bluuebunny/crossref_metadata_2025 huggingface dataset:
The association of octopamine with specific neurones along lobster nerve trunks.
Authors: Evans P D , Kravitz E A , Talamo B R , Wallace B G
Published: December 2014

Octapamine and its synthetic enzyme, tyramine beta‐hydroxylase (TBH), are found in high concentrations at two points along second thoracic nerve roots in lobsters. The first is in the proximal section of the second root between the ventral nerve cord and the bifurcation of the root into medial (to flexor muscles) and lateral (to extensors) branches. The second region of high concentration is within a well known crustacean neurosecretory system, the pericardial organ, located close to the ends of the lateral branches of the roots. 2. With several different staining procedures, small clusters of nerve cell bodies are found within the connective tissue sheath in the proximal regions of the second roots. No cell bodies are seen in the pericardial organ regions. Cell bodies are variable in number and position between corresponding roots in the same animal and homologous roots among different animals. The average numbers of cell bodies, however, correlate well with TBH and octopamine content, and with the synthesis of octopamine in these same regions of roots. 3. Small clusters of root cell bodies dissected from preparations have greater than 500‐fold higher activities of TBH than isolated efferent excitatory and inhibitory or afferent sensory axons. 4. Along with octopamine, the preferential synthesis of acetylcholine and serotonin is also seen in proximal segments of roots. Acetylcholine synthesis in these regions may represent transmitter synthesized in the nerve terminals innervating the root cells. The role of serotonin in these regions is not understood at this time but the amounts of endogenous serotonin found are only a tenth of the amounts of octopamine present. 5. Dopamine is not synthesized from tyrosine in second thoracic roots. However, if DOPA or dopamine are used as precursor compounds, then noradrenaline, which is usually not found in lobsters, can be accumulated in proximal segments of roots. 6. Phenolamines are converted to two further metabolites by lobster tissues. The compounds are unidentified and are named fast and slow product on the basis of their migration on electrophoresis at acid pH. Some partial characterization of slow product reveals that it is a mixture of compounds that can be converted on mild acid hydrolysis to fast product and the parent phenolamine. 7. The several lines of evidence presented suggest that nerve cells found in the proximal segments of the second thoracic roots contain and can synthesize octopamine. Since not all the cells in any single root have been analysed for octopamine or TBH, however, the possibility that one or more of the cells contain physiologically interesting substances other than octopamine is not eliminated.
Octopamine release at two points along lobster nerve trunks.
Authors: Evans P D , Kravitz E A , Talamo B R
Published: December 2014

Nerve cells in the proximal regions of second thoracic roots in lobsters have been injected with the fluorescent dye Procion Yellow. Examination of the roots reveals an elaborate array of cell branches in a superficial layer of the root in the vicinity of the cell bodies. Large varicosities, up to 10 mum in diameter, are seen lined up along fine nerve branches. 2. In these same regions, electron microscopic examination shows the presence of large profiles filled with 0‐1‐0‐2 mum dense cored granules, and having the appearance of nerve endings. These profiles probably correspond to the varicosities seen in the Procion Yellow injections. The dense cored granules within the endings have a crystalline substructure. All the endings are found within 7 mum of the surface of the root and no obvious physiological target tissue exists in their surroundings. Endings have not been traced directly to root cell bodies.However, granules of similar dimensions to those seen in endings are found in cell bodies, axon‐hillock regions and numerous axonal profiles in the superficial root regions near cell bodies. The morphological studies suggest that the root neurones have the typical appearance of neurosecretory cells. 3. Octopamine pools in cell body regions of second thoracic roots can be isotopically labelled by incubation with either [3H]tyramine or [3H]‐tyrosine. After labelling, pulsing with 100 mM potassium causes an increase in the rate of release of radioactive material. Upon return to normal media background rates of release are re‐established. The enhanced efflux has the following properties: (a) repeated pulses of potassium release less radio‐active material each time; (b) a prolonged potassium pulse produces first a peak of release, then a decline to a plateau, and the plateau level of release is maintained for the duration of the potassium pulse; (c) release is dependent on the presence of calcium ions in the bathing fluid and 40 mM cobalt prevents release; (d) release is selective for octopamine. With tyrosine as a precursor compound, as much radioactive tyrosine as octopamine is found in tissues after incubation, yet pulsing with potassium causes an enhanced efflux only of octopamine from preparations. 4. Release of octopamine also can be demonstrated from pericardial organs near the ends of lateral branches of the roots and the properties of the release are identical to those seen with cell body regions. 5. Physiological studies, in which root cells are antidromically activated while recording from cell bodies, suggest that the distal endings of at least some of the root cells are at the pericardial organs. 6. The results suggest that root cell neurones are neurosecretory cells capable of releasing octopamine at two points: one near cell bodies, the other at the pericardial organs near the distal ends of the roots...
Spontaneous subminature end‐plate potentials in mouse diaphragm muscle: evidence for synchronous release.
Authors: Kriebel M E , Llados F , Matteson D R
Published: December 2014

