bluuebunny/crossref_metadata_2025 huggingface dataset:
The inhibitory nerve fibres in the vagal supply to the guinea‐pig stomach
Authors: Campbell G.
Published: December 2014

1. A comparison was made between the inhibitory responses of the isolated atropinized guinea‐pig stomach to stimulation of the vagus and to stimulation of the perivascular nerves.

2. When low frequencies of stimulation were used, the vagi were more effective than the perivascular nerves in causing relaxation of the stomach.

3. The responses to vagal stimulation were faster in onset than were the responses to perivascular nerve stimulation.

4. Responses to perivascular nerve stimulation were abolished by low concentrations of bretylium, whereas responses to vagal stimulation were only slight reduced. Vagal responses were strongly reduced by higher concentrations of bretylium.

5. Amphetamine relieved the blockade of perivascular nerve responses which was caused by bretylium, but never relieved the reduction of the vagal responses.

6. It is argued that the vagal inhibitory fibres are not susceptible to ‘adrenergic neurone blockade’, the observed reduction of the responses being due to some other action of bretylium.

7. These differences between the vagal and perivascular inhibitory innervations of the stomach suggest that the post‐ganglionic fibres in the vagal pathway and the intramural inhibitory nerves described in the guinea‐pig caecum are similar.
The effects of alteration of blood‐volume on the concentration of circulating angiotensin in anaesthetized dogs
Authors: Hodge R. L. , Lowe R. D. , Vane J. R.
Published: December 2014

1. The blood‐bathed organ technique was used to assay the concentration of angiotensin in the blood of anaesthetized dogs.

2. Alterations of blood volume caused inverse changes of angiotensin concentration owing to changes in the rate of generation of angiotensin which are probably due to changes of the rate of renin secretion.

3. Haemorrhage of 14‐26 ml. blood/kg caused an increase of 0·25‐1·5 μg/min in the rate of generation and an increase of 0·1‐0·33 ng/ml. in the blood concentration of angiotensin.

4. The changes of angiotensin generation rate were not due to changes of renal arterial or venous pressure. They were abolished by blocking the renal nerves with lignocaine; they showed a consistent inverse correlation with central venous pressure but not with systemic arterial pressure.

5. It is concluded that changes of blood volume bring about changes of the rate of generation of angiotensin by a reflex mechanism the efferent limb of which involves the renal nerves. The afferent pathway remains to be elucidated, but the systemic baroceptors do not appear to be of primary importance.

6. The renin‐angiotensin system is important in the homeostatic response to changes of blood volume.
The isolation of hyaluronic acid and chondroitin sulphate from kidneys and their reaction with urinary hyaluronidase
Authors: Dicker S. E. , Franklin C. S.
Published: December 2014

1. Extracts of the cortex and the medulla of fresh kidneys from pigs, sheep and dogs were analysed for the presence of acid mucopolysaccharides.

2. Acid mucopolysaccharides were found in the kidneys of the three species and were evenly distributed between cortex and medulla.

3. The acid mucopolysaccharides isolated from either the medulla or the cortex of kidneys contained equal amounts of sulphated and nonsulphated fractions; these could be identified as chondroitin sulphate and hyaluronic acid, respectively.

4. Urinary hyaluronidase was isolated from urine and estimated by means of turbidity measurements.

5. Urine hyaluronidase depolymerizes the acid mucopolysaccharides extracted from either the cortex or the medulla of the kidneys from pig, sheep and dog.

6. The enzymic activity of urine hyaluronidase could be expressed as units/mg of protein. The optimum pH activity of the enzyme is at about 4·0.
Acetylcholine sensitivity of cerebellar neurones in the cat
Authors: Crawford J. M. , Curtis D. R. , Voorhoeve P. E. , Wilson V. J.
Published: December 2014

1. Cholinomimetics, acetylcholine antagonists and some other compounds of pharmacological interest were administered electrophoretically near neurones within the vermal cerebellar cortex of anaesthetized (pentobarbitone) and unanaesthetized (cerveau isolé) cats.

2. The neurones were identified by position within the cortex, spontaneous activity, and the responses to afferent and antidromic stimulation.

3. Purkinje cells, but neither granule nor basket cells, were excited by cholinomimetics, and the acetylcholine receptors had muscarinic properties. Excitation was often preceded by depression of the spontaneous firing.

4. Intravenously administered atropine and dihydro‐β‐erythroidine did not depress the synaptic excitation of cerebellar neurones evoked by impulses in mossy, climbing or parallel fibres.

5. Acetylcholine is thus unlikely to be an excitatory transmitter within the feline cerebellum, particularly at mossy fibre‐granule cell synapses, despite the presence of relatively high levels of acetylcholinesterase within mossy fibre terminals.
The relation between external potassium concentration and the relaxation rate of potassium‐induced contractures in frog skeletal muscle
Authors: Foulks J. G. , Perry Florence A.
Published: December 2014

1. Frog toe muscles and isolated fibres from frog semitendinosus muscles were allowed to develop maximum K‐contractures, and after reaching peak tension were transferred to media containing intermediate [K]0 (20‐40 m
M‐K). Under these circumstances, relaxation displayed an early rapid phase, and a subsequent slower phase whose magnitude and rate varied with [K]0. The removal of activator (calcium ion) from the sarcoplasm appears to have a potential‐dependent component.

