bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of muscle length on energy balance in frog skeletal muscle.
Authors: Curtin N A , Woledge R C
Published: December 2014

1. Measurements were made of the extents of ATP splitting and the creatine kinase reaction and the heat + work (h+w) produced during 5s isometric tetani of frog semitendinosus muscle at 0 degrees C. A comparison was made of tetani at two different muscle lengths. These lengths were l0 (sarcomere length 2.3 micrometers before stimulation), which is near the optimum for interaction of actin and myosin, and lmax (sarcomere length 3.8 micrometers) at which actin‐myosin interaction is largely prevented. 2. As in earlier studies of muscle at l0, the observed h+w was significantly greater than the amount explained by the energy from ATP splitting and the creatine kinase reaction. Our main new finding is that a significant amount of unexplained energy is also produced at lmax where there is a negligible amount of actin‐myosin interaction. This suggests that the unexplained energy cannot be due solely to actin‐myosin interaction. 3. On average less unexplained energy is produced at lmax than at l0. Thus it seems likely that the process (or one of the processes) producing this energy is dependent on muscle length. 4. The observed h+w was divided on the basis of its time course into the two parts, labile and stable, which were defined by Aubert (1956). The labile part of the h+w has an exponentially declining rate, and the stable part has a constant rate. The production of labile h+w influenced by muscle length in two ways: the total amount and the rate of its production are significantly smaller at lmax than at l0. 5. At both lengths the labile h+w is equal, within experimental error, to the unexplained h+w.
Sugar transport in giant axons of Loligo.
Authors: Baker P F , Carruthers A
Published: December 2014

1. The transport of glucose and a number of other sugars has been investigated in the giant axons of Loligo forbesi. 2. Glucose and 2‐deoxy‐D‐glucose are phosphorylated by squid axons, alpha‐methyl‐D‐glucopyranoside and 3‐O‐methylglucose are not metabolized. All four sugars can diffuse freely in axoplasm. 3. Sugar uptake in squid axons is a passive, saturable process. The maximum rate of sugar uptake increases in the order 3‐O‐methylglucose less than 2‐deoxy‐D‐glucose less than D‐glucose. Competition between these sugars suggests a common uptake mechanism. 4. The uptake of D‐glucose but not 3‐O‐methylglucose or 2‐deoxy‐D‐glucose is reduced when the external Na concentration is lowered. 5. Glucose uptake is sensitive to temperature with a Q10 for saturated uptake of 1.9 between 14.5 and 5 degrees C. Uptake is unaffected by external pH in the range 5‐10 but is reduced by cyanide (2 mM). 6. Glucose and 2‐deoxy‐D‐glucose uptake and metabolism are increased by electrical stimulation. These effects are prevented by ouabain. The uptake of 3‐O‐methylglucose is unaffected by stimulation. 7. The maximum rate of 3‐O‐methylglucose efflux is higher than the maximum rate of uptake of the sugar suggesting that transport of this sugar is asymmetric. 8. 3‐O‐methylglucose efflux is reduced by external sugars with order of potency 3‐O‐methylglucose greater than 2‐deoxy‐D‐glucose greater than D‐glucose. These effects persist when the internal 3‐O‐methylglucose concentration is as high as 50 mM. 9. 3‐O‐methylglucose efflux is inhibited reversibly by cytochalasin B and phloridzin but irreversibly by phloretin. Efflux is reduced reversibly by cyanide (2 mM). 10. 3‐O‐methylglucose efflux is sensitive to temperature with a Q10 of 3.2 over the range 10‐20 degrees C. Efflux is unaffected by external pH in the range 6‐9 but is reduced reversibly by internal acidification.
Sodium efflux in rabbit myocardium: relationship to sodium—calcium exchange
Authors: Bridge J. H. B. , Cabeen W. R. , Langer G. A. , Reeder S.
Published: December 2014

1. The washout of 22Na, 45Ca and 58CoEDTA− has been observed in arterially perfused rabbit interventricular septa both in the presence and absence of intoxicating doses of the aglycone, 3 acetylstrophanthidin (ACS).

2. The washout of 22Na from paced septa (21·0/min) was rapid with approximately 99% of the exchange occurring in 30 min.

3. Septa labelled with 22Na and washed out in the presence of 10−5
m‐ACS were quiescent, exhibited marked contracture and a slowed 22Na exchange with 99% of the initial 22Na leaving the tissue in approximately 200 min.

4. Comparison of the washout of the extracellular marker 58CoEDTA− from paced and intoxicated septa revealed no differences, suggesting that regions of the extracellular space had not become inexchangeable as a result of the contracture that these septa exhibited.

5. Simultaneous measurements of the distribution of 22Na and 58CoEDTA− in the presence of 10−5
m‐ACS revealed an apparent cellular Na concentration of 54·8±10·4 (
s.e.). This was considerably in excess of the maximum amount of Na contributing to the slowest component of Na efflux from intoxicated septa. Origins of this discrepancy are considered.

6. The slowest component of 22Na efflux from intoxicated septa could be markedly stimulated by increasing the external Ca concentration from a nominal 1·5 to 16 m
m. The magnitude of stimulation was 44·3±7·8% (
s.e.). Increases in the concentration of Mg from 1·0 to 16·0 m
m were without effect on the 22Na efflux.

