bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rate of fast axoplasmic transport in mammalian nerve fibres
Authors: Ochs Sidney 
Published: December 2014

1. Fast axoplasmic transport in mammalian nerve fibres was determined by the presence of a crest of activity in the sciatic nerve after injection of [3H]leucine into the L7 dorsal root ganglion or the L7 motoneurone region in the ventral horn region of the spinal cord. After incorporation into proteins by the cell bodies, a rate of transport close to 410 mm/day was found for cat sensory nerves. A closely similar rate was found in the motor and sensory sciatic nerve fibres of the monkey, dog, rabbit, goat and rat. In the longer nerves where longer downflow times were possible, there was no decrement of rate with distance, or presence of later appearing crests of activity indicative of multiple fast transport systems.2. The rate of fast transport found in the long L7 dorsal roots of the rhesus monkey was the same as that in the corresponding length of sciatic nerve and the same fast rate was shown by the crest of activity ascending in the dorsal columns of the spinal cord.3. Labelled activity was found present inside myelinated nerve fibres ranging in diameter from 3 to 23 μm in nerve segments taken at the forward part of the crest suggesting that the rate of fast axoplasmic transport is independent of fibre diameter.
Intracellular potentials from intrafusal muscle fibres evoked by stimulation of static and dynamic fusimotor axons in the cat
Authors: Bessou P. , Pages B. 
Published: December 2014

1. Membrane potential changes of single intrafusal muscle fibres were intracellularly recorded in spindles of cat's tenuissimus muscle on stimulating single static or dynamic fusimotor axons.2. One third of responses elicited on stimulating static fusimotor axons were action potentials while the remainder were junction potentials. Repetitive stimulation of static axons eliciting junction potentials produced summation, facilitation and in some instances the appearance of propagated potentials.3. All the responses evoked on stimulating dynamic fusimotor axons were junction potentials which summated but never produced propagated potentials during repetitive stimulation.4. Most of the impalements leading to junction potentials were located in the transition zone between intra‐ and extra‐capsular regions of spindle poles.5. The relation between extracellular and intracellular potentials elicited by stimulation of a fusimotor axon (static or dynamic) makes it possible to assign a physiological nature to the junction potentials recorded intracellularly and to exclude effects attributable to injury.6. A coupling between junction potential and local contraction is indirectly inferred from the frequencygrams which have been previously obtained during single shock stimulation of dynamic fusimotor axons.
The role of electrogenic sodium pumping in the response of smooth muscle to acetylcholine
Authors: Bolton T. B. 
Published: December 2014

1. Intracellular recording of membrane potential was made from the separated longitudinal muscle of the guinea‐pig terminal ileum in physiological salt solution.2. When acetylcholine was washed from the tissue following a brief application the membrane repolarized and then hyperpolarized (‘after‐hyperpolarization’) beyond the level existing before the application of acetylcholine.3. No after‐hyperpolarization was observed following acetylcholine in potassium‐free solution, in sodium‐deficient (17 m
M) solution, or in the presence of ouabain (1.7 × 10−6
M). Repolarization under these conditions was delayed, especially after the membrane potential reached −20 to −30 mV, and was generally incomplete.4. The after‐hyperpolarization was significantly (P < 0.01) greater when acetylcholine was applied in chloride‐deficient (13 m
M) solution.5. It was incidentally observed that the membrane potential in the presence of acetylcholine was more positive in potassium‐free solution (significance P < 0.025), unchanged in chloride‐deficient solution (P > 0.4), and much more negative in sodium‐deficient (17 m
M) solution (P ≪ 0.001), confirming previous results using carbachol.6. When a 2 min application of 1.4 × 10−6
M carbachol was made, the membrane potential 15–20 sec after beginning its application was not affected by ouabain (10−5
M), but showed a significantly (P < 0.005) greater positive shift subsequently, so that the potential after 120 sec in carbachol was significantly (P < 0.025) more positive in the presence of ouabain. After 45 sec in 5.5 × 10−5
M carbachol the membrane potential was also significantly (P < 0.005) more positive in the presence of ouabain (10−5
M).7. Calculations based on hypotheses concerning the movements of sodium and potassium showed that the positive shift of the membrane potential in the presence of carbachol when sodium pumping was arrested, could be quantitatively explained by a decline in the sodium and potassium gradients across the membrane. It appeared that the electrogenic fraction of the sodium pumped was small in the presence of carbachol.8. It was concluded that the application of acetylcholine or carbachol (> 10−6
M) to this smooth muscle disturbs the sodium and potassium gradients across the membrane. These disturbances are in a direction which stimulates electrogenic sodium pumping. Some limitation of depolarization results, and the increased electrogenic extrusion of sodium is responsible for the after‐hyperpolarization which follows the application of acetylcholine.
Elevation in set point for body temperature regulation after prolonged exercise
Authors: Haight J. S. J. , Keatinge W. R. 
Published: December 2014