2. The relation between relaxation and [K]0 suggests that, with progressive depolarization, membrane sites from which calcium is initially released become converted into sites which are again capable of binding calcium and removing it from the sarcoplasm.

3. The rate of relaxation of frog toe muscle after maximum K‐contractures can be either accelerated or retarded by abrupt alterations in [Ca]0 or by sudden replacement of the major extracellular anion. These effects are attributed to shifts in the relation between calcium rebinding and membrane potential.
Contractures in a superfused frog's ventricle
Authors: Lamb J. F. , McGuigan J. A. S.
Published: December 2014

1. A new perfused preparation of frog's ventricle is described, whose main advantage is that there are short diffusion distances between the cells and the washing fluid.

2. This preparation responds within a few seconds to alterations in sodium, potassium or calcium concentration, or alteration in the osmotic pressure of the bathing fluid. The speed of these alterations is consistent with the diffusional distances involved measured histologically.

3. On depolarizing the preparation with Ringer + excess potassium, tension development starts at about ‐25 mV and is still increasing at ‐8 mV (the lowest voltage studied). As in earlier experimetns in frog ventricle (Niedergerke, 1956b) and in skeletal muscle (Hodgkin & Horowicz, 1960) the relation between potential and tension is very steep.

4. Sodium free contractures (Lüttgau & Niedergerke, 1958) are very rapid in onset with this preparation. To maintain the tension developed, a rapid rate of washing is necessary for 1–2 min. After this, slow washing is sufficient. It is proposed that this is due to the leaching out of cellular sodium.

5. In fresh preparations the twitch and maximum K contracture are of similar size when stimulated at 30/min in 1–2 m
M‐Ca. With the onset of hypodynamia the twitch tension falls, but the K contracture remains unaltered. In hypodynamic ventricles the sensitivity of the twitch to the ratio [Ca]/[Na]2 declines, whereas that of the K contractures remains unaltered. Hypodynamia therefore does not affect the contractile elements themselves.

6. During the staircase phenomenon the K contracture and twitch size alter in a similar manner, as previously described by Niedergerke. The sodium free contracture, however, remains unaltered. This tends to favour the hypothesis that the staircase phenomenon is due to effects at the cell membrane rather than in the cell interior.

7. Maximum K contractures occur at a [Ca]/[Na]2 ratio of about 0·7 × 10−4 m
M−1, a figure similar to that obtained in earlier experiments (Lüttgau & Niedergerke, 1958).

8. The length—tension curves of K contractures are similar to those previously described for heart muscle, using single twitches to generate tension.

9. Application of K free solutions produced no rapid contractures in this preparation.
Effects of oxygen tension on vascular and other smooth muscle
Authors: Smith D. J. , Vane J. R.
Published: December 2014

1. The resting tension of various isolated intestinal and vascular smooth muscle preparations varied directly with the PO2 of the stream of blood used to bathe them.

2. This effect was also obtained when artificial salt solution was used and was therefore not due to circulating hormones.

3. The effect could not be antagonized by specific pharmacological antagonists such as hyoscine, phenoxybenzamine, hexamethonium, bromolysergic acid, diethylamide or mepyramine.

4. The reactions of the isolated organs to catecholamines and 5‐hydroxytryptamine (5‐HT) were increased by the higher PO2.

5. These results support the view that oxygen tension may play a major role in autoregulation of blood flow.
Hypercapnia and acetylcholine release from the cerebral cortex and medulla
Authors: Metz B.
Published: December 2014

1. The cerebral cortex and medulla of fifty‐eight anaesthetized dogs released ACh spontaneously through push‐pull cannulae after perfusion with the anticholinesterase, sarin. Hypercapnia (12% CO2) evoked a significant release of ACh above the basic spontaneous level, from the medullary and cortical areas. Hypercapnia + hypoxia (12% CO2 + 8% O2), in combination, produced an ACh release comparable to hypercapnia; hypoxia (8% O2) had no effect in any region.

2. Areas in the medullary reticular formation responsive to injections of CO2‐bicarbonate solutions (‘respiratory responsive areas’) produced a significant increase of ACh after exposure to hypercapnia or hypercapnia + hypoxia, over that obtained from either the ‘non‐respiratory responsive areas’ of the medulla or the cerebral cortex.

3. The evidence supports the concept that ACh may participate as a neurotransmitter within the cerebral cortex and medulla. Also the results would suggest but do not prove, that a cholinergic factor may be a component in respiratory control under certain circumstances, such as exposure to hypercapnia.
The role of arterial oxygen tension in the respiratory response to localized heating of the hypothalamus and to hyperthermia
Authors: Findlay J. D. , Whittow G. C.
Published: December 2014

1. Rectal temperatures, respiratory rates, arterial blood gas tensions, arterial pH and the percentage of red cells in arterial blood have been measured in the unanaesthetized ox in a cool environment (15/12° C, dry bulb/wet bulb [DB/WB]), in a hot, dry environment (40/21° C, DB/WB), during hyperthermia, during infra‐red irradiation, and during localized heating of the anterior hypothalamus. In some experiments the gas tensions and pH of mixed venous blood, and the percentage saturation of the arterial blood with oxygen, were also measured.