1. Miniature end‐plate potentials (min.e.p.p.s) were recorded from small muscle cells of mouse diaphragms. Min.e.p.p. amplitude histograms showed successive peaks which were integral multiples of the smallest peak. The smallest potentials (submin.e.p.p.s) averaged 0‐3‐0‐6mV and the mean of the larger min.e.p.p.s averaged 3‐7 mV, depending on the muscle cell diameter. There was a positive correlation between time‐to‐peak and min.e.p.p. amplitude. Time‐to‐peak of the submin.e.p.p.s fell slightly below the regression line through the larger min.e.p.p.s. 2. Sometimes min.e.p.p. amplitude distributions changed spontaneously such that the mean of the major mode min.e.p.p.s decreased twofold during which time the mean of the submin.e.p.p.s did not change. Spontaneous decreases were most pronounced during low frequencies of release (10/min) achieved at 32 degrees C. 3. Small changes in temperature (2 degrees C steps in the range 32‐40 degrees C) greatly altered the number of peaks of min.e.p.p. amplitude histograms without noticeably changing the position of the submin.e.p.p. peak. At 32 degrees C submin.e.p.p.s composed 5‐20% of the histograms and the amplitude of the major mode peak was twelve to fifteen‐times that of the submin.e.p.p.s. Over‐all bell‐shaped distributions were obtained at 37 degrees C which showed up to eight peaks with the major peak at the fourth to sixth peak. Temperatures slightly above 37 degrees C gave a flat distribution with the mean amplitude at the third peak. Min.e.p.p. amplitude histograms were initially skewed (mostly small min.e.p.p.s) after a 40 degrees C heat challenge. 4. Two to eight‐times the normal concentration of Ca2+ in the saline reversibly increased the min.e.p.p. frequency and also decreased the mean of the major mode min.e.p.p.s (two to nine‐times) without noticeably changing the mean of the submin.e.p.p.s. 5. Botulinum toxin A, 10(5) X intraperitoneal median lethal dose (10(5)I.P.LD50)/ml., almost abolished min.e.p.p.s in 30‐90 min. The relative proportion of submin.e.p.p.s increased and the mean of the major mode min.e.p.p.s usually did not change during the initial decrease in frequency. Major mode min.e.p.p.s essentially ceased after 200‐1000 were generated and remaining min.e.p.p.s of some cells showed skewed distributions with three small peaks that were integral multiples of the submin.e.p.p. peak. Smaller min.e.p.p.s were more resistant to block than the larger min.e.p.p.s and, although frequencies were low, small min.e.p.p.s were recorded after 4 hr of botulinum toxin incubation. 6. Colchicine (5 X 10(‐4)M) within minutes reduced the major mode min.e.p.p.s by half (mean of major peak reduced to sixth or seventh peak). Additional colchicine (10(‐3)M reduced the major mode min.e.p.p. amplitude to a fifth of that of control (mean of major mode min.e.p.p.s at the third peak) with no change in position of the submin.e.p.p. peak. Min.e.p.p. amplitudes slowly recovered to half control values after washing. 7...
The sources of external work in level walking and running.
Authors: Cavagna G A , Thys H , Zamboni A
Published: December 2014

The work done at each step during level walking and running to lift the centre of mass of the body, Wv, and to increase its forward speed, Wf, and the total mechanical energy involved (potential + kinetic) Wext, have been measured at various 'constant' speeds (2‐32 km/hr) with the technique described by Cavagna (1975). 2. At intermediate speeds of walking (about 4 km/hr) Wv = Wf and Wext/km is at a minimum, as is the energy cost. At lower speeds Wv greater than Wf whereas at higher speeds Wf greather than Wv: in both cases Wext/km increases. 3. The recovery of mechanical energy, through the pendular motion characteristic of walking, was measured as (/Wv/ + /Wf/ ‐ Wext)/(/Wv/ + /Wf/): it attains a maximum (about 65%) at intermediate speeds. 4. A simple model, assuming that in walking the body rotates as an inverted pendulum over the foot in contact with the ground, fits the experimental data better at intermediate speeds but is no longer tenable above 7 km/hr. 5. In running the recovery defined above is minimal (0‐4% independent of speed), i.e. Wext congruent to /Wv/ + /Wf/: potential and kinetic energy of the body do not interchange but are simultaneously taken up and released by the muscles with a rate increasing markedly with the speed (from about 1 to 4 h.p.). 6. Wext increases linearly with the running speed Vf from a positive y intercept owing to the fact that Wv is practically constant independent of Vf. On the contrary, Wf = aVf2/(1 + bVf), where b is the ratio between the time spent in the air and the forward distance covered while on the ground during each step.
Direct measurement of the intracellular pH of mammalian cardiac muscle.
Authors: Ellis D , Thomas R C
Published: December 2014

1. The intracellular pH (pHi) of sheep heart Purkinje fibres and rat, ferret and guinea‐pig ventricle has been measured using recessed‐tip pH‐sensitive micro‐electrodes. 2. In the absence of CO2 the pHi was approximately 7‐2 in all the preparations used. In 5% CO2 the mean pHi was 7‐14 in rat and ferret ventricle and 7‐02 in sheep Purkinje fibres. 3. The pHi response to an increase or a decrease in the CO2 level (at constant external pH) was biphasic with a large transient change followed by a partial recovery to a new sustained pHi. 4. The intracellular buffering capacity was 34‐8 +/‐ 2‐7 m‐equiv H+/pH unit per l. (+/‐ S.E. of mean) in sheep Purkinje fibres, 76‐6 +/‐ 13‐6 in rat ventricle and approximately 69 in ferret ventricle. 5. The pHi of all the preparations tested indicated that H+ ions were not passively distributed across the cell membrane. There was also little or no pHi change produced by depolarization with high K solutions. 6. Short exposures to hypertonic solutions (100 mM sucrose or 50 mM‐KCl) produced a decrease in pHi of approximately 0‐1 pH units. 7. Acetazolamide slowed the pHi response to CO2 changes. 8. Restoration of the pHi after displacement by increasing the CO2 was not blocked by ouabain or SITS. 9. The relationship between pHi and cardiac contractility is discussed.
The regulation of the calcium conductance of cardiac muscle by adrenaline.
Authors: Reuter H , Scholz H
Published: December 2014

