bluuebunny/crossref_metadata_2025 huggingface dataset:
The active transport of 5‐hydroxyindol‐3‐ylacetic acid and 3‐methoxy‐4‐hydroxyphenylacetic acid from a recirculatory perfusion system of the cerebral ventricles of the unanaesthetized dog
Authors: Ashcroft G. W. , Dow R. C. , Moir A. T. B.
Published: December 2014

1. An operation on dogs for the implantation of guide tubes to the lateral ventricle and cisterna magna and a method whereby the ventricular space can be repeatedly perfused in conscious and unrestrained animals are described.

2. The characteristics of a recirculatory perfusion system were examined and the bulk formation and absorption of cerebrospinal fluid and the volume of the ventricular space perfused were derived from the concentrations achieved during the infusion of inulin into the system.

3. 5‐hydroxyindol‐3‐ylacetic acid (5‐HIAA), the acid metabolite of 5‐hydroxytryptamine, and 3‐methoxy‐4‐hydroxyphenylacetic acid (HVA), the main acid metabolite of dopamine, were demonstrated to be mainly removed from cerebrospinal fluid (c.s.f.) by an active transport system localized in the region of the fourth ventricle.

4. It was possible to inhibit the active transport of these acids from cerebrospinal fluid by pre‐treating the dogs with probenecid.
Cord cells responding to fine myelinated afferents from viscera, muscle and skin
Authors: Pomeranz B. , Wall P. D. , Weber W. V.
Published: December 2014

1. Micro‐electrode recordings were made in the thoracic cord of acute spinal cats. Cells, which were located in the histologically defined lamina 5, responded both to the fine myelinated afferents from the splanchnic nerve and to afferents from the skin. Splanchnic afferents inhibit the effect of converging cutaneous inputs for periods up to 150 msec. Skin stimuli may also inhibit the effect of afferent nerve impulses from viscera. Some cells respond monosynaptically to the splanchnic afferents, others indirectly.

2. Fine myelinated afferents from gastrocnemius (group 3) stimulate lamina 5 cells which also have cutaneous receptive fields. Cutaneous and group 3 muscle afferents interact by mutual inhibition in their effect on the cells.

3. Fine myelinated afferents from skin excite lamina 5 cells. The cutaneous responses of lamina 5 cells contrast with those of lamina 4 cells in the following respects: (a) the receptive fields are larger, (b) they respond with an increased latency to Aβ afferents, (c) there is a low pressure threshold at the edge, (d) they respond to a wide range of pressure stimuli from light brush to heavy pinch applied to the centre of the receptive fields and (e) they respond to AΔ afferents.

4. Lamina 5 cells receive fine myelinated afferents either from viscera or from muscle or from skin. Lamina 4 receives large myelinated afferents from skin and lamina 6 receives large myelinated afferents from muscle. The results suggest the hypothesis that some fine myelinated afferents form a class of afferents which signal the state of tissue, and end on lamina 5 cells.
The analysis of image motion by the rabbit retina
Authors: Oyster C. W.
Published: December 2014

1. Micro‐electrode recordings were made from rabbit retinal ganglion cells or their axons. Of particular interest were direction‐selective units; the common on—off type represented 20·6% of the total sample (762 units), and the on‐type comprised 5% of the total.

2. From the large sample of direction‐selective units, it was found that on—off units were maximally sensitive to only four directions of movement; these directions, in the visual field, were, roughly, anterior, superior, posterior and inferior. The on‐type units were maximally sensitive to only three directions: anterior, superior and inferior.

3. The direction‐selective unit's responses vary with stimulus velocity; both unit types are more sensitive to velocity change than to absolute speed. On—off units respond to movement at speeds from 6′/sec to 10°/sec; the on‐type units responded as slowly as 30″/sec up to about 2°/sec. On‐type units are clearly slow‐movement detectors.

4. The distribution of direction‐selective units depends on the retinal locality. On—off units are more common outside the ‘visual streak’ (area centralis) than within it, while the reverse is true for the on‐type units.

5. A stimulus configuration was found which would elicit responses from on‐type units when the stimulus was moved in the null direction. This ‘paradoxical response’ was shown to be associated with the silent receptive field surround.

6. The four preferred directions of the on—off units were shown to correspond to the directions of retinal image motion produced by contractions of the four rectus eye muscles. This fact, combined with data on velocity sensitivity and retinal distribution of on—off units, suggests that the on—off units are involved in control of reflex eye movements.

7. The on—off direction‐selective units may provide error signals to a visual servo system which minimizes retinal image motion. This hypothesis agrees with the known characteristics of the rabbit's visual following reflexes, specifically, the slow phase of optokinetic nystagmus.
A blood‐testis barrier restricting passage from blood into rete testis fluid but not into lymph
Authors: Setchell B. P. , Voglmayr J. K. , Waites G. M. H.
Published: December 2014

1. A permeability barrier in or around the seminiferous tubules of rams has been demonstrated by studying the rate of passage of a variety of substances from blood plasma into fluid collected from the rete testis and into testicular lymph.

