bluuebunny/crossref_metadata_2025 huggingface dataset:
Absorptive and secretory functions of the perfused rat cauda epididymidis.
Authors: Wong P Y , Yeung C H
Published: December 2014

1. A microperfusion technique has been developed to study transport processes in the rat cauda epididymidis in vivo. 2. Na+ and water were found to be reabsorbed by the perfused rat cauda epididymidis at the rates of 3.000 +/‐ 0.25 n‐equiv cm‐1 min‐1 (mean +/‐ S.E., n = 14) and 20.7 +/‐ 1.7 nl. cm‐1 min‐1 (mean +/‐ S.E., n = 14) respectively. Reabsorption of Na+ was isotonic. 3. K+ was found to be secreted into the ductal lumen at the rate of 0.124 +/‐ 0.016 n‐equiv cm‐1 min‐1 (mean +/‐ S.E., n = 14). 4. Na+ reabsorption and water reabsorption were abolished by removing Na+ ions from the perfusion medium. The dependence of rate of net Na+ reabsorption on the intraluminal Na+ ion concentration showed saturation kinetics, with the apparent Km values of about 20 mM Na+. The dependence of water reabsorption on the intraluminal Na+ ion concentration also followed closely that of Na+. 5. Application of amiloride 10(‐4) M) to the perfusion fluid abolished both Na+ and water reabsorption by the rat cauda epididymidis. 6. Removal of chloride from the perfusion fluid had no effect on Na+ and water reabsorption but increased the K+ secretion rate by threefold. 7. Proteins were also found to be secreted by the rat cauda epididymidis at a rate of 11.7 +/‐ 1.8 ng cm‐1 min‐1 (mean +/‐ S.E., n = 11). The secretory rate was not dependent on the intraluminal Na+ ion concentration. 8. Castration in rats abolished the reabsorption of Na+ and water and secretion of K+ and proteins by the rate cauda epididymidis. These effects could be reversed by injecting testosterone propionate into castrated rats. 9. The possible role of these transport processes in sperm maturation is discussed.
Sodium and water metabolism under the influence of prolactin, aldosterone, and antidiuretic hormone.
Authors: Burstyn P G
Published: December 2014

1. Rabbits were placed in metabolism cages in order to measure their intakes of food, water, and sodium chloride (as 1% saline solution), and to measure urinary and faecal excretion of sodium, potassium, and water. 2. Antidiuretic hormone (0.2 i.u./day) caused a reduction in urine volume and no change in sodium excretion. There was full compensatory reduction in water intake so that no accumulation of water occurred. 3. Aldosterone (4 mg/da) caused a reduction in renal sodium excretion for 1‐‐2 days. The saline intake was reduced, though this was insufficient to prevent some sodium accumulation. 4. Renal mineralocorticoid 'escape' resulted in a large increase in sodium excretion at the end of the aldosterone treatment period. This was fully compensated through increased saline intake, and balance was maintained. 5. Prolactin (200 i.u./day) caused a reduction in urine volume and in renal sodium excretion and since there were no compensatory changes in water and sodium intake, this led to substantial accumulation of both water and sodium. 6. The effects of smaller doses of both aldosterone and prolactin were investigated and found to be similar but smaller. 7. It is suggested that whereas prolactin may have little or no role to play in the sodium homoeostasis of the normal animal, the hormone may well be responsible for the substantial increase in body fluids in pregnancy.
EGTA and motoneuronal after‐potentials.
Authors: Krnjević K , Puil E , Werman R
Published: December 2014

1. Intracellular iontophoretic injections of EGTA (5‐‐20 nA) into cat spinal motoneurones consistently greatly reduce the amplitude of the delayed after hyperpolarization (a.h.p.) that follows the spike. 2. This effect is accompanied by a large reduction (on average by 3/4) in the marked increase in input conductance normally associated with the a.h.p. 3. There is also a consistent, though less regular, tendency for the resting input conductance to decrease (on average by 1/5), as well as some depolarization. 4. Recovery of the a.h.p., the associated conductance increase and the resting conductance is ver slow. It is sometimes accelerated by injections of citrate and Cl‐, or CA2+. 5. Other hyperpolarizing phenomena, such as recurrent or othodromically‐evoked i.p.s.p.s, are not depressed by injections of EGTA. 6. When depolarization is minimal EGTA injections that markedly depress the a.h.p. do not affect the rate of rise or fall of the spike. If, as a result of depolarization, an early a.h.p. is visible, it is patently insensitive to EGTA. 7. The post‐spike depolarizing after‐potential (delayed depolarization) is not obviously affected by EGTA, apart from the usual diminution seen during depolarization. 8. Since the main action of EGTA is to bind free Ca2+, the marked depression of the a.h.p. indicates that the sharp increase in K conductance which generates the a.h.p. is probably caused by a influx of Ca2+ accompanying the action potential. It is suggested that this inward Ca2+ current may be manifested in the depolarizing after‐potential.
Calcium and strontium concentration changes within skinned muscle preparations following a change in the external bathing solution.
Authors: Moisescu D G , Thieleczek R
Published: December 2014