7. Application of 10−5
m‐ACS produced marked depolarization of the membrane to new stable levels that lay between ‐10 and ‐20 mV.

8. Washout of ACS after several hours of intoxication resulted in a partial decline in contracture tension, an acceleration of Ca efflux, little change in 22Na efflux and a repolarization of the cell membrane.

9. Some of the Na and Ca movements reported in this paper have been interpreted by supposing that there is, in this preparation, a coupled exchange of three Na ions for a single Ca ion.
Modification of cation permeability of rabbit descending colon by sulphydryl reagents.
Authors: Luger A , Turnheim K
Published: December 2014

1. Addition of the organic mercurials mersalyl, p‐chloromercuribenzoate, and p‐chloromercuribenzene sulphonate to the Ringer solution (140 mM‐Na) bathing the luminal side of isolated epithelia of rabbit descending colon increases short‐circuit current (Isc) and tissue conductance (Gt) when the spontaneous Isc is below 2‐3 muequiv/cm2 hr. 2. The stimulation of Isc by mersalyl is due to an increase in Na absorption, simultaneously K secretion is induced, whereas Cl absorption is not affected. 3. Mersalyl inhibits Isc at Na concentrations below 50 mM. The Na concentration at which Isc is half‐maximal (KNa) is shifted by mersalyl from 25 to 133 mM. The overshoot in Isc to a peak volume of 5 muequiv/cm2 hr observed when Na‐depleted tissues are suddenly exposed to Na is markedly depressed by mersalyl. 4. Mersalyl inhibits non‐competitively the blocking effect of amiloride on Isc. Both the stimulation of Isc and the inhibition of the amiloride effect by mersalyl have the same time course (half‐time of the effects 30‐40 min) and similar concentration‐response curve (half‐maximal effects with 2.0‐2.6 x 10(‐4) M), indicating a common mechanism. 5. The mersalyl effects on Isc and on the amiloride action are only partially reversed by dimercaptopropanol. p‐Chloromercuribenzoate conjugated with dextran (mol. wt. 10,000) elicited the same effects as mersalyl. 6. The stoichiometry of the mersalyl‐amiloride interaction, estimated by use of the Hill plot, is 1:1; a Hill coefficient of 1 was also obtained for the stimulating effect of mersalyl on Isc. 7. It is concluded that one sulphydryl group per luminal Na entry site controls both its Na conductance and cation selectivity. Titration of these sulphydryl groups by organic mercurials appear to fix the conductance of the luminal Na entry mechanism in a submaximal position and prevent its modulation by amiloride or variations in intra‐ and/or extracellular Na concentrations.
Effects of quinine and apamin on the calcium‐dependent potassium permeability of mammalian hepatocytes and red cells.
Authors: Burgess G M , Claret M , Jenkinson D H
Published: December 2014

1. K‐sensitive electrodes placed in the extracellular fluid have been used to show that ATP and noradrenaline cause a rapid loss of up to 10% of the K content of isolated guinea‐pig hepatocytes. 2. The hypothesis tha this response is a consequence of a rise in the K permeability of the hepatocyte membrane triggered by an increase in cytosolic Ca is supported by the finding that the divalent cation ionophore A23187 also initiated K loss, in this instance of up to 20‐25% of the amount in the cells. 3. Under similar conditions A23187 caused a transient increase, followed by a larger decrease, in the 45Ca content of guinea‐pig hepatocytes equilibrated with this isotope. The decrease alone was seen with ATP and noradrenaline. 4. Quinine (1 mM) and the bee venom neurotoxin apamin (10 nM) greatly reduced the effect of ATP, noradrenaline and A23187 on K content without affecting the changes in 45Ca movement. 5. Apamin (10 nM) also abolished the increase in 42K efflux which follows the application of the alpha‐adrenoceptor agonist amidephrine to rabbit liver slices; the concurrent rises in 45Ca efflux and glucose release were unaffected. 6. It was concluded that quinine and apamin are able to block either the Ca‐dependent K channels present in guinea‐pig and rabbit liver cell membranes or the mechanism that controls them. 7. Surprisingly, rat hepatocytes took up rather than lost K when treated with the concentrations of ATP, noradrenaline or A23187 that initiated K loss from guinea‐pig cells. This response was greatly reduced by ouabain. 8. Application of large concentrations of A23187 to rat hepatocytes caused K loss associated with cell death. 9. The influence of apamin (10‐1000 nM) and quinine (200‐1000 micro M) on the Ca‐dependent K permeability of red blood cells and ghosts was also studied. Apamin was without effect even when applied to both sides of the ghost membrane, whereas quinine caused inhibition, as reported by others. 10. The results suggest that Ca‐dependent K channels or carriers are present in the membranes of liver cells of the guinea‐pig and rabbit, but are either lacking or inactive in rat liver. The finding that apamin blocks this mechanism in hepatocytes but not in erythrocytes may mean that the channels differ in these cells.
The dependence of sodium pumping and tension on intracellular sodium activity in voltage‐clamped sheep Purkinje fibres.
Authors: Eisner D A , Lederer W J , Vaughan‐Jones R D
Published: December 2014