2. All substances studied passed readily into testicular lymph.

3. Tritiated water, urea, ethanol and bicarbonate in rete testis fluid equilibrated with blood plasma within 3 hr; Na+, K+, Rb+, Cl−, I−, CNS−, creatinine and galactose entered slowly and p‐aminohippurate (PAH), glutamate, iodinated albumin, inulin and [51Cr]EDTA did not appear in rete testis fluid at all.

4. Rubidium was excluded relative to iodoantipyrine from the testes of control and hypophysectomized rats and from rat testes heated to 37, 40, 43 and 45° C; no such exclusion was seen in testes of rats which had been given cadmium chloride 5 months earlier so as to destroy the seminiferous tubules.

5. It is suggested that this permeability barrier will regulate the access to the seminiferous epithelium of some constituents of blood plasma, isolate the germinal cells immunologically and help to maintain the concentration differences between rete testis fluid and lymph or blood plasma.
Factors influencing the time course of S‐potentials resulting from brief flashes
Authors: Naka K. I.
Published: December 2014

1. Wave forms of the S‐potential (luminosity‐type) from the tench retina were analysed with single or repetitive flashes.

2. In tench the slope of the ‘
ON’ phase was dependent on the relative flash intensity but was independent of flash duration (if it was longer than 15 msec) and the state of adaptation.

3. The slope of the ‘
OFF’ phase was a dual function of flash duration and of the state of adaptation. Light adaptation brought forth a sharp ‘
OFF’ phase, referred to as ‘cut‐off’ in this paper.

4. Temporal or spatial contrast of light and darkness was necessary for the appearance of the cut‐off which was partly responsible for complex wave forms of the L‐type potential.

5. As far as the wave form is concerned the information on the state of adaptation is well processed before it is fed into the S‐space as voltage and does not appear there as a shift in d.c. level.
Classification of inferior collicular neurones of bats in terms of responses to pure tones, frequency‐modulated sounds and noise bursts
Authors: Suga Nobuo
Published: December 2014

1. Single unit activity in the inferior colliculus of bats was studied with pure tones, FM (frequency‐modulated) sounds and noise bursts which are the most basic three components of the complex sounds produced by many different animals including man. Neurones were divided into three groups, (i) ‘generalized’ units responding to all three elements, (ii) ‘deaf’ units responding to two out of the three and (iii) ‘specialized’ units responding to only one of the three. Each of these was divided into three subgroups.

2. Three subgroups of generalized units were called ‘symmetrical’, ‘asymmetrical’ and ‘upper‐threshold’ units. The symmetrical unit had a wide excitatory area and responded to any sounds which had components falling in this area. The asymmetrical unit had a narrow excitatory area abutting on a large inhibitory one and showed different responses to FM sounds depending on the directions of frequency sweep. The upper‐threshold unit had not only an excitatory area, but also an inhibitory one. The neurone failed to respond to strong sounds, i.e. these showed upper thresholds.

3. Three subgroups of deaf units were called ‘pure tone‐deaf’, ‘FM‐deaf’ and ‘noise‐deaf’ units. The pure tone‐deaf unit did not respond to any pure tones but did respond to FM sounds and noise bursts. The noise‐deaf unit did not respond to noise bursts but did respond to pure and FM tone pulses. An FM‐deaf unit has not yet been confirmed.

4. Three subgroups of specialized units were called ‘pure tone‐specialized’, ‘FM‐specialized’ and ‘noise‐specialized’ units which responded exclusively to either pure tones, FM sounds or noise bursts, respectively. In the FM‐ and noise‐specialized units, pure tone pulses caused only inhibitory processes.

5. About 95% of neurones studied showed phasic on‐responses to sound stimuli and almost no spontaneous discharges. Only a small percent of neurones showed spontaneous discharges higher than a few impulses per second. Response patterns of some of these neurones changed with frequency, intensity, duration and repetition rate of sound stimuli. These neurones responded to any of pure tones, FM sounds and noise bursts.

6. All neurones except the symmetrical ones had inhibitory areas, in which sounds inhibited responses to excitatory ones when these are delivered simultaneously. Therefore the structure in complex sounds is very important in the excitation of these neurones.
The effect of temperature on the membrane conductance of the smooth muscle of the guinea‐pig taenia coli
Authors: Brading Alison , Bülbring Edith , Tomita T.
Published: December 2014

1. The effect of temperature on the membrane conductance of the smooth muscle of guinea‐pig taenia coli was investigated electrophysiologically, using the double sucrose gap method, and by ion‐flux determinations.

2. In the range between 19° C and 37° C, the membrane conductance increased with rising temperature and decreased with cooling (Mean Q10 about 2·5).

3. When the Cl concentration in the external medium was low (Cl− substitution with benzene‐sulphonate), the effect of changing the temperature was smaller (Mean Q10 about 1·5).

4. In muscle depolarized by excess K (27 m
M) in a solution containing low Cl, cooling repolarized the membrane and markedly increased membrane resistance.

