bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of graded forelimb afferent volleys on acetylcholine release from cat sensorimotor cortex.
Authors: Mullin W J , Phillis J W
Published: December 2014

1. The acetylcholine (ACh)‐releasing system in the cerebral cortex of pentobarbital anaesthetized cats was investigated by examining the effect of graded afferent volleys in forelimb nerves on ACh release from the sensorimotor cortices contralateral and ipsilateral to the site of stimulation. 2. Cortical ACh release was determined by bio‐assay of neostigmine‐containing perfusates which had been in contact with the cortical surfaces for 5‐10 min periods. 3. Afferent volleys, generated by stimuli that were effective in activating as many fibres of a fibre group as possible without stimulating fibres in the group with the next highest threshold for activation, were monitored from dorsal roots C7 or C8 before entering the spinal cord. 4. Stimulation of the deep (DR) and superficial (SR) radial nerves and the radial (R) nerve proximal to the junction of the DR and SR were effective in enhancing ACh release only when either group III or groups III and IV fibres were included in the afferent volley. 5. The rates of ACh release from the primary receiving area of the sensorimotor cortex contralateral to the site of stimulation did not differ from those from the same area of the ipsilateral sensorimotor cortex. 6. The pertinence of this data to the various hypotheses concerning the nature of the ACh‐releasing pathways to the cerebral cortex is discussed.
Release of catecholamines and dopamine beta‐hydroxylase from the perfused adrenal gland of the cat.
Authors: Dixon W R , Garcia A G , Kirpekar S M
Published: December 2014

1. Secretion of catecholamines (CA) and dopamine beta‐hydroxylase (DBH) activity from the perfused cat adrenal gland was studied following splanchnic nerve stimulation or infusion of acetylcholine (ACh). 2. Splanchnic nerve stimulation (30 Hz) or perfusion with a low concentration of ACh (10‐minus5 M) caused a marked release of CA in the venous effluent, but release of DBH activity was minimal while a higher concentration of ACh (10‐minus 4 M) enhanced the release of CA and DBH. 3. The ratio of DBH/CA released in the perfusate by splanchnic nerve stimulation or ACh infusion was only a small fraction of the ratio in the soluble lysate of purified chromaffin vesicles. 4. Following reserpine treatment, adrenal CA levels fell to 25% of the control value in 24 hr, remained depressed on days 2, 3, 4 and 5 at 5% of the control and recovered to 60% of the control value on the 6th day. DBH activity was unchanged from the control value at 24 hr after treatment, then rose as high as 5 times the control on the 5th day and was still twice the control value on the 6th day. 5. CA secretion in response to ACh (10‐minus 4 M) perfusion was reduced to 30% of the control value on the first day after reserpine treatment, while DBH secretion was unchanged. On the 2nd day, CA secretion was depressed further to 5% of the control and remained at this low level up to 5 days after treatment while DBH secretion was twice the control value at 48 hr and then on days 3, 4 and 5 rose up to 5 times the control value. On the 6th day, secretion of CA recovered to 30% of the control while DBH secretion was now twice the control. 6. Isopycnic sucrose density (discontinuous) gradient centrifugation of vesicles from adrenal glands of control cats, and of cats given reserpine 1 or 2 days perviously, indicated that new vesicles or vesicles depleted of CA by reserpine had a lower equilibrium density than the original population of vesicles. 7. These results suggest that the release of CA is quantal in nature, but the release of DBH is not necessarily coupled with it. Release of DBH by ACh from reserpinized glands suggests that the vesicles which were once involved in secretion may be re‐used for synthesis and storage of CA.
Membrane properties of the smooth muscle cells of the rat anococcygeus muscle.
Authors: Creed K E
Published: December 2014

1. The membrane properties of the rat anococcygeus muscle, during rest and activity, were investigated with micro‐electrodes and partition stimulation. 2. Intercellular current spread occurred within the muscle and the mean length constant was 2‐7 mm. The membrane showed rectification to depolarizing pulses. 3. The mean resting potential was ‐‐62‐1 mV and the input resistance was 23‐0 MOMEGA. Stimulation of intramural nerves produced depolarization to ‐‐21 mV and a 10% reduction in input resistance. Displacement of the membrane potential indicated that the transmembrane potential at the peak of the response was independent of the membrane potential. 4. Noradrenaline also produced depolarization and this was accompanied by a decrease in membrane resistance as indicated by a reduction in amplitude of the electrotonic potential. 5. It was concluded that the muscle possesses cable properties and that the action of the transmitter, noradrenaline, is to increase membrane permeability so that the membrane potential moves towards an equilibrium potential.
The transmission of −125‐I‐labelled immunoglobulin G by proximal and distal regions of the small intestine of 16‐day‐old rats.
Authors: Morris B
Published: December 2014

