long than at short muscle lengths.

6. When at low rates of stimulation pulses were distributed among the motor units in rotation to give a smooth contraction, the tension rose higher than during the unfused tetanus that accompanied synchronous stimulation of the same motor units at the same rate. It is suggested that in an unfused tetanus internal movement of the muscle reduces the tension below that developed in a truly isometric state.

7. The rate of rise of tension in an isometric tetanus varied with both muscle length and rate of stimulation. At each stimulus rate there was a range of lengths in which the isometric tension developed slowly, this was the same length range in which, at that stimulus rate, the length tension curve was steep.
Structure and some contractile properties of fast and slow muscles of the chicken
Authors: Page Sally G.
Published: December 2014

1. A comparative study has been made of the structure of the posterior and anterior latissimus dorsi muscles (
P.L.D. and
A.L.D.) of the chicken. Some of the contractile properties of these muscles, particularly of the
A.L.D. muscle, have also been examined.

2. In confirmation of earlier work, it is found that structural differences between these two muscles mainly reside in the organization of the T‐system and the sarcoplasmic reticulum.

3. In the
P.L.D. muscle the T‐system and sarcoplasmic reticulum are tubular networks of regular pattern, with frequent regions of contact between them in the form of the familiar triads. As described earlier, two series of triads are present in each sarcomere, near the level of the A—I boundary.

4. The presence in the
A.L.D. muscle of both T‐system and sarcoplasmic reticulum has been established here by the combined use of electron microscopic and histochemical techniques. The appearance of these structures is considerably less regular in this than in the
P.L.D. muscle, and the area of contact between them relatively small: in terms of contact area per sarcomere, about 15% or less of that in the
P.L.D. muscle. Regions of contact are mainly in the form of dyads, but a few triads are also present.

5. Contractures of the
A.L.D. muscle in high K fluids have been recorded and their modification due to variation of the external concentration of Ca, K and Mg examined. The K contracture consists of two phases: an initial transient and a later maintained phase. The response of these phases to variation in the external medium is markedly different.

6. Application of Ca‐free fluids causes contracture tension of the late phase to subside within a few minutes whilst that of the initial phase declines completely only after several hours. High Mg concentrations depress the later but not the early phase of contracture.

7. Tentative interpretations of both the morphological and physiological differences described have been proposed.
The rate of osmotic influx of water by flexible and inflexible erythrocytes
Authors: Sirs John A.
Published: December 2014

1. The rate of osmotic influx of water into flexible and hardened erythrocytes has been studied using a stopped‐flow rapid‐reaction method, and diluting the cells 1:20 in hypotonic media.

2. Neither the initial rate of swelling nor the time to the onset of haemolysis were changed after making the erythrocytes inflexible by adding formaldehyde or by heating at 48° C for 30 min.

3. From a plot of the initial rate of uptake with hypotonicity, the permeability coefficient k can be calculated as 0·098 μ3/μ2. sec atm (± 10%) at 20·5° C.

4. The value of k calculated from the time to the onset of haemolysis is 0·28 μ3/μ2 sec atm. This suggests individual cells may differ over a wide range of permeability.

5. The results are consistent with the pores being at fixed sites in the membrane and unaffected by flexing of the cell.
The break‐down of [131I]γ‐globulin in the digestive tract of the new‐born pig
Authors: Hardy R. N.
Published: December 2014

1. The intestinal absorption of [131I]porcine and bovine serum γ‐globulin after oral administration has been investigated in conscious pigs less than 20 hr old. Absorption was measured by the concentration of 131I in venous blood during the 6 hr after feeding and also by the distribution of 131I between homogenates of the alimentary tract and the rest of the animal at the end of the experiment.

2. The concentration of 131I in the blood was always low after feeding [131I]γ‐globulin, although a large proportion of the isotope fed was found to have left the alimentary tract. This indicated that much of the [131I]‐γ‐globulin had been hydrolysed into fragments of low mol.wt. which were not retained in the plasma. There were no significant differences between results obtained with homologous and heterologous γ‐globulin.

3. Examination by gel‐filtration confirmed that, after feeding [131I]‐serum γ‐globulin, much of the 131I in the plasma was associated with material of mol.wt. less than 12,400 and demonstrated that the break‐down of bovine γ‐globulin was comparable with that of homologous γ‐globulin.

4. Comparison of the absorption of [131I]serum γ‐globulin from colostrum with that from a chloride solution with a similar Na+ and K+ concentration showed that, although the blood concentration remained low, colostrum reduced the hydrolysis of the labelled protein.

5. This effect of colostrum could be simulated by the addition to the chloride solution of either the synthetic trypsin inhibitor Trasylol or a higher concentration of unlabelled protein.

6. Gel‐filtration of samples of the contents of the stomach, duodenum and terminal ileum after feeding [131I]serum γ‐globulin showed that proteolysis occurred at all these sites.
Binocular depth discrimination and the nasotemporal division
Authors: Blakemore C.
Published: December 2014

1. If classical partial decussation exactly segregates the projections of right and left hemi‐retinae on to the two optic tracts, the images of an object in central vision, nearer or further than the fixation point, should project to separate hemispheres. This would prevent the encoding of retinal disparity by binocularly driven neurones of the visual cortex.