1. Intracellular Na activity (aiNa) was measured in sheep cardiac Purkinje fibres using a recessed‐tip Na+‐sensitive micro‐electrode. The membrane potentials was controlled with a two‐micro‐electrode voltage clamp. Tension was measured simultaneously. 2. Removing external K produced a rise of aiNa and both twitch and tonic tension. On adding 4‐10 mM‐[Rb]0 to reactivate the Na‐K pump aiNa and tension declined. An electrogenic Na pump current transient accompanied the fall of aiNa. 3. The half‐time of decay of the electrogenic Na pump current transient was similar to that of aiNa, (mean tNa0.5/tI0.5 = 0.97 +/‐ 0.03 (S.E.M.; n = 28)). Following the re‐activation of the Na‐K pump, the electrogenic Na pump current transient was linearly related to aiNa. 4. The duration of exposure to K‐free, Rb‐free solutions was varied to change the level of aiNa. On subsequently re‐activating the Na‐K pump with 10 mM‐[Rb]0, the ratio of the charge extruded to the total change of aiNa was constant. It is concluded that the fraction of Na extruded electrogenically is unaffected by changes of aiNa. About 26% of the total Na extrusion appeared as charge transfer. 5. The relationship between tonic tension and aiNa was usually different during Na‐K pump inhibition in a K‐free, Rb‐free solution compared with the relationship during Na‐K pump re‐activation. In general, a given aiNa was associated with a greater level of tonic tension during Na‐K pump inhibition compared with that during pump re‐activation. A similar hysteresis was often seen between twitch tension and aiNa.
The kinetics of ouabain‐sensitive ionic transport in the rabbit carotid artery.
Authors: Heidlage J F , Jones A W
Published: December 2014

1. Ouabain (0.1 mM)‐sensitive 42K influx and 24Na efflux have been measured in rabbit carotid arteries under conditions of high cellular potassium, [K]i, as well as sodium, [Na]i. About 50% of the total fluxes are ouabain‐sensitive (active) under conditions of high [K]i. 2. The extracellular space, determined by 60Co‐EDTA, was relatively large in comparison to cellular water. The ionic concentrations in normal solution, estimated from isotope flux components, are: [Na]i = 24; [K]i = 169; [Cl]i = 68 mmol/l cell water. 3. The ouabain=sensitive 42K influx and 24Na efflux in high‐K tissues were measured at varying external concentrations of potassium, [K]o, and normal concentrations of external sodium, [Na]o. Sigmoidal kinetics were observed and fitted to a co‐operative interaction model. The maximal efflux of 24Na, 0.245 muequiv/g wet weight per minute, was about 1.4 times that for 42K influx. Half‐maximal stimulation was achieved at [K]0.5o of 2.4 mM for Na, and 3.4 mM for K transport. The flux ratio of Na to K approximated 1.5. 4. Increased 42K efflux was found in the presence of ouabain and the passive influx of 42K was corrected for this effect. In the absence of this correction the ouabain‐sensitive 42K influx would be reduced, and the Na/K flux ratio raised to about 2. 5. The [K]o‐dependence of ouabain‐sensitive fluxes was measured on Na‐loaded tissues. 24Na efflux exhibited saturation kinetics with a maximum of 1.18 muequiv/g wet weight per minute and [K]0.5o = 3.1 mM. The 42K influx was two thirds the active Na efflux for [K]o less than or equal to 5 mM. At high [K]o, however, the influx greatly exceeded the predicted levels. Evidence is presented for a ouabain‐sensitive membrane hyperpolarization being responsible for an additional influx of 42K. 6. The ouabain‐sensitive 24Na efflux showed a sigmoidal dependence on [Na]i in the presence of [K]o = 10 mM and normal [Na]o. The maximal efflux was 0.88 muequiv/g weight per minute and [Na]0.5i = 49 mmol/l cell water, which is about twice the physiological operating point. 7. It is concluded that active Na and K transport in rabbit carotid artery follow sigmoidal kinetics and the flux ratio is about 1.5. Changes in [K]o and [Na]i over the physiological range can markedly affect transport, and may regulate vascular contraction by their action on electrogenic transport.
Exchange characteristics of the noradrenaline‐sensitive calcium store in vascular smooth muscle cells or rabbit ear artery.
Authors: Casteels R , Droogmans G
Published: December 2014

1. The amplitude of the noradrenaline‐sensitive Ca stores has been estimated by measuring the amplitude of the transient contraction induced by the agonist in Ca‐free solution. or by measuring the amount of 45Ca released under these conditions. 2. The rate of filling of this store after depletion is much faster than the rate of depletion in Ca‐free solution, and depends on [Ca]o in the bathing solution. The degree of filling also depends on [Ca]o. 3. At the same [Ca]o the degree of filling is higher in K‐depolarized tissues than in control tissues. However at 10 mM‐[Ca]o and 5.9 mM‐K the amount of Ca taken up by the store is larger than that after loading in 0.2 mM‐Ca and 141.4 mM‐K, although the tissues remain relaxed during loading at 5.9 mM‐K and contracted at 141.4 mM‐K. 4. The Ca antagonists D600 and nicardipine selectively block the contraction induced by K depolarization, but do not affect appreciably the noradrenaline‐induced contraction. 5. The filling of the store is not significantly reduced by the presence of the Ca antagonists in solutions containing 5.9 mM‐K. However these antagonists reduce the degree of filling in K‐rich loading solution to a level which is lower than that observed in the control. 6. Mn blocks both the contraction induced by K‐rich solution and the tonic component of the noradrenaline‐induced contraction and its also inhibits filling of the store. 7. The results suggest that the filling of the store under physiological conditions occurs by a direct pathway between the store and the extracellular medium.
Rat mast cells permeabilized with ATP secrete histamine in response to calcium ions buffered in the micromolar range.
Authors: Bennett J P , Cockcroft S , Gomperts B D
Published: December 2014

