bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cellular specificity of serotonin storage and axonal transport in identified neurones of Aplysia californica
Authors: Goldman James E. , Schwartz James H. 
Published: December 2014

1. [3H]
D,L‐5‐hydroxytryptophan ([3H]5HTP) was injected under pressure into cell bodies of identified cholinergic and serotonergic neurones in the central nervous system of the marine mollusc, Aplysia californica.2. Both serotonergic and cholinergic neurones converted [3H]5HTP to [3H]5‐hydroxytryptamine ([3H]5HT).3. The fate of [3H]5HT in the two types of neurones differed. In serotonergic cells, 5HT was present primarily in particulate form; the transmitter readily moved from cell bodies into nerves by selective transport. In contrast, 5HT remained free in the cytoplasm of the cholinergic neurone, and was not transported from the cell body.4. Treatment of Aplysia with reserpine decreased the proportion of [3H]5HT associated with particulate material, and also decreased the amount of [3H]5HT recovered.5. Serotonergic neurones possess specific mechanisms for the storage and axonal transport of 5HT which are absent in cholinergic cells.
Adaptation of the discharge of frog muscle spindles following a stretch
Authors: Brokensha G. , Westbury D. R. 
Published: December 2014

1. Stretching a frog muscle spindle evoked a discharge of action potentials in its sensory axon. As the rate of this discharge decreased during the adaptation that followed the dynamic phase of a stretch, the variability of the interspike intervals of the impulse train increased.2. Adaptation occurred in two phases. At first the impulse train was almost regular and adapted rapidly, but later this gave way to a phase of slower adaptation where the variability of the discharge was much increased. In the second phase of adaptation the interspike intervals increased in length less than half as quickly as in the first phase.3. When the rate of adaptation changed from the more rapid to the slower phase there was often an abrupt change in the character of the discharge and the relationship between the mean interspike interval and the variability changed. The interspike interval at which this change‐over occurred was relatively constant in records of the discharge from one afferent fibre even though stretches of different amplitude were employed, though it differed from one afferent fibre to another.4. These features of the discharge during adaptation suggest that the two sections of the impulse trains were derived from different spike generators by a process of probabilistic mixing.
The release of histamine during gastric acid secretion in conscious rats
Authors: el Munshid H. A. , Lake H. J. 
Published: December 2014

1. Conscious gastric‐cannulated rats were given [3H]histidine and aminoguanidine by dosage procedures intended to build up fast‐turnover and slow‐turnover pools of tissue [3H]histamine. Acid secretion was stimulated by I.V. infusion of pentagastrin, and the [3H]histamine content of gastric juice and excretion in urine were determined at 30 min intervals.2. The amount of [3H]histamine in gastric juice derived from either a slow‐turnover or fast‐turnover pool was very low in unstimulated animals, and was not altered during pentagastrin‐stimulated acid secretion.3. From a slow‐turnover pool pentagastrin caused increased urinary excretion of [3H]histamine. This was abolished by gastrectomy, so that the [3H]histamine liberated by pentagastrin from this pool appears to have been derived from the stomach. Evidence was not found for the existence of a slow‐turnover histamine pool in the glandular mucosa of the stomach, and the source within the stomach of this pentagastrin‐liberated histamine is thus uncertain.4. From a fast‐turnover pool pentagastrin did not cause an increased urinary excretion of [3H]histamine. The amount of [3H]histamine excreted by gastrectomized rats was not different from that produced by gastric‐cannulated animals. This suggests that a high proportion of urinary histamine derived from a fast‐turnover pool was non‐gastric in origin.5. Differences in the time scale of [3H]histamine release and acid secretion were not found. In some experiments the urinary output of [3H]histamine was prolonged beyond the end of pentagastrin administration and gastric acid secretion. However, the overall data do not suggest that urinary histamine output and gastric acid secretion take different time courses.
The effects of extracellular pH and buffer concentration on the efflux of lactate from frog sartorius muscle
Authors: Mainwood G. W. , Worsley‐Brown Pauline 
Published: December 2014