1. Standard doses of −125‐I‐labelled rat IgG were injected into the intestinal lumen of rats aged 16 days, and their sera were sampled 2 and 3 hr later. High concentration quotients were obtained after injection into the proximal small intestime, whereas very little immunoglobulin was transmitted from doses injected into the terminal 20 cm of the small intestine. 2. The villi of the terminal 18‐‐20 cm of the small intestine of 16‐day‐old rats, the region from which very little transmission of IgG occurred, were lined by tall columnar absorptive cells with very larg supra‐nuclear vacuoles. The extent of the terminal intestine, in which this cell type predominated in the absorptive epithelium, varied with age. The importance of defining the precise location of the region of the intestine under examination is stressed. 3. The experimental results and the histological observations are discussed in relation to (a) the results which have been obtained using PVP, which is unsuitable as an indicator of immunoglobulin transport in the rat and (b) the histological composition of the absorptive epithelium and the maturation changes which affect the epithelium between 18 and 21 days.
Variability of the relative preference for stimulus orientation and direction of movement in some units of the cat visual cortex (areas 17 and 18).
Authors: Donaldson I M , Nash J R
Published: December 2014

1. The responses to visual stimuli of single units in the cortex of cats anaesthetized with pentobarbitone were recorded extracellularly with glass micropipettes. All had receptive field centres more than 5 degrees and most lay between 5 and 20 degrees from the area centralis. Most units were in Area 18 but some were in the corresponding field representation in Area 17. 2. A quantitative method is described in which the visual stimuli (slits or light bars) were presented repetitively by mechanical means in each of four orientations of the stimulus and in two directions of movement for each orientation. The responses were analysed quantitatively and criteria are described for classification of units according to their preference for particular orientations or directions of movement of the stimulus. 3. Some units were studied continuously for up to 2 hr using the quantitative technique. In Area 18, of nineteen units, eighteen showed changes in their preference for direction of stimulus movement and, in seven of eleven units, the orientation preference changed. In Area 17 direction preference changed in eight of nine units and orientation preference in six of seven. In some cases both orientation and direction preference altered. 4. The relationship of these changes to alterations in the ‘spontaneous activity’ of the cortical units and to variations in the depth of anaesthesia are considered. Neither would appear to be the sole cause of the phenomenon.
Studies on convulsants in the isolated frog spinal cord. II. Effects on root potentials.
Authors: Barker J L , Nicoll R A , Padjen A
Published: December 2014

1. In the isolated frog spinal cord picrotoxin, bicuculline, and strychnine were evaluated for their effects on synaptically induced root potentials recorded by the sucrose gap technique. 2. Picrotoxin (greater than 10‐ minus 4 M) completely blocked the dorsal root potential (DRP) elicited by stimulating the ventral root of the same segment (VR‐DRP). Although picrotoxin antagonized the DRP elicited by stimulation of either an adjacent dorsal root (DR‐DRP) or the lateral column (LC‐DRP), a slower component to these potentials appeared and increased in size as the concentration of picrotoxin was increased. Thus picrotoxin brings out a later, picrotoxin resistant component to the DR‐DRP and LC‐DRP. 3. Strychnine (10‐ minus 8–10‐ minus 5 M) reduced and abolished the VR‐DRP without prolongation and progressively increased and prolonged the DR‐DRP (and LC‐DRP) and the DR‐VRP. Strychnine in higher concentrations (greater than 10‐ minus 4 M) also reduced the amplitude and prolonged the duration of the compound action potential of afferent fibres. 4. These results combined with those presented in the preceding paper (Barker, Nicoll & Padjen, 1975) suggest that (1) a GABA‐like transmitter mediates the final step in the DR‐DRP and LC‐DRP pathways and that (2) either taurine or beta‐alanine may mediate the last step in the VR‐DRP pathway.
The effect of sodium salicylate on bile secretion in the dog.
Authors: Rutishauser S C , Stone S L
Published: December 2014

1. The I.V. injection of sodium salicylate (100 mg/kg) in the dog caused a rapid and maintained choleresis of the order of 300–600 percent of control levels. 2. The total amount of salicylate excreted in bile was only 1‐2 percent of that injected. 3. The secretion of bile salt into bile was not increased by salicylate. 4. The choleresis caused by salicylate was associated iwth a decrease in the concentrations of sodium and of bile salt in bile, and with an increase in the concentration of chloride; the biliary concentration of bicarbonate was either temporarily increased or unchanged. 5. The choleresis could not be inhibited by the intra‐portal injection of of ouabain (0–1 mg/kg). 6. The secretion of bromsulphthalein into bile was not potentiated by the choleresis. 7. The choleretic efficiency of sodium taurocholate was not increased in the presence of salicylate. 8. The injection of acetazolamide (20 mg/kg) in the presence of a salicylate choleresis, caused an increase in the osmolaity of bile and an increase in biliary sodium concentration, such that the composition of bile more nearly approached that of plasma. 9. The possible mechanisms underlying the choleretic effect of sodium salicylate are discussed.
Aspects of bile secretion in the rabbit.
Authors: Rutishauser S C , Stone S L
Published: December 2014

