bluuebunny/crossref_metadata_2025_split huggingface dataset:
The significance of deep body temperature in regulating the concentration of thyroxine in the plasma of the pig
Authors: Evans S. E. , Ingram D. L. 
Published: December 2014

1. The activity of the thyroid gland in the pig has been assessed while thermosensitive regions of the hypothalamus or the spinal cord were cooled.2. If the cervical region of the spinal cord was cooled for 3 hr, by means of a thermode in the epidural space, the concentration of thyroxine in the plasma increased to a maximum within the first hour but fell again to the control level or lower within 2 hr of the onset of cooling.3. When a thermode in the preoptic region of the hypothalamus was cooled to 18 or 25° C for 3 hr, the concentration of thyroxine in the plasma increased within the first hour and then declined again. Cooling the thermode to 10° C led to a sustained increase in thyroxine concentration.4. The increase in the concentration of thyroxine in the plasma, on cooling the hypothalamus, was of a similar magnitude whether the ambient temperature was 25 or 15°C.5. Observations on the disappearance of radioactive thyroxine from the plasma indicated that the distribution or metabolism of thyroxine was altered by the cooling of either the hypothalamus or the spinal cord.6. It was concluded that when the preoptic region of the hypothalamus or the cervical region of the spinal cord was cooled the rise in the concentration of thyroxine in the plasma was due at least in part to a change in the metabolism or distribution of thyroxine within the body and not entirely to the stimulation of the thyroid gland as has previously been suggested.
Dynamic properties of inferior rectus muscle of the rat
Authors: Close R. I. , Luff A. R. 
Published: December 2014

1. Isometric responses of rat inferior rectus muscle to indirect and direct stimulation were compared, and conditions were found for selective direct stimulation of twitch fibres in vitro.2. Most of the twitch fibres were qualitatively ‘fast’.3. The influence of length on isometric contractions and the relation between relative load and speed of sarcomere shortening of fast‐twitch fibres were determined.4. The isometric twitch contraction and half‐relaxation times of fast‐twitch inferior rectus fibres were only about one half of those of rat extensor digitorum longus fibres in the same conditions, whereas the force: velocity properties of these two fibre groups were virtually the same. These results show that the relation between intrinsic speed of shortening and duration of the active state of the contractile material is not the same for rat extraocular and hind‐limb muscles.
Two types of neurones in the myenteric plexus of duodenum in the guinea‐pig
Authors: Hirst G. D. S. , Holman Mollie E. , Spence I. 
Published: December 2014

1. Intracellular recordings have been made from neurones lying in the myenteric plexus of guinea‐pig duodenum; some aspects of their membrane properties have been studied by passing current through the intracellular electrode while recording changes in membrane potential.2. The current—voltage relationship was linear for small changes in membrane potential, input resistances ranging from 125 to 250 MΩ. Larger hyperpolarizing currents (causing changes of 20–40 mV) caused the input resistance to fall.3. Depolarizing currents of 1 to 10 × 10−10 A initiated action potentials with amplitudes of up to 95 mV.4. Two types of cell were distinguished when an action potential was initiated. In one group the action potential and undershoot had a form similar to that recorded from other mammalian ganglia. In the second group an action potential was followed by both an undershoot and a prolonged afterhyperpolarization which was associated with a decrease in cell resistance.5. The two groups of cells were further distinguished by their responses to transmural stimulation. Only those cells which did not show an afterhyperpolarization could be shown to receive a synaptic input.6. The mechanism by which each cell type generates an action potential was different. The action potentials recorded from cells which had a detectable synaptic input were abolished by tetrodotoxin. In contrast, those recorded from the other type of cells persisted in the presence of tetrodotoxin. Preliminary experiments suggest that during an action potential these cells become permeable to both sodium and calcium ions.7. Abolition of the calcium component of the action potential in cells which generated an afterhyperpolarization abolished this latter potential.8. The role of these two groups of cells is discussed.
Two factors responsible for the development of denervation hypersensitivity
Authors: Jones Rosemary , Vrbová Gerta 
Published: December 2014

