bluuebunny/crossref_metadata_2025 huggingface dataset:
Corticofugal effects from sensorimotor area I and somatosensory area II on neurones of the pontine nuclei in the cat.
Authors: Rüegg D , Wiesendanger M
Published: December 2014

1. The objective of the present experiments was to study the cortical influence from sensorimotor area I (SM I) and from somatosensory area II (S II) on single neurones of the pontine nuclei (PN) in cats under N2‐‐thiamylal anaesthesia. 2. Extracellular single unit recordings revealed a considerable convergence from S II and SM I. Out of ninety‐one PN neurones (identified as ponto‐cerebellas neurones by antidromic stimulation of the contralateral brachium pontis), fifty‐seven neurones were influenced by stimulation of at least one cortical site. Slightly less than half of these neurones (twenty‐five) had a convergent input from SM I and S II; twenty‐three PN neurones were excited by SM I only and nine PN neurones by S II only. The proportion of PN neurones excited via collaterals of cortico‐spinal neurones was small and restricted to those neurones which had an input from SM I. 3. Sixty per cent of the ponto‐cerebellar neurones were reliably activated by natural stimulation such as tapping or passive manipulations of limbs of various joints. The vast majority (thirty‐three out of thirty‐six PN neurones) which had receptive fields were also influenced by electrical stimulation of one or both cortical areas. The long latency and low probability of discharge to peripheral nerve stimulation suggest a complex, probably transcortical, pathway from the periphery to the PN. 4. The distribution of latencies to both cortical and brachium pontis stimulation indicates that the PN are a relay for fast and slow cerebro‐cerebellar connexions. 5. The convergence from cortical areas on PN indicates that the neurones influenced from somatic areas SM I and S II transmit integrated patterns of activity to the cerebellum.
Muscle load and constriction of the rabbit ear artery.
Authors: Speden R N
Published: December 2014

This isolated, perfused ear artery of the rabbit has been used to examine the effect of alterations in muscle load on the construction of arteries. The equilibrium muscle load, taken as the difference in wall stress between the relaxed and constricted artery at the same external radius, was varied by changing the transmural pressure and by constricting the artery. 2. The equilibrium muscle load increased initially and then declined with decreasing external radius when the transmural pressure was kept constant. The maximum muscle load was reached when the relaxed external radius had been reduced by 11% at 80 mmHg and by 4‐5% (relative to the radius at 80 mmHg) at 160 mmHg. 3. Arteries from young rabbits (3–6 months in age) which were partially constricted by adrenaline or spontaneous activity responded better to 60 sec of 4 Hz field stimulation at transmural pressures above 100 mmHg than did relaxed arteries. Neither field stimulation nor high concentrations of noradrenaline ( is greater than 800 ng/ml.) were able to constrict most arteries effectively at pressures above 160–170 mmHg unless partial constriction was present. The partial constriction reduced the load placed on the muscle by the same transmural pressure. Constrictio n during field stimulation was due largely to the release of neurotransmitter. 4. Ear arteries from young and older rabbits differed little in their ability to constrict against different transmural pressures. The one major difference was a lesser maximum constriction of arteries from older rabbits (18–24 months in age). However, arteries from older rabbits constricted well at the higher transmural pressures only because wall thickening largely compensated for a decreased ability of the muscle to develop active tension. 5. It is concluded that a decrease in internal radius to wall thickness ratio by either sufficient partial vasoconstriction or by wall thickening favours constriction of arteries because the load placed on the muscle by the same transmural pressure is reduced. Wall thickening may be an important compensatory reaction for deteriorating muscle contraction.
The interactions of calcium with mpyxicola giant axons and a description in terms of a simple surface charge model.
Authors: Schauf C L
Published: December 2014

1. Myxicola giant axons were examined under voltage clamp in solutions with [Ca2+] ranging from 2 to 200 mM. 2. The magnitude of the shifts in the Na and K conductance‐voltage curves, as well as membrane rate constants, caused by changes IN [Ca22+] were comparable and consistent with a model in which there exists a negative surface charge density of −0.013 charges/A‐2, but there is no significant binding of divalent cations to the external membrane surface. 3. There was no effect of equimolar substitution of magnesium for Ca on the positions of the conductance‐voltage curves along the voltage axis, consistent with the above conclusion. 4. Ca2+ has no effect on the shape of the steady‐state Na inactivation relation but simply causes a translation along the voltage axis. 5. It is concluded that a simple surface charge model in which divalent cations do not bind is adequate for Myxicola axons, and that there is no evidence to support a specific involvement of Ca with gating processes.
Descending inhibitory influences exerted by the brain stem upon the activities of dorsal horn lamina V cells induced by intra‐arterial injection of bradykinin into the limbs.
Authors: Besson J M , Guilbaud G , Le Bars D
Published: December 2014