1. The effect of adrenaline on the Ca‐dependent slow inward current, Is, of mammalian cardiac muscle has been investigated by the voltage‐clamp method. The mechanism of the increase in the conductance, gs, was analysed on the basis of a kinetic scheme (Hodgkin & Huxley, 1952) applicable to this system. 2. The rate constants alphad and betad, of activation of gs were not influenced by adrenaline, although the limiting conductance, gs, was greatly increased. 3. Reduction of [Ca]o from 1‐8 to 0‐2 mM decreased the amplitude of inward tail currents when gs was fully activated; however, the relative decrease of the current amplitude was the same with and without adrenaline. The reversal potential, ER, of Is was not changed by the drug. This indicates that the catecholamine has no influence on the selectivity of these conductance channels. 4. An increase in the number of functional conductance channels by adrenaline is discussed as a possible mechanism for the increase in Gs.
Current—voltage curve of sodium channels and concentration dependence of sodium permeability in frog skin
Authors: Fuchs W. , Larsen E. Hviid , Lindemann B.
Published: December 2014

1. The inward facing membranes of in vitro frog skin epithelium were depolarized with solutions of high K concentration. The electrical properties of the epithelium are then expected to be governed by the outward facing, Na‐selective membrane.

2. In this state, the transepithelial voltage (V) was clamped to zero and step‐changes of Na activity in the outer solution ((Na)o) were performed with a fast‐flow chamber at constant ionic strength, while the short‐circuit current was recorded.

3. At pre‐selected times after a step‐change of (Na)o the current response (I) to a fast voltage staircase was recorded. This procedure was repeated after blocking the Na channels with amiloride to obtain the current—voltage curve of transmembrane and paracellular shunt pathways. The current—voltage curve of the Na channels was computed by subtracting the shunt current from the total current.

4. The instantaneous INa—V curve thus obtained at a given (Na)o could easily be fitted with the constant field equation in the range between ‐50 and zero mV. This fit yielded approximate estimates of PNa, the Na— permeability of the Na‐selective membrane (at this (Na)o) and the cellular Na activity, (Na)c. As residual properties of the serosal membrane were ignored the computed values are expected to underestimate the true ones.

5. At constant (Na)c, the steady‐state value of 1/PNa increases linearly with (Na)o. Error analysis and the effect of drugs show that the dependence is not due to the residual properties of the inward facing membranes but reflects the true behaviour of PNa.

6. The steady‐state PNa at a given (Na)o is smaller than the transient PNa observed right after a stepwise increase of (Na)o to this value. The time constant of PNa‐relaxation is in the order of seconds.

7. In conclusion, Na transport through open Na‐selective channels of the outward facing membrane of the stratum granulosum cells can be described as an electrodiffusion process which as such does not saturate with increasing (Na)o. However, when added to the outer border of the membrane Na causes a decrease of PNa within several seconds. It is considered that binding of Na results in closure of Na channels.
Endogenous pyrogen‐like substance produced by reptiles.
Authors: Bernheim H A , Kluger M J
Published: December 2014

1. Injection of lizards (Dipsosaurus dorsalis) with rabbit endogenous pyrogen led to a fever. Injections with denatured endogenous pyrogen did not affect body temperature. 2. Injection of lizards with lizard endogenous pyrogen led to a fever of short duration, while injection of denatured lizard endogenous pyrogen produced no change in body temperature. 3. These data support the hypothesis that the febrile mechanism observed in the higher vertebrates has its origins in some primitive vertebrate.
Internal recording of the early receptor potential in turtle cones.
Authors: Hodgkin A L , Obryan P M
Published: December 2014

1. Early receptor potentials (E.R.P.s) were recorded with internal electrodes in turtle cones by applying brief flashes from a xenon tube with a maximum photon density equivalent to 2‐3 x 10(8) photons micronm‐2 at the optimum wave‐length. 2. The E.R.P. was separated from the late receptor potential (L.R.P.) by superposing in flash on a step of light which was strong enough to saturate the L.R.P. 3. In red‐sensitive cones the E.R.P. consisted of a brief depolarizing phase (R1) followed by a hyperpolarizing phase (R2) of maximum amplitude 10 mV and duration 30‐40 msec. R1 was small or absent in green‐sensitive cones. 4. With flashes of increasing intensity the E.R.P. approached its maximum exponentially with an exponential constant Q of about 10(8) photons micronm‐2 which is of the same order as the reciprocal of the photosensitivity of porphyropsin; the implication of this result, which is considered in the theoretical section, is the the E.R.P. is proportional to the number of photoisomerizations. 5. When tested with a constant xenon flash at varying times after the beginning of a bleaching light the E.R.P. declined exponentially with a similar value of Q. 6. After prolonged bleaches the E.R.P. recovered with a time constant of about 100 sec but much quicker recoveries were observed after relatively brief bleaches. 7. The form and size of the E.R.P. are consistent with the accepted view that it arises from a redistribution of charge in the cone pigment molecule. 8. The effect of a single photoisomerization in an isolated cone was estimated as about 10(‐10) V or one electronic charge through about 10% of the membrane.
Effects of combining static and dynamic fusimotor stimulation on the response of the muscle spindle primary ending to sinusoidal stretching.
Authors: Hulliger M , Matthews P B , Noth J
Published: December 2014