1. Bile secretion was studied in anaesthetized rabbits from whom hepatic bile was collected by cannulation of the common bile duct. 2. The flow and composition of bile formed by rabbits anaesthetized with urethane differed significantly from that formed by rabbits anaesthetized with pentobarbitone sodium. 3. The I.P. injection of a hypertonic solution of sucrose (3 M) decreased bile flow and produced changes in the ionic composition of bile and of plasma. 4. The infusion of sodium taurodeoxycholate (1‐5‐20 mumole/min I.V.) gave higher rates of bile flow than did equimolar infusions of sodium taurocholate, and unlike taurocholate, increased the bicarbonate concentration of bile. 5. Acetazolamide (10–100 mg/kg) increased the concentration of bicarbonate both in bile and in plasma, and had little effect on bile flow. 6. The infusion of bromsulphthalein (5 mg/kg I.V.) decreased the excretion of bicarbonate into bile, and was associated with the formation of a hypotonic bile. 7. The implications of these results in relation to the mechanisms of bile secretion are discussed.
The electrogenic sodium pump in the hyperpolarizing and secretory effects of pancreozymin in the pancreatic acinar cell.
Authors: Kanno T
Published: December 2014

1. Transmembrane potential, effective membrane resistance, and amylase release were recorded simultaneously from acinar cells of isolated rat pancreas perfused with Krebs‐Henseleit solution. 2. The hyperpolarizing effect of pancreozymin (Pz) was confirmed by perfusing with a solution containing 5 m‐u. Pz/ml. 3. The hyperpolarizing effect of Pz disappeared in the following environments: (a) in low ambient temperature, (b) in K‐free medium, (c) in low Na medium, and (d) in the presence of ouabain. In these environments, transient depolarization was frequently observed immediately after stimulation. It is suggested that there are two components in the effect of Pz on the membrane potential of the acinar cells: transient depolarization which coincides with an increase in Na permeability in the initial phase, and continuous hyperpolarization due to an electrogenic Na pump which conceals transient depolarizing phase when the pump is dominant. 4. The secretory effect of Pz was inhibited under conditions that suppressed the electrogenic Na pump. It is proposed that the Na pump activated by Pz maintains the passive Na‐influx, increases [Ca2+]i, and, in consequence, uphold the amylase output during continuous stimulation. 5. A medium which was used to bathe the sectioned pancreas with Pz was found to contain a substance which depolarized the acinar cells.
The effect of substances releasing intracellular calcium ions on sodium‐dependent calcium efflux from guinea‐pig auricles.
Authors: Jundt H , Porzig H , Reuter H , Stucki J W
Published: December 2014

1. 45‐Ca efflux and resting tension were measured in isolated guinea‐pig auricles under conditions known to change the intracellular free Ca ion concentration. 2. In the presence of [Na]o, caffeine (2mM) increases 45‐Ca efflux, but does not produce a contracture, while in the absence of [Na]o and [Ca]o caffeine causes a contracture without increasing 45‐Ca efflux. Adrenaline (10‐minus5–10‐minus 4M) with or without theophylline (0–5‐1‐0mM) has no effect on either 45‐Ca efflux or resting tension. 3. In the presence of caffeine the rate of net efflux of Ca depends on [Na]o‐2. Caffeine contractures of muscles in Na‐free solution relax upon the addition of [Na]o. Relaxation is correlated with the increase in net efflux of Ca. 4. Cyanide (2mM) produces a variable increase in 45‐Ca efflux without a concomitant contracture in Na‐containing solutions, but in Na, Ca‐free solutions a large contracture occurs without significant increase in 45‐Ca efflux. 5. A large increase in 45‐Ca efflux and a contracture were observed with the ‘Ca‐ionophore’ X 537 A. 6. Changes in membrane potential (K‐depolarization) in hypertonic solutions have no significant effect on Na‐dependent 45‐Ca efflux, which is an agreement with an electroneutral 2:1 Na‐Ca exchange. 7. Cyanide and X 537 A both cause a considerable release of Ca ions from isolated guinea‐pig heart mitochondria, while caffeine has no effect. 8. The results suggest a powerful role of the Na‐Ca exchange system in reducing the intracellular Ca concentration after Ca release from intracellular stores.
The relationship between kallikrein and water excretion and the conditional relationship between kallikrein and sodium excretion.
Authors: Mills I H , Ward P E
Published: December 2014

1. The renal kallikrein‐kinin system has previously been linked with renal control of sodium and water excretion. The present investigations were carried out to examine more closely these relationships. 2. In physiological studies with rabbits, urinary kallikrein was measured by a modification of the [3‐H]TAME method. 3. With rabbits on free sodium and water intake, urinary kallikrein was positively correlated with both sodium and water excretion. Kallikrein excretion was also negatively correlated with urinary osmolality. 4. In rabbits on chronic high and low sodium diets, urinary kallikrein was positively correlated with urinary volume but not with sodium excretion. 5. In rabbits held to a constant fluid intake but with sodium intake changed, urinary kallikrein was not correlated with sodium excretion. 6. These results indicate that the positive correlation of kallikrein excretion with sodium excretion under conditions of free sodium and water intake may be only secondary to the positive relationship of kallikrein excretion with urinary volume. 7. The results of the present investigations do not support the hypothesis that the renal kallikrein‐kinin system is necessarily involved in renal control of sodium excretion under normal conditions but it is where a change in sodium intake leads to a change in fluid intake and consequently of urinary volume. 8. In the above experiments, urinary kallikrein was always positively correlated with urinary volume and negatively correlated with urinary osmolality. This may indicate a functional relationship between renal kallikrein and water excretion.
The detection of gratings by independent activation of line detectors.
Authors: King‐Smith P E , Kulikowski J J
Published: December 2014