1. In order to study descending influences of the brain stem upon the transmission of nociceptive messages at the spinal level, the activities of lumbar lamina V dorsal horn cells, induced by intra‐arterial injection of brandykinin into the limbs, were recorded in unanaesthetized cats in both decerebrate and temporary spinal states (reversible cold block applied at the thoracic level). 2. In the decerebrate state, the intra‐arterial injection of bradykinin had little or no effect. 3. During the reversible spinalization, the effects of bradykinin were revealed or considerably enhanced. As described in a previous study, in the C1‐transected cat, three types of effects were encountered: excitatory, inhibiitory and mixed (inhibitory‐excitatory). 4. These modifications observed after spinalization were generally associated with a large increase of the spontaneous firing rate. 5. These results emphasize, in the decerebrate cat, the importance of descending inhibitory controls exerted by the brain stem upon the transmission of nonciceptive messages at the spinal cord level.
Comparative study of the effects of propranolol and tetracaine on cation movements in resealed human red cell ghosts.
Authors: Porzig H
Published: December 2014

1. The effects of two positively charged local anaesthetic amines, tetracaine and propranolol, on cation permeability were studied in resealed human red cell ghosts prepared from metabolically depleted erythrocytes. 2. The K permeability was reduced by tetracaine but increased by propranolol. The effect of tetracaine was independent of extracellular Ca concentration but was raised to 2‐5 x 10(−7) M. The effect of propranolol, which was enhanced when the external Ca concentration was raised, could be completely inhibited by lowering the internal free Ca to less than 10(−7) M. 3. Propranolol, but not tetracaine, increased the intracellular Ca ion concentration by releasing up to 20% of the membrane‐bound Ca to the cell interior. This increase in intracellular Ca was sufficient to mediate the observed change in K permeability. 4. Tetracaine and propranolol reduced the Ca binding capacity of the ghost membrane by about 20 and 40% respectively. The Ca permeability was increased by propranolol and was slightly reduced by tetracaine. 5. In high concentrations (2–7 mM) propranolol by itself moderately increased K and Na permeability, but supressed completely the Ca‐induced increase in K permeability. Tetracaine in concentrations up to 4 mM enhanced the Ca‐induced increase in K permeability. Higher concentrations of the drug caused lysis of the cells. 6. Maximally effective concentrations of tetracaine and propranolol inhibited the ATP‐dependent Ca outward transport by 30 and 70% respectively. 7. The effects of tetracaine on K permeability were shared by the local anaesthetics prilocaine and lidocaine, those of propranolol were shared by practolol, a beta‐adrenergic antagonist and tetraethylammonium, a ganglionic blocking agent. 8. It is suggested that the differences in the effects of tetracaine and propranolol on cation permeability reflect qualitatively different interactions of the two drugs with Ca binding sites on the inner surface of the membrane.
The heat production associated with the passage of a single impulse in pike olfactory nerve fibres.
Authors: Howarth J V , Keynes R D , Ritchie J M , von Muralt A
Published: December 2014

1. A study has been made of the temperature changes associated with the passage of a single impulse in the non‐myelinated fibres of the pike olfactory nerve. 2. The initial heat occurs in two phases: a burst of positive heat, followed by an evolution of negative heat. The positive and negative heats, and the net initial heat, are temperature‐dependent. 3. At 0 degrees C the measured positive initial heat is 44.2 mucal/g.impulse; and the corresponding negative initial heat is 48.9 mucal/g.impulse. There is thus a net initial heat that is negative, of about 4.7 mucal/g.impulse. 4. The positive heat has a positive temperature coefficient, being increased by a factor of 1.86 when the temperature is rasied from 0 degrees C to 10 degrees C. 5. The negative initial heat also increases when the temperature is raised, but less than the positive initial heat. As a result, the net initial heat tends to become positive at higher temperatures. 6. Because of temporal dispersion of the action potential over the face of the thermopile, the observed temperature changes are smaller than those that occur at a single point in the nerve close to the stimulating cathode. The value of the positive heat at 0 degrees C corrected for temporal dispersion is estimated to be about 62 mucal/g.impulse: the corresponding value for the negative heat is about 67 mucal/g.impulse. 7. All records were analysed in terms of only two phases of initial heat (one positive, one negative). No analysis required four phases; but it is unclear whether this finding reflects a true absence of four phases, or merely the inability of the recording equipment to resolve them. 8. The positive heat seems to be derived from two sources. First, there is a dissipation of the free energy stored in the membrane capacity. Secondly, there is an evolution of heat corresponding with a decrease in entropy of the membrane dielectric with depolarization.
Bronchial hysteresis in excised lungs.
Authors: Hughes J M , Jones H A , Wilson A G
Published: December 2014

1. Intrapulmonary bronchi in excised dog lungs were outlined with tantalum dust and stereoscopic radiographs taken during deflation and inflation of the lung with air, saline, Ringer or EDTA solutions. Dimensions of airways as a percentage of their values at full inflation were calculated from measurements of the stereoscopic X‐ray images. 2. The mean deflation‐inflation diameter difference at a transpulmonary pressure of 5 cm H2O was 20% in the air‐filled lung, 9% in the saline filled preparation and 2% after filling with EDTA in saline. 3. These results show that the intrapulmonary bronchi have an intrinsic hysteresis separate from the hysteresis imposed on them by the expansion of the surrounding parenchyma. This intrinsic hysteresis is mainly due to the tone of the smooth muscle in the bronchial wall.
Characterization of acetylcholine receptors in the Schwann cell membrane of the squid nerve fibre.
Authors: Villegas J
Published: December 2014