1. The rate of efflux of lactate from isolated frog sartorius muscles is measured with a superfusion technique. Efflux curves are followed after raising the internal lactate level of the muscles by repetitive electrical stimulation over a 200 sec period.2. With an external pH of 7·0 or below the measured efflux rates following stimulation reach 100–150 n‐mole/g.min. Increasing the pH of the superfusion fluid to 8·0 results in a two or threefold increase in the peak efflux rate. The effect is independent of the buffer system used and occurs fairly rapidly when the pH of the superfusion fluid is changed. This suggests that the effect of pH on lactate efflux is extracellular.3. The increase in efflux rate due to an increase in pH is dependent on buffer concentration. This fact together with measurements of surface pH changes in muscles following arrest of superfusion indicates that a pH gradient exists through the muscle thickness during lactate efflux.4. The low lactate efflux rate seen at a low buffer concentration (1 m
M) is reduced to an even lower level by depolarization with potassium sulphate suggesting a membrane potential dependent component. At pH 8·0 with a high buffer concentration (25 m
M) potassium sulphate only reduces efflux rate slightly.The observations are interpreted as indicating that a fraction of lactate lost is in the form of undissociated acid and that this fraction increases with increasing external pH.5. Conditions which favour loss of hydrogen ions and lactate from muscle are also associated with improved recovery of twitch tension.
Appearance of new acetylcholine receptors on the baby chick biventer cervicis and denervated rat diaphragm muscles after blockade with α‐bungarotoxin
Authors: Chang C. Chiung , Su M. Jai , Tung L. Hsien 
Published: December 2014

1. The recovery of contractile responses and appearance of new α‐bungarotoxin‐binding sites were studied in the baby chick biventer cervicis and the rat diaphragm muscles after saturating the existing acetylcholine (ACh) receptors (AChR) with α‐bungarotoxin in vitro.2. Washout of α‐bungarotoxin restored gradually the response to exogenous ACh attaining about 30% recovery in 3 hr either in the chick muscle or in the denervated rat diaphragm. No recovery was obtained, however, for the response to nerve stimulation.3. The recovery of ACh‐response was abolished by decreasing the bath temperature to 9° C during the washout of the toxin whereas the recovery was not reduced in the presence of cycloheximide.4. The half‐life of [3H]acetyl α‐bungarotoxin bound specifically on the existing AChRs, junctional and extrajunctional receptors combined, was 16 hr in the chick muscle. That on the extrajunctional AChR was estimated to be 8 hr.5. New toxin‐binding sites were found to be incorporated on the membrane of extrajunctional site rapidly after treatment with α‐bungarotoxin in the chick and the denervated rat muscles along the muscle fibres but not in the innervated rat diaphragm. Treatment with (+)‐tubocurarine, ACh or decamethonium did not cause an appreciable increase of the toxin‐binding sites.6. The appearance of new binding sites was progressive during 5 hr at a rate of 24 sites/μm2.hr in the chick muscle and 42 sites/μm2.hr in the rat diaphragm denervated for 7 days. The existing extrajunctional AChR were about 50/μm2 and 192/μm2, respectively.7. ACh effectively antagonized the binding of α‐bungarotoxin with the new sites whereas (+)‐tubocurarine was less effective than its effect on the existing AChR.8. The new toxin‐binding sites appeared to have a reduced capacity to evoke ACh response.9. The incorporation of new binding sites was reduced by lowering of the temperature, treatment with dinitrophenol, high K+, high Ca2+ and by the stimulation of either nerve or muscle. Cycloheximide, ACh, decrease of [Na+]o and increase of [Mg2+]o were without effect.10. It is suggested that binding of the extrajunctional AChRs with α‐bungarotoxin cause a change of membrane architecture and trigger the incorporation of cytoplasmic AChR‐precursor or hidden AChR into the membrane.
Post‐tetanic potentiation, habituation and facilitation of synaptic potentials in reticulospinal neurones of lamprey
Authors: Wickelgren Warren O. 
Published: December 2014

