bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anion permeability of the inhibitory post‐synaptic membrane of the crayfish neuromuscular junction
Authors: Takeuchi A. , Takeuchi Noriko 
Published: December 2014

1. The membrane conductance of the crayfish muscle fibre was calculated and the increase in the membrane conductance brought about by the application of γ‐aminobutyric acid (GABA) was investigated under various conditions. The permeability of the activated inhibitory post‐synaptic membrane was estimated from the conductance change.2. When the concentration of Cl− was changed by substituting Cl− with methylsulphate, a linear relation was obtained between the membrane conductance change produced by GABA and the concentration of Cl−. Cations have no appreciable effect on the GABA induced conductance change (less than 0·4%).3. The conductance change produced by GABA on the inhibitory post‐synaptic membrane was measured in various solutions in which the Cl− was replaced by various anions. The degree of permeability depended on the anion species in the following order:Br− > Cl− > SCN− > I− > NO3− > HCOO− > ClO3− > ClO4− > BrO3−4. At high pH the conductance change produced by GABA was decreased, while at low pH it increased.5. These results show that the activated inhibitory post‐synaptic membrane of crayfish muscle fibres has the characteristics of an anion selective membrane, suggesting the fixed positive charges in the inhibitory membrane.
The effects of soaking the skin in water at various temperatures on the subsequent ability to sweat
Authors: Brebner D. F. , Kerslake D. McK. 
Published: December 2014

1. The ability of two human subjects to produce sweat was measured before and after immersion for up to 4 hr in water at 32‐36° C (soak).2. The ability to produce sweat declined about 4 times as rapidly when the subject was soaked at 36° C as at 32° C.3. The rate of decline characteristic of soaking at 36° C was shown by subjects exercising in water at 35° C, but not at rest at 35° C. The difference appeared to be related to the presence or absence of moderate sweating (300 g/hr) during the soak. At higher rates there was no further increase in the rate of decline.4. Soaking at 39° C for 5 min, after which the water temperature was reduced to 33° C, caused a decline consistent with the supposition that while the subject was sweating the rate of decline was the same as that at 36° C and for the rest of the time the same as that at 32° C.5. It is concluded that the rate of decline is increased if the sweat ducts are perfused, and some possible mechanisms are discussed.
The origin of acetylcholine released from guinea‐pig intestine and longitudinal muscle strips
Authors: Paton W. D. M. , Zar M. Aboo 
Published: December 2014

1. Strips of longitudinal muscle can be obtained from guinea‐pig ileum either retaining or free from Auerbach's plexus.2. The denervated strip is unresponsive to electrical stimulation by brief shocks, whether given singly or in trains; it also fails to respond to nicotine or dimethylphenylpiperazinium iodide (DMPP), and eserine causes no spasm.3. Denervated strips neither contain detectable acetylcholine (< 0·4 ng/mg), nor release it spontaneously (< 5 pg/mg/min) or in response to stimulation (< 31 pg/mg/min). The acetylcholine metabolism of the innervated strip is therefore that of the adherent Auerbach's plexus. Innervated strips had a mean acetylcholine content of 28 ng/mg, a mean resting output of 94 pg/mg/min and an output in response to stimulation at 10 c/s of 700‐1200 pg/mg/min.4. By comparing the responses of innervated and denervated strips it was concluded that arecoline, methylfurmethide, α,β‐ethylal‐γ‐tri‐methylammonium propanediol iodide (2268 F), muscarine, histamine, tremorine, oxytocin, and substance P, like acetylcholine, act primarily on the smooth muscle directly; and that angiotensin, barium, potassium, m‐bromophenyl choline ether and 5‐hydroxytryptamine have a progressively increasing proportionate effect on the nerve plexus. Nicotine and DMPP were inactive in the absence of the plexus.5. The longitudinal muscle with its accompanying plexus contains about one quarter of the acetylcholine of the whole ileum, and is responsible for about one fifth of the output to electrical stimulation.6. The volley output of acetylcholine by the innervated strip declines sharply as rate of stimulation increases. Output of acetylcholine was reduced by morphine and by cocaine, particularly when resting or when stimulated at low rates.7. Acetylcholine output by whole ileum from guinea‐pig declines in the absence of glucose, but is insulin‐independent. Output by strips of ileum from rats made diabetic with alloxan was similar to that from normal rats.8. The similarity in properties of acetylcholine output from innervated strips, where it must come from nervous tissue, to that from whole ileum, and the insulin‐independence of output from whole ileum suggest that the whole of the acetylcholine output of intestine is nervous in origin.9. Comparison of the acetylcholine metabolism of the innervated strip with that of the superior cervical ganglion suggests that the typical features of the former (high resting output, high volley output at low rates, low minute output at high rates of stimulation, and sensitivity to morphine) may be linked with the absence of specialized neuro‐effector junctions and represent a relatively primitive transmission process.
The action of caffeine on the activation of the contractile mechanism in striated muscle fibres
Authors: Lüttgau H. C. , Oetliker H. 
Published: December 2014