1. A method for producing rapid [Ca2+] and [Sr2+] changes in the frog skinned muscle fibre preparation while maintaining constant all other cationic concentrations (Moisescu, 1976a, b) is described and analysed in detail. 2. Different experiments, some of them involving the Ca2+‐sensitive photoprotein aequorin, as well as theoretical considerations, indicate that with this method one can produce a Ca2+ (or Sr2+) concentration change within 0.1‐‐0.15 sec in a whole preparation having a diameter of 50 micrometer. 3. The rate of force development was similar to that observed in vivo. 4. The radial diffusion coefficient of EGTA in relaxed myofibrillar preparations was measured and found to be 4.6 x 10(‐6) cm2sec‐1 at 20 degrees C. 5. The sarcoplasmic reticulum in myofibrillar bundles was found to be active with respect to both Ca2+ and Sr2+ in the solutions used ([Mg2+] 1 mM; [Na] 30 mM; [K] 140‐170 mM; [Cl] less than or equal to 20 mM; pH 7.10). 6. The amount of Ca released by caffeine from internal stores (previously loaded with Ca) can raise the total Ca concentration in the muscle fibre preparation by at least 1.8 mM. 7. The presence of 10 mM‐caffeine in all bathing solutions reduced drastically the ability of the sarcoplasmic reticulum to accumulate both Ca and Sr.
Biphasic effects of insulin and ouabain on fluid transport across rabbit corneal endothelium.
Authors: Anderson E I , Fischbarg J
Published: December 2014

1. Low levels of insuling stimulate transendothelial fluid transport from preswollen stroma to aqueous in rabbit corneal preparations. The rate of stromal thinning at the end of the first hour averages 30% faster with insulin, 3.5 x 10(‐22) M (4.8 micromicron/ml.), than that of the paired control. This concentration is about the physiological level in rabbit aqueous. 2. The stimulation with insulin is transient. Rates of thinning average higher but not significantly different from control rates by the second hour. 3. High levels of insulin between 3.5 x 10(‐9) M (480 micromicron/ml.) and 2.0 x 10(‐6) M (2.75 X 10(5) micromicron/ml.) inhibit fluid transport. The inhibition at the low end of this range of concentrations becomes more pronounced with longer perfusion times but appears not to exceed ca. 50% of the control rate. 4. Ouabain also induces a biphasic effect on fluid transport which is characteristically different from that with insulin. The maximal stimulation observed at all times occurred with a fixed concentration of 10(‐10) M. The stimulation is not transient but increases throughout the duration of the perfusion; the average rate is elevated 50% above the control rate by the third hour. 5. The transition from a stimulatory to an inhibitory effect occurs consistently at ca. 10(‐8) M with ouabain, while a similar transition with insulin occurs at ca. 10(‐9) M and appears to shift towards slightly higher concentrations during a 3 hr perfusion period. 6. Inhibition of fluid transport with ouabain, 3 x 10(‐7) M, is increased from ca. 50% after 1 hr to more than 70% at the end of the third hour of perfusion. 7. The combined presence of stimulatory concentrations of ouabain and insulin affects tromal thinning in a manner resembling the effect of ouabain alone more than that of insulin; additive effects could not be discriminated. Progressively raising the concentration of insulin to a level (10(‐8) M) that alone inhibits stromal thinning, ultimately abolishes the stimulatory effect of ouabain. Based on other evidence and current models of drug/hormone‐membrane interaction, these results can be interpreted to indicate a concentration‐dependent interaction between receptor complexes of ouabain and insulin with (Na+ + K+)‐ATPase.
Effects of phlorizin on glucose, water and sodium handling by the rat kidney.
Authors: Bishop J H , Elegbe R , Green R , Thomas S
Published: December 2014

1. The effect of phlorizin on glucose, water and sodium handling by the kidney in anaesthetized rats was investigated, using clearance techniques, during infusion of saline (200 microliter min‐1) or saline to which either low (0.1 mumole kg body weight‐1 ml.‐1) doses of phlorizin had been added. 2. Phlorizin increased the absolute and fractional excretion of glucose, urine osmolality and negative free water clearance; and reduced urine flow rate, glomerular filtration rate (GFR), absolute and fractional excretion of sodium, absolute excretion of sodium, absolute excretion of potassium and absolute and fractional rates of glucose reabsorption. 3. The data indicate that phlorizin has sites of action and effects additional to those on glucose transport in the proximal tubule. 4. Within each series there was a positive correlation between sodium and glucose reabsorption; but the rate of glucose reabsorption was different between each series even though the sodium reabsorption was not. 5. It is suggested that since both sodium and glucose reabsorption correlate with GFR, they may be related via GFR. 6. The data indicate that for the whole kidney any effect of glucose on sodium transport is small relative to total renal handling of sodium.
A depolarizing inhibitory potential in neurones of the olfactory cortex in vitro.
Authors: Scholfield C N
Published: December 2014

1. Stable intracellular recordings were obtained from neurones in slices of the guinea‐pig olfactory cortex maintained in vitro. 2. Single stimuli applied to the lateral olfactory tract (l.o.t.) produced an excitatory post‐synaptic potential (e.p.s.p.) usually generating a single spike. 3. The e.p.s.p. was followed by a long (200‐500 msec) after‐depolarization (l.a.d.) of peak amplitude 5‐16 mV. This was accompanied by a very large conductance increase and was associated with an inhibition of the intracellularly recorded e.p.s.p. and of spike generation. 4. The l.a.d. was more susceptible than the e.p.s.p. to depression by (i) repetitive l.o.t. stimulation and (ii) raising external [Mg2+]. The l.a.d. could be generated without a preceding spike. 5. At an average resting membrane potential of ‐74 mV the average reversal potential for the l.a.d. (El.a.d.) was ‐63 mV.El.a.d. became more positive on reducing [Cl‐]out or on using KCl‐filled electrodes. 6. It is concluded that the l.a.d. represents a Cl‐ ‐mediated inhibitory post‐synaptic potential, generated through deep‐lying recurrent inhibitory loops.
Uptake and binding of calcium by axoplasm isolated from giant axons of Loligo and Myxicola.
Authors: Baker P F , Schlaepfer W W
Published: December 2014