1. Rat mast cells with ATP (0.5‐4 micro M) in the absence of divalent cations (so that almost all the ATP is present as ATP4‐) became permeable to normally impermeant aqueous solutes, added extracellularly. These include the stable complexes Co HEDTA and Ca EDTA, and 6‐carboxyfluorescein but not inulin. At 4 micro M‐ATP4‐ the space accessible to Ca EDTA is 89% of that occupied by 3H2O. 2. The kinetics of solute entry are regulated by the concentration of ATP4‐. 3. Ca2+, buffered in the range 1‐10 micro M with HEDTA, causes histamine secretion from mast cells that have been rendered permeable with ATP4‐. The extent of secretion increases as the concentration of ATP4‐ is raised from 3 to 5 micro M. With extracellular Ca2+ present as physiological (millimolar) concentrations, the effect of increasing ATP4‐ through this range is to inhibit secretion. 4. The rates of histamine secretion and of 32P‐metabolite leakage from 32P‐prelabelled cells in the presence of micromolar concentrations of Ca2+, were compared. The kinetics of both processes are regulated by the concentration of ATP4‐, but not Ca2+.
Action of vibration on the response of cat muscle spindle Ia afferents to low frequency sinusoidal stretching.
Authors: Matthews P B , Watson J D
Published: December 2014

1. A study has been made of the effect of continuous vibration, at 150 Hz, upon the response of muscle spindle afferents to low frequency sinusoidal stretching (1 and 8 Hz). Using the soleus muscle of the anaesthetized cat, with severed ventral roots, recordings were made of single Ia afferents and of the massed Ia afferent discharges in the main bulk of the cut L7 dorsal root. 2. When the amplitude of vibration was large (50 micrometers, short pulses) and that of the sinusoidal stretching was not too great (50‐100 micrometers, peak‐to‐peak) the discharge of the afferents was largely locked 1:1 to the vibration and the response to the sinusoidal stretching was abolished. 3. When the amplitude of the vibration was reduced to below that eliciting continuous afferent driving, then the response to sinusoidal stretching of any amplitude was often markedly increased. This arose through the vibration having a much more powerful excitatory action during the rising phase of the sinusoidal stretch than it did during the falling phase. 4. Averaged over a full cycle, the phase of the response to the sinusoidal stretching tended to be delayed during the vibration in comparison with the normal. This was largely dependent upon the afferents continuing to respond maximally to the vibration around the peak of the sinusoidal stretch, at which stage their unvibrated response is declining, rather than to a phase lag of the whole pattern of response. 5. The results are discussed in relation to the effects of vibration on tremor and the human stretch reflex, and on the determination of the frequency‐response of spindle afferents.
Episodic growth hormone secretion in sheep in relation to time of feeding, spontaneous meals and short term fasting.
Authors: Driver P M , Forbes J M
Published: December 2014

1. Blood samples were taken every 20 min (for at least 28 hr) from five castrate male and two anoestrus female and libitum fed sheep. Analysis for plasma growth hormone (GH) showed that two of the males, on two occasions, had regular, although individually specific, patterns of GH secretion (peaks 3.5‐5 hr). The other animals all had irregular patterns of GH release. 2. Throughout the experiments, meal sizes and frequency were recorded and it was found that out of eighty spontaneous meals of at least 50 g, 57 (71%) occurred in the hour after GH peaks, which accounted for 50% of the total time. Furthermore, on twenty out of twenty‐four occasions GH levels were found to be falling before the ‘expected’ feeding time when fresh food was offered and the animals normally consumed a large meal. The removal of the food from three of the males for 10 hr during an experiment prompted an increase both in the size and frequency of the GH peaks. After re‐feeding, GH levels immediately fell and remained low for 1‐2 hr. 3. We believe that these results show an association between GH secretion and meal feeding in sheep, and that GH secretion quickly responds to fasting. As GH levels fell before, or in the early stages of meals, this indicates a neural reflex in the inhibition of GH before a meal.
The effects of tetracaine on the membrane currents and contraction of frog atrial muscle.
Authors: Chapman R A , Leoty C
Published: December 2014

1. The effects of tetracaine on the membrane currents and contraction of isolated frog atrial trabeculae under voltage clamp has been investigated. 2. Tetracaine inhibits the slow inward current in a competitive way with a Ki of 0.13 mM, and the phasic component of the contractile response in a non‐competitive manner with a Ki of 0.25 mM. 3. The tonic phase of contraction is little affects by tetracaine while the outward current is reduced. 4. The effects of tetracaine on contraction closely resemble those obtained previously with K contractures and further emphasize that two processes, both of which depend on the membrane potential, are involved in the initiation of contraction in amphibian heart. 5. The effect of tetracaine on the phasic tension would seem to be due to an inhibition of both the slow inward current and the release of Ca2+ from the sarcoplasmic reticulum.
A study of the effect of the rate of stimulation on the transient outward current in sheep cardiac Purkinje fibres.
Authors: Boyett M R
Published: December 2014