1. Synaptic potentials evoked by electrical stimulation of cranial nerves were recorded in giant reticulospinal neurones (Müller cells) of lamprey. A variety of patterns of stimulation was employed to explore further the functional properties of the pathways intervening between the cranial nerve fibres and Müller cells.2. Simultaneous low intensity stimulation of two different cranial nerves produced excitatory short‐latency synaptic potentials whose amplitudes summed linearly.3. Tetanic (10/sec) stimulation of a cranial nerve depressed the evoked short‐latency synaptic response, but following the tetanus the synaptic response was potentiated above control amplitude for several minutes. Tetanic stimulation of one cranial nerve had no effect upon the synaptic responses evoked by stimulation of other cranial nerves.4. Low‐frequency stimulation (1/sec to 1/20 sec) of a cranial nerve produced a progressive decrease in the amplitude of the evoked short‐latency synaptic response. This phenomenon was termed synaptic habituation because its characteristics were functionally similar to behavioural habituation in animals.5. Habituation of the synaptic response to stimulation of one cranial nerve had no effect on the synaptic responses produced by stimulation of other cranial nerves.6. Synaptic afterdischarges lasting from several seconds to several minutes were recorded in Müller cells. They occurred both spontaneously and in response to strong electrical stimulation of cranial nerves. For several minutes following an afterdischarge the amplitudes of short‐latency synaptic potentials produced by stimulation of any one of the cranial nerves were increased as much as twofold. This facilitation occurred equally well whether the short‐latency synaptic responses had been habituated or not.7. A theoretical cell‐wiring diagram is proposed to account for the properties of short‐latency evoked synaptic responses and synaptic afterdischarges and for the facilitation of short‐latency responses by afterdischarges.
Protection from habituation of the crayfish lateral giant fibre escape response
Authors: Bryan Joan S. , Krasne Franklin B. 
Published: December 2014

1. Habituation of the lateral giant fibre escape response in the crayfish to repetitive tactile stimuli is believed to result from homosynaptic depression at the first synapse of the reflex, between tactile afferents and interneurones. Normally, habituation of escape responses to repeated innocuous stimuli is presumed to be adaptive. Experiments reported here were undertaken to determine whether habituation would occur under circumstances when it would presumably be maladaptive — in particular, when tactile receptors are stimulated by an animal's own tail‐flip movements.2. Experiments were carried out on the crayfish isolated abdominal nerve cord, which contains the lateral giant reflex pathway.3. Compound e.p.s.p.s elicited in the lateral giant by electrical stimulation of tactile afferents decline by from 25 to 36% over a series of eleven trials at 1/5 sec (control series).4. To determine whether such a decline would occur when sensory afferents are stimulated during a ‘tail‐flip’, stimuli were given as in the control series but each stimulus occurred 20 msec after direct electrical stimulation of a medial giant or lateral giant escape‐command fibre at which time tail flexion movements of an intact animal would be in progress. Under these conditions% e.p.s.p. decline over 11 trials at 1/5 sec was only 16‐45% of that occurring on the control series.5. This protective effect starts at about 10 msec after escape command neurone firing, is maximal at 20 msec, and thereafter declines, remaining weakly detectable at 100 msec. This time course is commensurate with that required for execution of a tail‐flip movement. Thus, sensory afferent‐to‐lateral giant transmission is protected from depression if stimuli occur when a tail‐flip movement is or should be occurring.6. Giant fibre spikes do not superimpose facilitation upon a depressed reflex pathway, nor accelerate rate of recovery from depression; rather, protection is attributable to actual prevention of development of the depressed state.7. Protection was also examined at the first synapse of the reflex, where the depression responsible for habituation is believed to occur, by recording intracellularly in the largest of the first‐order interneurones (interneurone A) of the pathway. In absence of protection, ten stimuli presented at 1/4 sec caused a mean decline of 32% in the e.p.s.p. in interneurone A. When such stimuli followed directly evoked escape command neurone firing by 20 msec this decline was reduced by 59‐100%.8. We suggest that protection serves to prevent crayfish from habituating to stimuli produced by their own tail‐flip movements.
Calcium requirement for activation of intact aortic smooth muscle
Authors: Van Breemen C. 
Published: December 2014