2. In the cool environment at a mean rectal temperature (Tr) of 38·8° C and a respiratory rate (f) of 28/min the mean values obtained from six animals were: arterial oxygen tension (Pa, O2), 93 mm Hg; arterial carbon dioxide tension (Pa, CO2) 42 mm Hg; arterial pH 7·49; arterial oxygen saturation (Sa, O2) 94%; arterial oxygen capacity (Capa, O2) 13·6 vol.%; arterial packed cell volume (P.C.V.) 29%.

3. Exposure to the hot, dry environment resulted in a small increase in the rectal temperature and thermal polypnoea, but there were no statistically significant changes in the blood gas tensions.

4. During hyperthermia statistically significant increases occurred in rectal temperature, respiratory rate, Pa, O2, pH and arterial haematocrit, while the Pa, CO2 decreased. The venous oxygen tension (Pv̄, O2) decreased also, and the tentative conclusion was made that although the oxygenation of arterial blood remained unimpaired during hyperthermia, tissue hypoxia may supervene. At very high levels of deep body temperature, some evidence for a secondary decrease in Pa, O2 was obtained.

5. Localized heating of the anterior hypothalamus caused an increase in respiratory rate and in Pa, O2. The Pv̄, O2 increased also. These changes were considered to be due to increased cardiac output and diversion of blood to the skin.

6. During infra‐red irradiation of three animals at an environmental temperature of 40/21° C, the respiratory rate increased, but the Pa, O2 decreased.
Factors determining the maximal rate of organic anion secretion by the liver and further evidence on the hepatic site of action of the hormone secretin
Authors: O'Máille E. R. L. , Richards T. G. , Short A. H.
Published: December 2014

1. Bromsulphthalein (BSP) was administered throughout the experiments at a constant rate well in excess of its excretory rate, to anaesthetized dogs in which the common bile duct had been cannulated. The maximal excretory rate of BSP into bile (BSP Tm) obtained in this manner was greatly elevated by choleresis arising from the administration of bile salt (usually taurocholate) at constant rate.

2. When bile flow rate was increased in stages by raising the taurocholate administration rate, successive increments in BSP excretion rate were obtained up to a limiting value of about 3 times the original Tm. Beyond this point further increases in taurocholate administration rate caused either no further enhancement of BSP Tm or a decline in the extent of enhancement produced at a previous lower rate of infusion.

3. When taurocholate maximal secretion was established first, the subsequent administration of BSP at progressively increasing rates led to reduction in the taurocholate secretion rate.

4. Portal infusion of secretin at constant rate (usually 0·2 units/kg body wt. min) which caused substantial increases in bile flow rate, had no effect on BSP Tm. Increases of bile flow rate of the same order following constant taurocholate infusion produced marked elevation of the BSP Tm.

5. These findings are discussed and the following conclusions reached:

(a) The limiting factor in BSP maximal transfer is the concentration of BSP in bile; increased bile flow rate at the site of BSP excretion (canaliculi) produced by bile salt administration permits an increase in the original Tm to occur without the limiting biliary concentration being exceeded.

(b) There is excretory competition between BSP and bile salt but over a certain range of bile salt administration the facilitatory effects of increased bile flow rate outweigh the inhibitory effects due to competition.

(c) Since secretin administration had no effect on BSP Tm, it is likely that the hydrocholeresis it produces originates downstream from the canaliculi, i.e. in the bile ductules or ducts; this supports previous evidence obtained in a different manner.
A Purkinje shift in the spectral sensitivity of grey squirrels
Authors: Silver Priscilla H.
Published: December 2014

1. The light‐adapted spectral sensitivity of the grey squirrel has been determined by an automated training method at a level about 6 log units above the squirrel's absolute threshold.

2. The maximum sensitivity is near 555 nm, under light‐adapted conditions, compared with the dark‐adapted maximum near 500 nm found by a similar method.

3. Neither the light‐adapted nor the dark‐adapted behavioural threshold agrees with electrophysiological findings using single flash techniques, but there is agreement with e.r.g. results obtained with sinusoidal stimuli.
Regulation of amino acid transport across intestines of goldfish acclimatized to different environmental temperatures
Authors: Mepham T. B. , Smith M. W.
Published: December 2014

1. Serosal transfers of valine and threonine were measured using everted sacs of anterior intestine taken from goldfish acclimatized to different temperatures.

2. Both valine and threonine were actively transported at incubation temperatures equal to or greater than the previous environmental temperature of the fish. There was also a positive serosal transfer of valine, but not threonine, at incubation temperatures below the previous environmental temperature of the fish.

3. The mean stable transmural potentials and amino‐acid‐evoked potentials depended both on the temperature to which the fish had been acclimatized and on the temperature at which the sacs were incubated.

4. There was a linear relation between the transmural potential and the serosal transfer of amino acid, one additional μmole of valine or threonine being transferred/2 hr incubation period for each 3 mV rise in potential. There was a less obvious correlation between the amino‐acid‐evoked potential and on serosal transfer of amino acid.

5. Acclimatization of the goldfish intestine from 8 to 25° C, assessed by changes occurring in the transmural potential and serosal transfer of amino acids, tended to stabilize both parameters, but the compensation in each case was only partial.

6. It is possible that the imbalance in transfer of valine‐like and threonine‐like amino acids, seen at incubation temperatures below the previous acclimatization temperature of the fish, has a special function in initiating the process of acclimatization to the new environmental temperature.
Gonadotrophin‐releasing activity of the median eminence at different ages
Authors: Campbell H. J. , Gallardo E.
Published: December 2014

1. Intrapituitary infusions of extracts made from the median eminence of various species at different ages were found to excite secretion of gonadotrophic hormone as shown by consequent ovulation, presumably due to their content of luteinizing hormone‐releasing factor (LRF).