1. A pair of fusimotor fibres, one static and the other dynamic, were stimulated simultaneously to test their combined action on the response of muscle spindle primary endings in the cat soleus to sinusoidal stretching. A frequency of 1 Hz was chiefly used, with a wide range of amplitudes (10 micronm‐2 mm). The response of the ending was assessed from the parameters of the sine fitted to its firing averaged throughout the course of the cycle; this was felt useful even though the responses to the larger stretches showed certain non‐linear features. 2. With small stretches (up to about 50 micronm amplitude) static action dominated, and the modulation of firing during conbined stimulation was little or no larger than that found during the static stimulation on its own, and much smaller than that found during the static stimulation on its own, and much smaller than that found during the dynamic stimulation. The phase of the response was, however, much the same for all three conditions. 3. With larger stretches the modulation with combined stimulation was intermediate between the values found on stimulating either fusimotor fibre on its own; the dynamic contribution increased progressively with the amplitude of stretching. 4. With larger stretches the phase of the response during combined stimulation was appreciably closer to that for static action than to that for dynamic action. But the differences between the various conditions were small (below 20 degrees) and seem attributable to various distortions of the response wave from away from a true sinusoid, rather than betokening a difference in the ratio of velocity to length sensitivity under the various conditions. This view was supported by the effects on phase of grading the rate of stimulation of one fusimotor fibre while holding that of the other constant. 5. Detailed comparison of the cycle histograms obtained under different conditions showed an interestingly asymmetrical pattern of summation and occlusion of the effects of the two kinds of fusimotor fibre. At the peak of the response to a large stretch static action summed with dynamic action, which was here the stronger, so that at this phase of the cycle the firing was greater with the combined stimulation than with either fibre on its own. But, in the trough of the response to the same stretch static action occluded any dynamic action, which was now the weaker, so that at this phase of the cycle the firing with combined stimulation was virtually the same as that with static stimulation on its own. With a small stretch, static action normally occluded dynamic action throughout the cycle; this is in line with the firing during static action now usually being greater than that during dynamic action for all phases of the cycle.
Human erythrocyte anion permeabilities measured under conditions of net charge transfer
Authors: Hunter M. J.
Published: December 2014

1. The permeability of the human erythrocyte to anions has been measured under conditions of net charge transfer: for Cl− and HCO3− ions, at 37° C, this permeability is 5 orders of magnitude too small to account for the rate of the electroneutral anion exchange which is responsible for the chloride, or Hamburger, shift.

2. The method is an indirect one in which the ionophore, valinomycin, is used to increase the erythrocyte K+ permeability: in the absence of permeant cation externally, the rate of the resulting K+ efflux may be limited by the slowness of the accompanying anion efflux, allowing the true anion permeability to be estimated.

3. The average Cl− permeability estimated in ACD‐stored erythrocytes (seven experiments) and erythrocytes from fresh blood (two experiments) was 2·1 × 10−8 cm/sec at 37° C and pH 7·4: this may also be expressed as a Cl− conductance of about 1·0 × 10−5 Ω−1 cm−2. The apparent activation energy for net efflux of Cl− was found to be 3·9 kJ/mole (16·4 kcal/mole).

4. In fresh cells, the ratios of Cl−, HCO3−, Br− and I− permeabilities (or conductances) were 1:0·8:1·5:5. The three halide ions follow Eisenman's Sequence I, representing a binding site of low field strength.
On the subdivision of static and dynamic fusimotor actions on the primary ending of the cat muscle spindle.
Authors: Emonet-Dénand F , Laporte Y , Matthews P B , Petit J
Published: December 2014

1. Using large ramp and triangular stretches a survey has been made of the effect of stimulating single gamma fusimotor fibres on primary endings of muscle spindles in the peroneus brevis to see whether 'intermediate' types of fusimotor action could be recognized, falling between the well known static and dynamic types. 2. Responses were classified into six groups, as detailed on pp. 844‐846, ranging from apparently 'pure' dynamic action (category I) to apparently 'pure' static action (category IV). Models for a putative mixed action were produced by combining the stimulation of a static and of a dynamic fibre to the same spindle. The clearest sign of static action was firing on the releasing phase of the stretch. The essential sign of dynamic action, which survived combination with the more dominant static action, was the low adaptive decay of firing with a time constant of about 0‐5 sec that occurs on the plateau of the ramp stretch. 3. Out of 153 responses, each elicited from a primary ending on stimulation of a single fusimotor fibre, 67% were apparently 'pure' examples of dynamic and static action. The remaining 33% of responses were to some degree suggestive of an admixture, in various proportions, of static and dynamic actions. For only 18% of them was there firm indication of such admixture. 4. When a given fibre was tested on more than one ending then, with one exception out of thirty‐six instances, its action always proved to be either predominantly static or predominantly dynamic. There was no special tendency for an axon with a mixed action on one spindle to have a similarly mixed action on other endings so that individual fusimotor fibres were best classified as static or dynamic without intermediate grades. 5. Simultaneous stimulation of two fusimotor fibres eliciting apparently 'pure static and dynamic actions, could mimic all the intermediate types of action. 6. The results are discussed in relation to recent studies, especially those based on glycogen depletion. It was concluded that dynamic action arises from activation of the bag1 intrafusal muscle fibre, and that static action arises from the bag2 and chain fibres, whether acting individually or collaboratively. The intermediate actions are suggested to arise from an overlap of motor innervation to contrasting types of intrafusal muscle fibre. 7. On the basis of effects on the regularity of the afferent discharge the findings support the view that a given static action axon can innervate bag2 and chain fibres in various proportions in different spindles, so that they do not provide separable effector pathways. 8. Responses to large amplitude sinusoidal stretching were also studied in relation to our classification.
Thyroid calorigenesis in isolated, perfused rat liver: minor role of active sodium‐potassium transport.
Authors: Folke M , Sestoft L
Published: December 2014

