bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.