1. Elevation of [K+]e induced a contraction of rabbit aorta. If 10 m
M‐La3+ was applied to rabbit aortae prior to [K+]e elevation no contraction occurred. When 10 m
M‐La3+ was applied simultaneously with, or at short time periods after, elevation of [K+]e graded contractions were obtained whose magnitudes were higher if La3+ was added at a later stage.2. Net cellular Ca fluxes associated with these graded contractions were measured using 45Ca as well as atomic absorption. Correlation of the graded contractions with the net inward Ca movements yielded a Ca activation curve for intact arterial smooth muscle cells. The curve was S‐shaped with half‐maximal activation at a net Ca uptake of 41 μmole/kg wet wt. of aorta and full activation at 64 μmole/kg. If corrections were made for the extracellular space, full activation occurred at a net Ca uptake of 102 μmole/kg smooth muscle cells or roughly 25 μmole in excess of the value calculated to bind to the activation sites on arterial smooth muscle myosin.3. The contractile force of the smooth muscle cells not only depended on the magnitude, but also on the rate of the net Ca uptake.4. Elevation of tissue c‐AMP through inhibition of phosphodiesterase greatly reduced both the rate and magnitude of contraction without affecting the size of the high K+ stimulated Ca influx. It was concluded that high K+‐induced depolarization activates the rabbit aorta by stimulating a net Ca uptake, and that the degree of activation is modified by c‐AMP sensitive Ca accumulation by intracellular organelles.
Atrial receptors in the dog and rabbit
Authors: Kappagoda C. T. , Linden R. J. , Mary D. A. S. G. 
Published: December 2014

1. Action potentials were recorded from slips of the cervical vagi in anaesthetized dogs and rabbits. Single functional units with atrial patterns of discharge (Paintal Type A, B and intermediate) were obtained and then attempts were made to alter (i.e. convert) their patterns of discharge. Finally the points of origin of these action potentials were located.2. Thirty unselected units were investigated in thirty dogs. Twenty‐seven of these were located in the endocardium of the vein‐atrial system and the ratio of the type A, type B and intermediate type receptors was 1:16:10; three units were located elsewhere in the chest. Conversion of the pattern of discharge was achieved in twenty of the twenty‐seven units; conversion was achieved in the single type A unit.3. In a second series of experiments in dogs, eight Paintal Type A units were selectively studied in fifteen animals. Four of these were located in the endocardium and all were converted. The remaining four were located outside the endocardium and conversion could not be achieved in two of these. Thus in the entire investigation, the ‘type A’ units which could not be converted were all located at sites other than the atrial endocardium.4. In the corresponding unselected study in the rabbit, eleven units were studied in eleven animals. Nine of these units were located in the atrial endocardium and the ratio of the type A, type B and intermediate type receptors was 2:1:6. Conversion was achieved in both type A units, the sole type B unit and two of the intermediate units. One of the two units found outside the atrial endocardium was a ‘type A’ unit and could not be converted.5. The present investigation has shown that the atrial receptors with a Paintal Type A pattern of discharge are relatively rare in both dogs and rabbits. Conversion of the pattern of discharge is a relatively common phenomenon. Evidence for the proposition that there is one basic type of atrial receptor whose pattern of discharge is determined by its precise location in the vein‐atrial system is discussed.
The role of bicarbonate, chloride and sodium ions in the regulation of intracellular pH in snail neurones
Authors: Thomas R. C. 
Published: December 2014

1. Intracellular pH (pHi), Cl− and Na+ levels were recorded in snail neurones using ion‐sensitive micro‐electrodes, and the mechanism of the pHi recovery from internal acidification investigated.2. Reducing the external HCO3− concentration greatly inhibited the rate of pHi recovery from HCl injection.3. Reducing external Cl− did not inhibit pHi recovery, but reducing internal Cl−, by exposing the cell to sulphate Ringer, inhibited pHi recovery from CO2 application.4. During pHi recovery from CO2 application the internal Cl− concentration decreased. The measured fall in internal Cl− concentration averaged about 25% of the calculated increase in internal HCO3−.5. Removal of external Na inhibited the pHi recovery from either CO2 application or HCl injection.6. During the pHi recovery from acidification there was an increase in the internal Na+ concentration ([Na+]i). The increase was larger than that occurring when the Na pump was inhibited by K‐free Ringer.7. The increase in [Na+]i that occurred during pHi recovery from an injection of HCl was about half of that produced by a similar injection of NaCl.8. The inhibitory effects of Na‐free Ringer and of the anion exchange inhibitor SITS on pHi recovery after HCl injection were not additive.9. It is concluded that the pHi regulating system involves tightly linked Cl−‐HCO3− and Na+‐H+ exchange, with Na entry down its concentration gradient probably providing the energy to drive the movement inwards of HCO3− and the movement outward of Cl− and H+ ions.
Blood flow in the resting forearm during prolonged contralateral isometric handgrip at maximal effort
Authors: Eklund Brita , Kaijser Lennart 
Published: December 2014