5. The slow phases of the 42K‐ and 36Cl‐exchange were greatly slowed by cooling which did not change the rate constants of the 24Na‐efflux curve. Thus observations on the rate of exchange of ions agreed with the electrophysiological findings indicating a reduction of K‐ and Cl‐conductance of the cell membrane at low temperature.

6. The depolarization produced by lowering the external Ca‐concentration was greatest at high temperature (37° C). With cooling the membrane was repolarized and membrane resistance increased.

7. The sustained state of depolarization observed when the external Ca was replaced by Ba (2·5 m
M) at high temperature (37° C) was terminated by cooling.

8. The observations may be interpreted by the hypothesis that Ca, located at two different membrane sites, controls, independently, at the outer layer mainly Na‐ (and Ba‐) permeability and at the inner layer mainly K‐permeability, the Ca‐binding at these sites being affected by temperature in the opposite direction.
Heart capillary permeability to lipid‐insoluble molecules
Authors: Alvarez O. A. , Yudilevich D. L.
Published: December 2014

1. A study has been made, in the isolated, beating dog heart perfused with blood, of the transcapillary exchange of the following substances: [3H]water, 22Na, 86Rb, 36Cl, [14C]urea, [3H]glycerol, [3H]glucose, [14C]sucrose and [3H]inulin.

2. The method used to study the exchange was the ‘indicator diffusion’ technique. It consists in a rapid arterial injection of a mixture containing a diffusible and a non‐diffusible molecule, followed by a rapid split collection of the venous outflow, up to 30 sec. The fractional extraction, E, of the diffusible substance was obtained by comparing the relative concentrations of both tracers in injected medium and in each venous sample.

3. E for [3H]water was the highest (0·90 ± 0·3), and it did not vary with flow. All other molecules had values for E that decreased as flow increased.

4. Capillary permeability constant, P, was estimated from PS = — F ln (1 — E), in which S is the surface area of exchange and F is the blood perfusion rate. To test the validity of the equation, E was measured at different blood perfusion rates. It was found that the equation did not apply at relatively low flows for the more diffusible substances.

5. The average values of P estimated for inulin, sucrose, glucose, glycerol and urea were 0·27, 0·8, 1·0, 1·5 and 3·1 × 105 (cm/sec), respectively. The ratio P/D (in which D is the free diffusion in water constant) was the same for all these substances. This can be interpreted as showing that if pores exist in the capillary endothelium, they must be larger than 80–100 Å diameter. It is concluded that the pores could actually be the intercellular slits as previously suggested by electron microscope studies. Endothelial cell participation in the exchange appears to be small except for [3H]water.
Supraspinal control of reflex activity in renal nerves
Authors: Coote J. H. , Downman C. B. B.
Published: December 2014

1. In anaesthetized cats distension of carotid sinus inhibited renal nerve activity and intercostal‐renal nerve reflexes. The degree of inhibition was dependent on the amount of rise in sinus pressure. Intercostal‐intercostal reflexes were not inhibited.

2. Inhibition of renal nerve activity and intercostal‐renal nerve reflexes could be obtained on stimulating in the dorsal reticular formation but mainly in the ventromedial reticular formation at the level of the obex. The intercostal reflex could also be inhibited at several of these points.

3. The possibility that two inhibitory mechanisms are available is suggested, at least one projecting on to spinal reflex arcs.

4. Other ways of inhibiting renal nerve activity were shown. One was similar to that produced by single shocks to peripheral skin and muscle nerves, and the other was due to a subnormal excitability of vasomotor neurones following intense activation.
Cardiovascular responses to partial and total immersion in man
Authors: Campbell L. B. , Gooden B. A. , Horowitz J. D.
Published: December 2014

1. Short‐term cardiovascular effects of partial and total immersion of eighteen human subjects in the horizontal plane have been examined. Brachial arterial pressure, heart rate, forearm blood flow and respiratory movements were monitored simultaneously throughout the experiments. Forearm vascular resistance was calculated from the mean blood pressure and mean flow.

2. Total immersion, including the face, with breath‐holding resulted in a 61 ± 43% increase in forearm vascular resistance with an associated 29 ± 15% reduction in forearm blood flow. The concurrent bradycardia was significantly different from the heart rate changes during breath‐holding with the torso only immersed, or during total immersion with snorkel‐breathing. Neither breath‐holding in air or with only the torso immersed, nor total immersion with snorkel‐breathing produced such a diving response.

3. Breath‐holding, after several minutes of total immersion and snorkel‐breathing, produced an attenuated diving response. It therefore appears that a full diving response can be obtained only when the apnoea commences at the moment of face immersion.

4. The present investigation supports the concept that in man face immersion is an essential predisposing factor for the diving response, and cortical inhibition of the respiratory centre is important for its initiation and maintenance.
Spindle secondary ending responses elicited by stimulation of static fusimotor axons
Authors: Bessou P. , Pagès B.
Published: December 2014

1. Indirect evidence on the time course of intrafusal events associated with stimulation of a static fusimotor axon was obtained by analysis of the responses from muscle spindle secondary endings of the cat.