1. In nine healthy men, after prolonged exercise (approximately 37 km walk and 2·5 km ascent and descent in 9 hr) deep body temperature at rest stabilized at a higher level than in the absence of previous exercise.2. The increase, approximately 0·36° C, was recorded at both oral and rectal sites. It persisted while the subjects rested in warm and in cool surroundings, and disappeared about 11 hr after the end of exercise.3. The increase in body temperature after exercise was accompanied by a similar increase in the body temperature at which sweating started during body heating.4. After exercise the subjects' metabolic response to cold air (13·6° C) was normal or increased in spite of the elevation in body temperature.5. Blood glucose concentration was never lower than 3·1 m
M during these experiments.6. The temperature changes are most easily explained by mild pyrexia due to the release of endogenous pyrogen associated with minor tissue damage.
Circadian rhythms of chicken brain temperatures
Authors: Aschoff Christoff , Aschoff Jürgen , Paul Ursula von Saint 
Published: December 2014

1. Brain temperature was recorded continuously for up to 18 days in unanaesthetized adult male chickens. With the use of a guide box of plexiglas screwed into a trephine of the calvarium, several thermocouples could be inserted at various depths into the brain at the same time.2. While brain temperatures were being recorded, each chicken was placed in a small circular arena and kept either in a light—dark cycle (LD 12:12 hr) or in conditions of constant dim illumination (LL) within a soundproof chamber.3. Under LD‐conditions, the range of oscillation (the difference between maximum and minimum within one period) in brain temperature at any one site was about 1·5° C. During the 12 hr of light the temperature often reached a plateau for several hours. During darkness, a minimum of temperature was usually reached shortly after light‐off. Brain temperature started to rise several hours before light‐on.4. All eleven chickens tested under LL‐conditions showed free running circadian rhythms of brain temperature, with mean periods varying between 22·75 and 25·00 hr (overall mean: 23·69 hr). The range of oscillation in LL‐conditions was smaller than in LD‐conditions, but was seldom less than 1·0° C.5. In LD as well as in LL, continuous fluctuations of temperature with a much higher frequency were superimposed on the circadian cycle. The fluctuations occurred synchronously at all sites of the brain and were of the same order of magnitude (frequency and range) during wakefulness as during sleep.
The contribution of membrane hyperpolarization to adaptation and conduction block in sensory neurones of the leech
Authors: Van Essen David C. 
Published: December 2014