1. The effects of alpha‐bungarotoxin, nicotine and muscarine on the Schwann cell membrane potential have been studied in the giant nerve fibre of the squid. The external application of alpha‐bungarotoxin (10(−6), 10(−8), 10(−9) M) irreversibly blocks the long‐lasting Schwann cell hyperpolarizations following the conduction of nerve impulse trains by the axon. It also blocks the Schwann cell hyperpolarizing response to the external application of carbamylcholine (10(−6)M) to the resting nerve fibre. 2. Externally applied D‐tubocurarine (10(−5)M) protects against the irreversible action of alpha‐bungarotoxin (10(−9)M) on the Schwann cell. Within 10 min of reimmersion in toxin‐free sea water there is complete recovery of the Schwann cell hyperpolarizing response to carbamylcholine (10(−6)M) which had been initially abolished. 3. Nicotine (10(−6)M) induces a prolonged hyperpolarization of the Schwann cells in the resting nerve fibre, wheras at the same concentration, muscarine has no appreciable effect on the Schwann cell membrane potential. 4. None of these drugs, at the concnetrations utilized in the present study, had any appreciable effect on the resting and action potentials of the axon. 5. These findings show the presence of acetylcholine receptors of the nicotinic type in the Schwann cell membrane, and give further support to the hypothesis on the role of the acetylcholine system in the genesis of the long‐lasting Schwann cell hyperpolarizations caused by the conduction of nerve impulse trains by the axon.
Effects of chronic treatment with various neuromuscular blocking agents on the number and distribution of acetylcholine receptors in the rat diaphragm.
Authors: Chang C C , Chuang S T , Huang M C
Published: December 2014

1. Acetylcholine receptors in the end‐plate and non‐end‐plate areas of the rat diaphragm, after treating the animal with hemicholinium‐3, alpha‐ or beta‐bungarotoxin in vivo, were studied by their specific binding of labelled alpha‐bungarotoxin. 2. Subcutaneous injection of maximum tolerable doses of hemicholinium‐3 (50 mug/kg) twice daily for 7 days increased the number of extrajunctional receptors along the whole length of muscle fibre, the approximate density of receptor on muscle membrane being increased from 6/mum2 in normal diaphragm to 38/mum2. Junctional receptors were also increased in number from 2‐2 x 10(7) to 2‐8 x 10(7) per end‐plate. 3. Five days after denervation, there were approximately 153/mum2 extrajunctional receptors and the number of receptors on the end‐plate was increased by 220%. 4. Intrathoracic injection of beta‐bungarotoxin (50 mug/kg) also increased the density of extrajunctional receptors to approximately 104/mum2, and the number of end‐plate receptors by 140% in 5 days. The neuromuscular block was extensive and prolonged. 5. [3H]Diacetyl alpha‐bungarotoxin (150 mug/kg) injected into thoracic cavity caused complete neuromuscular blockade for 12 hr. At 24 hr, the synaptic transmission was restored in 80% of the junctions with less than 10% end‐plate receptors freed, whereas the safety factor for transmission in normal diaphragm was 3‐5. Extrajunctional receptors appeared to increase within 24 hr. This increase continued despite the restoration of neuromuscular transmission, and the receptor density at 5 days was approximately 5l/mum2. The number of junctional receptors, however, was not increased. Repeated injection of the toxin gave the same result. 6. It is concluded that the numbers of junctional and extrajunctional acetylcholine receptors are regulated in different ways, and the possible role of acetylcholine is discussed.
Response of ventrobasal thalamic cells to hair displacement on the face of the waking monkey.
Authors: Hayward J N
Published: December 2014

1. In the unanaesthetized, moving monkey, single cell firing patterns in the region of the ventrobasal complex (VB) of the thalamus that respond to facial hair displacement were the basis for a statistical analysis of the effects of tactile, thermal and behavioural stimuli. 2. There were facial hair responses throughout the dorsoventral extent of the ventralis posterior medialis (VPM) nucleus of the contralateral thalamus over a rostro‐caudal distance of about 2 mm (Fr. 5.1 to Fr. 7.1). 3. The three different anatomical types of facial hairs that activated thalamic neurones were common facial hairs, circumoral vibrissae and facial whiskers. 4. Displacement of the intermediate length, soft, yellow‐brown common facial hairs on the central and lateral face from fields of 1–9 cm2 produced a fast‐adapting burst discharge in single thalamic cells in the upper half of the contralateral VPM. 5. Tactile stimuli applied to the short, stiff, white circumoral vibrissae in fields of 0‐2‐0‐9 cm2 along the margins of the upper and lower lips resulted in fast‐adapting phasic firing of units in the lower half of the contralateral VPM. Engagement or disengagement of the interlocking hairs of upper and lower lips resulted in increased or decreased, respectively, firing of these thalamic units. 6. Bending a single, long, stiff, black facial whisker extending out from the side of the face resulted in a sustained increased firing of contralateral VPM cells with directional sensitivity. 7. Cells in the ventrobasal thalamus relay mechanoreceptor input from three specialized hair types on the face of the monkey. These somatotopically organized hairy receptive fields are unique, registering response patterns from tactile, thermal and behavioural stimuli. Facial hairs must play an important part in primate feeding, drinking, and oral‐exploration.
Muscular reflex stimuli to the cardiovascular system during isometric contractions of muscle groups of different mass.
Authors: McCloskey D I , Streatfeild K A
Published: December 2014