2. It is proposed that there is a central vertical strip of retina in each eye which is represented in both hemispheres. The angular width of this strip should be exactly one half the actual range of horizontal disparities of binocular receptive fields near the central vertical meridian.

3. By recording from single neurones in the area 17/18 region in both hemispheres of a cat, it was found that there is such a strip of bilateral projection. The centres of receptive fields for units from the two hemispheres overlap in the middle of the visual field by about 1·5° and the
S.D. of the distribution is about 0·5°.

4. The horizontal disparities of the centres of binocular receptive fields were measured for samples of units representing different parts of the visual field. The range of horizontal disparity for fields near the area centralis is about 2·3°, the
S.D. of the distribution about 0·9°. The proposed relationship between bilateral projection and disparity coding is thus confirmed.

5. The origin of the bilateral projection is a matter of speculation, but in the cat some of it is almost certainly due to imprecision in the nature of the nasotemporal division of optic nerve fibres at the optic chiasma. A case can be made, however, that the overlap is partly due to connexions through the corpus callosum between the two occipital lobes.

6. Evidence for the importance of the callosal pathway in man is drawn from the effects on stereopsis of section of the chiasma and the callosum.
Adaptation of canine pancreatic enzymes to diet composition
Authors: Behrman Harold R. , Kare Morley R.
Published: December 2014

1. Lipase, protease and amylase activity in canine pancreatic juice were determined during the feeding of basal, high fat, high protein and high carbohydrate diets for 3‐week periods.

2. The level of lipase in pancreatic juice was significantly augmented by increasing the dietary intakes of fat (P < 0·05) and carbohydrate (P < 0·05) but was not affected by increasing the protein intake.

3. Protease activity was highly augmented by increasing the intake of protein (P < 0·01), was less strongly augmented by increasing carbohydrate (P < 0·10), but was not affected by the level of dietary fat ingested.

4. Enzyme activities in canine pancreatic juice were modified by the nature of the diet on which the animals were maintained and the response for a given enzyme may be influenced by more than one dietary constituent.
The effect of the renin—angiotensin system on mucosal water and sodium transfer in everted sacs of rat jejunum
Authors: Crocker Ann D. , Munday Kenneth A.
Published: December 2014

1. Mucosal water and sodium transfer were measured in everted sacs of rat jejunum.

2. Rats maintained on a high sodium diet did not show consistently reduced mucosal water transfer and aldosterone also failed to stimulate transfer unless the control untreated values were low.

3. Adrenalectomy produced little reduction in mucosal water transfer and aldosterone was without effect on water transfer in sacs from adrenalectomized rats.

4. Vasopressin had no effect on mucosal transfer.

5. Levels of water transfer were not reduced after hypophysectomy nor did aldosterone injection increase transfer.

6. Mucosal water transfer in sacs from adrenalectomized—nephrectomized rats was low and was significantly increased by aldosterone injection or by injection of crude kidney extract.

7. A significant increased mucosal water and sodium transfer was observed when sacs from adrenalectomized—nephrectomized rats were incubated with angiotensin at a concentration of 10−10g/ml.

8. It is suggested that the renin—angiotensin system may be involved in the maintenance of sodium homoeostasis by a direct action on sodium transporting mechanisms.
Species and tissue variation in extraneuronal and neuronal accumulation of noradrenaline
Authors: Gillespie J. S. , Muir T. C.
Published: December 2014

1. The ability of arterial and non‐arterial smooth muscle in five tissues (vas deferens, heart, bladder, colon, spleen) in four species (mouse, rabbit, rat, guinea‐pig) to accumulate and retain noradrenaline (NA) was measured in thin tissue slices exposed to NA for 30 min, then washed in cold saline solution for 30 min. NA accumulation was assessed histochemically by measuring the fluorescence brightness of the tissue with the Leitz MPV microphotometer. In addition, similar measurements were made on smooth muscle in the cat spleen, on cardiac muscle and on the terminal adrenergic nerves.

2. In general, arterial smooth muscle had a greater capacity to accumulate and retain NA than non‐arterial smooth muscle, but there was a great species and organ variability. The ability to accumulate and retain NA was best developed in the mouse, followed by the rabbit, rat and guinea‐pig in that order. Among organs the artery to the vas and the coronary arteries showed the greatest retention. Among non‐arterial smooth muscle the mouse vas and the rabbit colon were notable.

3. Cardiac muscle accumulates NA during exposure to the amine but, unlike smooth muscle, cannot retain it when washed with NA‐free solution.

4. Terminal adrenergic nerves in different tissues show some variability in fluorescence intensity, and this is increased after exposure to NA. This may indicate a variable capacity of these cells to accumulate and retain NA.
Place and modality analysis in nucleus of posterior commissure
Authors: Bowsher David , Petit Denise
Published: December 2014

1. Single units (157) responsive to somatic stimulation in the nucleus of the posterior commissure were examined in the cat under chloralose anaesthesia. 87·3% responded to stimulation of all four limbs, 2·4% to three limbs, 8·7% to two limbs and 2% to one limb.