1. The transient outward current, Ito, of sheep Purkinje fibres has been recorded using the two micro‐electrode voltage clamp technique. 2. Ito is strongly rate‐dependent: the magnitude of Ito activated during a test voltage clamp pulse after a train of action potentials is less at higher rates of stimulation. 3. After an increase or decrease in rate there is an abrupt change in Ito in the first response followed by slower changes over the next several hundred responses. 4. When a preparation is rested after repetitive activity Ito recovers in two phages: there is an initial rapid, approximately exponential phase of recovery in the first 10 s which is probably due to reactivation; this is followed by a slower phase of recovery lasting several hundred seconds. 5. Curves showing the time course of reactivation of Ito have been obtained at different rates. At high rates the curves approach smaller values of Ito and the steady‐state control values of the current occur on the shoulder of the curves, i.e. before reactivation is complete. 6. It is proposed that the reduction of Ito at high rates is due to two factors: incomplete reactivation which accounts for the rapid changes of Ito and a second unknown factor which accounts for the slower changes in the current. 7. Inspection of current‐voltage relationship for Ito suggests that the reduction of Ito at high rates is mainly due to a decrease of conductance rather than to a reduction of the reversal potential. 8. Replacement of the calcium in the bathing solution by strontium does not abolish Ito in sheep Purkinje fibres, suggesting that the current is distinct from the transient outward current in calf Purkinje fibres described by Siegelbaum & Tsien (1980).
Effect of glucose and hyperosmolality on the electrical characteristics of dog colon mucosa in vivo.
Authors: Gazitúa S
Published: December 2014

1. A method has been developed to maintain the electrical characteristics of dog colon mucosa stable over prolonged periods in vivo. This was achieved by paying special attention to the constancy of the volume of the organ and its intraluminal pressure during perfusion. 2. Intraluminal glucose elicits an increase in transmural potential and short‐circuit current; this has been attributed to the presence of a Na‐glucose co‐transport process in this tissue. 3. Na replacement by K in the perfusate caused an increase in the transmural potential, whereas mannitol substitution evoked an inversion. These observations are probably the result of diffusion potentials. In the mannitol solution, glucose effectively abolished the negative transmural potential, whereas in the K solution, the effect of the sugar was smaller than in the control. 4. Perfusion of a hyperosmotic solution containing mannitol resulted in the development of streaming potentials across the mucosa. Their magnitude was reduced by addition of 2,4‐dinitrophenol or by removal of Na from the perfusate. They were counteracted by replacement of mannitol by glucose. The streaming potentials showed no sign of saturability, reflecting a pronounced hydraulic conductivity of the epithelium. 5. The rapidity of onset of the potential response to glucose was enhanced by increasing the perfusion rate, but the response to hyperosmolality was unaffected. 6. Streaming potentials, diffusion potentials and glucose‐evoked potentials are generally considered to be features of the small intestinal mucosa; their existence in the dog colon indicates that this epithelium has more in common with small gut than with the majority of mammalian colons.
Influence of electric fields on the excitability of granule cells in guinea‐pig hippocampal slices.
Authors: Jefferys J G
Published: December 2014

1. Monosynaptic evoked potentials were recorded from the granule cell layer of slices of guinea‐pig hippocampus maintained in vitro. Current pulses of 25‐250 msec duration were passed across the slices, between gross electrodes in the bathing liquid. 2. Polarizing current modified the excitability of the granule cells as judged by changes in their population discharge during postsynaptic responses. All durations of polarization had at least qualitatively similar effects. Conventional current from dendrites to cell bodies increased excitability (and vice versa). This is consistent with altered membrane potential of a spike trigger zone, at or close to the granule cell bodies, imposed by the fraction of polarizing current which flows intracellularly. 3. In some experiments polarization also affected the presynaptic volley and (hence?) the synaptic potential. When this occurred it was in the wrong sense to explain the concomitant changes in population spike. 4. Focal polarization, where currents were applied across the cell body layer between a small electrode on the mid or outer dendritic regions and a remote gross electrode, altered granule cell excitability in the same direction as in (2). Thus conventional current injected at the dendritic electrode increased excitability. 5. The smallest effect polarizing currents caused extracellular voltage gradients of 5‐10 mV/mm, which is less than occurs in this tissue during synchronous activation of the neurons or during seizure activity. Therefore such field potentials could increased the synchrony of discharge of the granule cells.
The effect of pregnancy on glomerular filtration rate and salt and water reabsorption in the rat.
Authors: Atherton J C , Pirie S C
Published: December 2014

1. Glomerular filtration rate (G.F.R.) and salt and water reabsorption were measured in age‐matched (12‐ to 13‐week‐old) virgin rats and rats at different stages of pregnancy and infused with saline at 37.5 and 200 microliters/min. 2. G.F.R. and salt and water reabsorption were significantly higher in early pregnancy and remained at steady, high values until at least mid‐pregnancy. G.F.R. was slightly lower close to term, but sodium and water reabsorption remained significantly enhanced. 3. Significant expansion of extracellular fluid volume (e.c.f.v) was first apparent during mid‐pregnancy, indicating that e.c.f.v. expansion could not be directly responsible for the early increase in G.F.R. 4. Proximal tubules were significantly elongated 5‐ days after mating until term, indicating that an increased reabsorptive area in the proximal tubule may be at least partly responsible for the increased reabsorption in pregnancy.
Acetylcholine content and release in denervated or botulinum poisoned rat skeletal muscle
Authors: Polak R. L. , Sellin L. C. , Thesleff S.
Published: December 2014

1. The acetylcholine (ACh) content and spontaneous and evoked release of ACh in rat extensor digitorum longus (EDL) muscles were determined by pyrolysis‐mass fragmentography. The determinations were made on muscles paralysed by local application of botulinum toxin (BoTx) type A, on unpoisoned muscles, surgically denervated or reinnervated muscles.