1. The visibility of composite stimuli (double lines, multiple lines and sinusoidal gratings) is analysed in terms of the visibility of single lines. 2. The detection mechanisms for the composite stimuli were examined by measuring the probabilities for seeing these stimuli, the probabilites of "recognition" near their detection thresholds and by using the method of subthreshold summation. 3. The simplest composite stimulus consists of two lines spaced apart by 15 min; it was found that both the probability of seeing this stimulus and the probability of reporting either one or two lines may largely be explained by assuming independent detection of the two lines. For a 12 min spacing some antagonistic interaction was observed between the two lines, confirming the existence of an antagonistic surround in the line detector. 4. The probability of seeing a multiple line target (rectangular grating) of spacing 15 min is slightly greater than that predicted assuming independent detection of its component lines; this probability can be calculated from the probabilities of seeing a central line (near the fixation point) and pairs of lines spaced 15, 30, 45, 60, 75 and 90 min on either side of the fixation point. The observed threshold for the grating was about 0.05 log units less than the prediction. 5. The probability that a subject reports only one line from a rectangular grating was found to be consistent with independent detection of its component lines when the subject used a low (detection) threshold criterion but not for higher criteria. 6. The spatial frequencies involved in the detection of the rectangular grating were determined by subthreshold summation; the high spatial frequency selectivity was shown to be consistent with independent detection of the component lines. 7. The detection mechanism for a 4 c/deg sinusoidal grating was found to be similar to that for the 15 min rectangular grating. 8. Evidence is presented that the detection of finer and coarser gratings may be analysed in similar terms. 9. It is shown that lines are not detected by independent activation of sharply tuned grating detectors but that sub‐units may be involved which are slightly more narrowly tuned than the line detector. 10. These sub‐units contain both inhibitory and disinhibitory regions; the disinhibitory responses may be the basis of the deviations from probability summation noted in 4. 11. The properties of the proposed sub‐units are in reasonable accord with the results of adaptation experiments.
Intracellular recordings of rod responses during dark‐adaptation.
Authors: Grabowski S R , Pak W L
Published: December 2014

1. Dark‐adaptation of rod photoreceptors has been studied in the isolated axolotl (Ambystoma mexicanum) retina by intracellular recordings. Rod responsiveness was greatly reduced immediately after a 30 sec partial bleach, but partially recovered with time in the dark. 2. In parallel spectrophotometric measurements using isolated retinas, regeneration of the rod pigment could not be detected after a 30 sec bleach. 3. During rod dark‐adaptation, the response of a rod to a given stimulus increased in amplitude, duration, and rate of rise but did not recover completely to the dark‐adapted values. Response latency was lengthened immediately after a bleach but ultimately returned to the dark‐adapted level. 4. The time courses of dark‐adaptation determined on the basis of the intensity of a stimulus needed to evoke a response having a criterion amplitude, a criterion duration, or a criterion rate of rise were similar. On the other hand changes in latency of the response and magnitude of the saturated amplitude followed different time courses. Change in log threshold was found to be related to change in saturated amplitude by an exponential function during dark‐adaptation. 5. After bleaching 10% or less of the rod pigment, the kinetics of both recovery of log threshold and decrease in absorbance at 400 nm (metarhodopsin II+free retinal) could be described by two concurrent first‐order processes having similar time constants. However, after bleaching more than 10% of the rod pigment, changes in sensitivity and absorbance did not follow parallel time courses. 6. Metarhodopsin III cannot be solely responsible for setting the axolotl rod sensitivity since rod thresholds decrease monotonically during dark‐adaptation whereas meta III concentration reaches a peak 3 min after the bleach and decreases thereafter.
The effect of calcium ions on the binomial statistic parameters which control acetylcholine release at synapses in striated muscle.
Authors: Bennett M R , Florin T , Hall R
Published: December 2014

A study has been made of the effects of changing [Ca]O and [Mg]O on the binomial statistic parameters p and n which control the average quantal content (m) of the synaptic potential due to acetylcholine release. 2. When [Ca]O was varied in the range 0–1 to 1‐0 mM, p increased as the first power of [Ca]O whereas n increased as the third power of [Ca]O. 3. Increasing [Mg]O depressed both p and n, however variations of [Ca]O in the presence of high [Mg]O did not significantly change the power relationship between either p and [Ca]O or between n and [Ca]O. 4. The facilitated increase in m during a short train was due to an increase in n, whereas the post‐tetanic increase in m during a tetanus was due to an increase in p. These results are considered in terms of the role of Ca ions in facilitation and post‐tetanic potentiation.
The effects of maternal hypercapnia on foetal oxygenation and uterine blood flow in the pig.
Authors: Hanka R , Lawn L , Mills I H , Prior D C , Tweeddale P M
Published: December 2014