2. 44·7% of units could be activated by phasic hair movement; 52·4% responded additionally to auditory stimuli and 34·6% to visual stimuli, although there are marked differences in degree of heterosensory convergence between hair‐sensitive units and others.

3. Analysis by spike numbers and latencies show marked preference for contralateral limbs.

4. Results are compared with those obtained under identical experimental conditions from units of the gigantocellular bulbar reticular formation, and show that anatomically discrete areas of the reticular formation are capable of differential analysis of afferent input.
The roles of striated and smooth muscle in the movement of the cat's nictitating membrane
Authors: Paton W. D. M. , Thompson J. W.
Published: December 2014

1. When the movement of the nictitating membrane is recorded in the usual way, pulled out under load in cat, dog, or rabbit, end‐plate‐depolarizing drugs such as succinylcholine, decamethonium, nicotine, and 2268F, cause a retraction.

2. This movement is due to activation of orbital striated muscle, as evidenced by the resistance of the movement to ganglion block or excision of the superior cervical ganglion and to administration of phentolamine or atropine, and by its great sensitivity to dimethyltubocurarine.

3. End‐plate‐depolarizing drugs produce contractions of the superior and inferior oblique and of the recti muscles strong enough to account for the movements of the nictitating membrane, provided the known fascial connexions of the orbit allow transmission of a fraction of the extraocular muscle movement to the membrane.

4. In post mortem specimens with the front of the orbit undisturbed, retraction of the central end of any of the ocular muscles produces movement of the nictitating membrane; the movement was greatest with the superior oblique and medial rectus. In vivo, detaching the superior oblique from its insertion into the globe sometimes abolished or reduced the response to end‐plate‐depolarizing drugs.

5. With the membrane unloaded and retracted into the medial canthus, in the lightly anaesthetized or unanaesthetized dog or cat, these drugs cause a protrusion of the membrane, which can be sufficient to cover the cornea. This response also resists ganglion‐block and is highly sensitive to dimethyltubocurarine.

6. It is suggested that in the normal conscious animal the nictitating membrane is held retracted by a relatively small amount of sympathetic activity, and that its protrusion is an active mechanism under voluntary control mediated by the striated muscles of the orbit.

7. The importance of these mechanisms in the interpretation of experiments in which the nictitating membrane is used are discussed.
The relation between body size and maximum and minimum metabolic rates in the new‐born pig
Authors: Mount L. E. , Stephens D. B.
Published: December 2014

1. Measurements of rates of oxygen consumption were made on a total of sixty‐two Large White pigs aged between 1 hr and 6 days, with a range of body weight from 0·75 to 2·40 kg.

2. The maximum rate was determined from the continuous estimation of oxygen consumption as the environmental temperature fell past the point at which the maximum occurred.

3. The minimum rate was determined both as the environmental temperature rose through the zone of thermal neutrality, and from measurements at thermal neutrality.

4. In animals aged 1‐6 days the mean maximum rate was 49·0 ml. O2/kg.min, and the mean minimum was 15·3 ml. O2/kg.min. Both rates were proportional to body weight and not to surface area.

5. Pigs less than 1 day old exhibited lower maximum and minimum rates than the older pigs.
The effect of adrenaline on the contraction of human muscle
Authors: Marsden C. D. , Meadows J. C.
Published: December 2014

1. Infusions of adrenaline in physiological amounts alter human muscle contractions evoked by nerve stimulation.

2. Adrenaline shortens the duration of the slow calf muscle twitch, but has no effect on the fast twitch of adductor pollicis.

3. Adrenaline decreases unfused tetanic tension and increases the oscillation of tension in 10/sec tetani of calf muscle and adductor pollicis. The usual rise of tension and decrease in oscillation in unfused tetani (‘ramp’ phenomenon) is abolished.

4. Adrenaline has no effect on maximal tetanic tension or maximal rate of rise of tension in a fused tetanus of adductor pollicis.

5. The effects of adrenaline on human muscle are due to stimulation of β‐adrenotropic receptors, for they are abolished by the β‐adrenotropic antagonist
DL‐propranolol (but not by
D‐propranolol), and are mimicked by isoprenaline but not by noradrenaline.

6. The effect of adrenaline on adductor pollicis is abolished by local β‐blockade of one arm with intra‐arterial
DL‐propranolol, indicating that the responsible β‐receptors lie peripherally.

7. The changes in muscle contraction observed cannot be explained by altered muscle temperature, for this falls during adrenaline infusion; nor are they due to an action on neuromuscular transmission, for these small doses of adrenaline do not affect the muscle action potential. The evidence points to a direct action of adrenaline on muscle.
Oxygen intake in track and treadmill running with observations on the effect of air resistance
Authors: Pugh L. G. C. E.
Published: December 2014

1. The relation of V̇O2 and speed was measured on seven athletes running on a cinder track and an all‐weather track. The results were compared with similar observations on four athletes running on a treadmill.