1. Axoplasm isolated from giant axons of the squid Loligo and of the polychaete worm Myxicola continues to bind Ca and maintain an ionized Ca concentration close to 0.1 microgram which is similar to that seen in intact axons. 2. Injection of Ca into isolated axoplasm only produces a transient rise in ionized Ca showing that axoplasm can buffer a Ca challenge. 3. In order to characterize the Ca‐binding systems isolated axoplasm was placed in small dialysis tubes and exposed to a variety of artificial axoplasms containing 45Ca. 4. In the presence of ATP, orthophosphate and succinate, Ca uptake appreciable and after 4 hr exposure of Loligo axoplasm to 0.1 microgram‐Ca, approximately 100 mumole Ca/kg axoplasm was bound. Binding could be divided operationally into two distinct processes, one that requires ATP or succinate togeth with orthophosphate and is blocked by cyanide and oligomyocin, and one that is unaffected by these reagents. 5. Energy‐dependent binding has a large capacity, but a rather low affinity for Ca, being half‐maximal between 20 and 60 microgram‐Ca. In Loligo, its properties closely parallel those of a crude mitochondrial preparation isolated from axoplasm; but there are some interesting differences in Myxicola. Energy‐independent binding is half‐maximal at ionized Ca concentrations between 80 and 160 nM but is readily saturated and has a capacity of 6‐60 mumole/kg axoplasm. 6. Ca binding by Loligo is greatest in media containing roughly physiological concentrations of K and is reduced by isosmotic replacement of K by Na. This effect seems to be confined to the energy‐dependent, presumed mitochondrial, component of binding. 7. Ca binding by Loligo axoplasm is reduced by both La and Mn ions.
Muscle spindle responses in man to changes in load during accurate position maintenance.
Authors: Burke D , Hagbarth K E , Löfstedt L
Published: December 2014

1. Single unit and multi‐unit recordings of muscle spindle activity were made from the peroneal nerves of human subjects. While the subjects attempted to maintain a constant ankle joint position, an external load on the receptor‐bearing muscle was altered unexpectedly. 2. The spindle discharge produced by a sudden increase in load was of similar strength when the receptor‐bearing muscle was relaxed as when it was contracting at the moment of the impact. A motor response at a latency consistent with a spinal reflex mechanism occurred only when the muscle was contracting. It is concluded that the potentiation of the reflex mechanism during contraction was not due primarily to a fusimotor action. 3. Sudden decrease in load produced a pause in spindle discharge followed by a pause in on‐going e.m.g. activity at a latency consistent with spinal reflex mechanisms. 4. Slow changes in load produced parallel changes in e.m.g. and spindle discharge. It is suggested that the voluntary effort involved in maintaining joint position in the face of gradually changing loads results in corticospinal activity adjusted in strength to the opposing torque and operating on alpha and gamma motoneurones in parallel.
Quantal analysis of the size of excitatory post‐synaptic potentials at synapses between hair cells and afferent nerve fibres in goldfish.
Authors: Furukawa T , Hayashida Y , Matsuura S
Published: December 2014

1. A statistical analysis has been made of the transmitter release at the hair cell afferent fibre synapse in the sacculus of the goldfish, using the amplitude of the excitatory post‐synaptic potentials (e.p.s.p.s) in response to stimulus tone as a measure of the transmitter release under application of tetrodotoxin. 2. Application of binomial statistics allowed a direct calculation of the mean probability of release (p) and the readily available store (n), and the X2‐test showed that the binomial predictions fitted fairly well with the observed distribution of the responses. 3. Adaptive rundown of e.p.s.p.s during sound stimulation, i.e. the successive rundown in the size of the mean quantal content (m), was found to be associated with a reduction in the size of parameter n, but not of p. 4. A marked negative correlation was demonstrated between the amplitude of two consecutive e.p.s.p.s, supporting the depletion hypothesis of the adaptive rundown of e.p.s.p.s. 5. The increase in the e.p.s.p. amplitude and the increase in the mean quantal content, m, brought about by an increase in the tone intensity were found mostly explicable in terms of an increase in the statistical parameter n. The probability parameter p was found largely in invariable, although in certain instances the increase in m was also accompanied by a slight increase in the parameter p.
Studies on kallikrein in the duct systems of the salivary glands of the cat
Authors: Shnitka T. K. , Maranda B. , Rodrigues J. A. A. , Schachter M. , Weinberg J.
Published: December 2014

By correlating immunofluorescence light microscopy with electron microscope studies and with kallikrein concentrations under various conditions, we have made the following observations and conclusions about kallikrein in the submandibular and other salivary glands.

1. In the submandibular gland, specific immunofluorescence to kallikrein was observed in the luminal region of the striated ducts particularly, but also in the outer epithelial cells of the stratified epithelial collecting ducts. Sympathetic nerve stimulation resulted in a reduction in intensity of specific fluorescence and in its increased localization towards the lumen. The nearly complete elimination of kallikrein from the gland by duct obstruction for four days resulted in complete disappearance of specific fluorescence in the gland. Prolonged parasympathetic nerve stimulation at frequencies which did not reduce the kallikrein concentration of the gland failed to alter the specific immunofluorescence despite copious secretion of saliva. Our results failed to reveal evidence of secretion of kallikrein either into or towards the interstitium of the gland.