2. In many instances, a single impulse in a single static fusimotor axon to a muscle spindle evoked a transient increase in discharge of the secondary ending the duration of which ranged from 30 to 60 msec with a rising phase of 6–20 msec. Increasing the length of the muscle increased the slope of the rising phase and augmented the magnitude of the response.

3. Different static fusimotor axons produced different effects upon secondary endings. A single impulse in some fusimotor axons did not produce an effect while repetitive stimulation produced a smooth increase in discharge frequency. When efficacious, a single fusimotor impulse evoked approximately a similar duration of increased discharge from a secondary ending and a primary ending of the same muscle spindle. The relative magnitude of effects of a given fusimotor axon on primary and secondary endings of a spindle varied.

4. During partial curarization the changes in the discharges of a secondary ending evoked by stimulation of a single static fusimotor axon occurred in a step‐like fashion.

5. These results are interpreted as supporting the idea that static fusimotor axons induce twitch‐like contractions of intrafusal elements (nuclear chain) through the intermediary of propagated action potentials.
The mechanoreceptors of the costo‐vertebral joints
Authors: Godwin-Austen R. B.
Published: December 2014

1. Unitary recording in the thoracic dorsal roots of mechanoreceptor discharges from the costo‐vertebral joints was carried out in the cat and rabbit. Criteria for the identification of costo‐vertebral joint mechanoreceptors were established.

2. The majority of rib joint mechanoreceptors are slowly adapting and fifty‐three such receptors were studied. Five rapidly adapting receptors were also identified.

3. The responses of these receptors have been correlated with rib position and movement. The slowly adapting receptors gave a monotonic response to different rib positions. 72% showed an increase of discharge rate with displacements towards expiratory rib positions.

4. In response to manually imposed rib movements slowly adapting joint mechanoreceptors gave a dynamic response which was directly related to the velocity of the movement and adapted within 2 sec. The movements of breathing produced a corresponding alteration of the discharge frequency of the slowly adapting receptors.

5. Slowly adapting receptors were localized to the capsule of the costo‐transverse joint by probing. They responded to increased intra‐articular pressure with an increase of discharge rate and were silenced by intra‐articular lignocaine, 0·4%.

6. Rapidly adapting joint mechanoreceptors responded to rib movement with a brief burst of discharges.

7. The rib joint mechanoreceptors signal rib joint position, and the direction and velocity of rib movement. It is suggested that these afferent discharges provide the basis for the perception of respiratory movements of the chest. The significance of these receptors to the ‘sense of effort’ resulting from a resistance to breathing is discussed.
On the existence of neurones in the human visual system selectively sensitive to the orientation and size of retinal images
Authors: Blakemore C. , Campbell F. W.
Published: December 2014

1. It was found that an occipital evoked potential can be elicited in the human by moving a grating pattern without changing the mean light flux entering the eye. Prolonged viewing of a high contrast grating reduces the amplitude of the potential evoked by a low contrast grating.

2. This adaptation to a grating was studied psychophysically by determining the contrast threshold before and after adaptation. There is a temporary fivefold rise in contrast threshold after exposure to a high contrast grating of the same orientation and spatial frequency.

3. By determining the rise of threshold over a range of spatial frequency for a number of adapting frequencies it was found that the threshold elevation is limited to a spectrum of frequencies with a bandwidth of just over an octave at half amplitude, centred on the adapting frequency.

4. The amplitude of the effect and its bandwidth are very similar for adapting spatial frequencies between 3 c/deg. and 14 c/deg. At higher frequencies the bandwidth is slightly narrower. For lower adapting frequencies the peak of the effect stays at 3 c/deg.

5. These and other findings suggest that the human visual system may possess neurones selectively sensitive to spatial frequency and size. The orientational selectivity and the interocular transfer of the adaptation effect implicate the visual cortex as the site of these neurones.

6. This neural system may play an essential preliminary role in the recognition of complex images and generalization for magnification.
The responses of cortical neurones to monoamines under differing anaesthetic conditions
Authors: Johnson E. S. , Roberts M. H. T. , Straughan D. W.
Published: December 2014

1. Noradrenaline, isoprenaline, 5‐hydroxytryptamine and acetylcholine have been applied into the environment of single neurones in the cat cerebral cortex by micro‐iontophoresis. The influence of anaesthesia on the neuronal responses to these drugs was studied.

2. In general, excitation of neurones by noradrenaline occurred commonly in both unanaesthetized encéphale isolé (48%) and N2O‐halothane anaesthetized preparations (57%) while depressions were less frequent (24 and 20% respectively). The picture differed markedly in barbiturate anaesthetized animals where excitation was uncommon (12%) and the majority of cells (59%) was depressed by noradrenaline. Although fewer cells were studied, similar differences were obtained with isoprenaline and 5‐hydroxytryptamine for the three types of preparation. In sharp contrast, the vast majority of cells was excited by acetylcholine in each of the preparations: encéphale isolé 84%; N2O‐halothane 92%; barbiturate anaesthetized preparations 85%.