The factors underlying sensory adaptation and conduction block have been studied in cutaneous mechanoreceptor neurones of the leech. A touch‐sensitive cell was activated by applying mechanical or electrical stimuli to its receptive field on the skin. Impulses were recorded extracellularly from its axons and intracellularly from its cell body, which is situated within the
C.N.S.1. Activation of the touch cell by mechanical stimuli revealed two distinct types of adaptation with characteristically different time courses. Sustained pressure on the skin caused a brief burst of impulses at the onset of the stimulus. This rapid adaptation to pressure was restricted to the part of the receptive field that had been stimulated mechanically. A second type of adaptation developed more slowly during the course of repetitive mechanical stimulation. It persisted for many seconds after the end of a train of impulses and appeared as an increase in the threshold to mechanical stimuli not only in the region of skin that had been rubbed but throughout the receptive field of the cell.2. Impulses initiated in the cell body propagated antidromically towards the skin and also raised the threshold to touch, indicating that after‐effects of impulse activity were responsible for the long‐lasting threshold increase.3. Repetitive mechanical stimulation could also produce a reversible conduction block in branches of the touch cell. The block occurred in discrete regions of low safety factor such as axonal branch points both within the ganglion and in the periphery. In some experiments impulses intermittently failed to reach one axonal branch yet continued to invade a separate branch of the same cell.4. Several lines of evidence indicate that both conduction block and the slow component of adaptation are linked to a prolonged hyperpolarization that follows repetitive stimulation of the touch cell. Strophanthidin, which blocks the after‐hyperpolarization in touch cells, reduced the adaptation following trains of impulses and also relieved a conduction block previously established by repetitive stimulation. Furthermore, a comparison of the effects of hyperpolarizations produced by current injection and by repetitive firing showed that most of the threshold increase in the cell body after a train of impulses could be attributed directly to the membrane hyperpolarization.5. These experiments suggest several ways in which repetitive activity can have pronounced and long‐lasting effects on the performance of a highly branched sensory cell. Thus a relatively small number of impulses in a touch cell can markedly decrease its sensitivity to touch. The functional role of the conduction block observed during vigorous stimulation is not as clear because activity for many seconds or minutes is usually needed to establish a block in the larger branches of the cell.
The transport of L‐tryptophan from cerebrospinal fluid in the dog
Authors: Geddes Claire , Martin M. J. , Moir A. T. B. 
Published: December 2014

1. Endogenous tryptophan is uniformly distributed in dog cerebrospinal fluid (c.s.f.) and is about one tenth of the normal fasting plasma level.2. Using a recirculatory ventriculo‐cisternal perfusion technique in conscious dogs it was found that
L‐tryptophan was removed from c.s.f. by a non‐saturable mechanism in addition to bulk absorption of c.s.f. The clearance of
L‐tryptophan from c.s.f. was unaffected by thiopentone anaesthesia.3. Dialysis of dog plasma against an artificial c.s.f. solution containing
L‐tryptophan demonstrated that a large proportion of the tryptophan in dog plasma was protein‐bound and that the unbound diffusible proportion would equilibrate with tryptophan concentrations equivalent to those normally found in dog c.s.f.4. Use of an open‐circuit ventriculo‐cisternal perfusion system in unanaesthetized dogs revealed the presence of a saturable component in the transport of tryptophan from c.s.f.5. As [14C]
L‐tryptophan infused into a recirculatory perfusion system produced no radioactively labelled metabolites, it was concluded that removal of tryptophan from c.s.f. by cerebral metabolism does not contribute substantially to maintaining the low levels of tryptophan in c.s.f. but that brain uptake associated with protein‐binding may give rise to a small saturable component. The results indicate that the actual concentration gradient of tryptophan between plasma and c.s.f. is much less than it appears from the total concentration of tryptophan in the two fluids, and that the mechanism by which the c.s.f. — plasma distribution of tryptophan is maintained is mainly attributable to simple diffusion.
Spontaneous quantal transmitter release: a statistical analysis and some implications
Authors: Hubbard J. I. , Jones S. F. 
Published: December 2014

1. Miniature end‐plate potentials (m.e.p.p.s) were intra‐ and extracellularly recorded from neuromuscular junctions in rat phrenic nerve—diaphragm preparations in vitro.2. Statistical analysis of the intervals between m.e.p.p.s showed that when the mean number of events in time t was plotted as a function of the variance of the events in time t there was a significant deviation from the straight line relationship expected for a Poisson process. Computer simulation showed that this deviation is explicable if release was generated by the random phasing of the activity of a number of releasing sites.3. There was no indication that release of one quantum influences the probability of release of remaining quanta (drag, clustering). It is suggested that m.e.p.p.s whose amplitude is larger than the mode result from the release of the contents of vesicles whose volume is also supramodal.4. The effects of depolarization of nerve terminals upon the variance‐mean curve suggest an increase in the activity of sites rather than an increase in their number.5. Statistical analysis indicated at least 200 ± 100 (mean ± 1
S.E.) releasing sites. This number is of the same order as the number of sites of vesicle aggregation and presynaptic membrane density seen in electron micrographs of nerve terminals of this preparation.
Body fluids and temperature responses of heat‐exposed women before and after ovulation with and without rehydration
Authors: Senay L. C. 
Published: December 2014