The luminal layer of stratified epithelial cells in the collecting ducts contained small secretory granules closely resembling those in the striated ducts. Our results are not conclusive, but do suggest that kallikrein is located in these granules whence it is secreted into the lumen of the duct.

2. The parotid gland was found to contain much lower concentrations of kallikrein than the submandibular gland. This finding was associated with the presence of far fewer striated ducts in the parotid gland. Otherwise, specific fluorescence and the response to sympathetic nerve stimulation was like that of the submandibular gland. Small secretory granules in the striated and collecting ducts resembled those of the submandibular gland.

3. The sublingual gland, like the parotid, had a low concentration of kallikrein and very few striated ducts. These ducts were unevenly distributed and were concentrated in only a few lobules of the gland. Specific immunofluorescence was seen only in sections containing striated ducts.

4. The possible physiological role of kallikrein in the salivary glands is discussed.
The effects of pH and curare on the time course of end‐plate currents at the neuromuscular junction of the frog.
Authors: Mallart A , Molgó J
Published: December 2014

1. The effect of pH changes on synaptic currents has been analysed by external recording of the miniature end‐plate currents (m.e.p.c.s) or by recording in voltage‐clamped end‐plates the current elicited by nerve stimulation (e.p.c.). 2. Changes in pH do not appreciably effect the peak amplitude of the current produced by a single quantum or by short ionophoretic pulses of acetylcholine. 3. The time constant of decay of the m.e.p.c.s is prolonged by about 50% in acid pH and shortened by about the same amount in alkaline pH. This effect is independent of the cholinesterase activity of the end‐plate. 4. In curarized preparations the decay of the e.p.c. is shorter than in Mg‐blocked end‐plate even in the absence of cholinesterase blocking agents. 5. The action of pH on the decays can be explained by a titration of the surface charges of the membrane which effects the voltage dependent reaction that controls the rate of closing of the synaptic channels.
Systemic angiotensin‐induced drinking in the dog: a physiological phenomenon.
Authors: Fitzsimons J T , Kucharczyk J , Richards G
Published: December 2014

1. Intravenous infusion of the individual components of the renin‐angiotensin system caused drinking in dogs in water balance. 2. Angiotensin II was the most potent and rapidly acting peptide inducing drinking. The minimum effective rate of infusion was between 8.3 and 16.6 X 10(‐12) mole kg‐1 min‐1 which yield blood levels of angiotensin II that fell well within physiological limits for the dog and were mildly pressor. Angiotensin I and synthetic renin substrate caused less drinking than angiotensin II, and angiotensin III was the least effective dipsogen. 3. Renin caused significant drinking when infused I.V. at a rate of 0.5 u. min‐1 for 15 min. Drinking was slower in onset and continued for longer than after other components of the renin‐angiotensin system. 4. Within the dose range 1875‐15,000 X 10(‐12) mole of angiotensin II the amount of water drunk depended more on the rate of infusion than on the duration of the infusion. 5. During an I.V. infusion of angiotensin II lasting 2 hr, the rate of drinking was greatest during the first 15 min. After this declined progressively. 6. A delay of 1 hr after the start of an intravenous infusion of angiotensin II before access to water was allowed, did not significantly reduce the amount of water drunk. Nor did infusion of isotonic saline for 105 min reduce drinking in response to a subsequent infusion of angiotensin II. However, a preload of dilute milk approximately equal in volume to the amount of water normally drunk in response to I.V. angiotensin II significantly reduced drinking. Therefore the dog stopped drinking during long‐term infusions of angiotensin II owing to the action of satiety mechanisms and not to tachyphylaxis or fatigue. 7. Intracarotid infusion of angiotensin II, angiotensin I, synthetic renin substrate and angiotensin III, at 40 X 10(‐12) mole min‐1 also caused drinking. Intakes of water were similar to the intakes after I.V. infusion at six times the arterial rate, except that angiotensin I was relatively less effective by intracarotid infusion than by I.V. infusion. 8. Renin, infused at 0.5 u. min‐1 for 15 min, was much less effective by intracarotid infusion than by intravenous. 9. These results are compatible with a role for circulating angiotensin II in the thirst of hypovolaemia or moderate extracellular dehydration.
The sacral parasympathetic reflex pathway regulating colonic motility and defaecation in the cat.
Authors: De Groat W C , Krier J
Published: December 2014

1. The sacral parasympathetic outflow to the large intestine of the cat was studied by monitoring simultaneously intestinal motility and the efferent firing in postganglionic fibres on the serosal surface of the mid‐distal colon. 2. Increases in efferent firing were noted during the occurrence of spontaneous propulsive activity (tonic pressure waves) or segmental contractions (slow rhythmic pressure waves). The neural discharge was not altered by transection of the lumbar sympathetic innervation to the colon but was blocked by interruption of the sacral parasympathetic outflow. 3. Electrical stimulation of pelvic nerve afferents arising in the colon or distension of the colon or rectum evoked reflex increases in efferent firing and sustained propulsive contractions that were associated with defaecation. Both responses were abolished by transection of the pelvic nerves or sacral dorsal roots. 4. Electrical stimulation of colonic afferent fibres also evoked synchronous reflex discharges in colonic efferents at latencies ranging from 180 to 300 msec. The discharges were enhanced during propulsive contractions, abolished by transection of the pelvic nerves but not altered by transection of the lumbar sympathetic nerves. 5. Sacral reflexes were present in cats with intact spinal cord and in chronic spinal animals (transection at T10‐T12). The reflexes recovered within minutes to several hours after acute transection of the spinal cord. 6. Electrophysiological measurements indicated that the sacral reflexes to the large intestine were mediated by non‐myelinated afferent and preganglionic efferent fibres. The central delay for the reflex was estimated to be 45‐60 msec. 7. It is concluded that the sacral parasympathetic reflexes to the large intestine are mediated via a spinal pathway and have an essential role in the initiation of propulsive activity during defaecation.
Structure‐activity relationships of eighteen somatostatin analogues on gastric secretion.
Authors: Brown M P , Coy D H , Gomez-Pan A , Hirst B H , Hunter M , Meyers C , Reed J D , Schally A V , Shaw B
Published: December 2014