1. Innervated adult skeletal muscle is sensitive to acetylcholine at the end‐plate region only. After denervation the entire muscle membrane becomes chemosensitive. The period of greatest increase in sensitivity in rat soleus muscles following section of the sciatic nerve in the thigh is between 48 and 72 hr post‐operatively.2. Direct electrical stimulation was found to prevent the onset of the development of denervation hypersensitivity during the first 2–3 days after nerve section. Thereafter, electrical stimulation only reduced the sensitivity of denervated muscles to acetylcholine (ACh).3. The period of greatest increase in sensitivity follows loss of transmission and degeneration of the nerve terminals. Once this degeneration is under way, electrical stimulation is no longer as effective in preventing the development of denervation hypersensitivity.4. Hypersensitivity is also seen in muscles on which a small piece of thread or degenerating nerve has been placed. Hypersensitivity following these procedures declines within a few days, unlike denervation hypersensitivity which persists until innervation is restored.5. The present results suggest that activity alone cannot prevent the development of hypersensitivity in the presence of degenerating nerve fibres, or muscle damage. Activity does however counteract increased sensitivity. It is suggested that two factors interact to produce denervation hypersensitivity; the presence of degenerating nerve tissue and concomitant cellular changes bring about changes in the muscle fibre membrane causing it to become hypersensitive; and the loss of muscle activity, resulting in the persistence of hypersensitivity until innervation is restored.
The role of the autonomic innervation in the control of glucagon release during hypoglycaemia in the calf
Authors: Bloom S. R. , Edwards A. V. , Vaughan N. J. A. 
Published: December 2014

1. The extent to which the autonomic innervation to the pancreas is implicated in the control of glucagon release during hypoglycaemia has been investigated in calves 3–6 weeks after birth.2. A pronounced rise in plasma glucagon concentration occurred in normal conscious calves in response to hypoglycaemia following administration of insulin (0·1 u./kg). Prior treatment with atropine caused no significant change in the hypoglycaemic response to insulin in these animals but the rise in plasma glucagon concentration was delayed.3. Section of both splanchnic nerves produced no significant change in the tolerance of conscious calves to this small dose of insulin and the changes in plasma glucagon concentration in these animals were within the normal range.4. In contrast, the same dose of insulin produced severe hypoglycaemia, accompanied by convulsions, in atropinized calves with cut splanchnic nerves. In spite of the intensity of the hypoglycaemic stimulus the rise in plasma glucagon concentration was both delayed and diminished in these animals.5. Administration of atropine alone (0·2 mg/kg) to normal fasting calves produced a significant fall in the mean plasma concentrations of both glucose and glucagon (P < 0·01) within 30 min, without affecting that of insulin.6. A significant increase in plasma glucagon concentration also occurred in response to stimulation of the peripheral ends of the thoracic vagi in adrenalectomized calves with cut splanchnic nerves under barbiturate anaesthesia. A rise in mean plasma glucose concentration was also observed in these experiments and found to be significantly correlated with the glucagon response.7. It is concluded that changes in either sympathetic or parasympathetic efferent activity may modify plasma glucagon concentration in the conscious calf, but that only the latter mechanism is likely to be implicated in the response to changes in plasma glucose concentration within the physiological range.
The occurrence in and actions of amino acids on isolated supra oral sphincter preparations of the sea anemone Actinia equina
Authors: Carlyle R. F. 
Published: December 2014