3. The differing neuronal responses observed in these experimental situations were not the result of variations in the depth of anaesthesia.

4. Although the depths at which neurones were encountered within the cortex did not differ in N2O‐halothane and encéphale isolé preparations, significantly more cells were found in deeper layers of cortex in barbiturate preparations. The proportion of cells excited or depressed by noradrenaline was generally similar at each depth in the three preparations used.

5. The distribution of rates of cell firing was strikingly similar in each preparation, and most of the cells studied had frequencies below 10/sec.

6. The direction in which a cell responds to noradrenaline is mainly determined by the type of anaesthetic used, and not by the depth of anaesthesia, the rate of cell firing, or cell depth within the cortex. This suggests important differences in the central pharmacology of halothane and barbiturates.
Characteristics of knee joint receptors in the cat
Authors: Burgess P. R. , Clark F. J.
Published: December 2014

1. The conduction velocities of 278 posterior articular nerve fibres studied in dorsal root filaments ranged from 10 to 110 m/sec. The conduction velocities were distributed similarly to posterior articular nerve fibre diameters determined histologically.

2. Two hundred and nine fibres were slowly adapting. Of these, 140 responded only at both marked flexion and marked extension, forty‐seven responded only during flexion and twelve only during extension. Four slowly adapting fibres were activated specifically at intermediate joint positions. Outward twist of the tibia (abducting the foot) enhanced the discharge of most slowly adapting joint fibres.

3. Two rapidly adapting receptor types were noted. Pacinian corpuscle‐like receptors (fourteen fibres) responded transiently to joint movement in any direction regardless of initial position. Phasic joint receptors (thirty fibres) were rapidly adapting at most joint positions but could give a low rate sustained discharge when strongly stimulated.

4. Six slowly adapting posterior articular nerve fibres responded to succinylcholine, suggesting that they originated from muscle spindles. Spindle‐like receptors were usually tonically active at intermediate joint positions.

5. Eleven slowly conducting myelinated fibres responded only to extreme joint movement, which was probably noxious.
The release of thyroxine from serum protein in the vessels of the liver
Authors: Hillier A. P.
Published: December 2014

1. An examination has been made of the uptake of [131I]L‐thyroxine and L‐3,5,3′‐tri‐iodothyronine by the perfused rat liver.

2. With no serum in the perfusion fluid and at flow rates less than 1·5 ml./g.min the liver removes about 85–90% of the hormone passing through in the perfusion fluid. At higher flow rates, the proportion of the hormone taken up is reduced and the results suggest that half of the hormone would be removed if the perfusion fluid spent about 1 sec in the liver.

3. The percentage of the hormone extracted by the liver is not affected by variations in temperature (between 22 and 37° C) or by variations in thyroxine concentration (between 1 × 10−4 and 1 × 10−1 μg/ml.).

4. Accumulated radioactive thyroxine is released only slowly into the perfusion fluid. The rate is doubled by perfusion with solutions containing 10% serum.

5. With serum present in the perfusion fluid the uptake of thyroxine can be resolved into two distinct components. A small proportion is taken up very rapidly and a large proportion very slowly. It is suggested that the rapid process represents uptake of free thyroxine and the slow process uptake of thyroxine released from the serum protein; the half‐time of the slow process being a measure of the rate of release.

6. The proportion of thyroxine taken up by the fast process is about 9% in solutions containing 1% serum and falls progressively at higher serum concentrations.

7. With tri‐iodothyronine the proportion of the hormone in the free state and the rate of uptake by the slow process are much greater than with thyroxine.

8. In the presence of high concentrations of thyroxine the proportion of the hormone in the free state and the rate of uptake by the slow process are both increased.

9. The rate of release of thyroxine from its binding protein is proportional to the percentage of the hormone in the free state.
A spinocerebellar climbing fibre path activated by the flexor reflex afferents from all four limbs
Authors: Larson B. , Miller S. , Oscarsson O.
Published: December 2014

1. A pathway ascending in the lateral funiculus of the spinal cord and terminating as climbing fibres in the cerebellar anterior lobe has been investigated in decerebrate cats with the cord partially transected in the third cervical segment sparing only part of the left lateral funiculus. The climbing fibre responses evoked in Purkinje cells were studied by recording from single cells and by recording the mass activity at the cerebellar surface.

2. The pathway is activated by the flexor reflex afferents from all four limbs. It ascends in an area of the lateral funiculus which partly overlaps that of the dorsolateral spino‐olivocerebellar path (Larson, Miller & Oscarsson, 1969) but also extends more ventrally. The pathway conducts relatively fast in the spinal cord and is considerably delayed in the brain stem suggesting several interneurones at that level. It projects to a narrow sagittal zone in lobule V of the pars intermedia (Fig. 4).

3. It is not known if the pathway relays in the inferior olive and it has provisionally been denoted the LF—CF—SCP (lateral funiculus—climbing fibre—spinocerebellar path).