1. The effect of somatostatin and eighteen somatostatin analogues on pentagastrin‐stimulated gastric acid and pepsin secretion was investigated in the conscious vagotomized cat prepared with chronic gastric fistulae. The majority of the analogues are peptides where D‐amino acids are incorporated into the molecule instead of the natural L‐isomers. 2. The ID50 for cyclic‐somatostatin inhibition of near‐maximal gastric acid secretion stimulated by pentagastrin 8 microgram kg‐1 hr‐1 was found to be 1.29 +/‐ 0.13 n‐mole kg‐1 hr‐1. Pentagastrin‐stimulated pepsin secretion had a lower threshold to somatostatin inhibition than did acid secretion. 3. D‐Phe6, D‐Phe7, D‐Thr10, D‐Thr12 and D‐Phe6‐D‐Trp8 analogues all show low biological activity against the secretion of gastric acid and pepsin, growth hormone, insulin and glucagon. None of these analogues are antagonists of the cyclic‐somatostatin inhibition of gastric secretion, suggesting that they have low affinity for this somatostatin receptor. 4. The analogues under investigation show parallel changes in activity against gastric and growth hormone secretion, suggesting a similarity between the gastric and growth hormone receptors for somatostatin. 5. D‐Cys14 analogues are equipotent with or have a greater potency than cyclic‐simatostatin in inhibiting the secretion of gastric acid, growth hormone and glucagon but show low insulin inhibiting activity.
A study of the canine gastric action potential in the presence of tetraethylammonium chloride.
Authors: Szurszewski J H
Published: December 2014

1. The effects of tetraethylammonium (TEA) ion on the action potential of isolated longitudinal muscle of the dog antrum were used to gain some insight into the mechanism of generation of the plateau potential of the action potential complex. The double sucrose gap was used. 2. In concentrations of TEA up to 5 mM, the amplitude of the upstroke potential was increased. In 10mM‐TEA there was also an increase in the amplitude of the plateau potential and in the maximum rate of rise of the upstroke potential. 3. Concentrations of TEA (3 mM and greater) increased the duration of the action potential. Five mM‐TEA produced spike potentials which occurred only during the plateau potential of the action potential. Each spike caused a contraction. 4. The steady‐state voltage‐current relation was studied in normal Krebs solution and in TEA containing Krebs solution. In normal Krebs solution the voltage response was not a linear function of the applied current when outward current pulses were used. In TEA solution the voltage response was a linear function of the entire range of applied depolarizing current. 5. In low concentrations of TEA (2‐4 mM), when the steady‐state voltage‐current relation was linear, constant current pulses were applied between action potentials and during the plateau potential to determine if there were a decrease in membrane slope resistance during the plateau. It was found that the amplitude of the electrotonic potential recorded during the plateau was significantly less than the amplitude of the electrotonic potential recorded between action potentials. 6. The rate of repolarization of the plateau potential was studied in normal Krebs solution and in 2 mM‐TEA Krebs solution. The rate of repolarization of the plateau potential was slowed in TEA Krebs solution. 7. It is concluded that there is an increase in the membrane conductance during the plateau potential. The repolarization following the plateau potential is due to a TEA‐sensitive outward current.
The permeability of the secretin stimulated exocrine pancreas to non‐electrolytes.
Authors: Dewhurst D G , Hadi N A , Hutson D , Scratcherd T
Published: December 2014

1. A method of measuring the permeability of the pancreas by determining the apparent reflexion coefficient (sigmaA) is described, in the isolated pancreas secreting maximally under the influence of secretin. The principle is to add a non‐electrolyte to the perfusate which will create an osmotic gradient (RTsigmadeltaC) counter to that of active transport and reduce the secretion rate. This is compared with the effect of an equal concentration (0.1 M) of sucrose (RTdeltaC; sigma = 1). The apparent reflection coefficient is obtained by dividing the percentage reduction in the secretion rate due to the test molecule with that due to sucrose. 2. Sucrose when added to the perfusate inhibits pancreatic secretion. For every 10 mM increase in sucrose concentration, the secretion rate was inhibited by 7.1%. It has been estimated that an osmotic gradient of 131 m‐osmole/kg water will cause zero flow rate. This is a measure of the pressure required to counteract the local osmotic gradient set up by active transport, it is equivalent to about 3.4 atm. 3. Non‐electrolytes with molecular volumes greater than about 85 cm3 mole‐1 are relatively impermeable, below this value they enter the pancreatic juice with increasing ease as the molecular volume decreases. 4. SigmaA for a number of compounds has been measured: urea 0.17; ethanediol 0.27; thiourea 0.51; glycerol 0.69; creatinine 0.81; erythritol 0.91; arabinose 0.96; xylose 0.98; sorbitol 0.98. 5. The addition of non‐electrolytes to the perfusate had effects on pancreatic secretion which were a function of sigmaA. For molecules with sigmaA lying between 0.81 and 1.0 an osmotic load of 0.1 M increased both the concentration of sodium plus potassium and the concentration of chloride plus bicarbonate by about 50 m‐mole/l. Whereas the cation change is almost exclusively one of sodium that of the anions was preferentially an increase in chloride. For compounds with sigmaA lying between 0 and 0.81 the concentration of sodium plus potassium was proportional to sigmaA. 6. A number of compounds have been described which inhibit pancreatic secretion, other than by an osmotic effect. These include acetaldehyde, thioglycerol, nicotinamide, ribose, dihydroxyacetone, and glyceraldehyde. 7. It is concluded that the pancreas is more permeable than the gall‐bladder of rabbit, fish and bullfrog, the proximal tubule of the kidney of rat and the small intestine of bullfrog, but is probably similar to that of small intestine of guinea‐pig and man.
Uniformity and diversity of structure and function in rhesus monkey prestriate visual cortex.
Authors: Zeki S M
Published: December 2014