2. The ACh content of unpoisoned control muscles was nearly uniform between animals and varied in the experimental series between 36 and 50 pmol. BoTx failed to affect the ACh content after 2 d of poisoning and caused a slight increase in content after 8 d. Surgical denervation reduced the ACh content within 24 h to less than 10% of innervated muscles and upon reinnervation the ACh content was restored. Following cholinesterase inhibition the ACh content of innervated and denervated muscles increased somewhat, about equally with time.

3. Spontaneous release of ACh varied in normal innervated muscles between 40 and 100 fmol/min. In the presence of 25 m
m‐KCl the rate of release increased about fourfold. In BoTx poisoned muscles spontaneous release was reduced by up to 60% of control and high potassium failed to accelerate the release at 2 d after poisoning and caused only a small increase at 8 d. Denervated muscles released ACh at a rate which was less than 20% of control and it was not accelerated by high potassium.

4. The results show that more than 90% of total ACh in the innervated EDL muscle is present in the nerve and its terminals. The remaining ACh is apparently formed and stored in the muscle tissue. BoTx caused a larger reduction in ACh release than can be accounted for by assuming a selective blockade of quantal release of transmitter. It suggests that BoTx has an inhibitory effect also on non‐quantal ACh release.
Determination with high resistance micropipettes of acetylcholine sensitivity in frog slow muscle fibres.
Authors: Lehouelleur J , Schmidt H
Published: December 2014

1. Acetylcholine (ACh) sensitivity was determined in slow muscle fibres of Rana temporaria by ionophoretic application of ACh from high resistance micropipettes. 2. The amplitude of ACh responses decreased with the third power of the distance between fibre surface and tip of the pipette; latency and time‐to‐peak of ACh responses increased with the second power of the distance. 3. ACh sensitivity values obtained by application of ACh at short distance (approx. 10 micrometers) were generally of the order of 150 mV/nC, but larger values (greater than 1000 mV/nC) pipette the ACh response was often completely lost or markedly reduced in amplitude. The latency of ACh responses was generally longer, but occasionally as short as observed in twitch fibres; time‐to‐peak and rate of decay were always longer than in twitch fibres. 4. It is concluded that ACh sensitive membrane areas in slow muscle fibres are generally of small diameter. There sensitivity is, however, similar to that of junctional areas in twitch muscle fibres.
Actions of indomethacin and prostaglandins on neuroeffector transmission in the dog trachea
Authors: Ito Yushi , Tajima Kikuo
Published: December 2014

Neuro‐effector transmission in the smooth muscle layer of the dog trachea was studied in vitro using the micro‐electrode and double sucrose gap methods.

1. Electrical field stimulations with short duration (50‐100 μsec) applied to the whole tissue produced an excitation of the intrinsic nerves, and evoked excitatory junction potentials (e.j.p.s) followed by twitch tension development and subsequent long lasting relaxation of the smooth muscle tissue.

2. The effects of field stimulations were abolished by tetrodotoxin (2 × 10−7
m), and atropine (1·7 × 10−5
m) selectively blocked both the e.j.p. and twitch tension. On the other hand, propranolol (1·9 × 10−5
m) suppressed the generation of the prolonged relaxation evoked by the field stimulations.

3. E.j.p.s recorded by the double sucrose gap method showed gradual and continuous reduction in amplitude during prolonged exposure in Krebs solution (1‐2 hr), and there were no changes in the membrane potential or in the input membrane resistance.

4. With application of indomethacin (10−5
m), a gradual and continuous reduction in the amplitude of e.j.p. was no longer observed, and (after the initial increase in the amplitude) e.j.p.s with a constant amplitude were obtained during 1‐1·5 hr. Indomethacin (10−5
m) modified neither the resting membrane potential nor the input membrane resistance of smooth muscle cells.

5. After pre‐treatment with indomethacin, low concentrations (10−11‐10−8
m) of prostaglandin E1 or E2 (PGE series) markedly suppressed the amplitude of e.j.p. with no changes in the resting membrane potential or in the input membrane resistance.

6. During the repetitive field stimulation at the stimulus frequency of 0·1‐1 Hz, the amplitude of the e.j.p.s was gradually reduced (the depression process). The depression was not affected by applications of prostaglandins, indomethacin or α‐ and β‐adrenoceptor blockers.