1. The purpose of this investigation was to determine the effects of maternal hyperoxaemia and hypercapnia on the uterine vascular bed and foetal oxygenation in the large white sow at 80–90 days gestation. 2. When maternal hyperoxaemia was induced with 100% oxygen, there was a highly significant rise in the maternal arterial oxygen tension, but no other significant blood gas or vascular changes were observed. 3. When mild maternal hypercapnia was superimposed on maternal hyperoxaemia (oxygen plus 6% carbon dioxide), the oxygen tension and saturation of both the maternal uterine venous and foetal umbilical venous bloods were found when severe hypercapnia was induced (oxygen plus 50% carbon dioxide) but in this case all blood samples showed dramatic changes in PCO2 and pH. These changes were accompanied by an increase in the systemic blood pressure and uterine blood flow, and a decrease in uterine vascular resistance. 4. When mild hypercapnia was induced without hyperoxaemia (air plus 5% carbon dioxide) significant increases were recorded in the oxygen tension and saturation of uterine venous and foetal umbilical venous bloods. Systemic and uterine vascular resistance fell. 5. It was concluded that the increased foetal oxygen tension during maternal hypercapnia was the result of the increased uterine blood flow and greater mass delivery of oxygen to the placenta, so that once the oxygen requirements of the placental tissues themselves were exceeded there would be an increased oxygen gradient at the site of gas exchange. 6. Carbon dioxide concentration in arterial blood plays an important role in determining blood flow through the pregnant uterus in the sow.
Tetrodotoxin binding to normal depolarized frog muscle and the conductance of a single sodium channel.
Authors: Almers W , Levinson S R
Published: December 2014

1. We have examined the binding of tritium‐labelled and unlabelled tetrodotoxin to frog twitch muscle. Bio‐assay as well as radioisotope experiments show a saturable component of tetrodotoxin binding with a binding capacity of about 22 p‐mole/g wet wt., and a dissociation constant of about 5 nM. 2. If the observed uptake of tetrodotoxin by muscles represents one‐to‐one binding of the drug to sodium channels, the channel density is about 380 channels/mum2 of a muscle fibre's surface membrane. On the basis of this result and electrical measurements of sodium conductance in frog muscle, we calculate that the conductance of a single sodium channel is of the order of 10(−12) reciprocal ohms. This is one to two orders of magnitude less than previous estimates. 3. We have looked for an effect of membrane depolarization on saturable tetrodotoxin binding, and have found none. This suggests that there is little molecular interaction between the “gating” portion of the sodium channel molecule, and that which binds tetrodotoxin.
The action of ether and methoxyflurane on synaptic transmission in isolated preparations of the mammalian cortex.
Authors: Richards C D , Russell W J , Smaje J C
Published: December 2014

1. The actions of ether and methoxyflurane on the evoked potentials of in vitro preparations of the guinea‐pig olfactory cortex were studied. Following stimulation of the lateral olfactory tract (l.o.t.) evoked potentials could be recorded from the cortical surface; these potentials consisted of an initial wave (the compound action potential of the l.o.t.) followed by a negative field potential which was associated with the synchronous excitation of many superficial excitatory synapses (population e.p.s.p.). Superimposed on the population e.p.s.p. was a number of positive peaks. These positive peaks reflect the synchronous discharge of many neurones and so have been called population spikes. 2. When ether or methoxyflurane was added to the gas stream that superfused the surface of the preparations, the population e.p.s.p.s. and population spikes were depressed at lower concentrations than those required to depress the compound action potential of the afferent fibres. 3. The evoked activity of individual cells in the cortex was depressed by ether and methoxyflurane. However, five of the twelve cells tested in ether showed an increase in their evoked activity at concentrations below 4‐5%, but at higher concentrations these cells also became depressed. 4. Both ether and methoxyflurane depressed the sensitivity of cortical neurones to iontophoretically applied L‐glutamate and may similarly depress the sensitivity of the post‐synaptic membrane to the released transmitter substance. 5. Neither anaesthetic appeared to increase the threshold depolarization required for nerve impulse generation. Thus, the decrease of the discharge of the post‐synaptic cells was primarily caused by a depression of chemical transmission. 6. Ether caused some cells in the cortex to alter their normal pattern of synaptically evoked discharge and both anaesthetics induced similar changes during excitation by glutamate.
The control of adaptive hypertrophy in the salt glands of geese and ducks.
Authors: Hanwell A , Peaker M
Published: December 2014

1. Factors controlling adaptive hypertrophy, which occurs when marine, or potentially marine, birds drink salt water, have been investigated in geese and ducks using changes in salt‐weight weight, RNA and DNA contents as indices of this process. 2. Unilateral post‐ganglionic denervation in geese prevented the changes in [RNA] and [RNA]:[DNA] that occurred in the intact gland of birds given salt water for 24 hr; denervation had no significant effect in birds on fresh water throughout. 3. Atropine treatment also prevented the adaptive changes in geese given salt water. 4. In ducks give 0.3 M‐NaCl for 48 hr salt‐gland weight, [RNA] and [RNA]:[DNA] increase markedly. Treatment of ducks drinking fresh water with large doses of corticosterone and mammalian ACTH for 48 hr had no significant effects on salt‐gland weight, RNA or DNA; mammalian prolactin treatment for 48 hr significantly raised [RNA]. 5. No changes in the total amount of DNA in the glands were observed in these experiments, thus indicating that hyperplasia does not occur within 48 hr of a bird first drinking salt water. 6. It is concluded that adaptive hypertrophy is controlled by secretory nerves, and that hormones, if they play any part in this process, have a permissive or secondary role. It is suggested that hypertrophy and the maintenance of the secretory cells in the fully‐adapted state may be obligatorily related to secretory activity induced by cholinergic secretory nerves.
Preparation and partial characterization of hepatic regenerative stimulator substance (SS) from rat liver.
Authors: LaBrecque D R , Pesch L A
Published: December 2014