1. The cardiovascular responses to voluntary isometric contractions performed by human subjects are determined by the proportion of maximal tension achieved by the muscles contracting, and not by the mass of the contracting muscles, nor by the absolute tension achieved (Lind & McNicol, 1967; confirmed here). When two or more muscle groups contract simultaneously at different relative tensions, the increments in heart rate and blood pressure are the same as when the muscle group at the higher relative tension contracts alone at that tension (Lind & McNicol, 1967). It is known that there are both central and reflex stimuli to the cardiovascular system in exercise, and the present study examines whether the muscular reflex stimuli are related to the proportion of maximal tension achieved or to the mass of contracting muscle. 2. Isometric hind‐limb contractions were induced in anaesthetized dogs and cats by stimulation of spinal ventral roots. Pressor responses to contraction of both hind limbs were greater than responses to contractions of either hind limb alone. No differences were observed between heart rate responses to single or combined hind‐limb contractions. 3. When human subjects perform isometric contractions, a pressor response can be maintained beyond the conclusion of the exercise by occluding muscle blood flow. This response is generally attributed to a reflex set up in the muscle by the action of chemical factors on afferent nerves. When comparable pressor responses were evoked by comparable proportional efforts with either the whole hand or the little finger, it was found here that the pressor responses remaining during the period of post‐exercise occlusion were greater when the greater mass of muscle had been exercised. 4. It is concluded that the muscular reflex drive in isometric exercise is related to the bulk of contracting muscle.
Discharges of relay cells in lateral geniculate nucleus of the cat during spontaneous eye movements in light and darkness.
Authors: Noda H
Published: December 2014

1. Discharges of 315 relay cells of the lateral geniculate nucleus (LGN) during spontaneous eye movements were studied in alert cats. 2. When tested in a stationary patterned field, 114 cells showed sustained discharges related to the direction of gaze (S cells) and to local differences in luminance; 109 cells showed transient response to quick shifts of retinal image during saccades (T cells); ninety‐two cells showed mixed responses (M cells), i.e. transient responses to rapid shifts of retinal image and sustained firing related to local differences in luminance. 3. Following saccades occurring in the light, T and M cells showed a burst discharge, while spontaneous discharges of S cells were completely suppressed for 150–200 msec. 4. When tested in total darkness, modifications in activity which were apparent in light disappeared completely. This was true for all 315 relay cells. 5. T cells responded to optic chiasm stimulation at shorter latencies (X = 1.15 msec) than S cells (X = 1.77 msec). M cells showed a latency distribution in between those for S and T cells with a mean latency 1.40 msec. 6. When tested with moving grating stimulation, S cells responded in only one manner; with discharges to each stripe of the grating (primary response), while T and M cells showed two different responses: a primary response to a slower motion and a non‐specific burst in response to a faster motion. The burst did not reflect the stimulus pattern (secondary response). 7. When tested with diffuse light switched on and off over the tangent screen, S cells showed a sustained response either to light or darkness, whereas T and M cells responded transiently either to the onset or offset of the light, or to both. M cells occasionally showed a mixture of transient and sustained responses either to light or darkness. 8. In over‐all response properties, most S cells correspond to X (sustained) cells and most T cells to Y (transient) cells previously known from acute experiments. M cells had intermediate response properties between X and Y cells. 9. Functional roles of these classes of cells in relation to previously proposed functions are discussed.
The effect of aldosterone and the renin‐angiotensin system on sodium, potassium and chloride transport by proximal and distal rat colon in vivo.
Authors: Dolman D , Edmonds C J
Published: December 2014

1. The roles of aldosterone and angiotensin in the direct control of epithelial sodium transport in vivo have been investigated by measurement of electrical p.d. changes and of the fluxes of sodium, potassium and chloride in rat colon, an organ actively involved in electrolyte homoeostasis. Exogenous angiotensin and aldosterone were given by both short‐ and long‐term infusions and endogenous secretion of the hormones was varied by dietary sodium variation and by nephrectomy and/or adrenalectomy. 2. In vitro angiotensin has been shown to influence colonic salt and water absorption but in the present in vivo experiments administered angiotensin had no significant action on p.d. or on the ionic fluxes of the proximal or distal colon. The increase in p.d. produced by infusing aldosterone was unaffected by giving angiotensin concurrently. The effect of sodium depletion in stimulating sodium absorption and potassium secretion was completely abolished by adrenalectomy but was unaffected by nephrectomy. 3. During prolonged infusion of angiotensin into adrenalectomized rats, a small fall in faecal fluid and sodium content was observed, but this change would have little significance in sodium homoeostasis. 4. Aldosterone and sodium depletion stimulated sodium absorption in both proximal and distal colon but significant increase in potassium secretion was demonstrable only in the distal colon. Bicarbonate secretion (by calculation) was unaffected. In the proximal colon, the increased sodium absorption appeared to be accompanied by increased chloride absorption while in the distal colon it was principally the sodium‐potassium exchange that was increased. 5. Adrenalectomy reduced potassium secretion in both proximal and distal colon but sodium absorption was only significantly reduced in the proximal colon. 6. It was concluded that there is no evidence that angiotensin in the living animal has a role as an important salt retaining hormone by direct epithelial action. Aldosterone has a considerable effect which is independent of the presence of angiotensin, and which differs in proximal and distal colon in regard to the relative effects on chloride absorption and potassium secretion.
The relative importance of central nervous catecholaminergic and cholinergic mechanisms in drinking in response to antiotensin and other thirst stimuli.
Authors: Fitzsimons J T , Setler P E
Published: December 2014