2. In treadmill running the relation was linear and the zero intercept coincided with resting V̇O2.

3. In track running the relation was curvilinear, but was adequately represented by a linear regression over a range of speeds extending from 8·0 km/hr (2·2 m/sec) to 21·5 km/hr (6·0 m/sec). The slope of this line was substantially steeper than the regression line slope for treadmill running.

4. The influence of air resistance in running was estimated from measurements of V̇O2 on a subject running on a treadmill at constant speed against wind of varying velocity.

5. The extra O2 intake (ΔV̇O2) associated with wind increased as the square of wind velocity. If wind velocity and running velocity are equal, as in running on a track in calm air, ΔV̇O2 will increase as the cube of velocity.

6. It was estimated that the energy cost of overcoming air resistance in track running is about 8% of total energy cost at 21·5 km/hr (5000 m races) and 16% for sprinting 100 m in 10·0 sec.
Conduction velocity in myelinated nerve fibres of Xenopus laevis
Authors: Hutchinson N. A. , Koles Z. J. , Smith R. S.
Published: December 2014

1. The relationship between conduction velocity and nerve diameter in single myelinated nerve fibres from Xenopus laevis was measured and was found to be linear.

2. The relationship between conduction velocity and temperature in nerve fibres of various diameters was measured over the range 15–30° C and was found to be linear for each fibre.

3. The slope of the conduction velocity—temperature relationship was directly proportional to the diameter of the nerve fibre.

4. The form of the conduction velocity—temperature relationship was determined by numerical solution of the Frankenhaeuser—Huxley equations for the case of a propagated action potential. The computation predicted that conduction velocity is a linear function of temperature over the range studied.
Role of naso‐buccal passages in thermoregulation in sheep
Authors: Phillips G. D. , Raghavan G. V.
Published: December 2014

1. Experiments with a face‐mask in which the temperature of the air in the face‐mask was raised to 40° C while the ambient temperature in the chamber was maintained at 20° C, resulted in a marked increase in respiratory frequency and a slight decline in carotid blood temperature of unshorn sheep. Partially shorn sheep showed only small respiratory responses.

2. Localized infra‐red irradiation of the naso‐buccal area of unshorn sheep also resulted in an increased respiratory rate.

3. It is suggested that the initiation of polypnoea during infra‐red irradiation of the naso‐buccal region and following rise in the temperature of the air in the face‐mask is due to stimulation of warm receptors in the upper respiratory tract.

4. Cooling the naso‐buccal air in the face‐mask to 10° C after thermal polypnoea had been established at an ambient temperature of 40° C resulted in a moderate decline of 30–40 respirations/min. This decline was attributed to the stimulation of cold receptors located in the upper respiratory tract.
Membrane properties of a barnacle photoreceptor examined by the voltage clamp technique
Authors: Brown H. Mack , Hagiwara S. , Koike H. , Meech R. M.
Published: December 2014

1. Electrical properties of the membrane of photoreceptor cells in the lateral ocelli of barnacles, Balanus amphitrite and B. eburneus were investigated by intracellular recording, polarization and voltage‐clamp techniques.

2. The resting potential of a dark adapted cell was 36·3 ± 6·6 mV (
S.D.) and depended mainly on the external K+ concentration.

3. Current—voltage relations obtained from voltage—clamp experiments in the absence of light were non‐linear and varied with time after the onset of a step change in membrane potential; the steady state was reached after about 0·5 sec.

4. Illumination resulted in a membrane potential change under current clamp and in a change of membrane current (light‐initiated membrane current (L.I.C.): total membrane current with illumination minus current without illumination) under voltage—clamp conditions. Amplitudes and time course of L.I.C. depended on the light intensity as well as membrane potential.

5. The L.I.C.‐voltage relation was non‐linear and corresponded with a slope conductance increase with increasing positive membrane potential.

6. The reversal potential of L.I.C. was independent of the light intensity and the time after onset of illumination; the average value obtained in normal saline was +26·9 ± 5·0 mV.

7. The membrane conductance estimated from instantaneous L.I.C.‐voltage relations agreed with the chord conductance of the non‐linear L.I.C.‐voltage relation.

8. Decreasing external Na+ concentration decreased the inward component of L.I.C. but not the outward component.

9. Decreasing external Ca2+ concentration increased the inward as well as the outward component of L.I.C.

10. The reversal potential shifted in the negative direction with decreasing external Na+ concentration (the rate was 10–15 mV for a tenfold change in concentration) and the rate was augmented in the absence of Ca2+ but did not exceed 21 mV.

11. The change of reversal potential with changes of external Ca2+ concentration was negligible in normal Na+ media but was significant in the absence of Na+ (rate as high as 20 mV).

12. Alteration of the external K+ or Cl− concentrations did not affect the amplitude or reversal potential of L.I.C.

13. The results indicate that illumination increases the membrane permeability mainly to Na+ ions and that the primary effect of Ca2+ ions is suppression of the permeability increase; Ca2+ permeability may increase slightly during illumination.
The recovery of resting potential and input resistance in sheep heart injured by knife or laser
Authors: Délèze J.
Published: December 2014

1. A lesion 100 μ in diameter with well‐defined boundaries was made with a laser in Purkinje fibres from sheep hearts. The membrane potential and the input resistance recorded in the intact tissue at about 0·5 mm from the edge of the lesion were found to drop at the instant of injury. The corresponding decrease of input resistance fits quantitatively the transmission line theory applied to a cable terminated by a short circuit at the lesion.