1. The effect of caffeine on the initiation of isometric tension in isolated twitch muscle fibres of the frog was recorded with a mechano‐electrical transducer.2. In Ringer solution as well as in solutions containing 95 m
M‐K2SO4, caffeine (6‐10 m
M) caused reversible contractures. Tension of maximal potassium contractures was reached with a half‐time of 2‐4 sec.3. Caffeine caused a shift to lower potassium concentrations of the S‐shaped curve which relates peak tension to log. [K]o or membrane potential. In subthreshold concentrations of caffeine (1·5 m
M) the potassium concentration at which half of maximal tension was reached shifted from 30 to 16 m
M‐K (‐39 to ‐53 mV).4. In the ‘steady state’ the ability of fibres to develop tension is related to log. [K]o or membrane potential by an S‐shaped curve whose half value shifted from 28 to 45 m
M‐K (‐41 to ‐29 mV) when 1·5 m
M caffeine was applied.5. Fibres were most sensitive to caffeine at membrane potentials between ‐50 and ‐20 mV.6. The mechanical activity caused by caffeine was ‘stabilized’ by an increase in [Ca]o or [Mg]o resembling the stabilizing action of these ions on potassium contractures or on the sodium permeability of excitable membranes.7. Tetracaine in low concentrations (0·04‐0·1 m
M) increased the threshold for mechanical activation and shortened the plateau of potassium contractures. Higher concentrations (1‐2 m
M) suppressed mechanical activity completely.8. Tetracaine, 0·04 m
M, was sufficient to suppress tension caused by a 100 times stronger concentration of caffeine. With higher concentrations of caffeine the inhibitory action of tetracaine could be reversed.9. Fibres which were immersed in subthreshold concentrations of caffeine either in Ringer solution or in a solution with 95 m
M‐K2SO4 developed a strong contracture after a sudden drop in temperature from 20 to 1‐3° C.10. The fast activation of the whole cross‐section of the muscle fibre caused by caffeine and its dependence on membrane potential, tetracaine and external alkali earth ions favours the idea that the drug acts at some part of the sarcotubular system which is easily accessible for external ions and drugs and in close connextion with the surface membrane.
Reticulospinal inhibition of transmission in reflex pathways
Authors: Engberg I. , Lundberg A. , Ryall R. W. 
Published: December 2014

1. The effect of electrical stimulation of the brain stem on reflex transmission has been investigated in decerebrate cats after partial transection of the spinal cord.2. Brain stem stimuli that do not evoke inhibitory post‐synaptic potentials (IPSPs) in motoneurones or primary afferent depolarization may still effectively depress the excitatory and inhibitory synaptic actions evoked from the flexor reflex afferents (FRA) and from Ib afferents. There is no effect on post‐synaptic potentials from Ia afferents or on Renshaw IPSPs. The depression is not associated with any measurable change in conductance over the motoneuronal membrane.3. There is also inhibition from the brain stem of transmission from the FRA (but not from Ia and Ib afferents) to primary afferent terminals and to ascending spinal pathways.4. It is concluded that this inhibition from the brain stem is exerted at an interneuronal level in spinal reflex paths.5. The inhibitory action is evoked from the region of Magoun's inhibitory centres in the brain stem and is mediated by axons with a conduction velocity of at least 20 m/sec. The axons are distributed in the dorsal part of the lateral funicle.6. The pathway mediating the inhibition from the brain stem is named the dorsal reticulospinal system. Its possible role in maintaining the decerebrate control of reflexes is discussed and related to the problem of a selective control of some paths from a primary afferent system.
A relation between the chain length of fatty acids and the slowing of gastric emptying
Authors: Hunt J. N. , Knox M. T. 
Published: December 2014