4. The Purkinje cells were usually activated by the flexor reflex afferents from all four limbs with equal effectiveness. On natural stimulation responses were obtained on deep pressure of the limbs.

5. The pathway and its functional significance are discussed.
The uptake of thyroxine and tri‐iodothyronine by perfused hearts
Authors: Hillier A. P.
Published: December 2014

1. An examination has been made of the uptake of radioactive thyroxine and tri‐iodothyronine by the perfused hearts of the rat, rabbit, chicken and frog.

2. In all species the uptake of both hormones reaches a steady state at which the uptake of tri‐iodothyronine is 2‐4 times that of thyroxine.

3. The uptake of thyroid hormones by perfused hearts can be resolved into two distinct components—first, an initial transient process which takes up hormone and then releases it with a peak uptake at about 20 min from the beginning of perfusion and second, a basic, slow‐uptake process which takes several hours to reach a steady state and which has a greater affinity for tri‐iodothyronine. Analysis of the ‘initial uptake‐and‐release effect’ suggests that it is due to the presence of plasma thyroxine‐binding protein in the interstitial fluid of the heart.

4. These two uptake processes provide the basis for the biphasic release of thyroid hormones previously described for the rat heart.
Vascular responses of the spleen to rapid haemorrhage in the anaesthetized cat
Authors: Greenway C. V. , Stark R. D.
Published: December 2014

1. Splenic blood flow, splenic weight and arterial pressure were recorded in cats anaesthetized with sodium pentobarbitone. The mechanisms of the splenic contraction and vasoconstriction which followed rapid haemorrhage were investigated.

2. When splenic arterial pressure was decreased progressively by mechanical occlusion of the coeliac artery, the decrease in splenic blood flow was proportional to the decrease in pressure; splenic weight did not change.

3. After denervation of the spleen and adrenalectomy, haemorrhage resulted in a decrease in splenic flow which was similar to but slower than that in the innervated spleen; there was no splenic contraction. After splenic denervation, adrenalectomy and nephrectomy, haemorrhage caused a smaller decrease in flow but this response was still greater than that expected as a consequence of the reduced arterial pressure.

4. Infusions of small doses of angiotensin caused splenic vasoconstriction with little change in splenic weight. Larger doses reduced both flow and weight.

5. The splenic flow and weight responses to stimulation of the sympathetic nerves remained unimpaired when splenic blood flow was substantially reduced for 1–2 hr by haemorrhage.

6. It is concluded that after a rapid haemorrhage, the splenic contraction is due only to activity of the splenic nerves and the adrenal medullae. The decrease in splenic flow is due to the reduction in arterial pressure, activity of the splenic nerves and the adrenal medullae, and the actions of angiotensin and some unidentified vasoconstrictor substance.
Accumulation of caesium and rubidium in vivo by red and white muscles of the rat
Authors: Kernan R. P.
Published: December 2014

1. Rats were given drinking water containing either 20 m
M‐CsCl or 20 m
M‐RbCl for a period of 2 weeks. Samples of blood were then taken from the rats under anaesthetic. They were immediately centrifuged and the plasma taken for analysis. Soleus muscles, diaphragm, extensor digitorum longus, white gastrocnemius and vastus lateralis muscles were then taken from the dead animals and these and the plasma were analysed for potassium, and for caesium or rubidium by means of the flame photometer.

2. The concentrations of potassium and rubidium or caesium in the fibre water of these various muscles and in the samples of plasma water were then calculated.

3. It was found that the red muscles including soleus and diaphragm generally tended to accumulate caesium and rubidium to a greater extent than did the white muscles such as the white gastrocnemius and vastus lateralis.

4. When the concentration ratio [K]i/[K]o was divided into the ratio [Rb]i/[Rb]o for the different muscles, values of about 1·3 were obtained for the red muscles compared with values about 1·14 for white muscles.

5. When in the case of the caesium‐treated rats the ratio [K]i/[K]o was divided into the ratio [Cs]i/[Cs]o values ranged from 1·94 ± 0·12 for the red soleus to 1·08 ± 0·09 for the white gastrocnemius.

6. When these values in the caesium‐treated animals were plotted against the percentage of red fibres in the five muscle types (as obtained from the data of Sreter & Woo, 1963) the graph indicated that the white fibres had similar ionic gradients for Cs+ and K+ and that affinity for Cs+ was confined to the red fibres.

7. The membrane potential measured in soleus and extensor muscles immersed in plasma from the same animal was not significantly different from EK but was much less than ECs.

8. These results are interpreted in terms of permeability differences between the slow red fibres and white twitch fibres.
Sodium pumps in the rat small intestine in relation to hexose transfer and metabolism
Authors: Barry R. J. C. , Eggenton J. , Smyth D. H.
Published: December 2014

1. The nature of Na transfer across rat jejunum was studied by measuring the Na and fluid transfers and the electrical potential in the presence of galactose, mannose and glucose.

2. Galactose, actively transferred but not metabolized, caused an increase in the potential but no change in Na transfer or tissue resistance.