2. The input resistance and the membrane potential were found to rise simultaneously during healing‐over. The membrane potential returned to its original level within 1 min. By then, the input resistance had settled either to the same value as before injury, or to a higher value matching quantitatively the theoretical resistance of a cable terminated by an infinite resistance at the lesion.

3. Neither membrane potential nor input resistance recovered in calcium‐free solutions. But healing‐over rapidly occurred when calcium was added to solutions that might otherwise differ widely in composition.

4. The transmission line model fits all observations if it is assumed that the injury causes a leak or short circuit in the ‘cable’ that is soon closed, or rendered open circuit, by the development of a new diffusion barrier in the presence of calcium ions.
Heterosynaptic facilitation and post‐tetanic potentiation in Aplysia nervous system*
Authors: Epstein R. , Tauc L.
Published: December 2014

1. Heterosynaptic facilitation was defined as an increase of amplitude of a test excitatory post‐synaptic potential (EPSP) after the activation of a pathway (heterosynaptic pathway) different from that which produced the test EPSP. This phenomenon has been studied in Aplysia central nervous system under conditions which excluded the participation of post‐tetanic potentiation.

2. A unitary test was produced in the left and right giant cells, by indirect stimulation of an interneurone located in the peri‐oesophageal ring.

3. During heterosynaptic stimulation, orthodromic and antidromic activation of the test interneurone was prevented by (1) isolating the synaptic afferent region of the test interneurone from the tested synapse on the right giant cell by a sucrose block applied on the left pleurovisceral connective, and (2) using physiological stimulation of a piece of skin as a heterosynaptic stimulus.

Under these conditions which prevented any firing in the test interneurone, heterosynaptic facilitation is observed as a 200% increase of amplitude of the test EPSP in the right cell which lasted more than 15 min.

When instead of the physiological stimulus a supramaximal electrical stimulation of the nerves afferent to the abdominal ganglion was used, the increase of amplitude of the test EPSP could reach as much as 500% of its original amplitude. The effectiveness of such heterosynaptic stimulus was smaller when it was applied in the absence of a block of the left pleuro‐visceral connective.

4. It was possible to produce heterosynaptic facilitation when the preparation was cooled to 7–9° C or if Li+ replaced Na+ in the medium. Both of these changes suppressed post‐tetanic potentiation.

5. It was concluded that heterosynaptic facilitation is a phenomenon different from post‐tetanic potentiation. Heterosynaptic facilitation is similar to heterosynaptic inhibition seen in other cells in the same preparation, except for the polarity of action. Both phenomena seem to result from comparable mechanisms, probably acting on the quantity of transmitter released.
Responses of cells in the brain stem of the cat to stimulation of the sinus, glossopharyngeal, aortic and superior laryngeal nerves
Authors: Biscoe T. J. , Sampson S. R.
Published: December 2014

1. The distribution and properties of 146 brain stem units whose activity was influenced by electrical stimulation of sinus, glossopharyngeal, aortic and superior laryngeal nerves were studied in cats.

2. Cells excited by electrical stimulation of one or more of the nerves were distributed throughout the brain stem in an area extending rostrocaudally from Horsley—Clarke co‐ordinates P 7·5 to P 16·5 and laterally between 1·5 and 5 mm from the mid line.

3. Most of the units excited (n = 129) or inhibited (n = 17) by nerve stimulation were localized in the nucleus reticularis gigantocellularis and nucleus reticularis parvocellularis.

4. The latencies of activation varied from as short as 1·5 msec to as long as 35–40 msec. A high degree of convergence was observed.

5. Evoked responses varied from single spikes to bursts of impulses, the frequencies of which were sometimes as high as 1000/sec following a single shock to the nerve.

6. Spontaneously active cells inhibited (seventeen) by nerve stimulation were located primarily in NRG and NRP. None of the cells was inhibited by stimulation of one nerve and excited by stimulation of the others.

7. The responses of cells to a sudden rise in carotid sinus pressure were similar in kind to the responses to electrical stimulation of the nerves.
Place and modality analysis in caudal reticular formation
Authors: Bowsher David
Published: December 2014

1. Evoked potentials and unit responses were studied under chloralose anaesthesia in a restricted region of the caudal bulbar reticular formation of the cat which is known anatomically to receive a preferential spinal input.

2. Responses were analysed in terms of place and sensory modality and show varying degrees of place and modality convergence, as well as preferential responses for certain loci of stimulation.

3. Evidence is presented which suggests that some unit responses are generated in dendrites.

4. The response properties of the whole population are compared with those obtained from other reticular regions in previous identical experimental series. It is shown that the integrated activity of the ascending reticular formation acting as a whole would enable the organism to discriminate, to a greater or lesser degree, place and modality from the convergent peripheral input to the reticular formation.
Observations on the change in shape of blood platelets brought about by adenosine diphosphate
Authors: Born G. V. R.
Published: December 2014

1. An optical method used for measuring platelet aggregation was adapted for measurements of the change in shape of platelets that rapidly follows the addition of the aggregating agent adenosine diphosphate (ADP).