1. Test meals of solutions and suspensions of potassium and sodium salts of a series of saturated fatty acids, from C2 to C18, were given to healthy subjects.2. From the volume of these meals recovered after a fixed interval the relative effectiveness of the salts of the acids in slowing gastric emptying was assessed.3. On a molar basis the salts of fatty acids from acetic up to decanoic were relatively ineffective in slowing gastric emptying.4. The salts of fatty acids with 12‐18 carbon atoms were much more effective than those with up to 10 carbon atoms. Myristate was the most effective of the salts.5. Buffering the test meals with 33 m
M sodium citrate increased the effectiveness of the salts in slowing gastric emptying.
Thalamic projection of muscle nerve afferents in the cat
Authors: Mallart A. 
Published: December 2014

1. Evoked responses on stimulation of hind‐ and forelimb muscle nerves have been recorded in the ventro‐postero‐lateral (VPL) and centre median (CM) nuclei of the thalamus of the cat.2. The stimulation of hind‐limb muscle afferents with increasing strength usually did not evoke a thalamic response, either in the CM or in the VPL, until the threshold for Group III muscle afferents was reached.3. Short latency potentials were evoked in the VPL on stimulation of low threshold Group I muscle afferents from forelimbs. The projection zone occupies the dorso‐medio‐rostral part of the nucleus.4. An attempt was made to locate the medullary relay for forelimb Group I afferents either in the lateral part of the cuneate or in external cuneate.5. Low threshold afferents from forelimb muscle nerves do not project to the CM. CM responses began to appear only when the threshold for Group II muscle nerve fibres was reached.6. Group II afferents from hind‐ or forelimb muscle nerves projecting to the CM are probably not connected to spindle secondary endings.7. The role played by muscle afferents in the somesthetic mechanisms is briefly discussed.
On the mechanism by which calcium and magnesium affect the spontaneous release of transmitter from mammalian motor nerve terminals
Authors: Hubbard J. I. , Jones S. F. , Landau E. M. 
Published: December 2014

1. The frequency of miniature end‐plate potentials (m.e.p.p.s) was recorded from neuromuscular junctions in rat diaphragm phrenic nerve preparations in vitro after preparations had soaked in solutions containing Ca in concentrations between 10−10 and 10−2
M and a similar range of [Mg].2. Ethylenediamine tetra‐acetate (EDTA) and ethyleneglycol bis (β‐aminoethyl ether) tetra‐acetate (EGTA) buffers were added to prepare solutions with [Ca] and [Mg] below 10−4
M. A computer program was used to estimate the free [Ca2+] in these solutions, and it was shown that the effects of Ca could be attributed to the free [Ca2+] in the bathing solution.3. M.e.p.p.s could still be detected without difficulty after soaking preparations for 6‐8 hr in solutions containing EDTA or EGTA buffers and no added Ca. The basal frequency was unchanged upon exhibition of Ca in concentrations up to 10−5
M and/or Mg in concentrations up to 10−3
M.4. Ca in concentrations of and above 10−4
M accelerated m.e.p.p. frequency from the basal level. This effect reached a maximum in [Ca] of 10 m
M and raising the [Ca] above this level did not further change frequency. These effects were explained by the combination of Ca molecules with a nerve terminal receptor site. It was postulated that this combination allosterically activated the spontaneous release mechanism.5. Mg could accelerate m.e.p.p. frequency in the absence of added Ca. The interactions of Ca and Mg upon m.e.p.p. frequency indicated that Ca and Mg competed for the same sites.6. Raising the [H+] of the bathing medium accelerated m.e.p.p. frequency. This effect was thought to be exerted partly by combination with the same receptor sites as Ca and Mg and partly by variation of the ionization of the CaCl2 of the bathing solution.
The influence of previous salt ingestion on the renal function of sheep subjected to intravenous hypertonic saline
Authors: Potter B. J. 
Published: December 2014