1.
L‐glutamic acid reversibly inhibits the contractions of isolated circular muscle preparations from different body regions of the sea anemone Actinia equina to electrical stimulation.2.
L‐glutamic acid does not cause inhibition of contraction by conversion to ammonia or γ‐amino‐butyric acid, but appears to act on a glutamate receptor.3. It is postulated that in Actinia equina there is a receptor for glutamic acid whose structural requirements for activation are met by comparatively few analogues of glutamic acid. Of thirty‐four analogues tested, only seven were active, most were less active, and only homocysteic acid had a greater activity than
L‐glutamic acid.4. Glutamic acid does not depress conduction of contraction in circular muscle preparations.5. The inhibition produced by
L‐glutamic acid does not appear to be conducted from one part of a preparation to another.6. Glutamic acid occurs in high concentrations in supra oral sphincter preparations of Actinia equina.7. Glutamic acid is released into sea water from sphincter preparations at rest and the amount released is increased by electrical stimulation of the preparation. However, many other amino acids are released at rest and following electrical stimulation, so that it is difficult to suggest that glutamic acid may be involved as a neurotransmitter in the sea anemone.
Interocular transfer of a visual after‐effect in normal and stereoblind humans
Authors: Mitchell Donald E. , Ware Colin 
Published: December 2014

1. Following inspection of a high contrast grating a test grating of a slightly different orientation will briefly appear rotated from its true orientation in a direction opposite to that of the adapting grating.2. The extent of interocular transfer of this phenomenon (the tilt after‐effect) was measured in a number of normal subjects and in four subjects (three of whom had a strabismus) who lacked stereopsis.3. In contrast to the normal subjects, none of the four stereoblind subjects showed any interocular transfer of the tilt after‐effect. Amongst the normal subjects the extent of transfer of this after‐effect was positively correlated with the subject's stereoacuity. Maximum transfer (70%) was found in the subject with the best stereoacuity. In many subjects transfer was greater from the dominant eye to the non‐dominant eye than vice versa.4. By analogy with experiments on cats deprived of congruent visual input to the two eyes early in life it is argued that the stereoblind subjects lack any binocularly driven cortical neurones.
Conductance changes associated with the secretory potential in the cockroach salivary gland
Authors: Ginsborg B. L. , House C. R. , Silinsky E. M. 
Published: December 2014

1. Conductance changes in the acini of the cockroach salivary gland have been examined during nerve stimulation by means of two intracellular electrodes placed in the same acinus, the first electrode being used for recording membrane potential and the second for current injection.2. The transient hyperpolarization (secretory potential) in the acinus evoked by nerve stimuli is accompanied by a rise in membrane conductance. The conductance, however, remains high for a longer period than that of the response.3. Applying the analysis of Trautwein & Dudel (1958) to the secretory potentials recorded in the acinus (assumed to behave electrically like a single cell) gives estimates of the ‘transmitter equilibrium potential’. The values indicate that the neurotransmitter increases the membrane potassium conductance.4. The hyperpolarization of the acinus evoked by 10−6
M dopamine in the bathing fluid is also associated with an increase in membrane potassium conductance.
Effect of denervation on the adaptation of sarcomere number and muscle extensibility to the functional length of the muscle*
Authors: Goldspink G. , Tabary C. , Tabary J. C. , Tardieu C. , Tardieu G. 
Published: December 2014

1. The effects of denervation on the response of the cat soleus muscle to immobilization at different lengths by plaster casts has been investigated for a period of 4 weeks.2. The passive length—tension properties of the denervated immobilized muscles were not significantly different from those of non‐denervated muscles. Muscles immobilized in the shortened position showed a marked decrease in extensibility whether they were denervated or not. In all the other cases the length—tension curves were not significantly differetn from those of normal muscles.3. The denervated soleus muscle immobilized in the lengthened position was found to produce 25% more sarcomeres in series, whilst those immobilized in the shortened position lost 35%. This adaptation was essentially the same as in muscles that had been immobilized but not denervated.4. Denervation was found to have no effect on the recovery of muscles that had been subjected to 4 weeks immobilization in the shortened position. In these muscles the sarcomere increased back to the normal level within 4 weeks after removal of the plaster cast.5. The adjustment of sarcomere number to the functional length of the muscles does not therefore seem to be directly under neuronal control. It appears to be a myogenic response to the amount of passive tension the muscle is subjected to.
Dynamic properties of denervated fast and slow twitch muscle of the cat
Authors: Kean C. J. C. , Lewis D. M. , McGarrick J. D. 
Published: December 2014