1. The effects of ouabain on hepatic oxygen uptake, cell membrane potential, and Na‐K transport were examined at 37 degrees C during non‐recirculating perfusion of isolated livers from fasted normal rats and rats treated with triiodothyronine (T3). The perfusate was Krebs‐Ringer bicarbonate buffer containing albumin and bovine erythrocytes. 2. Treatment with T3 increased the rate of hepatic oxygen uptake by 30% (i.e. by 0‐83 (micromole/min) per gram liver). 3. After shifting to perfusate containing 2‐5 mM ouabain, a 4‐5 mV depolarization and maximal rates of net hepatic K release and Na uptake occurred within 2 min in both thyroid states. These changes were not accompanied by any significant change in the rates of hepatic oxygen uptake. 4. T3‐treatment increased the maximal, post‐ouabain net flux of K by 29% (i.e. by 0‐52 (muequiv/min) per gram liver). The T3‐indlced increase in the net flux of Na (19%) did not achieve statistical significance. 5. In either thyroid state, the observed passive fluxes of Na and K were calculated to be balanced by active vluxes at the expense of 5‐6% of the observed rate of hepatic oxygen uptake. 6. The results indicate that hyperthyroidism may enhance the rate of hepatic Na‐K transport, but the energy expenditure due to this process appears to be too small to make any important contribution to thyroid calorigenesis in perfused rat liver.
Baroreflex inhibition of the human sinus node: importance of stimulus intensity, duration, and rate of pressure change.
Authors: Eckberg D L
Published: December 2014

1. Carotid baroreceptors were stimulated with electronically controlled neck suction in five healthy young men and pulse interval prolongation was measured. Timing of the onset of stimuli in relation to cardiac activity was held constant, and stimulus intensity, duration, and dP/dt were varied independently. 2. In the subjects studied, sinus node responses to neck suction were proportional to dP/dt. However, variations of stimulus dP/dt within or above the normal range for arterial dP/dt did not influence the magnitude of integrated baroreflex responses, or the earliest portion of baroreflex sinus node inhibition. 3. Carotid baroreflex responses were linear over a wide range which extended beyond the normal range for human systolic arterial pressures. 4. Saturation of the carotid baroreceptor‐cardiac reflex occurred at distending pressures of about 160 mmHg. 5. The average baroreflex responses of the group studied were highly reproducible over time. 6. Baroreflex gain correlated very strongly with base line pulse interval. 7. The magnitude of baroreflex responses increased linearly with the duration of carotid sinus distension and reached a maximum level with stimuli lasting 0‐5 sec or more. 8. The results demonstrate that carotid sinus transfer characteristics can be measured in normal man, and that human response patterns are strikingly similar to those observed earlier in experimental animals.
Effects of innervation on acetylcholine sensitivity of developing muscle in vitro.
Authors: Betz W , Osborne M
Published: December 2014

1. Chick embryo skeletal muscle fibres were grown in culture. The acetylcholine (AACh) sensitivity of non‐innervated fibres was compared with that of fibres innervated in vitro by chick embryo ciliary ganglion neurones. 2. The general pattern of ACh sensitivity was unchanged by innervation: ACh hot spots were superimposed on a background of uniform ACh sensitivity. 3. Quantitative comparisons revealed two differences between non‐innervated and innervated fibres. First, hot spots were encountered about one third more often on innervated fibres. Secondly, about one‐third of the hot spots on innervated fibres had significantly higher ACh sensitivities than the remainder, which were similar to those on control fibres. 4. Apossible explanation of these results is that nerves which form synapses induce the appearanceof end‐plates which have higher ACh sensitivities than the pre‐existing ACh hot spots.
Daily changes in the blood composition of conscious pigs with catheters in foetal and uterine vessels during late gestation
Authors: Randall G. C. B.
Published: December 2014

1. Catheters were inserted into the foetal carotid artery and maternal middle uterine artery and vein in twenty foetuses from fifteen sows, 91‐105 days pregnant. Blood samples were collected from foetal and maternal circulations for periods of 7‐21 days after surgery.

2. Blood gas tensions, pH, packed cell volume (PCV) and the levels of glucose, fructose and lactic acid in conscious pigs were followed in foetal and maternal bloods during late pregnancy.