3. Mannose, not actively transferred but metabolized, caused a large increase in Na and fluid transfer without affecting the potential or tissue resistance. Similar results were obtained with glucose in the presence of phlorrhizin.

4. Galactose in the presence of mannose increased fluid and Na transfer to the level found with glucose, which is both actively transferred and metabolized.

5. These results are consistent with the view that there are two Na pumps associated with hexoses in rat jejunum, both moving Na towards the serosal side. One is an electrogenic pump, stimulated by hexose transfer, and which results in a rise in potential, and the other is a neutral pump which is stimulated by hexose metabolism and which does not affect the potential.
Antidromic responses of orthodromically identified ganglion cells in monkey retina
Authors: Gouras Peter
Published: December 2014

1. Conduction velocities of two types of on‐centre monkey ganglion cells, called phasic and tonic, have been measured by stimulating their axons in the optic tract while recording from their cell bodies in the retina.

2. The average conduction velocity of twenty‐two phasic and twenty‐seven tonic cells is 3·8±
S.D. 0·6 and 1·8±
S.D. 0·4 m/sec respectively. Since the latter, but not the former, show opponent‐colour responses, retinal signals carrying information about colour appear to be travelling in smaller axons than those not handling such information.

3. Stimulation of the optic tract elicits several graded intraretinal potentials, which are negative in the optic nerve fibre layer and positive in the inner plexiform layer. One of these potentials, which is largest near the fovea, occurs simultaneously with the antidromic impulses of tonic ganglion cells and is considered to result from extracellular current generated by these cells.

4. Stimulation of the optic tract suppresses the orthodromic responses of ganglion cells, more for phasic than for tonic ones. This suppression is only observed after a cell is antidromically driven and is considered most likely due to a transient hyperpolarization of the cell's membrane potential following an impulse.
The use of dietary‐restricted rat intestine for active transport studies
Authors: Neale R. J. , Wiseman G.
Published: December 2014

1. The effect of dietary restriction (sufficient to produce a loss of about 32% of initial body weight) on intestinal active transport has been studied in the rat by the use of sacs of everted mid‐small intestine. Eight
D‐sugars, four
L‐sugars and two
D‐amino acids were employed.

2. Dietary restriction enhanced the normally occurring active transport of
D‐galactose, 3‐O‐methyl‐D‐glucose and
D‐methionine. In addition, sacs of dietary‐restricted small intestine were able to concentrate in the serosal fluid
D‐fucose,
D‐xylose and
D‐histidine, which sacs of normal rat intestine could not do. The final (1 hr) serosal/mucosal concentration ratios produced for these actively transported substances were independent of net water movement.

3. Sugars which were not concentrated in the serosal fluid of sacs of fully fed or dietary‐restricted intestine were
D‐arabinose,
D‐fructose,
D‐glucosamine,
D‐mannose,
L‐arabinose,
L‐fucose,
L‐sorbose and
L‐xylose.

4. The characteristics of
D‐fucose and
D‐xylose active transport suggest that they are transported by the mechanism which actively transports
D‐glucose. The comparatively low content of
D‐glucose in dietary‐restricted intestine, compared with fully fed intestine, may be part of the explanation for observable active transport of
D‐fucose and
D‐xylose by dietary‐restricted sacs.

5. Thinning of the intestinal wall is believed not to be the cause of the enhanced active transport found during dietary restriction.

6. The results show that dietary‐restricted rat small intestine may, at times, be more useful than fully fed rat small intestine in the study of intestinal active transport.
A study of the action of picrotoxin on the inhibitory neuromuscular junction of the crayfish
Authors: Takeuchi A. , Takeuchi Noriko
Published: December 2014

1. The effect of picrotoxin on the neuromuscular junction of the crayfish (Cambarus clarkii) was investigated. The potential changes were recorded intracellularly and extracellularly with micro‐electrodes. The membrane conductance of the muscle fibre was also measured.

2. Picrotoxin depressed the amplitudes of the inhibitory junctional potentials and the potential changes produced by iontophoretically applied γ‐aminobutyric acid (GABA), but had no appreciable effect on the excitatory junctional potentials and the potential changes produced by
L‐glutamate.

3. The presynaptic action of GABA and the neural transmitter was depressed by picrotoxin. The presynaptic action of β‐guanidinopropionic acid was also depressed by picrotoxin.

4. The increase in the membrane conductance produced by the addition of GABA in the bath fluid was depressed by picrotoxin. The dose—response relation showed that picrotoxin depressed the conductance increase produced by GABA in a non‐competitive manner. The action of picrotoxin on the conductance increase produced by GABA was more effective in low Cl‐ solution.