7. These results indicate that in the dog tracheal smooth muscles, the endogenous PGE series may play an important role in feed‐back inhibitory mechanisms, at the nerve terminals related to acetylcholine release.
The nature of afferents from the large dorsal neck muscles that project to the superior colliculus in the cat.
Authors: Abrahams V C , Turner C J
Published: December 2014

1. A 3.5‐5 mm passive stretch of dorsal neck muscles at velocities of 50 mm/sec, a stimulus adequate to excite most neck muscle spindles, was usually ineffective in eliciting unit discharge in the superior colliculus. The sudden release of muscle tension was effective and excited fifty‐seven of sixty‐seven units tested. 2. When electrical stimulation of neck muscle nerves was used, a stimulus strength sufficient to excite Group III muscle afferents was usually required to elicit unit discharge in the superior colliculus. 3. It is concluded that the projection from neck muscles to the superior colliculus largely takes origin in Group III afferent whose function remains to be determined. Some contribution to the projection to the superior colliculus from proprioceptive afferents served by larger fibres cannot be ruled out.
The interaction of potassium ions and ATP on the sodium pump of resealed red cell ghosts.
Authors: Eisner D A , Richards D E
Published: December 2014

1. Ouabain‐sensitive K or Rb influx was measure into ghosts resealed to contain ATP concentrations of 1 micrometers‐3 mM and no K. 2. Increasing ATP from 1 to 100 micro M, at saturation external K, increased K influx about twentyfold while have no effect on the ratio of ouabain‐sensitive K influx to ouabain‐sensitive ATPase activity. 3. Increasing external K decreased the apparent affinity for ATP. Similarly increasing ATP decreased the apparent affinity for external K. 4. The K influx can be empirically described as: influx = VmaxK2/(K + Kapp)2. Increasing ATP increased Vmax and (Kapp)2 by the same amount. 5. These results are consistent with a consecutive model for the Na pump in which an ATP‐dependent reaction follows a K‐activated dephosphorylation.
Effects of sodium gradient manipulation upon cellular calcium 45Ca fluxes and cellular sodium in the guinea‐pig taenia coli
Authors: Aaronson P. , van Breemen C.
Published: December 2014

1. Sucrose and choline were utilized as NaCl substitutes in order to investigate Na—Ca interactions in the smooth muscle of the guinea‐pig taenia coli.

2. Progressive substitution of NaCl by sucrose caused a progressive increase in cellular exchangeable Ca. This uptake, which amounted to about 300 μmole Ca/kg tissue upon total Na replacement, reached a plateau within 20 min. Complete substitution of NaCl by choline chloride caused cellular Ca to increase rapidly to an initial peak, and then decrease to a stable plateau which was also about 300 μmole/kg above control.

3. Replacement of NaCl by either sucrose or choline chloride caused a transient increase in the Ca influx rate, which was measured using a 3 min pulse labelling with 45Ca. This increase was more pronounced in choline chloride.

4. NaCl substitution by either sucrose or choline chloride caused a decrease in the 45Ca efflux rate. Two exponential components of transmembrane 45Ca efflux were found in control and Na‐free media.

5. Treatment of tissues with 3 × 10−5
m‐ouabain did not significantly affect the cellular Ca content after 80 min, at which time the Na and K gradients were largely dissipated.

6. Removal of medium K caused a slower dissipation of the Na and K gradients. This treatment decreased cellular Ca, did not affect the Ca influx rate, and increased the 45Ca efflux rate.

7. Tissues were incubated in depolarizing media containing 10−4
m‐ouabain in order to remove the Na gradient. Subsequent measurement of cellular Na indicated the absence of a significant fraction of bound Na.

8. The ratio [Na]o/[Na]i had a value of 6.3 in control medium, and decreased as [Na]o was progressively lowered by sucrose substitution, reaching a value of < 1 in a medium containing 5 m
m‐Na.

9. These experiments provide evidence that a Na—Ca exchange carrier does not play an important role in regulation of tension in this muscle, and also indicate that the Ca gradient is not solely dependent on the Na gradient in guinea‐pig taenia coli.
Striate cortex responses to periodic patterns with and without the fundamental harmonics
Authors: Albrecht Duane G. , De Valois Russell L.
Published: December 2014

1. The visual system has been modelled as a set of independent linear channels each tuned to a limited band of spatial frequency with the average bandwidth being approximately 1 octave. A great deal of psychophysical and physiological evidence supports this basic notion. However, Henning, Hertz & Broadbent (1975) have shown reciprocal masking between a fundamental frequency (1F) and a complex grating composed of higher harmonics several octaves removed ((4+5+6)F); their results clearly indicate a lack of independence.

2. We recorded the activity of cells in the striate cortex of monkeys and cats using stimuli similar to those of Henning et al. to make comparisons with their psychophysical data and to test specific physiological predictions.

3. We found that cells tuned to the fundamental frequency did not produce an excitatory response to the (4+5+6)F pattern. However, the response of such cells to 1F could be reduced by simultaneous presentation of (4+5+6)F. Similarly, the response of cells tuned to high frequencies, when presented with (4+5+6)F, was reduced by simultaneous presentation of 1F. However, this reciprocal inhibition could be produced between single harmonics (e.g. 1F and 4F) and was not dependent upon a special relationship between 1F and (4+5+6)F.

4. When cells tuned to high frequencies were presented with the (4+5+6)F pattern they generated predictable responses in the higher harmonics (4, 5, 6) but they also generated an unexpected, non‐linear, response at the fundamental frequency, 1F, even though no such low frequency component was present in the stimulus. This effect is due to the response rectification which striate cells show.