1. Four females (21–25 yr) were exposed to 43·3° C dry bulb, 28–29° C wet bulb, for 10 hr both early and late in two menstrual cycles. During the experiments in one cycle, the subjects were rehydrated while during the experiments in another cycle, the subjects were allowed to progressively dehydrate.2. Rates of weight loss and oral temperatures were determined hourly while venous blood samples were obtained before and then after 1, 2, 3, 4, 6, 8, and 10 hr of heat exposure.3. Pre‐ovulatory results were compared with post‐ovulatory results and dehydration experiments with rehydration experiments. In addition, the data on these female subjects were compared with those presented elsewhere for similarly treated male subjects.4. When compared to males, these resting females did not significantly haemodilute when heat exposed. In addition, the female subjects apparently suffered a decrease in plasma volume and body water at a rate some 1·5 times that of similarly exposed males.5. In general,% change in total protein/unit volume of plasma for these female subjects was similar to previously published results for males. However, there were significant differences in the manner in which albumin and globulin fractions changed before and after ovulation.6. The rates of body weight loss for these subjects were similar to those determined for males. No difference was noted between pre‐ and post‐ovulatory rates of weight loss. Dehydration significantly depressed the rates of weight loss during heat exposure.7. Stimulation of sweating (assessed as weight loss) appeared to require similar amounts of heat storage before and after ovulation though initial post‐ovulatory temperatures were generally higher.8. Progressive dehydration of females before ovulation was accompanied by rates of increase in oral temperatures that were similar to those seen for similarly exposed males.9. When females progressively dehydrated after ovulation, there was no statistically significant correlation between temperature rise and weight loss as had been noted in pre‐ovulatory experiments. In addition, for all subjects, the rise in body temperature with dehydration was less after than before ovulation. Two subjects showed an ability to decrease their body temperature in the face of continued dehydration.10. Based on these results, the differences in the responses of males and females to heat exposure were ascribed mainly to two causes: a, inherent differences such as skin surface: blood volume ratios, and b, the inability of females to maintain their vascular volume during heat exposure.
Long‐lasting potentiation of synaptic transmission in the dentate area of the anaesthetized rabbit following stimulation of the perforant path
Authors: Bliss T. V. P. , Lømo T. 
Published: December 2014

1. The after‐effects of repetitive stimulation of the perforant path fibres to the dentate area of the hippocampal formation have been examined with extracellular micro‐electrodes in rabbits anaesthetized with urethane.2. In fifteen out of eighteen rabbits the population response recorded from granule cells in the dentate area to single perforant path volleys was potentiated for periods ranging from 30 min to 10 hr after one or more conditioning trains at 10–20/sec for 10–15 sec, or 100/sec for 3–4 sec.3. The population response was analysed in terms of three parameters: the amplitude of the population excitatory post‐synaptic potential (e.p.s.p.), signalling the depolarization of the granule cells, and the amplitude and latency of the population spike, signalling the discharge of the granule cells.4. All three parameters were potentiated in 29% of the experiments; in other experiments in which long term changes occurred, potentiation was confined to one or two of the three parameters. A reduction in the latency of the population spike was the commonest sign of potentiation, occurring in 57% of all experiments. The amplitude of the population e.p.s.p. was increased in 43%, and of the population spike in 40%, of all experiments.5. During conditioning at 10–20/sec there was massive potentiation of the population spike (‘frequency potentiation’). The spike was suppressed during stimulation at 100/sec. Both frequencies produced long‐term potentiation.6. The results suggest that two independent mechanisms are responsible for long‐lasting potentiation: (a) an increase in the efficiency of synaptic transmission at the perforant path synapses; (b) an increase in the excitability of the granule cell population.
Innervation of extrafusal and intrafusal fibres in snake muscle
Authors: Cliff G. S. , Ridge R. M. A. P. 
Published: December 2014