3. Foetal blood gas tensions, pH, PCV, lactic acid and glucose levels did not change markedly during the last 20‐25 days of gestation. Blood fructose concentration fell during this period with the greatest change occurring after 100 days gestation. Foetal and maternal blood pH values were higher than those reported in the sheep, cow, mare and rhesus monkey.

4. Small changes in PCO2 and pH in foetal carotid blood were associated with similar changes in maternal uterine venous blood, so that gradients between sow and foetus remained relatively constant.

5. Daily changes in maternal blood glucose levels were associated with smaller changes in foetal blood glucose and fructose levels. Blood glucose concentrations in foetal blood were generally 40‐70% of maternal concentrations. Over‐all relationships between maternal blood glucose and foetal blood fructose concentrations were masked by the independent fall in foetal fructose levels with age.

6. The present findings have been compared with previous observations on acute, anaesthetized preparations in pigs, and chronic preparations in other domestic animals.
Effects of fusimotor stimulation on the response of the secondary ending of the muscle spindle to sinusoidal stretching (cat)
Authors: Cussons P. D. , Hulliger M. , Matthews P. B. C.
Published: December 2014

1. The responsiveness of the spindle secondary ending to sinusoidal stretching has been studied using the soleus muscle of the anaesthetized cat. The sensitivity (impulses/sec firing per mm stretching) and the phase of the response were determined by computer averaging. The small linear range was studied at frequencies of 0·5‐500 Hz, and also the larger non‐linear range at 1 Hz.

2. In the linear range, stimulation of single fusimotor fibres (which were presumed to be static axons) approximately halved the sensitivity of the ending to low frequency stretching (up to 30 Hz), but did not produce any change in the phase of the response. Thus, from the point of view of motor function, fusimotor activity provides control of gain and a biasing signal, but not control of the relative sensitivity of the secondary ending to length and velocity.

3. In contrast, such stimulation slightly increased the responsiveness of the secondary ending to high‐frequency stretching (100‐500 Hz) and slightly advanced the phase of the response above that of the passive ending.

4. The results are discussed in relation to the effect of static fusimotor stimulation on the primary ending, and to findings on secondary endings in the decerebrate cat.
Presynaptic inhibition: the mechanism of protection from habituation of the crayfish lateral giant fibre escape response.
Authors: Bryan J S , Krasne F B
Published: December 2014

1. Mechanism of protection from habituation of the lateral giant escape reflex of the crayfish was studied. Experiments were designed to determine whether presynaptic inhibition of primary afferents for the reflex occurs following escape command neurone firing, and if so, whether it could account for protection of the first synapse from depression. 2. Synaptic transmission between afferents and interneurone A of the escape reflex is strongly inhibited following giant fibre spikes. 3. Giant fibre firing results in post‐synaptic inhibition of interneurone A. However, inhibition of afferent input to interneurone A consistently outlasts both i.p.s.p.s and post‐synaptic conductance increases in the neurone; the inhibition, therefore, is probably not exclusively post‐synaptic. 4. Giant fibre firing results in excitability changes in sensory afferent terminals as measured by the amplitude of antidromic compound action potentials to focal electrical stimuli applied in the region of afferent terminals in the last abdominal ganglion. The time course of this effect parallels those of protection and inhibition of the first synapse. 5. The magnitude and time course of protection and inhibition of transmission to interneurone A parallel each other closely. Both processes considerably outlast measurable signs of post‐synaptic inhibition. 6. We conclude that following giant fibre activity the first synapse of the lateral giant reflex is presynaptically inhibited and the presynaptic inhibition is responsible for the protection effect described in the preceding paper.
Kinetics of synaptic transfer from receptors to ganglion cells in turtle retina
Authors: Baylor D. A. , Fettiplace R.
Published: December 2014

1. Synaptic transfer between the retinal input and output was studied in turtle eyecups by injecting rectangular current pulses into a single cone or rod while recording externally from a ganglion cell.

2. When a receptor was activated with weak steps of polarizing current, the probability of obtaining a ganglion cell impulse rose after an S‐shaped delay to a peak at about 0·1 sec and then declined. This suggests that the transmission chain behaves like an electrical band‐pass filter containing delay and differentiating elements.

3. To further characterize the kinetics of excitation in the subthreshold region, the duration and polarity of the polarizing current pulses were varied while determining the magnitude of the threshold current and the delay to the ganglion cell impulses. The results of these experiments were described with linear models which assume that synaptic transfer occurs over a cascade of first‐order delay stages and a single differentiating stage.

4. The pathways which relay off responses to light from rods and red‐sensitive cones were formally similar, but the time scale in the rod path was several times slower. The path carrying off responses from the red‐sensitive cones was faster than the on path. These kinetic differences indicate that independent pathways mediate each of the three categories of response and suggest that the kinetics of each path are ‘matched’ to the input signals generated by light.

5. The strength—latency relations for the responses of on‐centre ganglion cells to flashes and steps of light were approximately predicted from the description of synaptic transfer developed here and the description of visual transduction in red‐sensitive cones from a previous study.

6. It is suggested that the retinal paths have kinetics which might be useful in transmitting light‐evoked signals whilst attenuating noise present near the input.
Antagonism by indomethacin of neurogenic hyperthermia produced by unilateral puncture of the anterior hypothalamic/preoptic region
Authors: Rudy T. A. , Williams J. W. , Yaksh T. L.
Published: December 2014

1. In unanaesthetized rats, restrained at an ambient temperature of 24 °C, the anterior hypothalamic/preoptic (AH/PO) region was lesioned unilaterally by acute mechanical puncture.