5. In support of the linear independent spatial frequency channel model, we find (a) striate cells provide an excitatory response to only a limited range of frequencies, (b) they do not provide such responses to the ‘apparent’ yet ‘missing’ fundamental in the (4+5+6)F beating pattern, and (c) the response wave form to complex stimuli like (4+5+6)F is reasonably predictable (at least for simple cells) from the model. Against the model we find that (a) frequencies outside the excitatory bandpass can produce inhibition and (b) the rectification of the response wave form introduces harmonics not present in the stimulus.
Internal potassium stimulates the sodium‐potassium pump by increasing cell ATP concentration.
Authors: Sachs J R
Published: December 2014

1. Intracellular K increases the ouabain‐sensitive Na‐K exchange in human red blood cells. Pump rate increases hyperbolically with internal K with a K12 for K of 2.58 m‐mole/l. red blood cells. Li also stimulates the pump rate, but with a much higher K12. The stimulation does not result from a change in the affinity of the pump for its substrates Na, K or Mg or for the product, phosphate. 2. The effect of cell K on the Na‐Na exchange is biphasic. At low concentrations it decreases the exchange rate but then the exchange increases linearly with cell k concentration. 3. Stimulation of the pump rate by internal K can be demonstrated in reconstituted ghosts but only if the ratio of the volume of cells to that of solution at the time of haemolysis is high. Stimulation is not observed if the ghosts contain an efficient system for rephosphorylating ADP to ATP, such as creatine phosphate and creatine kinase, or if the measurements are made with iodoacetamide which inhibits rephosphorylation of ADP by inhibiting the enzyme glyceraldehyde‐3‐phosphate dehydrogenase. 4. Cells with low internal K and Li have low ATP concentrations, and ATP increases hyperbolically with internal K or Li with the same K12 as does the pump rate. In cells depleted of substrate intracellular K does not stimulate the pump rate. 5. The effect of K and Li on the pump rate probably does not result from enhanced activity of any of the enzymes below phosphofructokinase in the glycolytic pathway.
Glucose transport by short loops of Henle in the rat.
Authors: Bishop J H , Green R , Thomas S
Published: December 2014

1. Short loops of Henle were artificially perfused with saline solutions containing 5 or 0 mM‐glucose in the presence and absence of phlorizin. 2. Net fluid reabsorption was greater when glucose but no phlorizin was present than in all other series. 3. Glucose was reabsorbed from glucose‐containing perfusate and this was abolished by phlorizin. Secretion of glucose occurred into the perfusate which initially contained no glucose and this secretion was enhanced by phlorizin. 4. Sodium reabsorption was inhibited by phlorizin, when glucose was present, but enhanced by phlorizin when glucose was absent. 5. It can be shown that there is secretion of some osmotically active solute in all series. Its secretion is enhanced by phlorizin in the absence of glucose.
Morphology and distribution of touch cell terminals in the skin of the leech.
Authors: Blackshaw S E
Published: December 2014

1. The receptor terminals of individual mechanosensory neurones responding to light touch (T cells) have been visualized directly in the skin of the leech by injecting horseradish peroxidase (HRP) into their cell bodies in the central nervous system. The axons of injected cells could be followed from their origin in the neuropile of the ganglion to their terminals in the skin. 2. The axons of T cells run through ipsilateral nerve roots in the body wall to the base of the layer of epithelial cells in the skin. Here axons branch extensively and turn between the epithelial cells to end a few microns from the skin surface. These terminals are situated in intercellular spaces immediately below the junctional complex joining the outer ends of the epithelial cells. 3. The T cell terminals are free nerve endings with a beaded appearance; they contain large mitochondria and clusters of vesicles. 4. An individual T cell makes about 100 endings within a square millimetre of skin in the centre of its territory, and is estimated to make a total of several hundred endings. 5. The distribution of T cell endings observed directly agrees with physiological studies of receptive field organization and emphasizes the high degree of specificity of connexions of these neurones with their peripheral targets.
Roles of subcutaneous fat and thermoregulatory reflexes in determining ability to stabilize body temperature in water.
Authors: Hayward M G , Keatinge W R
Published: December 2014

1. The lowest water temperature in which different young adults could stabilize body temperature was found to vary from 32 degrees C to less than 12 degrees C, because of large differences in both total body insulation and metabolic heat production. 2. Total body insulation per unit surface area, in the coldest water allowing stability, was quite closely determined by mean subcutaneous fat thickness measured ultrasonically (r = 0.92), regardless of differences in distribution of this fat between men and women. 3. Reactive individuals developed high metabolic rates, and often rather high insulations in relation to fat thickness, which enabled them to stabilize their body temperatures in water more than 10 degrees C colder than was possible for less reactive individuals of similar fat thickness. 4. Measurements of heat flux, after stabilization in the coldest water possible, showed that the trunk was the main site of heat loss and that over half of the internal insulation there could be accounted for by subcutaneous fat; by contrast, fat could account for less than a third of higher insulations found in muscular parts of the limbs, and for less than 3% of very high insulations in the hands and feet. 5. After stabilization of body temperature at rest in the coldest possible water, exercise reduced internal insulation only in muscular parts of the limbs. Exercise also increased heat loss elsewhere by exposing skin of protected regions such as flexural surfaces of joints. During exercise total heat production increased rather more than heat loss in unreactive subjects, but less than loss in subjects whose heat production had already risen to a high level when they were at rest in cold water. 6. In warm (37 degrees C) water, tissue insulations were lower and much more uniform between subjects and between different body regions than in the cold. Even in the warm, however, insulations remained rather higher in fat than thin subjects, higher at rest than during exercise, and usually higher in the limbs than the upper trunk.