1. In earlier studies we have shown that muscle contraction performed as handgrip at constant force, one third of maximal voluntary contraction (MVC), induces a rapid vasodilation in the resting contralateral forearm which in all probability is neurogenically mediated, followed by a relative increase in resistance.2. The maintenance of contraction at one third MVC for 2 min requires continuously increasing effort because of fatigue, as also evidence by the e.m.g. The biphasic response of the vascular bed may then be related to the increasing intensity of somatomotor activation which is needed to maintain contraction force, or, alternatively, to differences in vasomotor activity on initiation of and continued muscle activity.3. To elucidate these two possibilities blood flow in the resting forearm was measured during contralateral handgrips at constant maximal effort for 6 min (in which case force will drop) and compared to handgrip at constant force, one third MVC, for 2 min.4. The flow reaction during prolonged contraction at maximal effort was similar to that induced by contraction at constant force with a marked transient lowering of vascular resistance, although maximal vasodilation tended to be more pronounced and occur earlier.5. The results indicate that the rapid decrease in vascular resistance is related primarily to the initiation of somatomotor activity, whereas continued muscle contraction produces a relative increase in vasoconstrictor activity irrespective of changes in contraction effort.
Reversible depletion of synaptic vesicles induced by application of high external potassium to the frog neuromuscular junction
Authors: Gennaro Joseph F. , Nastuk William L. , Rutherford Dorothy T. 
Published: December 2014

1. Reversible depletion of synaptic vesicles from frog cutaneous pectoris neuromuscular junctions was studied by application of a Ringer solution containing 115 m
M‐K propionate.2. During the release of transmitter, the synaptic vesicle membrane is added to the axolemmal membrane. Under the conditions of high K+‐induced release, the synaptic vesicle membrane accumulates as folds formed in the region of the axolemmal membrane between the active zones. In depleted terminals, large vesicular structures appear and the evidence shows that some of them (possibly all) are formed as axolemmal infoldings. During formation of such infoldings the active zones remain fixed in position with respect to the post‐junctional membrane.3. During recovery in normal Ringer solution, which followed 30 min depolarization in high K+ Ringer solution, spontaneous m.e.p.p.s were detected as early as 9 min after the start of the recovery period and the average time for their reappearance was 17 min.4. At the end of a 20 min recovery period which followed K+ depolarization, small accumulations of synaptic vesicles were again found within the terminal close to the active zones. At this time coated vesicles and coated pits were seen associated with the prejunctional axolemma and its infoldings. It appears that synaptic vesicles are re‐formed directly from these coated vesicles.5. After 60 min recovery from K+ depolarization, at which time stimulation of the motor nerve induced a muscle twitch, the structure of the terminals closely resembled that of control preparations.6. The entire synaptic vesicle recycling process can take place in the absence of the neurone soma.
The effects of tenotomy upon the contraction characteristics of motor units in rabbit soleus muscle
Authors: Bagust J. 
Published: December 2014

1. Isometric contractions of tenotomized rabbit solei have been compared with a group of unoperated control muscles. A large decrease in the tension developed by the tenotomized muscle was accompanied by a slight shortening of the twitch contraction time, and a larger, progressive, reduction in the time to half relaxation.2. A comparison of motor units obtained from muscles which had been tenotomized for six weeks with those of the control muscles showed a large reduction in the range of contraction and half relaxation times of the units from the tenotomized muscles.3. The mean motor unit tension (expressed as a percentage of the whole muscle tension) was similar for both those units from the control muscles and those from muscles which had been tenotomized for six weeks, indicating a uniform atrophy of motor units within the tenotomized muscles.4. It was concluded that the change in the pattern of motor unit contraction times was not the result of a process of differential atrophy favouring the preservation of the faster contracting motor units.5. A correlation between axon conduction velocity and both the speed of contraction and the size (tension) of the motor units was demonstrated in the control muscles. Following tenotomy the relationship between axon conduction velocity and motor unit tension was lost.