1. Intrafusal fibres of snake receive motor supply from branches of axons innervating extrafusal motor units. By intramuscular stimulation of motor units by single shocks, and critical curarization of the muscle, we have identified at least some of the motor units contributing motor supply to individual intrafusal fibres. Intrafusal fibre activation was observed by visual examination of the contracting intrafusal fibre, and by recording the resulting spindle afferent discharge.2. The main finding is that in some cases the motor supply to one intrafusal fibre comes from more than one motor unit. The contributing motor units may be either dissimilar twitch units, or twitch and tonic units. Thus some of the intrafusal fibres studied showed polyneuronal motor innervation of heterogeneous origin.3. In critically curarized muscle, the time course of a spindle afferent discharge, following single‐shock stimulation of a motor unit contributing motor supply to the intrafusal fibre, showed little variation with the type of motor unit being stimulated.4. The response of each spindle to a standard stretch was recorded. There was no correlation between dynamic index and type of motor unit or units contributing motor supply. However, the method limits the value of negative findings, and this is discussed.5. The contraction times and tensions of a sample of motor unit isometric twitches are described.
Effect of lateral cervical cord lesions on the respiratory rhythm of anaesthetized, decerebrate cats after vagotomy
Authors: Remmers John E. , Tsiaras W. G. 
Published: December 2014

1. The lateral cervical cord of vagotomized, anaesthetized cats was superficially lesioned at the C3 or the C7 level before or after midcollicular decerebration.2. These cord lesions eliminated the inhibition of diaphragmatic discharge caused by chest compression. Previous work (Remmers, 1973) indicates that this change can be attributed to loss of reflex inhibition of inspiratory activity by intercostal afferents, probably as a result of interruption of tracts ascending in the lateral columns.3. Decerebrate cats with bilateral cervical cord lesions displayed abnormal respiratory patterns, ranging from apnoea to apneusis.4. The results are consistent with the hypothesis that the lateral columns carry proprioceptive feed‐back from intercostal mechanoreceptors which promotes rhythmic breathing in the anaesthetized decerebrate cat.
Splanchnic slowly adapting mechanoreceptors with punctate receptive fields in the mesentery and gastrointestinal tract of the cat
Authors: Morrison J. F. B. 
Published: December 2014

1. A class of slowly adapting mechanoreceptors with A‐delta and C fibres running in the splanchnic nerves of cats is described.2. The mechanoreceptors have punctate regions of mechanical sensitivity at macroscopic vascular branching points and have been found in the lesser omentum, the mesentery of the gall‐bladder, porta hepatis, portal vein, pancreas, spleen and the duodenum, jejunum, ileum, colon and their mesenteries.3. The receptive fields of these mechanoreceptors vary considerably in size in the different regions. The largest receptive fields were found in the small intestinal mesentery and consisted of up to seven points of mechanical sensitivity at vascular divisions, each separated by distances of a few up to about 40 mm. The smallest receptive fields were single or double points of mechanical sensitivity which were most commonly found in relation to the portal vein in the root of the mesentery.4. Maintained stretch of the receptive field elicited a train of impulses which had phasic and tonic components. The tonic discharge was sometimes maintained for more than 1 min.5. Distension of a neighbouring viscus often caused a discharge which had a phasic component and a variable tonic component. The occurrence of the latter appeared to depend on the relative positions of the bowel and mesentery, and was probably associated with a change in tension on the mesentery.6. Occlusion of the portal vein resulted in some units in a discharge which began soon after the start of the occlusion.7. The receptors do not appear to be affected by acid, hypoxia or hypercapnia.