2. Extracts from very immature animals (e.g. new‐born rabbits and rats; 1‐2‐month‐old calves) were found to be highly active with regard to LRF content.

3. Extracts from foetal rabbits at 20 days of gestation showed no evidence of containing LRF.

4. It is suggested that (a) LRF may have a trophic action upon the anterior pituitary gland during the pre‐puberal phase of life, and that (b) the first formation of LRF coincides with the development of the primary plexus of the pituitary portal system.
The threshold conditions for initiation of action potentials by excitable cells
Authors: Noble D. , Stein R. B.
Published: December 2014

1. The relation between the strength and duration of a just threshold stimulus (strength—duration curve) is analysed for an excitable membrane polarized uniformly and for an excitable cable polarized at one point.

2. The effect on the strength—duration curve of non‐linearity in the membrane current—voltage curve has been analysed. The strength—duration curve can be derived if the membrane current—voltage relation is independent of time. The effects of changes in the current—voltage curve with time due to the existence of a finite membrane activation time and membrane accommodation are analysed.

3. The strength—duration curve for the Hodgkin—Huxley membrane equations (Hodgkin & Huxley, 1952) is compared to that of Hill's (1936) two‐time constant model.

4. The relation between membrane current—voltage curves and those for a point‐polarized cable are derived for the steady‐state condition. The cable properties tend to linearize the current—voltage curve and to sharpen the voltage threshold.

5. The strength—duration curve for a point‐polarized cable whose membrane obeys the Hodgkin—Huxley equations is computed numerically. There is an additional large effect on the cable strength—duration curve arising from the redistribution of charge during passage of a constant current; and the resulting strength—duration curve lies within the range of curves predicted by Hill's model.

6. The conditions required for a constant charge threshold (Hodgkin & Rushton, 1946) are shown to be satisfied for short, intense stimuli applied to a cable at one point.

7. The results are discussed with reference to the experimental studies available.
The effect of amino acids on the intestinal transport of L‐ and D‐xylose in vitro
Authors: Duthie H. L. , Hindmarsh J. T.
Published: December 2014

1. The intestinal transport of
D‐xylose by sacs of everted small intestine of the hamster is partially inhibited by
L‐histidine in concentrations of 5, 10 and 20 m
M but not of 2 m
M.

2. 20 m
M concentrations of
D‐histidine and
L‐methionine also produce inhibition.

3. The inhibition is not due to an alteration in water transport or to a change in pH of the incubating medium.

4. The rate of the intestinal transport of
L‐xylose is about ¼ of the rate of
D‐xylose transport and is unaffected by a 20 m
M concentration of
L‐histidine.
The effects of urea and hydrochlorothiazide on the renal functions of rat and domestic fowl
Authors: Dicker S. E. , Eggleton M. Grace , Haslam J.
Published: December 2014

1. Rats and domestic fowls were given by stomach tube water, urea and hydrochlorothiazide, alone or in combination, in the following amounts: water, 5 ml./100 g; urea, 4 ml. of 1·5% solution + 1 ml. water/100 g; hydrochlorothiazide, 4 ml. of 1·5% urea solution + 1 ml. containing 0·1 mg hydrochlorothiazide/100 g.

2. The onset of water diuresis was faster in the fowl than in the rat. It was accompanied by a lower rate of excretion of osmotically active solutes in the former than in the latter. The rate of excretion of creatinine in rats was fourfold that in birds.

3. After urea administration, the amount of urea excreted by the fowl was about one fifth that excreted by the rats. While urea produced in rats an osmotic diuresis, with enhanced excretion of osmotically active solutes, in birds it had little effect on either urine flow or solutes excretion.

4. Administration of hydrochlorothiazide in rats produced a moderate antidiuresis accompanied by a marked increased excretion of Na and K; in birds, a small increase in the excretion of Na and K but no effect on the urine flow.

5. The differences observed between rats and birds can be attributed to the poor development of filtration rate and the absence of a well developed counter‐current system in the fowl.
The relation between the concentrations of bicarbonate and protein in the pancreatic juice in the dog
Authors: Henriksen F. W. , Worning H.
Published: December 2014

1. In accordance with the admixture theory of the exocrine pancreatic secretion a linear relation between concentrations of bicarbonate and protein in the pancreatic juice is to be expected.

2. Pancreatic juice was obtained through a Thomas cannula in three unanaesthetized dogs during digestion of a meal.

3. The actual concentration of bicarbonate and protein showed a good approximation to a straight‐line relation.

4. The calculated concentration of bicarbonate in the distal secretion was nearly identical with the highest concentration of bicarbonate obtained in the pancreatic juice after stimulation with secretin.
The effect of tiring the forearm muscles in different ways on venous blood pH, PCO2 and standard bicarbonate
Authors: Barcroft H. , Youlten L. J. F.
Published: December 2014

1. The changes in venous blood pH, pCO2 and standard bicarbonate caused by tiring the forearm by (a) rhythmic work with free circulation, (b) rhythmic work with ischaemic circulation, were determined using the Astrup apparatus.