2. In control (no pre‐treatment) rats, unilateral AH/PO puncture produced a neurogenic hyperthermia which began immediately, reached its peak magnitude (mean peak magnitude = +2.3 °C) within 60‐90 min and persisted usually for 8‐16 hr. At defervescence, core temperature fell to a level near that of the pre‐lesioning base line.

3. The prostaglandin synthesis inhibitor, indomethacin, administered
I.P. at doses of 5 and 15 mg/kg 1 hr before puncture of the AH/PO region, attenuated the lesion‐induced hyperthermia in a dose dependent fashion. The higher dose reduced peak magnitude by 80% and the 6 hr Fever Index by 88%. The vehicle used to dissolve the indomethacin (60% DMSO/40% saline) did not significantly attenuate the hyperthermia.

4. In rats that were hyperthermic after AH/PO damage, indomethacin (10‐15 mg/kg
I.P.) caused core temperature to fall promptly to near the prelesion base line. Reversal occurred whether the indomethacin was injected while core temperature was still rising or late in the plateau phase of the hyperthermia.

5. It is suggested that the neurogenic hyperthermia elicited by unilateral lesioning of the AH/PO region was mediated by prostaglandins released from injured tissue and possibly from extravasated blood. Evidence is cited indicating that the most likely sites of action of the released prostaglandins are the surviving portion of the AH/PO region on the punctured side and the intact contralateral AH/PO region.
The morphology of hair follicle afferent fibre collaterals in the spinal cord of the cat
Authors: Brown A. G. , Rose P. K. , Snow P. J.
Published: December 2014

1. The enzyme horseradish peroxidase (HRP) was injected into single axons that innervated hair follicle receptors to study the morphology of their collaterals in the dorsal horn of the cord. The axons were impaled near the dorsal root entrance zone in the lumbosacral spinal cord of anaesthetized cats and HRP injected by passing current through the intra‐axonal micro‐electrode. The morphology was revealed by subsequent histochemistry.

2. Thirteen hair‐follicle afferent fibres were stained including six that innervated tylotrichs (type T hair follicle afferent units) and one that innervated guard hairs (type G unit). The remaining six axons were not classified according to hair type, but, on the basis of their axonal conduction velocities, would have been either type G or T.

3. Eleven axons could be traced back into the dorsal roots. Eight of these, upon entering the cord, turned and ran towards the brain. They did not divide into rostral and caudal branches. Three of the eleven did divide and gave rise to both rostral and caudal branches.

4. Sixty‐three collaterals were given off the thirteen stained axons. All well‐filled collaterals had a strikingly similar morphology. They descended through laminae I‐III of the dorsal horn into the deeper parts of lamina IV or into lamina V, before turning and ascending back into superficial lamina IV and lamina III where they branched profusely to give rise to their terminal arborizations. Terminal boutons, most commonly of the ‘en passant’ type, were numerous in lamina III, but were also seen in the dorsal part of lamina IV and in ventral lamina II. None were observed in dorsal lamina II or near the junction of the grey and white matter (lamina I) or in lamina V.

5. The terminal arborizations of collaterals from a single hair follicle afferent fibre were in line with one another in the longitudinal axis of the cord. In the better‐stained preparations the terminal arborizations of adjacent collaterals from a single axon formed a continuous longitudinal column through the dorsal horn. There was a gradual shift of the column of arborizations from lateral to medial as the more rostral collaterals were given off.

6. The hair‐follicle afferent fibre collaterals are now identified as the ‘collaterales grosses et profondes de la substance de Rolando’ of Ramón y Cajal (1909) which give rise to the ‘flame‐shaped arbors’ of Scheibel & Scheibel (1968).

7. The importance of the longitudinal organization of the terminal arborizations for an understanding of the topographical properties of dorsal horn neurones is discussed.
Further evidence for adrenergic transmission in the human vas deferens.
Authors: Anton P G , McGrath J C
Published: December 2014

1. Isolated portions of human vas deferens responded to field stimulation of the intramural nerve fibres or to exogenously applied noradrenaline with rhythmical contractions of both longitudinal and circular muscle layers. 2. In guinea‐pig and rabbit vas deferens field stimulation produced an initial rapid 'twitch' response which was not found with human vasa. 3. Responses of the human vas to field stimulation were depressed by the alpha‐adrenoceptor blocking agents phentolamine and yohimbine. 4. It is concluded that the motor innervation of the human vas deferens is adrenergic and the relevance of this to the physiological operation of the tissue is discussed.
Thin‐fibre receptors responding to mechanical, chemical, and thermal stimulation in the skeletal muscle of the dog
Authors: Kumazawa T. , Mizumura K.
Published: December 2014

1. Unitary activities of muscular thin fibre afferents, which were not sensitive to muscle stretching, were recorded from the nerve of the medial gastrocnemius muscle of the dog. Responses to mechanical stimulation, intra‐arterial injection and local application of chemical solutions, and thermal stimulation of the surface of the muscle were studied. It was observed that polymodal receptors which responded to all types of stimulation existed in the thin fibre afferents of the muscle.

2. The receptive area of these units tested by mechanical stimulation was spot‐like and appeared to be located not only on the surface but in the midst of the muscle.