1. Recordings were made from single neurones, or small clusters of cells, in five prestriate visual areas of rhesus monkey cortex. The cells were studied for their binocularity, as well as for their orientational, motion and colour preferences. In all, 1500 cells were studied, 250 cells for each of the areas V2, V3, V3A and the motion area of the posterior bank of the superior temporal sulcus, and 500 cells for V4. All the cells referred to in this study can be placed in one prestriate area or another unambiguously. 2. The great majority of cells in all areas were binocularly driven, without monocular preferences. Within each area, there were cells that either preferred binocular stimulation markedly, or were responsive to binocular stimulation only. The ocular interaction histograms for all areas are remarkably similar when tested at a fixed disparity. 3. Over 70% of the cells in areas V2, V3 and V3A were selective for orientation. The receptive fields of cells were larger in V3 and V3A than in V2. By contrast, less than 50% of the cells in V4 and the motion area of the superior temporal sulcus were orientation selective. 4. Directionally selective cells were found in all areas. But they were present in small numbers (less than 15%) in areas V2, V3, V3A and V4. By contrast, 90% of the cells in the motion area of the superior temporal sulcus were directionally selective. 5. 8% of the cells in V2 had opponent colour properties. Cells with such properties were not found in V3, V3A or in the motion area of the superior temporal sulcus. By contrast, 54% of the cells in the V4 complex had opponent colour properties. 6. It is argued that despite its uniformity in cytoarchitectural appearance and in ocular interaction patterns, there is a functional division of labour within the prestriate cortex. Evidence for this is seen not only in the different concentrations of functional cell types in distinct areas of the prestriate cortex, but also in the differential anatomical and callosal connexions of each area.
Calcium transients in isolated amphibian skeletal muscle fibres: detection with aequorin.
Authors: Blinks J R , Rüdel R , Taylor S R
Published: December 2014

1. Single twitch muscle fibres isolated from frogs and toads were microinjected with the Ca2+‐sensitive bioluminescent protein aequorin. The fibres contracted normally and emitted flashes of light (aequorin responses) in response to stimulation for many hours thereafter. 2. No luminescence was detected from healthy fibres at rest. 3. The aequorin diffused from the site of injection at a rate consistent with a diffusion coefficient of 5 x 10(‐8) cm2/sec. 4. During trains of isometric contractions there was a progressive reduction in both the amplitude and the rate of decline of the aequorin response, an observation consistent with the theory that Ca is redistributed from sites of release to sites of sequestration under such circumstances. 5. In isometric tetani light emission continued to rise long after the plateau of force had been achieved. This and the fact that the amplitude of the tetanic aequorin response increased steeply with increasing stimulus frequency suggest that in tetani the sarcoplasmic [Ca2+] may normally be above the level required to saturate the contractile apparatus. 6. Both in twitches and in tetani the amplitude of the aequorin response increased slightly and then decreased substantially as the fibre was stretched progressively beyond slack length. 7. In potassium contractures the luminescent and mechanical responses first became detectable at about the same [K+], but for equivalent force luminescence was less intense than in twitches. The aequorin response was biphasic in solutions of high [K+]. 8. Exposure of the fibre to Ca2+‐free solutions had no influence on either the mechanical or the luminescent responses in twitches. In Ca2+‐free solutions tetanic aequorin responses tended not to be maintained as well as normally, suggesting that intracellular Ca stores do become somewhat depleted. 9. In twitches the amplitude of the aequorin response probably reflects the amount of Ca2+ liberated into the cytoplasm rather than a [Ca2+] in equilibrium with the myofilaments. Changes in the rate of decay of the aequorin response may reflect changes in the rate of Ca sequestration by the sarcoplasmic reticulum. 10. In K+‐contractures and during the plateaus of tetani the aequorin signal changes slowly enough so that it seems unlikely that substantial gradients of [Ca2+] exist at the sarcomere level. Under such circumstances the amplitude of the aequorin response probably does reflect the [Ca2+] in equilibrium with the myofilaments.
Changes in the intracellular sodium activity of sheep heart Purkinje fibres produced by calcium and other divalent cations.
Authors: Deitmer J W , Ellis D
Published: December 2014