2. For rhythmic work, opening and shutting the hand as quickly as possible for 2 min, the averaged results on six subjects were: pH fell 0·19 units; pCO2 (after full oxygenation of venous blood) rose 52 mm Hg; standard bicarbonate fell 2·9 m‐equiv/l.

3. For rhythmic work during ischaemia and accompanied by pain, the averaged results on six subjects were: pH fell 0·19 units; pCO2 (after full oxygenation of venous blood) rose 26 mm Hg; standard bicarbonate fell 6·3 m‐equiv/l.

4. These results are compared with those obtained in an earlier investigation on the effect of strong hand grips for 1 min.
The effects of acute haemorrhage on respiration in the cat
Authors: D'Silva J. L. , Gill D. , Mendel D.
Published: December 2014

1. The effect of haemorrhage on minute ventilation, arterial blood pH and end‐tidal CO2 has been investigated in cats anaesthetized with Nembutal. There was no change in minute ventilation with alteration of blood pressure above 100 mm Hg. Below this level ventilation progressively increased, the minute ventilation at 60 mm Hg being 33% above that at 100 mm Hg. The increase in minute ventilation was always associated with a fall in end‐tidal CO2 and a decrease in arterial blood hydrogen ion concentration.

2. The effects were not influenced by vagotomy, but were abolished by carotid sinus denervation or carotid body destruction. After vagotomy and sinus denervation or aortic and carotid chemoreceptor destruction, haemorrhage resulted in a depression of respiration.

3. The changes in arterial blood pH and end‐tidal CO2 did not occur without a change in minute ventilation.

4. When the changes in arterial blood pH during haemorrhage were prevented by administration of CO2 there was a marked increase in minute ventilation. It is concluded that the respiratory drive to respiration in the cat during haemorrhage is controlled mainly by carotid body chemoreceptors and that the resultant alkalaemia decreases the respiratory response.
Algebraical summation in synaptic activation of motoneurones firing within the ‘primary range’ to injected currents
Authors: Granit R. , Kernell D. , Lamarre Y.
Published: December 2014

1. In intracellular studies of cat lumbar motoneurones constant synaptic stimuli such as stretch, contraction or a high‐frequency stimulation of a cut afferent nerve have been superimposed on firing in response to injected currents.

2. As long as the slope relating spike frequency to injected current remained constant, which by definition is the ‘primary range’ of firing, algebraical summation of superimposed synaptic stimulation prevailed. Added quantities in these experiments were then between 2·0 and 56·2 impulses/sec for excitation, between ‐2·8 and ‐21·8 impulses/sec for inhibition.

3. Data were obtained correlating firing rates with amount of synaptic potential and current respectively.

4. Theoretical implications are dealt with in the Discussion.
The effect of orientation on the visual resolution of gratings
Authors: Campbell F. W. , Kulikowski J. J. , Levinson J.
Published: December 2014

1. Visual resolving power is known to be poorer for objects oriented obliquely as compared with horizontal and vertical orientations. Experiments were designed to evaluate the optical and neurophysiological factors involved.

2. Gratings with a sinusoidal light distribution were generated on the face of an oscilloscope. Spatial frequency and contrast could be varied while keeping the mean luminance of the grating constant.

3. Using a homatropinized eye with an artificial pupil and carefully corrected refraction, high resolution in the vertical and horizontal meridians as compared with the oblique meridians was found for gratings ranging in spatial frequency from 1 to 35 c/deg.

4. It is concluded from the similar behaviour of low and high frequency gratings that neither focus errors nor optical aniseikonia can account for these findings.

5. Additional proof that optical factors cannot significantly account for these preferred directions of resolution was obtained by forming interference fringes directly on the retina using a neon—helium laser as a coherent light source.

6. Similar orientational changes in resolution were found by by‐passing the dioptrics with interference fringes. It is concluded that the effect is due to some orientational inequality in the visual nervous system.
Rod and cone independence in the electroretinogram of the dark‐adapted monkey's perifovea
Authors: Gouras P.
Published: December 2014

1. Rod and cone interaction has been studied in the vitreal and intraretinal e.r.g. in the perifovea of the dark‐adapted Rhesus monkey retina.

2. Rod and cone responses can be completely isolated in the e.r.g. using dim, monochromatic stimuli. The threshold cone response begins at about 50 msec whereas that of the rods begins at 150 msec. There is no detectable interaction between these two responses.

3. By comparing the e.r.g. with ganglion cell responses, it is concluded that the time delays and interactions of rod and cone signals arriving at the ganglion cell layer are determined respectively before and after the origin of the b‐wave.
The contrast sensitivity of retinal ganglion cells of the cat
Authors: Enroth-Cugell Christina , Robson J. G.
Published: December 2014

1. Spatial summation within cat retinal receptive fields was studied by recording from optic‐tract fibres the responses of ganglion cells to grating patterns whose luminance perpendicular to the bars varied sinusoidally about the mean level.

2. Summation over the receptive fields of some cells (X‐cells) was found to be approximately linear, while for other cells (Y‐cells) summation was very non‐linear.

3. The mean discharge frequency of Y‐cells (unlike that of X‐cells) was greatly increased when grating patterns drifted across their receptive fields.

4. In twenty‐one X‐cells the relation between the contrast and spatial frequency of drifting sinusoidal gratings which evoked the same small response was measured. In every case it was found that the reciprocal of this relation, the contrast sensitivity function, could be satisfactorily described by the difference of two Gaussian functions.