1. Intracranial or subcutaneous doses of atropine or atropine methyl nitrate that were fully effective at preventing drinking in response to intracranial carbachol did not block angiotensin‐induced drinking. 2. The nicotinic antagonist dihydro‐beta‐erythroidine given intracranially affected neither angiotensin‐ nor carbachol‐induced drinking. 3. The dopaminergic antagonists haloperidol and spiroperidol injected intracranially blocked angiotensin‐induced drinking but did not affect carbachol‐induced drinking. 4. Angiotensin‐ and carbachol‐induced drinking were unaffected by alpha‐ or beta‐adrenergic antagonists except at toxic doses. 5. Destruction of catecholaminergic neurones with 6‐hydroxydopamine markedly reduced angiotensin‐induced drinking, but had relatively little effect on carbachol‐induced drinking. 6. Intracranial haloperidol reduced the amount of water drunk in response to overnight deprivation of water, but did not affect feeding in response to overnight starvation or to intracranial noradrenaline. 7. Drinking following overnight water deprivation was unaffected by intracranial alpha‐ or beta‐adrenergic antagonists. 8. Preventing dopaminergic transmission with intracranial haloperidol decreased the water to food ratio of the rat's intake after overnight starvation, whereas increasing the dopamine levels with the combination of FLA‐63 and L‐DOPA increased the ratio. 9. Intraventricular dopamine in large amounts caused the water‐replete rat to drink. 10. It is concluded that among the many functions of dopaminergic systems in the brain is a role in the control of water intake, and that these systems participate in an important way in drinking in response to angiotensin.
The sinus nerve and baroreceptor input to the medulla of the cat.
Authors: Lipski J , McAllen R M , Spyer K M
Published: December 2014

Electrical stimulation within the medulla of cats revealed that myelinated primary afferent fibres of the sinus nerve terminated within the immediate vicinity of the tractus solitarius and its nucleus. 2. The activity of neurones within this area was also evoked on sinus nerve stimulation, although few (17%) were activated within a latency compatible with monosynaptic excitation. Additional projections over polysynaptic pathways have been shown to the parahypoglossal area and to the area of the nucleus ambiguus. 3. These three areas were shown to contain neurones whose activity was enhanced by stimulation of the baroreceptor endings of the ipsilateral carotid sinus. 4. No evidence for a projection of sinus nerve afferents to the medial reticular formation (an area extending medially from the hypoglossal nucleus and nerve tract and including the paramedian reticular nucleus) was obtained in either antidromic or orthodromic studies. 5. The organization of the central pathway of the carotid sinus baroreceptor reflex is discussed in the light of these results.
The effect of curare on the release of acetylcholine from mammalian motor nerve terminals and an estimate of quantum content.
Authors: Fletcher P , Forrester T
Published: December 2014

Curarized and non‐curarized rat hemidiaphragm muscles were indirectly stimulated in vitro. 2. The fluid bathing the active curarized muscles was eluted through a dextran gel (Sephadex G‐10), effecting a complete separation of ACh from curare. The acetylcholine fraction was then assayed on an isometric leech muscle preparation. 3. Prostaglandin (PGE1) in a concentration fifteen times that estimated to be released from the skeletal muscle preparation did not affect the response of leech muscle to ACh. 4. The amount of ACh released by curarized muscles (4‐9 X 10(‐18) mole/impulse‐junction) was not significantly different from that released by non‐curarized muscles (4‐6 X 10(‐18) mole/impulse‐junction). These quantities are similar to those obtained by previous workers. It is concluded that curare in a paralytic dose does not affect the output of ACh from motor nerve terminals stimulated at low frequencies. 5. Spontaneous release of ACh from non‐curarized muscles was estimated at 0‐45‐0‐65 p‐mole/min. hemidiaphragm. It is calculated that only 2% of this amount could give rise to post‐synaptic electrical events, the remainder having a non‐synaptic source. 6. The number of molecules of 'quantal' ACh released by stimulated muscle is calculated as 2‐5 X 10(6)/impulse‐junction, taking account of the non‐synaptic release. The number of ACh molecules in one quantum was estimated to be 6250, an amount that could be easily accommodated in one synaptic vesicle.
Voltage dependence of agonist effectiveness at the frog neuromuscular junction: resolution of a paradox.
Authors: Dionne V E , Stevens C F
Published: December 2014