1. The elucidation of the biochemical controls of growth processes is basic to understanding both normal and malignant growth. The exquisitely sensitive control demonstrated in the regenerating liver provides an excellent model system for growth studies. 2. Intraperitoneal injection of an extract from weanling rat liver into 34% hepatectomized rats stimulates [3H]thymidine incorporation into recipient hepatic DNA 2.5‐fold. This stimulation is seen after a 10 hr lag period. 3. Extracts from weanling rat liver contain the highest level of the hepatic regenerative stimulator substance (SS), whereas extracts from adult liver give no significant stimulation. 4. If adult rats are partially hepatectomized, SS is demonstrated in their livers 12–15 hr after hepatectomy. 5. Partial characterization of SS shows that it is a soluble material not sedimented by centrifugation for 2 hr at 145,000 g. The stimulator activity is stable to heating at 65 degrees C and 100 degrees C for 15 min but is lost when treated with 10% perchloric acid.
Thermal receptors in the scrotum of the rat.
Authors: Hellon R F , Hensel H , Schäfer K
Published: December 2014

1. The technique of single fibre dissection has been used to study the warm and cold thermoreceptors in the rat scrotum. 2. The warm receptors showed dynamic activity during increases of scrotal temperature and static activity when temperature was constant. The static activity/temperature curve was bell‐shaped, with minima at 31 and 45 degrees C and a peak at 42 degrees C. 3. The cold receptors also showed dynamic and static responses to reductions of temperature. At steady temperatures the impulses from some receptors were grouped in bursts. The number of impulses in each burst increased from zero at 30 degrees C to four at 20 degrees C.
Rhodopsin flash photolysis in man.
Authors: Pugh E N
Published: December 2014

1. Human rhodopsin in vivo was flash bleached by a 600 musec xenon flash which could deliver to the retina up to 15 rod‐equivalent quanta per rhodopsin molecule, and the fraction bleached measured by fundus reflexion densitometry. 2. The curve relating fraction rhodopsin bleached to intensity of flash saturates at 0.5 to 0.6. Thus, 40–50% of the rhodopsin is left photo‐regenerated by the brightest flashes. 3. Three types of densitometry experiments confirm the saturation of the bleaching curve. 4. The kinetic constants required to account for the observed photo‐regeneration were somewhat discrepant with in vitro and in situ estimates from infrahuman species. Specifically, (i) the quantum efficiency of the back reaction, metarhodopsin I hv leads to rhodopsin, was inferred to be nearly as high as that of the forward reaction; and (ii) the rate of the metarhodopsin I leads to metarhodopsin II dark reaction was inferred to be less than 500 sec(−1).
Rushton's paradox: rod dark adaptation after flash photolysis.
Authors: Pugh E N
Published: December 2014

1. Rod dark adaptations after a photoregenerating flash and quantum‐equivalent 30 sec bleach are found to be in exact agreement, while the measured rhodopsin regenerations are grossly different. This finding confirms and clarifies ‘Rushton's paradox’, the failure of the Dowling‐Rushton equation (linking log sensitivity linearly with unregenerated rhodopsin) to account for human rod dark adaptation after flash photolysis. 2. The hypothesis that the agreement between rod dark adaptation curves after a photoregenerating flash and after a quantum‐equivalent 30 sec bleach is coincidental is rejected on the basic of two classes of experiments. 3. Rod ‘bleaching’ adaptation is demonstrated to be entirely determined by the number of rhodopsin molecules which absorb at least one quantum in a temporal period T, whose range includes the time interval 600 musec less than or equal T less than or equal 30 sec. This generalization obtains over the entire scotopic energy range (congruent to 3 log units) where rod dark adaptations has been studied. 4. Thus, the state of ‘bleaching’ adaptation is determined by some by‐product of the normal chain of events in scotopic excitation. About this by‐product three important deductions are made: (i) its production is a monotonic function of the initial effective quantum absorptions; (ii) its production occurs before the metarhodopsin I leads to to metarhodopsin II dark reaction; (iii) it cannot be any photoproduct of the rhodopsin cycle.
Effects of afferent volleys from the limbs on the discharge patterns of interpositus neurones in cats anaesthetized with alpha‐chloralose.
Authors: Armstrong D M , Cogdell B , Harvey R
Published: December 2014