2. Measurements were made using dilute suspension of platelets with sufficient EDTA to prevent their aggregation.

3. Measurements of the velocity and magnitude of the optical effects of the shape change were highly reproducible.

4. Volumetric measurements showed that the shape change is not associated with an increase in mean platelet volume.

5. The velocity of the shape change had a temperature coefficient of about 4·5.

6. The velocity and magnitude of the shape change were not affected by pH between 5·8 and 9·2.

7. The dependence of the velocity of the shape change on the ADP concentration was in accordance with Michaelis—Menton kinetics. The Km was about 7·2 × 10−7
M.

8. The velocity of the shape change was inhibited competitively by ATP, adenosine and 2‐chloroadenosine but not by AMP. When the inhibitors were added after the maximum of the shape change they caused a concentration‐dependent diminution in the record of the change.

9. The results suggest that the shape change is initiated by reaction of the agonist ADP with specific receptor sites on the platelet membrane which leads to energy‐requiring changes in the structures responsible for maintaining the disk shape of normal platelets.
The effect of noradrenaline on the toad skin potential
Authors: House C. R.
Published: December 2014

1. The electrical response of isolated toad skins to the presence of 4 × 10−5
M noradrenaline in the inner medium has been studied.

2. When skins were bathed in Ringer solution, noradrenaline initiated a partial depolarization of the skin potential (inside surface becoming less positive) followed by a hyperpolarization; however, noradrenaline depolarized skins in sulphate Ringer.

3. The origin of the hyperpolarizing phase of the response to noradrenaline was studied by comparing the size of perturbations in the skin potential, produced by identical changes in external sodium, external chloride or internal potassium concentrations, before and during the response to noradrenaline.

4. Measurements of skin conductance were made in different sulphate media in order to estimate the magnitudes of the conductance of the shunt pathway through the skin and the conductance of the pathway for actively transported sodium ions.

5. Interpretation of both the variations in the perturbations of skin potential and the skin conductance measurements led to the conclusion that the hyperpolarizing phase of the response to noradrenaline was generated by an increase in the sodium to chloride permeability ratio for the outer barrier. It was considered that other evidence was compatible with this view.

6. Similar experimental methods were employed to study the action of antidiuretic hormone (ADH) and an elevated external concentration of calcium on the outer barrier. It was found that ADH increased the sodium to chloride permeability ratio whereas calcium decreased it. The separate actions of ADH and calcium on the sodium permeability of the outer barrier did not interfere apparently with the subsequent ability of noradrenaline to increase the sodium to chloride permeability ratio for this barrier in the skin.
Physiological and morphological properties of motoneurones in the central nervous system of the leech
Authors: Stuart Ann E.
Published: December 2014

1. A number of motor cell bodies have been identified in the segmental ganglia of the ventral nerve cord of the medicinal leech. These motoneurones supply either excitatory or inhibitory innervation to the muscles in the body wall.

2. Several tests were made to establish that each of the identified motoneurones directly innervates muscle fibres. (a) By injecting a fluorescent dye into the cell bodies of motoneurones, their axons were traced through one or both contralateral roots. (b) Electrical stimulation of a motoneurone by an intracellular electrode caused a single nerve impulse to travel through the roots to the muscles where it set up an excitatory or an inhibitory junctional potential. (c) Impulses set up in the roots were conducted antidromically to the cell body. (d) If the preparation was bathed in 20 m
M‐Mg2+, which blocks chemical synapses, conduction from the cell body to the muscles was not interrupted. Thus it is unlikely that an interneurone was interposed in the pathway within the ganglion.

3. Fourteen pairs of excitatory cells and three pairs of inhibitory cells can be identified in each of the twenty‐one segmental ganglia. These neurones together supply the five different muscle layers in each segment which execute the movements of the leech. Each neurone innervates a territory of muscle fibres which has a consistent size and location from segment to segment. Several lines of evidence suggest that the identified cells form a major fraction of the total number of excitatory motoneurones in the ganglion.

4. The territories of the motoneurones are arranged in a quilt‐like pattern closely resembling that already found for the receptive fields of sensory cells on the skin. Within the longitudinal muscle sheet, individual cells supply narrow or wide strips. The firing of each cell thus could produce bending of the segment in various directions or symmetrical shortening of it, depending on which of the motoneurones were active.

5. It is possible to deduce which motoneurones are firing to produce a particular movement of the animal. Thus these experiments provide a basis for studying reflex integration between motoneurones and the identified mechanosensory cells in the ganglion.
Acidosis and hypercalciuria: renal mechanisms affecting calcium, magnesium and sodium excretion in the sheep
Authors: Stacy B. D. , Wilson B. W.
Published: December 2014

1. Observations were made on the excretion of calcium and magnesium by the sheep's kidney following manipulation of the acid—base status.