1. End‐plate currents produced by nerve‐released acetylcholine and iontophoretically applied acetylcholine and carbachol have been recorded from voltage‐clamped frog cutaneous pectoris neuromuscular junctions made visible with Nomarski differential interference contrast optics. 2. The effectiveness of agonists ‐ that is, the end‐plate conductance change produced by a given dose‐has been determined as a function of post‐junctional membrane potential. 3. As the post‐junctional membrane potential is made more negative, nerve‐released acetylcholine becomes less effective whereas iontophoretically‐applied agonists become more effective. 4. This voltage dependence of agonist effectiveness is mediated neither by end‐plate current iontophoresis of agonist into the cleft nor through electric field effects on the esterase. 5. Influences of membrane potential on the opening and closing of end‐plate channel gates can account quantitatively for the voltage‐dependent effectiveness of both nerve‐released and iontophoretically applied agonist.
Metabolic changes associated with the slowing of relaxation in fatigued mouse muscle.
Authors: Edwards R H , Hill D K , Jones D A
Published: December 2014

1. The biochemical basis of the slowing of relaxation seen in fatigue has been examined using an isolated mouse soleus preparation. 2. Slowing of relaxation occurred during prolonged tetani under anaerobic conditions when ATP and PC fell and lactate accumulated. 3. Slowing of relaxation was also demonstrated with muscles poisoned with cyanide and iodoacetic acid when there was a fall in ATP and PC but no accumulation of lactate. During a period of anaerobic recovery following a fatiguing tetanus, relaxation became faster at a time when lactate was accumulating in the muscle. 4. It is concluded that the slowing of relaxation in fatigue is not a consequence of lactate accumulation, and a relationship is demonstrated between the ATP content of the muscle and the rate of relaxation in muscles fatigued by prolonged stimulation, 5. Rates of ATP turn‐over in fresh muscle, and at intervals throughout a tetanus are consistent with the suggestion that the rate limiting step for myofibrillar ATPase may be directly related to the rate limiting step for the decay of tension during relaxation.
Heat production and chemical changes during isometric contractions of the human quadriceps muscle.
Authors: Edwards R H , Hill D K , Jones D A
Published: December 2014

1. Development of a new thermal probe and use in conjunction with chemical analysis of needle biopsy samples, has made possible a thermodynamic study of the energetics of muscular contraction in the human quadriceps. 2. The observed rate of muscle temperature rise was proportional to the force of the contraction. During maximal contractions the rate of heat production was 54 +/‐8‐5 W/kg wet muscle (mean +/‐ s.d.). 3. The observed rates of muscle temperature rise agreed well with the rates calculated from the measured metabolite changes when standard values for the enthalpy changes of the reactions involved were used. 4. During prolonged stimulation of the quadriceps at 15/sec via the femoral nerve, the rate of heat production per unit force fell to nearly half the initial value. It is estimated that this represented a two‐ to fourfold increased in economy of ATP turn‐over required to maintain a given force. 5. Relaxation becomes progressively slower during prolonged contractions and it is suggested that the slowing of relaxation and the increased economy of force maintenance may both be due to an increased cross‐bridge cycle time in the fatigued muscle.
Autonomic nerve stimulation, kallikrein content anc acinar cell granules of the cat's submandibular gland.
Authors: Barton S , Sanders E J , Schachter M , Uddin M
Published: December 2014

The parasympathetic and sympathetic nerves to the submandibular gland of the anaesthetized cat were stimulated under specific conditions. 1. It was possible to decrease the kallikrein (kininogenase) content of the gland by as much as 90‐95% by sympathetic nerve stimulation. In such a gland the appearance and concentration of secretory granules in the acinar cells were indistinguishable from an unstimulated gland. 2. Parasympathetic nerve stimulation, in contrast to sympathetic nerve stimulation, whilst having no significant effect on the kininogenase content of the gland, resulted in the disappearance of a great majority of the acinar granules. 3. These results demonstrate that the acinar granules in the submandibular gland of the cat are not a significant source of kallikrein. 4. Our experiments also failed to indicate any obvious correlation between the granules of the demilune cells and the kallikrein content of the gland. 5. The possibility is raised that kallikrein is located in the cells of the striated ducts.
Intracellular chloride activity in frog heart.
Authors: Ladle R O , Walker J L
Published: December 2014

1. Chloride liquid ion exchanger micro‐electrodes have been used to measure intracellular chloride activity (aiCl) in isolated pieces of frog sinus venosus, atrium and ventricle. 2. aiCl was found to be 35‐0 +/‐ 3‐2, 17‐3 +/‐ 0‐8 and 17‐6 +/‐ 0‐8 mM in sinus venosus, atrium and ventricle, respectively. 3. In atrium and ventricle aiCl is independent of whether the tissue is beating or non‐beating. 4. In non‐beating ventricle aiCl changes rapidly and reversibly when aOCl is reduced by replacing chloride with glucuronate. 5. ECl calculated from the measured aiCl has been compared with ECl calculated from the constant field equation assuming either constant chloride conductance or constant chloride permeability. 6. It is suggested that chloride is actively transported into the cells in all three kinds of frog heart tissue.
Evidence for a transient potassium membrane current dependent on calcium influx in crab muscle fibre.
Authors: Mounier Y , Vassort G
Published: December 2014