1. Sheep, which had access to a solution containing 1·3% sodium chloride as their sole source of drinking water for 6 months or more, were infused with a hypertonic solution (10%) of sodium chloride, and their ability to tolerate this salt load was compared with that of a similar group of sheep which drank only rain water.2. The sheep which drank the rain water were often affected by the infusion and exhibited signs resembling potassium deficit. No such signs were apparent in the animals which consumed saline water.3. Glomerular filtration rates were increased in all sheep by the hypertonic saline infusion, the increases being greater in the sheep which were maintained on the saline water. Effective renal plasma flow rates, though extremely variable, behaved in a similar manner.4. Plasma values for sodium and chloride were increased in all sheep, but remained at a higher level for a longer period in the sheep which consumed rain water. The diuresis produced by hypertonic saline appeared to persist for a longer period in the sheep which drank rain water, while the excretion of sodium and chloride tended to be greater in the sheep maintained on saline water.5. Plasma potassium was reduced in all sheep and urinary excretion of potassium increased. The latter response was more pronounced in the sheep which drank the rain water.6. Filtered loads of sodium, chloride and potassium were greater in the sheep which were accustomed to drinking saline water. However, the amounts of potassium excreted were greater than those filtered in the rain water sheep and less than those filtered in the sheep which drank saline water. It therefore seems that secretion of potassium into the kidney tubules predominated in the former group and reabsorption prevailed in the latter.7. Reabsorption of free water in excess of solute was greater in the kidney tubules of the sheep which drank saline water.8. Increased blood volume and greater dilution of plasma proteins occurred in the sheep which drank rain water.
The effect of temperature on the competitive inhibition of glucose transfer in human erythrocytes by phenolphthalein, phloretin and stilboestrol
Authors: Forsling Mary L. , Widdas W. F. 
Published: December 2014

1. Phenolphthalein, like other diphenols, has been shown to be a competitive inhibitor of the facilitated transfer system for glucose in the human erythrocyte.2. The concentration producing 50% inhibition is lower at low temperatures and increases steadily over the temperature range 10‐40° C. An Arrhenius plot of the results gives a slope of 19,300 cal/mole.3. The effect of temperature on inhibition by phloretin and stilboestrol has also been studied. The temperature variation of the concentration of phloretin giving 50% inhibition is similar to that for phenolphthalein, but that for stilboestrol is much less.4. There is a high cell/medium distribution ratio for stilboestrol, and the possibility that this may affect the temperature dependence of the aqueous concentrations required to give 50% inhibition is discussed.
Thyroxine feed‐back on the regulation of thyrotrophin secretion*
Authors: Panda J. N. , Turner C. W. 
Published: December 2014

1. The role of thyroid hormone as a feed‐back at the hypothalamic level in the control of thyrotrophin (TSH) secretion and release has been investigated by estimating the plasma and pituitary TSH levels following intrahypophysial and intrahypothalamic thyroid autotransplants.2. Thyroidectomized rats bearing thyroid autotransplants in the pituitary had a significantly lower (P < 0·001) plasma TSH than that of controls at 26° C but not at 4° C.3. Thyroidectomized rats bearing thyroid autotransplants in the supraoptic area showed a significantly lower (P < 0·001) level of plasma TSH and higher pituitary TSH at 4° C but not at 26° C.4. Study with both unilaterally and bilaterally thyroidectomized rats bearing thyroid autotransplants either in the pituitary or in the hypothalamus revealed that thyroxine feed‐back operates at pituitary level in normal situations (26° C) and there exists a feed‐back through higher centres, specifically the TSR secreting area of the hypothalamus, in situations demanding higher thyroid function, as in cold exposure.
The release of a bradykinin‐like pulmonary vasodilator substance in foetal and new‐born lambs
Authors: Campbell A. G. M. , Dawes G. S. , Fishman A. P. , Hyman A. I. , Perks A. M. 
Published: December 2014