3. The mechanical response varied among these units with respect to the threshold and the pattern of discharges.

4. In these units, NaCl, KCl, and bradykinin consistently evoked responses, with differences in the latencies and discharge patterns, while solutions of histamine, acetylcholine and sodium citrate caused responses less consistently and less effectively. In the stretch receptors, chemical stimulation applied in the same way as tested in the thin fibre afferents produced quite different features in their responses.

5. Heating the receptive area of the muscle surface caused responses in twenty‐five out of thirty‐six units, which were sensitive both to mechanical and to chemical stimulations. The threshold varied from 38·0 to 48·3 °C, with a mean of 43·1 °C for C fibre units and 41 °C for A‐δ fibre units.

6. The responses to heating were consistently obtained in the units responding to the surface application of chemical solutions. However, the above response was never obtained in the units which did not respond to surface chemical stimulation but responded to intra‐arterial injection. These results suggest a large population of polymodal receptors in the muscular thin fibre afferents.
Specific responses of rat raphé neurones to skin temperature.
Authors: Dickenson A H
Published: December 2014

1. The responses of single neurones in the nuclei raphés magnus, medianus, dorsalis and pontis to changes in skin temperature were recorded in rats anaesthetized with urethane. Skin temperature was altered by means of a water‐perfused jacket. 2. Of 210 neurones studied, thirty‐five were specifically excited by warming the skin whilst twenty were cold responsive. The greatest proportion of cells responding to skin temperature were in the nucleus raphé magnus, whilst few neurones in the raphé dorsalis and pontis were influenced. 3. The warm units had peak activity at a mean skin temperature of 37.7 degrees C whilst the cold cells had a corresponding maximal rate at 29.0 degreet C. Mechanical and noxious peripheral stimulation, blood pressure changes and temperatures other than that of skin did not affect the neurones. 4. The neurones influenced by skin temperature were histologically verified as being within the raphé system. 5. LSD inhibited all neurones tested, indicating that the cells were serotonergic. 6. The responses to skin temperature were unchanged in rats with midcollicular sections suggesting an ascending thermal system. 7. The results suggest that any involvement of 5‐HT in central thermo‐regulation is in terms of an afferent thermal pathway mediated by serotonergic raphé neurones.
The effect of age on neuromuscular transmission.
Authors: Kelly S S
Published: December 2014

1. Resting membrane potentials (RMPs), spontaneous miniature end‐plate potentials (m.e.p.p.s), and evoked end‐plate potentials (e.p.p.s) were recorded in phrenic nerve‐hemidiaphragm preparations from rats at ages from 11 to 375 days. 2. The mean RMP increased from ‐64.1 +/‐ 1.2 mV (mean +/‐ S.E.) at age 11 days to ‐71.3 +/‐ 1.0 mV at age 30 days, after which there was no significant change with age. 3. The mean amplitude of m.e.p.p.s decreased from 1.088 +/‐ 0.070 mV at 11 days of age to 0.405 +/‐ 0.030 mV at 175 days of age, after which there was no significant change. 4. There was a rpaid, large increase in the frequency of m.e.p.p.s from 0.02/sec to 0.97/sec (geometric means) between 11 and 23 days of age, followed by a slower increase to 3.19/sec at 175 days of age. Subsequently there was a decrease by 2.58/sec at 375 days of age. 5. The mean of quantum content of plateau e.p.p.s elicited at a frequency of 10 Hz increased from 20.5 quanta/e.p.p. to 169.9 quanta/e.p.p. (geometric means) between 11 and 175 days of age and then decreased to 120.4 quanta/e.p.p. at 375 days of age. 6. The mean quantum content of the first e.p.p.s of trains of e.p.p.s increased from 44.2 quanta/e.p.p. to 468.8 quanta/e.p.p. (geometric means) between 11 and 175 days of age and then decreased to 358.1 quanta/e.p.p. at 375 days of age. 7. The calculated safety factor of neuromuscular transmission increased with age up to 110‐175 days and subsequently decreased. 8. The change in all the above parameters occurred most rapidly in the first 6 weeks of life. The rapidity of these changes indicates that great care must be taken to ensure that control and experimental animals are adequately matched according to age, especially when rats weighing less than about 300 g are used.
The effect of age upon the influx of glucose into the brain.
Authors: Daniel P M , Love E R , Pratt O E
Published: December 2014

1. Rats aged from 1 to 116 weeks were studied. 2. Influx of glucose into the brain is low in suckling rats but rises after weaning, to reach its highest level in the young adult, thenceforward declining slowly as age increases. 3. The blood‐brain barrier for glucose is fully developed in the rat by the age of 18 days and glucose enters the brain, at this stage, by carrier‐mediated transport, as in the adult. 4. The results show that the low influx of glucose into the brain of the suckling animal is due to a low maximum rate of transport of glucose rather than to a low affinity of the carrier‐molecule for glucose. 5. In the young adult rat, efflux of glucose back from the brain into the blood is greater than in either the suckling or the old animals. Thus the margin of safety, i.e. the extent to which the blood glucose can be reduced without affecting the utilization of glucose by the brain, is highest in the young adult. 6. The lower margin of safety in the suckling animals is compensated for by the high influx of the ketone bodies which provide an alternative source of energy at this age. In the old animals there is no alternative source of energy, so that the older brain is at greatest risk in hypoglycaemia.