1. Voltage‐clamp experiments were achieved on crab muscle fibre with the double sucrose‐gap technique. 2. The accuracy of the imposed voltage has been controlled with an impaled micro‐electrode connected to an external circuit. 3. Step depolarizations elicit two kinds of records. In type I fibres, the initial current exhibits only an inward calcium component. In type II fibres, the initial current exhibits a hump, transient outward current, mixed with the calcium current; these fibres exhibit always action potentials with fast repolarization. 4. A potassium origin is suggested for this outward current, due to its dependence on [K]o and its inhibition by TEA. 5. In fibres with a composite initial current, the voltage dependence of the availability of the measured inward current appears complex. It can be shown to be the sum of a simple calcium inactivation (which is observed alone in TEA solution) and a fast potassium inactivation. This potassium conductance is nearly half‐available at the resting membrane potential. 6. The origin of the transient outward current is tentatively described. Consecutive to a transient internal increase of calcium ions (due to the calcium current) its activation curve is shifted in an hyperpolarizing direction resulting in an increased activation for an apparent identical depolarization. 7. This fast outward current which overlaps the calcium inward current can account for the low amplitude and the variability of the electrical activity of crab muscle fibres.
Breathing in man during steady‐state exercise on the bicycle at two pedalling frequencies, and during treadmill walking.
Authors: Kay J D , Petersen E S , Vejby-Christensen H
Published: December 2014

1. The breathing pattern, that is the changes in tidal volume (VT), and in inspiratory (TI) and expiratory (TE) durations, has been studied as ventilation increases in exercise. 2. Five healthy subjects were studied in steady‐state exercise on a bicycle ergometer, breathing air, at two speeds of pedalling and at six different loads. The pattern was recorded for single breaths. Two of the subjects were also studied while walking on a treadmill with four combinations of speed and gradient. 3. In bicycle exercise, as the CO2 output increased mean VT increased, and mean TI and TE decreased, the absolute decrease in TI being small. The pedalling speed did not affect these relationships. 4. Individual breath durations showed no tendency to group around multiples of the period of rotation of the pedals. 5. In treadmill exercise, no clear influence of stride rate on respiratory rate could be found. The pattern was similar to that found in bicycle exercise. Again no grouping could be found. 6. No evidence of an effect of frequency of limb movement on breathing pattern in submaximal exercise has been found. The selection of breathing pattern seems to be unrelated to the nature of the stimulus but closely geared to the metabolic needs of the body.
Binding of adenosine diphosphate to intact human platelets.
Authors: Born G V , Feinberg H
Published: December 2014

1. Human platelet‐rich plasma was incubated at 37 degrees C with [8‐14C]ADP and with human serum albumin labelled with 125I. The platelets were rapidly separated by centrifugation through silicone oil. From radioactivity determinations of plasma and platelet pellets the uptake of ADP, without or with break‐down products, by the platelets was calculated on the assumption that the 125I radioactivity in the pellet represented trapped plasma. 2. ADP radioactivity was taken up by platelets within 10 sec and increased with time of incubation. The uptake of other nucleotide diphosphates was less initially and increased much more slowly. 3. Radioactivity added as ADP was recovered as ATP to the extent of 60%; as ADP of 30%; and as AMP of 10%. 4. Prostaglandin E1 which inhibited platelet aggregation had no effect on the initial or subsequent uptake or on this distribution of radioactivity. 5. The rate of rise in uptake was much slower when platelets were resuspended in plasma heated to 56 degrees C for 30 min. 6. Unlabelled adenosine inhibited the later, but not the initial, uptake while unlabelled ADP inhibited both. Dipyridamole, which blocks adenosine uptake, prevented the later but not the initial uptake. 7. [alpha‐32P]ADP radioactivity was taken up at the earliest sampling time and the extent of uptake did not further increase. 8. Guinea‐pig platelets, which do not take up adenosine, took up [8‐14C]ADP radioactivity from purine‐labelled ADP initially. 9. It was concluded that the initial uptake represented binding of ADP and that the later uptake represented labelled adenosine originating as a break‐down product of ADP. 10. A Scatchard plot of ADP uptake indicated more than one type of binding site. There were approximately 88,000 high affinity sites per platelet which had an affinity constant of 5‐41 X 10(5) M‐1.
A comparison of radioactive thallium and potassium fluxes in the giant axon of the squid.
Authors: Landowne D
Published: December 2014

1. The influx and the efflux of 204Tl and 42K were measured in intact squid giant axons. 2. The resting efflux of 204Tl was found to be about one half of 42K and to have a temperature coefficient (Q10) of 1‐3 as compared to 1‐1 for K. 3. The extra efflux of 204Tl associated with nerve impulses was 30% greater than 42K. 4. From either Cl or NO3 sea water, the resting influx of 204Tl was about three times that of 42K. Ouabain reduced the influx of either isotope by about two thirds without changing the Tl/K ratio of the fluxes. This indicates that the Na pump can transport Tl. 5. From NO3 sea water the extra influx of 204Tl assoicated with nerve impulses was about the same as 42K. From Cl sea water there was no detectable extra influx of 204Tl. 6. The flux ratio, ouabain‐insensitive influx/efflux, was different for the two ions. The resting flux ratio for Tl was consistent with a passive non‐interacting flux, whereas K movements were consistent with 'single file' passage through the membrane. 7. The extra flux associated with nerve impulses is different from the resting flux both in Tl/K selectivity and in the effect of anion in the sea water. There is also a much higher flux per unit time during the nerve impulse. These differences suggest differences in the mechanisms underlying ion permeability at rest and during nervous activity.
The influence of pH on the rate of tetrodotoxin action on myelinated nerve fibres.
Authors: Ulbricht W , Wagner H H
Published: December 2014