2. Intravascular administration of a synthetic solution resembling saliva abolished the naturally occurring acidosis in sheep during feeding, and it also prevented the normal onset of post‐prandial hypercalciuria and hypermagnesiuria.

3. Non‐respiratory acidosis (induced by infusion of hydrochloric acid) and respiratory acidosis arising from inhalation of 6% (v/v) CO2 in air both caused an acute increase in calcium excretion.

4. Measurement of filtered loads showed that feeding exerted an effect on the functional characteristics of the sheep's kidney. The renal clearances of calcium and magnesium increased, whereas sodium clearance decreased.

5. Experimental conditions were arranged so that variations in acid—base status could be imposed at a time when the filtered load of calcium was declining.

6. With hydrochloric acid‐acidosis the renal excretion of calcium increased, despite a steady fall in the filtered load. With sodium bicarbonate alkalosis, the filtered load and the renal excretion of calcium decreased in unison.

7. These variations in calcium excretion were not accompanied by corresponding changes in the excretion of sodium.

8. It is concluded that the renal tubules in the sheep are sensitive to acid—base status and that they respond to a lowering of the blood pH by decreasing the tubular reabsorption of filtered calcium.
Movement of water, protein and crystalloids between vascular and extravascular compartments in heat‐exposed men during dehydration and following limited relief of dehydration
Authors: Senay L. C.
Published: December 2014

1. Five male subjects were exposed to a hot environment (43–44° C dry bulb, 28–29° C wet bulb) and allowed to dehydrate for 4 hr. Water was then provided ad libitum for drinking during a 20‐min period; thereafter the subjects continued at rest in the hot room for an additional 140 min.

2. Through periodic samples of venous blood, water and protein movement into or out of the intravascular compartment were assessed during dehydration and during and following water ingestion that partially relieved dehydration.

3. Consideration of changes in blood osmolarity, plasma protein content and haematocrit values led to the conclusion that protein was added to plasma during heat exposure and that plasma, as previously supposed, did not lose water at rates greater than that of the whole body under such conditions.

4. Haemodilution occurred when dehydration was partially relieved by drinking water and this dilution was maintained even when sweat loss exceeded the amount of water ingested.

5. For similar levels of bodily dehydration before and after water ingestion, body temperatures were lower when haemodilution was present.

6. A hypothesis that relates changes in plasma volume and constituents with levels of exercise is presented.
Enhancement of synaptic transmission by dendritic potentials in chromatolysed motoneurones of the cat
Authors: Kuno M. , Llinás R.
Published: December 2014

1. Monosynaptic transmission in cat lumbosacral motoneurones undergoing chromatolysis was studied by intracellular recording from 7 to 20 days after section of the appropriate ventral roots.

2. The average input resistance measured by passing polarizing currents across the cell membrane showed no significant difference between normal and chromatolysed motoneurones. Average rheobasic current for chromatolysed motoneurones was significantly lower (by about 30%) than that for normal motoneurones.

3. Spike‐like partial responses were commonly superimposed on monosynaptic EPSPs in chromatolysed motoneurones. These responses could be eliminated by stimulation of the bulbar inhibitory reticular formation, but could not be blocked by hyperpolarization applied to the motoneurone soma.

4. The spike‐like partial response in chromatolysed motoneurones showed a refractory period following (i) the antidromic invasion of the neurone generated by ventral root stimulation, and (ii) in response to two successive afferent stimuli. The refractory period ranged from 5 to 13 msec.

5. Initiation of the partial response had no direct relation with the amplitude of the underlying EPSP. The partial response could be evoked by small EPSPs of about 0·5 mV.

6. The action potential of a chromatolysed motoneurone arose from the partial response at different levels of depolarization, showing multiple trigger zones for spike initiation. Occasionally, chromatolysed motoneurones discharged in response to stimulation of a single afferent fibre.

7. In neurones where more than one spike‐like response was obtained, interaction between dendritic responses showed no refractoriness.

8. It is concluded that the partial response is an all‐or‐none event originating at some discrete site on dendrites, and that its presence increases the efficacy of synaptic excitation in chromatolysed motoneurones.
Selective hypersensitivity to bradykinin in salivary glands with ligated ducts
Authors: Hilton S. M. , Torres Sonia H.
Published: December 2014

1. In submandibular salivary glands of cats in which the ducts have been tied for at least 3 days, the kallikrein activity of ‘chorda’ saliva is much reduced; but it is never absent, even after prolonged sympathetic stimulation.

2. The relationship between the extent of the vasodilatation accompanying secretory activity and frequency of chorda stimulation is similar in normal glands and those with ducts ligated for 3 days, though, in the latter group, the variability is much greater.

3. In glands of which the ducts have been tied for 3 days, the responses to close arterial injections of bradykinin are greatly increased, the dose—response curve being steeper and shifted to the left. This appears to be a selective increase in sensitivity, as the responses to the close arterial injections of ACh are, if anything, less than those in normal glands.

4. In glands with ligated ducts, prolonged sympathetic stimulation reduces the vasodilatation following chorda stimulation.