1. The intracellular Na activity of sheep heart Purkinje fibres was recorded with Na+‐sensitive glass micro‐electrodes. The effects of various external divalent cations on the intracellular Na activity were investigated. 2. Raising the external concentration of divalent cations (Ca, Mg, Mn, Sr or Ba) from 3 to 16 mM resulted in a decrease in the intracellular Na activity of 10‐50%. 3. Raising the external concentration of Ca, Sr or Ba could produce a decrease in the intracellular Na activity even when the Na‐K pump was inhibited (with strophanthidin, 10(‐5) M); but raising the external concentration of Mg or Mn could not. 4. Mn inhibited the decrease in the intracellular Na activity produced by raising external Ca while the Na‐K pump was inhibited. 5. Raising external Ca or adding Mn reduced the rate of rise of the intracellular Na activity on inhibition of the Na‐K pump. 6. The removal of external K resulted in an increase in the intracellular Na activity. This increase could be stopped and even reversed by raising external Ca. 7. Removal of divalent cations from the external solution produced an increase in the intracellular Na activity. However, replacing external Ca and Mg by another divalent cation, e.g. Mn, did not result in a rise in the intracellular Na activity, except when the Na‐K pump was inhibited. 8. The intracellular Na activity decreased by approximately 50% for a tenfold increase in the external Ca concentration. 9. The extent of the decrease in internal Na activity produced by raising external Ca was directly proportional to the internal Na activity before external Ca was raised. 10. We conclude that external Ca influences the intracellular Na activity in two ways: (a) by changing the passive Na influx: the resultant change in the intracellular Na depends on the activity of the Na‐K pump; and (b) by a process where internal Na ions are exchanged for external Ca ions.
Contractile activation by voltage clamp depolarization of cut skeletal muscle fibres.
Authors: Kovács L , Schneider M F
Published: December 2014

1. Single frog skeletal muscle fibres bathed in a relaxing solution were cut close to the tendon and mounted across a single Vaseline gap so that a short segment of intact terminated fibre extended beyond one side of the gap. 2. A compensating circuit, set with a micro‐electrode in the terminated fibre segment, was used both to correct total current for external current crossing the gap and to correct pool voltage for the voltage drop across the fibre segment in the gap. 3. The micro‐electrode was then removed and the fibre voltage‐clamped using the compensating circuit. This allowed movement without damage under controlled voltage. 4. Strength‐duration curves for contraction thresholds of cut fibres exposed externally to TTX Ringer solution and internally to a predominantly K glutamate solution were similar to strength‐duration curves reported for intact fibres. 5. The change from TTX Ringer to a predominantly (TEA)2SO4 external solution shifted the strength‐duration curve for cut fibre contraction thresholds in the negative direction as reported for intact fibres. 6. When studied at 3‐4 degrees C, fibres from warm‐adapted frogs appeared to have higher contraction thresholds than fibres from cold‐adapted frogs. 7. Delayed rectifier currents recorded from cut fibres were similar to those reported for intact fibres.
Oxytocin release following osmotic activation of oxytocin neurones in the paraventricular and supraoptic nuclei
Authors: Brimble M. J. , Dyball R. E. J. , Forsling Mary L.
Published: December 2014

1. Recordings were made from a total of 35 antidromically identified neurones in the paraventricular (PV) and supraoptic (SO) nuclei of urethane‐anaesthetized lactating rats. During recording plasma osmotic pressure was raised by 12 m‐osmole/kg by injection of hypertonic solutions of NaCl, LiCl, or mannitol.

2. Nine PV neurones (mean firing rate 4·2 ± 1·0 (
S.E.) spikes/sec) were classified as oxytocin cells because they gave a burst of activity before reflex milk‐ejections. None of these showed a bursting (phasic) firing pattern. Ten PV neurones (mean firing rate 1·8 ± 0·2 spikes/sec) fired phasically either before or after injection of hypertonic NaCl and were classified as vasopressin cells. The remaining six PV cells (mean firing rate 1·6 ± 0·9 spikes/sec) showed no bursts of firing related to milk ejection and did not fire phasically.

3. Increasing plasma osmotic pressure by injection of hypertonic NaCl increased the mean firing rate of PV oxytocin cells to 7·0 ± 1·0 spikes/sec. Vasopressin cells in the PV nucleus were much less responsive and the mean firing rate after injection was 2·9 ± 0·4 spikes/sec. The third group of PV neurones was unresponsive.

4. Plasma oxytocin concentration (determined by radioimmunoassay) increased from 2·1 ± 0·3 μu./ml. in the control period to 10·9 ± 2·8 μu./ml. 30 min after
I.P. injection of 1 ml. 1·5
M‐NaCl and to 14·8 ± 2·8 μu./ml. following injection of a second 1 ml. 1·5
M‐NaCl.

5. The responses of oxytocin and vasopressin neurones in the SO nucleus to an increase in plasma osmotic pressure following injections of hypertonic solutions of LiCl or mannitol were similar to those observed when plasma osmotic pressure was raised by NaCl.

6. It may be concluded that both oxytocin and vasopressin cells in the neurohypophysical system are responsive to the osmotic pressure of the blood plasma rather than to Na+ or Cl− concentration, that osmotic activation of oxytocin cells releases sufficient oxytocin to increase its plasma concentration, and that there may be a functional difference between the SO and PV nuclei.
The properties of surround antagonism elicited by spinning windmill patterns in the mudpuppy retina.
Authors: Thibos L N , Werblin F S
Published: December 2014

1. A truncated spinning windmill pattern, illuminating only the receptive field surround, shown previously to activate amacrine cells, was used to elicit activity at the inner plexiform layer and to reduce the response of ganglion cells to test flashes at the receptive field centre. 2. The spinning windmill pattern reduced the ganglion cell response over its entire graded range by a fixed amount, and reduced the domain of test intensities required for graded activity. 3. The windmill effect was graded for windmill intensities over a domain of about 1000 to 1. The effect was constant for windmill velocities from about 0.05 to 0.5 rev/sec, and diminished beyond these velocities. 4. The windmill effect varied with windmill area as though each retinal point contributed to the reduction of ganglion cell response with a weighting which fell exponentially from the receptive field centre. The space constant was 0.35 mm. 5. The graded reduction in ganglion cell response was closely correlated with the graded increase in amacrine cell activity when the windmill intensity, area, and velocity were varied. It is inferred that amacrine cells, activated by the windmill, act to reduce the response range of the ganglion cells, primarily through a feed‐forward pathway.
Ionic currents in cultured mouse neuroblastoma cells under voltage‐clamp conditions.
Authors: Moolenaar W H , Spector I
Published: December 2014