1. In cats anaesthetized with alpha‐chloralose, micro‐electrodes have been used to record the discharge patterns of single neurones in the region of the nucleus interpositus. 2. Almost all cells tested could be antidromically invaded following electrical stimulation of the contralateral red nucleus, showing that they were cerebellar efferent neurones. 3. A little over half of the interpositus neurones were spontaneously active, usually at rates of less than 20 impulses/sec. 4. About 40% of the cells had no spontaneous activity, although they gave brisk responses to electrical stimulation of cutaneous nerves. Such silent units were encountered most frequently in the earlier stages of an experiment, but a number were found more than 15 hr after the beginning of an experiment. 5. Stimulation of cutaneous and mixed nerves of the fore and hind limbs provoked impulse discharges of the cells and also produced phases of deceleration of the resting discharge of spontaneously firing cells. 6. The typical response of an interpositus neurone consisted of a short latency (6–35 msec) discharge, usually separated from a long latency (50–500 msec) discharge by a period of inhibition or return to the resting discharge rate. The two phases of excitation appeared to be independently generated, since in a number of cells one phase appeared without the other. In addition, the later phase of excitation was abolished in all cells tested by a small dose of pentobarbitone which produced very little effect on the earlier phase. The long latency response was quantitatively much greater, sometimes consisting of 50 or more impulses in a response which lasted several hundred msec, but was very variable from one trial to another. 7. The long latency discharge and sometimes the preceding inhibition could readily be mimicked by single shock stimulation of the region of the contralateral inferior olive. Short latency discharges were, however, rarely evoked by olivary stimulation. 8. It is suggested that the short latency responses of the interpositus neurones were a result of synaptic excitation via cerebellar afferents, while the ensuing inhibition was a result of post‐synaptic inhibition resulting from the Purkinje cell excitation due to the afferent volleys. It is suggested that the long latency excitation is due to the afferent volleys. It is suggested that the long latency excitation is due at least in part to disinhibition resulting from long pauses in Purkinje cell firing following their activation by climbing fibre afferents. 9. The possibility that these long latency responses have a physiological significance in relation to locomotion is discussed.
The interaction of adenosinetriphosphate and inorganic phosphate with the sodium pump in red cells.
Authors: Garay R P , Garrahan P J
Published: December 2014

1. An increase in the intracellular concentration of inorganic phosphate (Pi) reduces the rate of the Na:K exchange catalysed by the Na pump in red cells. The inhibitory effect of Pi is exerted on the maximum rate of flux, Pi having no appreciable effect on the apparent affinity of the Na pump for either internal Na or external K. The effect of Pi is exerted along a rectangular hyperbola which tends to zero as Pi tends to infinity and is half‐maximal at about 17 mM internal Pi. 2. Pi does not modify the rate of Na:Na exchange catalysed by the Na pump. 3. A reduction in the intracellular concentration of ATP reduces the maximum rate of Na:K exchange having no effect on the apparent affinity for either internal Na or external K. 4. The effects of ATP and Pi are mutually independent. 5 The lack of effect of ATP and Pi on the apparent affinity for internal Na is compatible with the idea that the affinity of the inner sites of the Na pump remains constant during a pump cycle. 6. The lack of effect of ATP on the apparent affinity for external K and the independence between the effects of ATP and Pi are difficult to explain if the only effect of ATP were its combination at a phosphorylating site. 7. The apparent affinities for K and phosphate become independent of the concentration of ATP, if it is assumed that in our experimental range the phosphorylating site is fully saturated with ATP, the rate of pumping being controlled by the state of occupation of a second non‐phosphorylating site whose affinity for ATP is much lower. 8. The lack of effect of Pi on the apparent affinity for external K seems to indicate that during Na:K exchange the conformations of the pump that predominate are endowed with a reactivity towards inorganic phosphate and have the same high affinity for K in both their phospho and their dephospho states. 9. The kinetic behaviour of the Na pump in regard to its interactions with inner and outer cations, ATP and Pi seems to indicate that, in contrast with what happens with soluble allosteric proteins, in the active transport system ligand‐induced changes in the reactivity are more important than ligand‐induced changes in affinity. In this respect therefore the Na pump behaves as an allosteric ‘V system’.
Rate of flow of digesta and electrical activity of the small intestine in dogs and sheep.
Authors: Bueno L , Fioramonti J , Ruckebusch Y
Published: December 2014

1. Spiking activity of the small intestine in the conscious dog and sheep was recorded continuously from electrodes chronically implanted on the jejunum and summed at intervals of 20 sec. The activity was related to the transit time and flow rate of intestinal contents as estimated by phenol red and by dilution of continuous marker infusions respectively. Also in some sheep the flow of digesta was measured directly from a cannula in the proximal part of the jejunum, and also by use of an electromagnetic flow meter. 2. In the fasted dog and in sheep on a normal diet the intestinal activity was characterized by a migrating myo‐electric complex comprising an irregular phase followed by a regular phase. These migrating myo‐electric complexes occurred regularly after a period of inactivity at a frequency of 15–20/24 hr. In dogs after feeding, a continuous spiking activity appeared and persisted for periods of 7–8 hr. This was associated with much higher rates of flow and shorter transit times than were observed during fasting. In sheep, continuous spiking activity could be induced by intravenous injection of 5‐hydroxytryptophan and this, similarly, was accompanied by a more rapid flow and a shorter transit time than recorded during the control period. 3. In both species the longest transit time occurred when a phenol red bolus was injected during the period of electrical inactivity. Relatively short transit times were observed when the bolus was administered just before the period of regular spiking activity. 4. When relaxation of the bowel was induced by intraperitoneal injection of hypertonic saline there was no spiking activity and the transit time for the infused solution was greatly lengthened, especially in the sheep. A noticeable flow of digestive contents persisted in the dog. 5. In the sheep the intestinal contents flowed intermittently during periods of 10–15 min and at the same frequency as the migrating myo‐electric complex. Two thirds of this flow took place in the 4–6 min immediately preceding the periods of irregular spiking activity. 6. It is concluded that in the fasted dog and in the sheep the migrating myo‐electric complex controls the pressure gradients on which the flow of intestinal contents depends. This is accomplished in the main by the prolonged phase of irregular spiking activity, and it is suggested that the regular spiking activity which follows it, though not in itself propulsive, serves as a barrier to prevent backflow of digesta into the quiescent part of the intestine. When continuous spiking activity is induced, by feeding in the dog and by injection of 5‐hydroxytryptophan in the sheep, no part of the intestine is quiescent and the transit time is shortened by the incessant irregular spiking activity.
Depression in the excitability of relay cells of lateral geniculate nucleus following saccadic eye movements in the cat.
Authors: Noda H
Published: December 2014