1. Isometric and isotonic contractions were recorded from cat flexor digitorum longus (FDL) and soleus muscles denervated for 28–35 days and compared with the responses of contralateral control muscles.2. Isometric twitch time to peak was longer in the denervated muscles than in the controls. Tetanic tension was reduced whether expressed as absolute units, per gram or per unit area. Absolute twitch tensions were reduced less below the control values with a consequent increase of twitch‐tetanus ratio. These results agree with earlier reports; but, in contrast, there was no reduction in the relative rate of rise of tension in the isometric tetanus of denervated compared with control FDL. The maximum rate of rise of tension in the twitch was only a little less than that in the fully fused tetanus in the denervated muscles.3. Whole muscle shortening velocity was reduced in the denervated soleus with no change in the number of sarcomeres per fibre. There was a smaller change in FDL muscles. This was the result of an increase in the number of sarcomeres per fibre which followed denervation in FDL, compensating for a decreased velocity of shortening of the sarcomere. Maximum sarcomere shortening velocity was reduced by 30% relative to control values in both muscles.4. Measurements were made of the isometric contractions resulting from pairs of stimuli in an attempt to assess the period of maximal activation in the twitch. Maximum summation occurred when the second stimulus was given close to the time of the peak of the twitch in the denervated muscles.
Potassium: potassium exchange catalysed by the sodium pump in human red cells
Authors: Simons T. J. B. 
Published: December 2014

1. When red cells were so depleted of Na that Na:K exchange had almost ceased, the ouabain‐sensitive K efflux seen in K‐containing media was accompanied by an almost equal ouabain‐sensitive K influx.2. This suggests that the Na pump in these cells was carrying out a one‐for‐one K:K exchange across the erythrocyte membrane.3. 30–40% of the 42K efflux from resealed ghosts was sensitive to ouabain when the ghosts contained 1 m
M‐ATP, 2 m
M orthophosphate, 10 m
M‐K and less than 1 m
M‐Na, and the suspending medium contained 10 m
M‐K and 0‐Na, choline being the predominant cation.4. In resealed ghosts, the rate of K:K exchange saturated as internal K was increased, and was half‐maximal at about 10 m
M‐K.5. When internal ATP was maintained with a phosphocreatine:creatine phosphokinase regenerating system, K:K exchange saturated as internal ATP was increased, and was half‐maximal at about 100 μ
M‐ATP.6. The rate of K:K exchange did not depend on whether the ADP concentration was roughly the same as the ATP concentration or very much less, suggesting that ADP did not affect the rate of K:K exchange.7. GTP, ITP and UTP were unable to substitute for ATP in supporting K:K exchange. CTP was a poor substitute.8. There was no evidence to support the hypothesis that K:K exchange is accompanied by a ouabain‐sensitive hydrolysis of ATP.9. Internal Na was a strong inhibitor of ouabain‐sensitive K efflux from ghosts containing 9 m
M‐K. 4 m
M‐Na was sufficient to produce 90% inhibition.10. The rate of K:K exchange depended on the orthophosphate concentration inside the ghosts (confirming Glynn, Lew & Lüthi, 1970). The curve obtained suggested that the rate was half‐maximal at about 1·7 m
M orthophosphate.11. These experiments suggested that inhibition by internal K is an important factor affecting the Na efflux from intact red cells. Experiments measuring Na:K exchange as a function of internal Na in low‐K ghosts supported this hypothesis.12. The significance of these findings is discussed.
The effect of contractile activity on fibrillation and extrajunctional acetylcholine‐sensitivity in rat muscle maintained in organ culture
Authors: Purves D. , Sakmann B. 
Published: December 2014