5. This finding supports the hypothesis that the sensitivities of the antagonistic centre and surround summating regions of ganglion cell receptive fields fall off as Gaussian functions of the distance from the field centre.

6. The way in which the sensitivity of an X‐cell for a contrast‐edge pattern varied with the distance of the edge from the receptive field centre was determined and found to be consistent with the cell's measured contrast sensitivity function.

7. Reducing the retinal illumination produced changes in the contrast sensitivity function of an X‐cell which suggested that the diameters of the summating regions of the receptive field increased while the surround region became relatively ineffective.
Mean carbon dioxide tension in the brain after carbonic anhydrase inhibition
Authors: Brzezinski J. , Kjällquist Å. , Siesjö B. K.
Published: December 2014

1. Measurements of the CO2 tensions in arterial blood, in blood from the superior sagittal sinus, in cisternal cerebrospinal fluid, and on the surface of the cerebral cortex were made in spontaneously breathing anaesthetized cats and rats after inhibition of carbonic anhydrase with acetazolamide in doses of 50‐150 mg/kg.

2. After an acetazolamide dose of 50 mg/kg in cats there was a mean increase in the c.s.f. CO2 tension of 8 mm Hg; after a dose of 100 mg/kg the corresponding mean increase was 13 mm Hg.

3. Since the CO2 tension measured in venous blood was only moderately influenced by the acetazolamide, the normal PCO2 difference between venous blood and c.s.f. was markedly reduced. The apparent arterial CO2 tension, i.e. the CO2 tension measured in vitro, always changed to the same extent as the c.s.f. CO2 tension.

4. The findings were confirmed by measurements of the CO2 tension on the surface of the cerebral cortex, and by measurements of the blood and c.s.f. CO2 tensions in the rat.

5. It is concluded that the mean tissue CO2 tension of the brain can be estimated from the measured arterial CO2 tension, even under conditions of carbonic anhydrase inhibition.
The lymphatic and venous pathways for the outflow of thyroxine, iodoprotein and inorganic iodide from the thyroid gland
Authors: Daniel P. M. , Plaskett L. G. , Pratt O. E.
Published: December 2014

1. Baboons and cats were given radioactive iodine and, at varying times after the injection, samples of thyroid and non‐thyroid lymph and of thyroid venous and peripheral venous blood were collected. The radioactive material in these samples was separated by paper chromatography or by differential precipitation and solvent extraction into three main fractions: inorganic iodide, iodoamino acid iodine and high molecular‐weight material (retained at the origin of chromatograms and not extractable by butanol or ethanol). The latter was considered to be iodoprotein.

2. Thyroxine was the main component of the radioactive iodoamino acid iodine in thyroid lymph, in thyroid venous and in peripheral blood. The concentration of thyroxine radioactivity in the thyroid lymph was several times greater than that in either thyroid venous or peripheral blood plasma, both before and after giving thyroid stimulating hormone.

3. An unidentified thyronine compound that was frequently found in thyroid lymph and also in blood samples contained an appreciable proportion of the radioactive iodine. This substance was probably a metabolite of one of the iodothyronines. In addition, iodotyrosines probably accounted for up to 4% of the radioactivity in the lymph and blood samples but radioactive triiodothyronine could not be detected with certainty.

4. In some experiments lymph was obtained from the cervical lymph trunk at a considerable distance from the thyroid gland, in order to avoid operative trauma to the gland. This cervical lymph contained diluted thyroid lymph but even so it contained more radioactivity in the form of iodoamino acid and iodoprotein than did peripheral blood or non‐thyroid lymph. Cervical lymph and thyroid lymph both contained less radioactive inorganic iodide than did non‐thyroid lymph.

5. The administration of thyroid stimulating hormone caused a prolonged rise in the output of radioactive iodoamino acid in the thyroid venous blood and, for a limited period, an increase in the output of radioactive inorganic iodide. At the same time there was an increase in the output of radioactive material in the thyroid lymph. The main part of the latter was due to a rise in the output of iodoprotein.

6. The lymphatics and the venous system provide alternative pathways for the outflow of iodine compounds from the thyroid gland. These pathways differ in relative importance for different iodine compounds. For iodoprotein the lymphatic pathway is the important one since there is no appreciable release of this substance into the thyroid venous blood. In the case of inorganic iodide, where there is no appreciable difference in concentration between thyroid lymph and blood, the greater flow of blood makes the venous pathway relatively more important than the lymphatic one. Thyroxine is released into the thyroid lymph in higher concentration than into the blood but the faster flow of blood makes the venous pathway relatively more important.
The inhibition of induced motor activity in transplanted fundic pouches
Authors: Brown J. C. , Johnson L. P. , Magee D. F.
Published: December 2014

1. An increase in motor activity of transplanted fundic pouches can be produced repeatedly by an alkaline buffer solution in the duodenum.

2. The response can be abolished by small doses of a cholecystokinin‐pancreozymin extract.

3. The secretagogues, olive oil and peptone will inhibit the response when introduced into the duodenum.

4. Acetylcholine in the duodenum will also inhibit the effect.

5. Hydrochloric acid will inhibit the motor activity produced by alkaline buffer in the duodenum and also resting activity of the pouches.
Effects of acetylcholine and other medullary secretagogues and antagonists on the membrane potential of adrenal chromaffin cells: an analysis employing techniques of tissue culture
Authors: Douglas W. W. , Kanno T. , Sampson S. R.
Published: December 2014

1. A method has been devised for isolating adrenal chromaffin cells (from gerbils) and maintaining them in vitro. Transmembrane potentials of these cells were recorded with intracellular micro‐electrodes.