1. Ionic currents in differentiated cells of mouse neuroblastoma clone N1E‐115 have been studied under voltage‐clamp conditions. 2. Depolarizing voltage steps from a holding potential of ‐85 mV to levels more positive than ‐40 mV produced fast transient inward currents followed by delayed outward currents. 3. The fast inward current is carried by Na+: it is blocked by tetrodotoxin and is absent in Na+‐free solutions. Its kinetic behaviour resembles that of the Na+ current in squid giant axon. A mean value of 85 mmho/cm2 was found for the maximum Na+ conductance (GNa).4. The delayed outward current is carried primarily by K+: it is blocked by externally applied tetraethylammonium (TEA, 15 mM) and has a reversal potential (mean ‐71 mV) close to the theoretical K+ equilibrium potential. Its instantaneous I‐‐V curve is linear. By analogy with the formulation of Hodgkin & Huxley (1952c), the outward current can be described by IK = ‐GKn2(V‐‐EK) where GK = 12 mmho/mc2. 5. During prolonged depolarizations the delayed outward current declines. This decline, which occurs in two phases, represents a partial inactivation of the K+ conductance. 6. A weak inward current with slow activation and inactivation kinetics appears in Na+‐free solution containing 10 mM‐Ca2+. It is activated at a membrane potential of ‐55 mV and reaches its maximum at ‐20 mV with a time to peak of about 10 msec. This current is tetrodotoxin‐resistant, reversibly blocked by Co2+ (5mM) and is suggested to be carried by Ca2+. 7. An increase in the external divalent cation concentration results in a parallel shift of the steady‐state I‐‐V curve along the voltage axis in positive direction. The activation of delayed outward currents is suggested not to depend on Ca2+ influx. 8. It is concluded that separate voltage‐dependent Na+, K+ and Ca2+ channels exist in the differentiated neuroblastoma membrane with kinetic and pharmacological properties similar to those observed in non‐mammalian preparations.
Asymmetry of the hexose transfer system in human erythrocytes. Experiments with non‐transportable inhibitors.
Authors: Baker G F , Basketter D A , Widdas W F
Published: December 2014

1. The asymmetrical nature of sugar affinity for the hexose transfer system in human red cells has been demonstrated using purified 4,6‐O‐ethylidene‐alpha‐D‐glucopyranose (ethylidene glucose) to inhibit the exchange of glucose, 3‐O‐methyl glucose and galactose. 2. The half‐saturation concentration for ethylidene glucose inside the cell is estimated at ca. 110 mM whereas on the outside the value for exchange inhibition is ca 11mM. 3. The asymmetrics of affinities of two related non‐transportable inhibitors 1,2‐O‐isopropylidene‐D‐glucofuranose and methyl‐2,3‐di‐O‐methyl‐alpha‐D‐glucopyranoside have also been studied. 4. From experiments at varying concentrations and on theoretical grounds the half‐saturation concentration for non‐transportable inhibitors on the outside surface is shown to be over‐estimated by measuring inhibition of exchange. In consequence the actual asymmetry of affinities may be greater than observed. 5. Experiments with ethylidene glucose also suggest that conformational changes redistributing components of the hexose transfer system between inward and outward facing modes may occur.
The effect of guanidine on transmitter release in the ciliary ganglion of the chick.
Authors: Banks F W
Published: December 2014

1. The effect of guanidine hydrochloride on synaptic transmission at the chick ciliary ganglion was studied. 2. In bathing solution containing low calcium concentrations, guanidine produced a dose‐dependent increase in the number of quanta released by the presynaptic action potential. No post‐synaptic effects were observed. 3. Intracellular presynaptic recordings and monitoring of the presynaptic action potential post‐synaptically via the coupling potential showed that the action of guanidine was independent of any alterations in the presynaptic spike.
Mechanism of slow discharges of sheep carotid artery.
Authors: Keatinge W R
Published: December 2014

1. Single and double sucrose‐gap methods were used to follow changes in membrane potential and conductance of smooth muscle of sheep carotid arteries. 2. K depolarization induced discharges lasting several seconds in various solutions containing Mn, or Mg, or Ca and procaine, sometimes with no other added cations and with only sulphate or ethanesulphonate as anions. 3. Membrane conductance usually rose substantially above resting level in the early part of these discharges, but fell towards resting level during the later part. 4. Large depolarizing currents caused porportionately less voltage displacement than small currents, and reduced voltage displacements induced by superimposed current pulses, even in Cl and HCO3 free solutions, indicating activation of K conductance by depolarization. 5. When procaine was added, or Ca replaced by Mn or Mg, conductance was lower both at rest and on depolarization, and the increase on depolarization often underwent slow inactivation which it never did in simple Ca containing solutions. 6. The results indicate that a slowly inactivated inward current dependent on Ca, Mn or Mg was largely responsible for the slow discharges, and that procaine, Mn or Mg assisted the discharges by reducing the normal rapid outward‐rectifying K conductance and allowing it to inactivate on prolonged depolarization.