1. Exposure to glass of whole blood from anaesthetized foetal lambs (at 0·6‐0·95 of term) causes the rapid development of a potent pulmonary vasodilator agent.2. The formation of the vasodilator agent on exposure to glass, its disappearance with time, and the inhibition of its production by soya bean trypsin inhibitor, suggest that it is bradykinin.3. Small doses of bradykinin (∼ 1 ng/kg) cause pulmonary vasodilatation on close arterial injection. Neither this, nor the vasodilatation caused by glass‐exposed whole blood, are affected by agents which block the vasodilator actions of acetylcholine, isoprenaline or histamine.4. Exposure of foetal plasma and/or red cells to glass rarely caused the development of a pulmonary vasodilator agent. Maternal plasma was always active. Injection of the buffy coat from foetal blood caused pulmonary vasodilatation.5. The capacity of plasma from sheep at different ages to produce kinin(s) was examined by assay on the isolated rat's uterus. In the foetus activity was very low; it increased with age.6. In adolescent lambs 5‐14 weeks after birth injection of ∼ 10 ng/kg bradykinin into the pulmonary artery caused only a trifling vasodilatation; this was greater when pulmonary vasoconstriction was induced by lung collapse, hypoxaemia and hypercapnia.7. The possible physiological consequences of these findings are discussed.
An analysis of the reflex systemic vasodilator response elicited by lung inflation in the dog
Authors: Daly M. de Burgh , Robinson B. H. 
Published: December 2014

1. A maintained inflation of the lungs caused a reflex reduction in total systemic vascular resistance in anaesthetized dogs under conditions in which the systemic circulation was perfused at constant blood flow and the arterial blood PO2 and PCO2 were maintained constant.2. The fall in systemic arterial perfusion pressure evoked by inflation of the lungs was accompanied by an increase in blood flow to the lower limbs and a reduction in their calculated vascular resistance. Since the fall in resistance occurred when the limb was perfused either at constant pressure or at constant blood flow, it must be due to vasodilatation.3. Lung inflation caused vasodilatation in skin, muscle, and in the splanchnic vascular bed. The responses in vertebral circulation were, however, small and variable.4. The vasodilator responses in the vascular territories studied were reflex in nature, being abolished by cutting the cervical vagosympathetic nerves, in which run the afferent fibres, or by interrupting the sympathetic pathways to the blood vessels.5. In the intact limb, muscle, skin and splanchnic vascular bed, the vasodilator responses to lung inflation were unaffected by atropine or propranolol, but were abolished by hexamethonium, dibenyline and bretylium tosylate, indicating that they were due predominantly to a reduction in the activity in sympathetic adrenergic vasoconstrictor fibres.
Thresholds of cortical activation of muscle spindles and α motoneurones of the baboon's hand
Authors: Koeze T. H. , Phillips C. G. , Sheridan J. D. 
Published: December 2014

1. Much current thinking about voluntary movement assumes that the segmental γ loops can function as a servomechanism operated by the brain. However, the α motoneurones of the baboon's hand receive a powerful monosynaptic (CM) projection from the precentral gyrus. If servo‐driving from the same cortical area is to be possible, it must project independently to the fusimotor neurones and have sufficient power to increase the afferent signalling from the muscle spindles. The cortical thresholds for contraction of m. extensor digitorum communis and for acceleration of the discharges of its muscle spindles have therefore been compared.2. Significant results in this context require that the spindles studied be coupled in parallel with the responding extrafusal muscle fibres. Many spindles were not unloaded by the submaximal contractions evoked by cortical stimulation, although all so tested were unloaded by maximal motor nerve twitches. Reasons are given for thinking that such apparent lack of parallel coupling is an artifact of complex intramuscular anatomy and limitation of shortening by ‘isometric’ myography.3. A brief burst of corticospinal volleys at 500/sec, which is specially effective in exciting α motoneurones over the CM projection, failed to excite spindle afferents at or below the threshold for a cortical ‘twitch’.4. In a few epileptiform discharges, bursts of spindle acceleration occurred independently of the clonic contractions. A relatively direct and independent cortico‐fusimotor (CF) projection may therefore exist.5. Prolonged near‐threshold stimulation at 50‐100/sec, which allows time for temporal summation in the less direct projections (e.g. cortico‐interneuronal, cortico‐rubro‐spinal) and does not cause frequency‐potentiation at CM synapses, gives abundant evidence of independent α and fusimotor projections, whose actions hardly outlast the stimulation period.6. Although independent CF projections would permit servo‐driving in natural movements of the hand (given adequate loop gain), there has been no evidence of servo‐driving by cortical stimulation or in the spontaneous contractions of light anaesthesia.7. Independent projections would provide for controlled αγ co‐excitation in the servo‐governing of natural movements (Matthews, 1964).8. Evidence is reviewed that the CM projection itself may be part of an important control loop for voluntary movement in primates. A corollary would be a diminished importance of CF projections for segmental loops and an increased importance for maintaining the spindle input to cortical loops.