2. Acetylcholine depolarized the chromaffin cells and so did various other substances known to evoke catecholamine secretion: nicotine, pilocarpine, histamine, 5‐hydroxytryptamine, angiotensin, and bradykinin.

3. The depolarizing effect of acetylcholine was partially antagonized by hexamethonium and was blocked completely by hexamethonium in combination with atropine.

4. Hexamethonium alone completely blocked the response to nicotine; and atropine alone abolished the response to pilocarpine. Thus both nicotinic and muscarinic receptors are present in gerbil chromaffin cells.

5. The experiments demonstrate that the various secretagogues and antagonists tested act on the plasma membrane of the chromaffin cell and raise the question whether depolarization may be an important event in stimulus‐secretion coupling.
The significance of adenosine cyclic 3′,5′‐monophosphate for the contraction of smooth muscle
Authors: Bartelstone H. J. , Nasmyth P. A. , Telford J. M.
Published: December 2014

1. The influence of adenosine cyclic 3′,5′‐monophosphate (3′,5′‐AMP) and of drugs believed to increase or decrease its concentration in the tissues has been determined on the response of vascular and uterine smooth muscles to catecholamines. Generally, drugs believed to increase tissue content of 3′,5′‐AMP potentiated the responses and those believed to decrease it depressed them.

2. The cardiovascular responses of dogs (with major vessels occluded in the chest) to carotid occlusion were potentiated by infusions of theophylline and sodium fluoride. Infusion of theophylline also potentiated the response of the occluded abdominal vessels to noradrenaline.

3. Intravenous infusions of theophylline and sodium fluoride potentiated pressor responses to catecholamines in the pithed rat. Infusions of iminazole depressed the responses in two animals and was without effect in two others.

4. In spinal cats intravenous infusions of theophylline potentiated pressor responses to catecholamines, but sodium fluoride was without effect.

5. Contractions of the isolated rat aortic strip to noradrenaline were always potentiated by sodium fluoride and by theophylline, and depressed by iminazole, when they were recorded isometrically. Theophylline always potentiated the contractions, when they were recorded isotonically but sodium fluoride was mostly, and iminazole always, ineffective.

6. 3′,5′‐AMP in concentrations from 0·1 to 20 μg/ml. potentiated the responses of the isolated rat aortic strip to noradrenaline in thirty‐eight experiments out of hundred. Concentrations from 10 to 500 μg/ml. sometimes depressed contractions recorded isometrically. In five experiments, exposure to low concentrations for 3 hr increased the resting tension of the preparation.

7. Responses to noradrenaline of uteri from oestradiol‐treated rabbits were potentiated by vasopressin and by sodium fluoride, but not by theophylline or iminazole. In progesterone‐treated animals the responses were unaffected by vasopressin and sodium fluoride, but potentiated by theophylline and depressed by iminazole. 3′,5′‐AMP was without effect on the uterine responses.

8. It is concluded that the results support the view that an increase in the tissue content of 3′,5′‐AMP potentiates the contraction of vascular and uterine smooth muscle in response to catecholamine. This view is supported by the observation that the nucleotide itself can potentiate the responses of the rat aortic strip to noradrenaline.
Release of noradrenaline by splenic nerve stimulation and its dependence on calcium
Authors: Kirpekar S. M. , Misu Y.
Published: December 2014

1. Cat spleens were perfused with Krebs bicarbonate solution using a constant flow pump. The amount of noradrenaline released during splenic nerve stimulation was measured at various frequencies. The dependence of noradrenaline release on the ionic composition of perfusion medium was also determined.

2. The effect of frequency of stimulation on the output of noradrenaline was studied in both normal and phenoxybenzamine treated cats. In normal cats, the output was 0·33 ng/stimulus at 10/sec, whereas it was 1·21 ng/stimulus at 30/sec. In phenoxybenzamine‐treated cats, the maximum output of noradrenaline of 4 ng/stimulus was obtained at 5 or 10/sec. Higher or lower frequencies of stimulation produced lower output.

3. In both normal and phenoxybenzamine treated cats, removal of calcium from the perfusing medium nearly abolished the release of noradrenaline in response to nerve stimulation. Replacement of calcium restored the noradrenaline release. The noradrenaline output/stimulus was linearly related to the log of the external calcium concentration.

4. Increasing the concentration of magnesium to (10‐20 m
M) reduced the noradrenaline output. This depressant effect of magnesium was partially antagonized by increasing the calcium concentration of the perfusion solution.

5. Divalent alkali metal earths such as barium and strontium were able to substitute for calcium. Barium substitution nearly doubled the noradrenaline output/stimulus and increased the pressor activity of the samples taken just before nerve stimulation.

6. Removal of potassium from the perfusion fluid or lowering the sodium concentration to 50 m
M had little effect on the release of noradrenaline. Lowering the sodium concentration to 37·5 m
M or less usually abolished the noradrenaline output; this effect is attributed to blockade of nerve conduction.