1. The effect of contractile activity on the initiation of spontaneous action potentials (fibrillation) and on extrajunctional acetylcholine‐sensitivity has been studied in single fibres in strips of previously denervated rat diaphragm maintained in organ culture for up to 10 days.2. Following removal of the diaphragm from the animal, fibrillation slowed and usually stopped altogether for about 24–36 hr. Thereafter, spontaneously active fibres were found in all cultured muscle strips.3. At any one time, about ¼ to ⅓ of fibres impaled with micro‐electrodes were active (defined as more than one action potential/10 sec), with a mean discharge frequency of 4·5/sec (range 0·1–24/sec).4. The duration of continuous activity in single fibres was, on average, 21–22 hr; a period of activity was followed by a longer inactive interval. Thus activity in single fibres is cyclical.5. Direct stimulation of fibrillating strips for 24 hr at 10/sec suppressed spontaneous activity for 1–3 days.6. Conversely, blockade of spontaneous activity with tetrodotoxin for 72 hr led to a two‐ to threefold increase in the number of fibrillating fibres when the drug was washed out; in some strips nearly all fibres became spontaneously active.7. The mean rate of activity of diaphragm fibres during normal breathing, determined by recording single units from the phrenic nerve in lightly anaesthetized animals, is about 18/sec.8. Direct stimulation of cultured diaphragm strips in a pattern similar to breathing for 7–8 days at an average rate of 10–12/sec (or 5/sec in some experiments), resulted in a marked reduction (about 95% in experiments at 10/sec) in extrajunctional sensitivity to ionophoretically applied ACh.9. Direct stimulation for 24 hr at 10/sec (comparable to a period of spontaneous activity) caused only a small reduction in extrajunctional ACh‐sensitivity.10. We conclude that spontaneous activity in single fibres under these conditions occurs cyclically because activity, over a period of hours, inhibits the ability of the fibrillating fibre to initiate further action potentials. Repeated self‐inhibition of spontaneous activity probably explains why denervated muscle fibres remain highly sensitive to extrajunctionally applied ACh.
Reversal of the physiological effects of monocular deprivation in kittens: further evidence for a sensitive period
Authors: Blakemore Colin , Van Sluyters Richard C. 
Published: December 2014

1. It was confirmed that suturing the lids of one eye (monocular deprivation), until only 5 weeks of age, leaves virtually every neurone in the kitten's visual cortex entirely dominated by the other eye. On the other hand, deprivation of both eyes causes no change in the normal ocular dominance of cortical neurones, most cells being clearly binocularly driven.2. Kittens were monocularly deprived until various ages, from 5 to 14 weeks, at which time reverse suturing was performed: the initially deprived right eye was opened and the left eye closed for a further 9 weeks before recording from the visual cortex.3. Reverse suturing at 5 weeks caused a complete switch in ocular dominance: every cell was dominated by the initially deprived right eye. Reverse suturing at 14 weeks, however, had almost no further effect on ocular dominance: most cells were still driven solely by the left eye. Animals reverse sutured at intermediate ages had cortical neurones strongly dominated by one eye or the other, and they were organized into clear columnar groups according to ocular dominance.4. Thus, between 5 weeks and 4 months of age, there is a period of declining sensitivity to both the effects of an initial period of monocular deprivation and the reversal of those effects by reverse suturing.5. The small proportion of binocular cells in reverse sutured kittens (which have never had simultaneous binocular vision) often differed considerably in their receptive field properties in the two eyes. In particular, if the cells were orientation selective in both eyes the two preferred orientations could differ by up to 70°.6. The relative importance of innate and environmental contributions to the properties of cortical cells is discussed.
A statistical analysis of the release of acetylcholine at newly formed synapses in striated muscle
Authors: Bennett M. R. , Florin T. 
Published: December 2014

1. A statistical analysis has been made of the changes in the binomial parameters n and p during transmitter release from motor‐nerve terminals when synapses are forming in either regenerating or reinnervated mammalian muscle.2. The amplitude—frequency distribution of e.p.p.s evoked by a single impulse was well predicted by binomial statistics at all junctions analysed allowing values of n and p to be determined. At most of these junctions, p > 0·5 and Poisson statistics did not predict the observed distributions at all.3. During the changes in quantal content which occur during short trains of impulses or during continual stimulation over minutes, no significant change in p was detected. Changes in quantal content of the e.p.p. were therefore determined by n.