1. The excitability of relay cells of the lateral geniculate nucleus during a saccadic eye movement was studied in alert cats. Excitability was assessed by the firing probability of the cells in response to electrical stimulation of the optic chiasm. Modifications in the excitability were evaluated during the period following eye movements, by triggering a stimulator from potential shifts in electro‐oculogram and altering delays in the stimulus pulse. 2. The cells were classified into S and T cells, based on their response properties and the latencies to chiasmatic stimulation. With a saccade in a stationary patterned field, T cells showed a burst discharge, while the discharges of S cells were completely suppressed. 3. The excitability was depressed in both S and T cells for 150–200 msec after a saccade, when the eye movement occurred in light. However, the depression did not occur in complete darkness. 4. The depression occurred also in the absence of eye movement, when the patterned visual field was moved in a saccadic fashion. 5. The depression in S cells occurred during an inhibitory period. Since S cells do not receive signals on image movement directly from the retina, the depression was due to a recurrent inhibition by signals transferred through the T ganglion‐relay cell channel. 6. The depression in T cells occurred concomitantly with the burst discharge. Since the recurrent inhibition was operating less effectively during the period, the depression may be due to a phasic occlusion of the test impulse by coincident high‐rate firings in the same cell. 7. The impairment in transmission of visual information through the lateral geniculate nucleus during the period following eye movements has been discussed in connexion with a neurophysiological basis for saccadic suppression.
Calcium and sodium ions as charge carriers in the action potential of an identified snail neurone.
Authors: Standen N B
Published: December 2014

1. The soma of cell A in Helix aspersa produced action potentials in sodium‐free or calcium‐free saline, but not in saline with neither sodium nor calcium. 2. The axon had a sodium‐dependent action potential. 3. Tetrodotoxin (5 x 10(−6) M) had no effect on the overshoot except at low external divalent ion concentrations. 4. The action potential in sodium‐free saline was blocked by cobalt. 5. The slope of action potential overshoot against sodium concentration in the presence of 10 mM calcium was 10.5 mV/tenfold change. That of overshoot against calcium concentration in the presence of 75 mM sodium was 22 mV/tenfold change. 6. In sodium‐free saline the slope of overshoot versus calcium concentration was 27 mV/tenfold change. 7. It is concluded that calcium is an important charge carrier in the action potential of cell A.
Synaptic potentials recorded from neurones of the submucous plexus of guinea‐pig small intestine.
Authors: Hirst G D , McKirdy H C
Published: December 2014

1. Intracellular recordings have been made from neurones lying in the submucous plexus of guinea‐pig mid small intestine. 2. Most neurones in this plexus receive an extensive excitatory input which could be abolished by tubocurarine. 3. A proportion of neurones also received a single inhibitory input which was activated by transmural stimulation. 4. Some of the characteristics of the inhibitory potentials evoked by transmural stimulation are described. 5. The observations are discussed in relation to the concept of descending excitation (Hirst, Holman & McKirdy, 1975).
Transport of deutherium oxide across isolated rat small intestine.
Authors: Bywater R J , Fisher R B , Gardner M L
Published: December 2014

1. Transport of deuterium oxide from a luminal perfusate containing 1% D2O was studied in Fisher & Gardners (1974) isolated preparation of perfused rat small intestine. 2. The kinetics of appearance of D2O in the intestinal secretion at the serosal surface fitted well to a single exponential function. 3. The steady‐state concentration of D2O in this secretion was not significantly different from the concentration in the luminal perfusate. 4. The total tissue water contained D2O at a concentration, on average, 5% lower than that in the luminal perfusate. 5. There is no evidence to suggest discrimination in transport across the intestinal mucosa between H2O and D2O. 6. The kinetics of wash‐in of D2O to intestinal secretion show that the ratio of flux out of the lumen to reflux back to the lumen is 1‐38;1.
The effect of ouabain on ion transport across isolated sheep rumen epithelium.
Authors: Harrison F A , Keynes R D , Rankin J C , Zurich L
Published: December 2014

1. The net flux of Na from the lumen to the blood side of isolated sheep rumen epithelium was reduced to zero in the third 30 min period after treatment with ouabain. 2. The net flux of K from blood to lumen side of the epithelium was reduced from 0–34 to 0–13 mumole/cm2. hr in the third 30 min period after ouabain treatment. 3. The net flux of Cl from lumen to blood side of the epithelium was reduced from 1–4 to 0–72 mumole/cm2. hr in the third 30 min period after ouabain treatment. 4. The results support the existence of a Cl pump independent of Na transport and also a K pump in sheep rumen epithelium.