1. The experiments were done on single myelinated nerve fibres of Rana esculenta. The rates of toxin effect were studied either by measuring the maximum rate of rise, VA, of repetitively evoked action potentials or by measuring Na currents during periodic impulses in the voltage clamp. 2. VA measurements showed that in alkaline solutions (pH up to 8‐8) the offset rate was unchanged while the onset was slowed in quantitative agreement with an assumed decrease in the active cationic form of tetrodotoxin. 3. Both VA measurements and those in the voltage clamp revealed a decrease in T'off, the offset time constant and in increase in the onset time constant, T'on, as the pH was lowered. 4. For tetrodotoxin concentrations, [TTX], up to 400 nM and pH values down to 5‐3 the simple relation T'on/T'off = p'R held, where p'T is the constant factor by which the Na permeability was reduced at equilibrium with a given [TTX]. 5. The agreement between kinetic and equilibrium results was also valid when, at constant [TTX] and pH. p'T was modified by the holding potential during equilibration. 6. No unequivocal explanation of the results can be given but some of their features resemble acid catalysis.
Ionic mechanism of the excitatory synaptic membrane of the crayfish neuromuscular junction.
Authors: Onodera K , Takeuchi A
Published: December 2014

1. The reversal potential for the excitatory neuromuscular junction of the crayfish (Cambarus clarkii) was measured using the voltage clamp method. The potential change was recorded with an intracellular microcapillary and the negative phase of the output of the feed‐back amplifier was connected to the stainless‐steel wire which was inserted longitudinally into the muscle fibre. 2. When the excitatory nerve was stimulated, a transient feed‐back current flowed inwardly through the membrane. This current was called the excitatory junctional current (e.j.c.). 3. Reversal potentials were determined by extrapolating the e.j.c.s measured at different membrane potentials. They were about 10‐20 mV positive with respect to the bath solution (11‐5 +/‐ 1‐2 mV, mean +/‐ S.E.). 4. The reversal potential for the iontophoretically applied glutamate was identical with that for the e.j.c. 5. In hypertonic solutions, the reversal potentials for e.j.c. and glutamate became more negative. 6. When the sodium concentration of the bath solution was decreased, the reversal potential became more negative. 7. When the chloride and potassium concentration were altered, little, if any, change was observed in the reversal potential. 8. It was concluded that the e.j.c. was carried mainly by sodium ions. Contribution of other ions, possibly calcium ions, was discussed.
Potassium‐induced increase in oxygen consumption of brown adipose tissue from the rat.
Authors: Barde Y A , Chinet A , Girardier L
Published: December 2014

1. In brown adipose tissue, noradrenaline induces an increase in respiration and a depolarization of the cells. The effect of an increase in potassium concentration in a range known to depolarize the brown adipocytes was tested on the O2 consumption. 2. Isolated interscapular brown adipose tissue from the rat was incubated in chambers that allowed O2 consumption to be measured over prolonged periods. 3. 45‐50 mM‐KC1 were found to induce a more that fourfold increase in O2 consumption, which was stable, reversible and dependent upon the presence of calcium in the meduim. 4. When rats were pre‐treated with reserpine or 6‐hydroxydopamine the KC1‐induced increase in O2 consumption was sharply reduced or entirely adsent. 5. The effect of KC1 was greatly inhibited by (‐)‐propranolol, but not by (+)‐propranolol. 6. Moderate increases in O2 consumption induced by low concentrations of potassium were potentiated by desipramine, a drug which is known to block the uptake of catecholamines by adrenergic nerve endings. 7. Surgical denervation caused a decrease in the catecholamine content of the tissue, but had no effect on the KC1 response. 8. It is concluded that in brown adipose tissue, potassium stimulates O2 consumption by causing a release of noradrenaline from nerve endings. This implies that surgical denervation as it is commonly performed on this tissue does not denervate the brown adipocytes but probably only the blood vessels.
Contrast constancy: deblurring in human vision by spatial frequency channels.
Authors: Georgeson M A , Sullivan G D
Published: December 2014

The perception of contrast was measured in humans by a technique of subjective contrast‐matching, and was compared with contrast sensitivity as defined by threshold measures. 2. Contrast‐matching between different spatial frequencies was performed correctly (especially at frequencies above 5 c/deg) despite the attenuation by optical and neural factors which cause large differences in contrast thresholds. 3. Contrast‐matching between single lines of different widths was also veridical, and was not limited by the spatial integration (Ricco's Law) present at threshold. Adaptation to gratings altered the appearance of lines, and this could be best understood in Fourier terms. 4. The generality of these results was shown by matching the contrast of pictures which had been filtered so that each contained a one octave band of spatial frequencies. 5. Within the limits imposed by threshold and resolution, contrast‐matching was largely independent of luminance and position on the retina. 6. Six out of eleven astigmatic observers showed considerable suprathreshold compensation for their orientation‐specific neural deficit in contrast sensitivity. 7. These results define a new property of vision: contrast constancy. It is argued that spatial frequency channels in the visual cortex are organized to compensate for earlier attenuation. This achieves a dramatic 'deblurring' of the image, and optimizes the clarity of vision.