7. It is suggested that depolarization of post‐ganglionic sympathetic nerve terminals may increase the influx of calcium ions which in turn leads to the release of noradrenaline from the nerve terminals.
The effect of adrenaline and noradrenaline on hormone secretion and blood flow from the thyroid vein in sheep with exteriorized thyroids
Authors: Falconer I. R.
Published: December 2014

1. Emotional stimulus to the sheep has previously been shown to cause increased thyroid hormone secretion; the influence of adrenaline and noradrenaline in this process has been investigated.

2. Sheep bearing exteriorized thyroid glands on carotid artery—jugular vein loops were used. Thyroid vein blood was collected through a cannula in the jugular vein within the loop, and blood flow was measured by a plethysmographic technique.

3. 131I (50 μc) was injected intramuscularly (
I.M.) into the sheep, and 4‐7 days later the concentration of total and protein bound 131I in thyroid vein blood was measured in samples taken every 10 min for 4 hr. Intracarotid injections of 1 μg,
I.V. injections of 5 μg, or
I.V. infusions at 10 μg/min for 10 min, of adrenaline or noradrenaline were administered 1·5 hr after commencement of sampling. Blood flow from the thyroid was measured in similar experiments.

4. No significant changes in thyroid hormone secretion could be attributed to adrenaline or noradrenaline, and it was concluded that circulating catecholamines do not influence the release of thyroid hormone observed after brief emotional stimulus in the sheep.
The progressive pressor response to angiotensin in the rabbit
Authors: Dickinson C. J. , Yu R.
Published: December 2014

1. The threshold for any detectable rise of systemic arterial pressure during the prolonged intravenous administration of angiotensin to conscious rabbits was observed to be an infusion rate of 0·003‐0·006 μg.kg−1.min−1.

2. At infusion rates between threshold and 0·04 μg.kg−1.min−1 the systemic arterial pressure rose progressively over a 3‐ to 7‐day period to a plateau.

3. On stopping the angiotensin infusion the blood pressure fell rapidly back to its base line much faster than it rose during the infusion. The time taken to reach control values was approximately related to the duration of the infusion.

4. At infusion rates of about 0·05 μg.kg−1.min−1 the full rise of blood pressure developed within a few minutes, and could be sustained without change for many days. At higher rates the blood pressure diminished with time.

5. Diurnal fluctuations of blood pressure were often seen during prolonged infusions of angiotensin at low rates; and more rapid fluctuations of blood pressure over an hour or two were frequently encountered immediately after an infusion was turned off.

6. The possible role of angiotensin in producing chronic renal hypertension is discussed in the light of these observations.
The effects of a single injection of progesterone on the oestrous cycle, thyroid gland activity and uterus‐plasma concentration ratio for radio‐iodide in the rat
Authors: Brown-Grant K.
Published: December 2014

1. A single subcutaneous injection of 5 mg, 1·25 mg or 625 μg, but not 312 μg, of progesterone in oil delayed ovulation in the rat by 1 or more days, when injected at the dioestrous stage of a 4‐day oestrous cycle.

2. When ovulation was delayed in this way the expected increase in the thyroid‐serum concentration ratio for 131I was also delayed but the ratio did increase when delayed ovulation occurred.

3. A single injection of progesterone resulted in an increase in the uterus‐plasma and oviduct‐plasma concentration ratios for 131I; the increase was greatest when steroid was injected at the dioestrous stage of the cycle and was delayed and least when the steroid was given at the pro‐oestrous stage.

4. Ovulation was advanced by 1 day when progesterone was injected on the second day of dioestrus in rats showing regular 5‐day cycles; this ovulation was not accompanied by an increase in the thyroid‐serum concentration ratio. In these experiments a dose of progesterone that failed to advance ovulation produced a rise in uterus‐plasma and oviduct‐plasma ratio for 131I but no rise was seen when ovulation was induced, suggesting that oestrogen secretion had been stimulated.

5. 20α‐Dihydroprogesterone (pregn‐4‐en‐20α‐o1‐3‐one) was not effective in delaying or advancing ovulation at a dose level of 2·5 mg per rat and had no effect on the uterus‐plasma concentration ratio for radio‐iodide.

6. These results are discussed in relation to the hypothesis that the increase in thyroid gland activity at the oestrous stage of the cycle is related to the neuro‐endocrine changes that lead to ovulation.
Actions of calcium and certain multivalent cations on potassium contracture of guinea‐pig's taenia coli
Authors: Imai S. , Takeda K.
Published: December 2014

1. Using a calcium buffer system, the effect of severe calcium lack on the shape of K‐contracture of the guinea‐pig's taenia coli was studied. Under conditions of calcium lack, the initial phasic response was preferentially affected and it disappeared completely at concentrations below 10−7
M, while the ensuing tonic response persisted, though considerably diminished in size, even at the concentration of 10−8
M.

2. In calcium‐free media, various multivalent cations, which according to Frank (1962) can support the K‐contracture of a skeletal twitch muscle fibre in calcium‐free solution, augmented the remaining tonic response, but did not restore the phasic response, when it was eliminated in calcium free environment.

3. When K‐contractures were induced in normal calcium media, these cations produced, in contrast, an abolition of the phasic response together with a partial depression of the tonic phase. They also inhibited a part of the fully developed contracture. The last effect was no longer obtainable in calcium‐free media.

4. It is concluded that the phasic response and a part of the tonic response of taenia coli depend upon the extracellular calcium for their initiation (and also for maintenance of tension in the case of the latter) and that the rest of the tonic response draws on a store of ‘bound’ calcium for its evolution.