5. These results strengthen the conclusion that kinins participate in the vasodilatation accompanying glandular activity.
Changes in axon birefringence during the action potential
Authors: Cohen L. B. , Hille B. , Keynes R. D.
Published: December 2014

1. Observations have been made on the changes in optical retardation accompanying the passage of impulses along crab leg nerves and squid giant axons.

2. The nerves were mounted on the stage of a polarizing microscope, at 45° to the planes of polarization and analysis, brightly illuminated with white light. During the nerve impulse the intensity of the light passing the analyser decreased temporarily by 1 part in 103‐106. Signal‐averaging techniques were used to obtain an acceptable ratio of signal to noise.

3. The changes in light intensity recorded under these conditions were shown to arise almost entirely from alterations in retardation, with little or no interference from scattering, absorption, linear dichroism or optical rotation effects; the occurrence of stimulus and coupling artifacts was also ruled out.

4. In the squid giant axon, the retardation change was shown to be located in a thin cylinder immediately surrounding the axoplasm, and to have a radially oriented optic axis.

5. The time course of the decrease in optical retardation was very similar to that of the action potential recorded with an intracellular electrode, suggesting that the retardation closely followed the electrical potential across the membrane.
Effects of catecholamines on the neuromuscular junction in the rat diaphragm
Authors: Kuba K.
Published: December 2014

1. The effects of noradrenaline, adrenaline and isoprenaline on neuromuscular transmission in the rat diaphragm and the influence of adrenergic blocking agents on these actions were investigated.

2. The resting membrane potential of the muscle fibre was increased by adrenaline (5 × 10−6‐10−5 g/ml.) and isoprenaline (5 × 10−6 g/ml.) up to 3‐4 mV, but noradrenaline (5 × 10−6‐10−5 g/ml.) had little effect.

3. The amplitude and the half‐decay time of the end‐plate potential (e.p.p.) were increased by noradrenaline (1 × 10−6 g/ml.), adrenaline (1 × 10−7‐10−5 g/ml.) and isoprenaline (1–5 × 10−6 g/ml.). The potentiation of the amplitude of the e.p.p. was greater with noradrenaline than with adrenaline and isoprenaline.

4. Noradrenaline (5 × 10−6 g/ml.) increased the frequency of miniature end‐plate potentials (m.e.p.p.), but not their amplitude. However, isoprenaline (5 × 10−6 g/ml.) increased the amplitude of m.e.p.p.s without change in frequency. Adrenaline (5 × 10−6 g/ml.) increased both frequency and amplitude of m.e.p.p.s.

5. Adrenaline (5 × 10−6 g/ml.) and isoprenaline (5 × 10−6 g/ml.) increased the input resistance of the muscle membrane. The effect was blocked by the β‐blocker, pronethalol (2 × 10−6 g/ml.), but not by the α‐blocker, phentolamine (2 × 10−6 g/ml.). Noradrenaline did not change the input resistance of the muscle fibre.

6. Noradrenaline (5 × 10−6 g/ml.) and adrenaline (5 × 10−6 g/ml.) augmented the extracellularly recorded end‐plate current (e.p.c.), but they had no effect on the half duration, nor on the action current (a.c.) of the nerve terminal, nor on the synaptic delay. Isoprenaline (5 × 10−6 g/ml.) had no effect on any of these parameters. The actions of noradrenaline and adrenaline on e.p.c. were abolished by phentolamine (2 × 10−6 g/ml.), but not by pronethalol (2 × 10−6 g/ml.).

7. Adrenaline (5 × 10−6 g/ml.) and isoprenaline (5 × 10−6 g/ml.) enhanced the amplitude of the acetylcholine potential elicited by iontophoretic application of acetylcholine. No such effect was produced by noradrenaline (5 × 10−6 g/ml.).

8. It was concluded that noradrenaline acts on the nerve ending increasing the release of transmitter, and that isoprenaline acts on the post‐synaptic membrane enhancing the input resistance, while adrenaline has both presynaptic and post‐synaptic actions. The effect on the nerve ending is concerned with the α‐action, whereas that on post‐synaptic membrane with β‐action of the catecholamines.
Sodium and potassium conductance changes during a membrane action potential
Authors: Bezanilla Francisco , Rojas Eduardo , Taylor Robert E.
Published: December 2014

1. A method for turning a membrane potential control system on and off in less than 10 μsec is described. This method was used to record membrane currents in perfused giant axons from Dosidicus gigas and Loligo forbesi after turning on the voltage clamp system at various times during the course of a membrane action potential.

2. The membrane current measured just after the capacity charging transient was found to have an almost linear relation to the controlled membrane potential.

3. The total membrane conductance taken from these current—voltage curves was found to have a time course during the action potential similar to that found by Cole & Curtis (1939).

4. The instantaneous current voltage curves were linear enough to make it possible to obtain a good estimate of the individual sodium and potassium channel conductances, either algebraically or by clamping to the sodium, or potassium, reversal potentials. Good general agreement was obtained with the predictions of the Hodgkin—Huxley equations.

5. We consider these results to constitute the first direct experimental demonstration of the conductance changes to sodium and potassium during the course of an action potential.