5. The analysis of the dose—response curves showed that the action of picrotoxin was well expressed by the Michaelis—Menten equation, but the slope of the dose—response curve of GABA was steeper than this relation. It is proposed that the conductance of the junctional membrane was increased by the combination of two molecules of GABA with a receptor, and the attachment of one molecule of picrotoxin to a specific site depressed the conductance increase.
The role of brown adipose tissue in the calorigenic effect of adrenaline and noradrenaline in cold‐acclimated rats
Authors: Himms‐Hagen Jean
Published: December 2014

1. Removal of the interscapular brown adipose tissue of the cold‐acclimated rat has no immediate effect on the calorigenic response of the rat to adrenaline or noradrenaline.

2. There is a progressive loss of the enhanced response to adrenaline and to noradrenaline during the 4 days following removal of the interscapular brown adipose tissue from cold‐acclimated rats. There is no loss of response in sham‐operated cold‐acclimated rats.

3. Removal of the interscapular brown adipose tissue from rats living at room temperature has no effect on the calorigenic response to adrenaline or noradrenaline, neither immediately afterwards nor 2‐4 days later.

4. It is concluded that interscapular brown adipose tissue is not the major site of oxygen consumption in the enhanced calorigenic response to adrenaline or noradrenaline in cold‐acclimated rats. However, it does play an important role in this enhanced metabolic response, probably as an endocrine gland whose secretory product modifies the ability of other tissues to respond calorigenically to catecholamines.
The effect of altered thyroid state on atrial intracellular potentials
Authors: Freedberg A. S. , Papp J. Gy. , Williams E. M. Vaughan
Published: December 2014

1. A group of rabbits was made hypothyroid by thyroidectomy, and another group was injected daily with
L‐thyroxine. After an appropriate interval respective alterations in thyroid state were confirmed by measurement of heart weight and of plasma iodine, and the animals' atria were isolated for recording.

2. Measurements were made of atrial contractions, conduction velocity, spontaneous heart rate and maximum driven frequency, and action potentials were recorded with intracellular micro‐electrodes.

3. The resting potential and action potential heights were not affected by differences of thyroid state.

4. Atrial arrhythmias are common in hyperthyroidism, rare in myxoedema. The possibility that hypothyroidism might reduce the rate of rise of the action potential, as do anti‐arrhythmic drugs, and hyperthyroidism increase it, was investigated. Although the rate of rise was slower in hypothyroid atria at some driving frequencies, this could not alone account for an anti‐arrhythmic effect, because at frequencies near the spontaneous heart rate the rate of rise of the action potential was not reduced.

5. The duration of the repolarization phase of the action potential was greatly prolonged in atria from thyroidectomized rabbits, and was shortened in hyperthyroid atria. These changes could account for a reduced probability of arrhythmias in hypothyroidism, and the converse in hyperthyroidism.
The total thermal insulation of the new‐born baby
Authors: Hey E. N. , Katz G. , O'Connell Bridget
Published: December 2014

1. One hundred and seventeen healthy new‐born babies weighing between 0·9 and 4·8 kg at delivery have been studied during the first ten days of life, and sixteen of these babies have been studied serially for 6 weeks after birth. The babies lay supine in a draught‐free environment (air speed 4‐5 cm/sec) of moderate humidity. The operative temperature was between 26 and 38° C for the babies who were studied naked.

2. Total non‐evaporative heat loss was calculated from simultaneous measurements of oxygen consumption, evaporative water loss and the concomitant change in mean body temperature.

3. Approximately 10% of the total body surface area was in contact with the mattress or floor. Conductive heat loss accounted for only about 5% of all non‐evaporative heat loss when the naked baby was lying on a thick foam mattress, but for as much as 25% when the baby was lying in a water‐jacketed chamber with a floor of clear plastic ∼ 5 mm thick.

4. Insulation to heat loss by convection and radiation varied with environmental temperature. Total specific insulation was low in a warm environment when the naked baby vasodilated, and rose by between 16 and 25% to a maximum in an environment of 31° C. It decreased significantly when the baby became physically active in environments with a temperature less than this.

5. Total specific insulation in an environment of 31° C varied with body size: it averaged 0·156° C.m2.hr/kcal in seven naked babies weighing 0·9–1·2 kg, rose to 0·190° C.m2.hr/kcal in twelve babies weighing 1·8–2·2 kg, and averaged 0·201° C.m2.hr/kcal in the thirty‐four babies who weighed over 3 kg. Tissue insulation accounted for 23% of this total specific insulation in the smaller babies, and about 28% of the total in babies weighing over 3 kg.

6. Clothing ten babies in a vest, napkin and long cotton nightdress increased the total specific insulation by an average of 0·23° C.m2.hr/kcal.
The partition of nutrients between mother and conceptuses in the pregnant rat
Authors: Frazer J. F. D. , Huggett A. St G.
Published: December 2014

1. Diminishing the food supply to pregnant rats was associated with a subnormal degree of foetal loss among the larger litters, but a greatly lowered intake increased this foetal loss.

2. Whether the food intake was lowered, normal or increased, the increase in conceptus weight over the last half of pregnancy could be related to the total maternal weight increase over this period by the formula y = ¼x + 4·5n, where n was the number of foetuses.

3. With values of x below 20 g, this no longer held, but y never fell below 4·5 (n + 1).

4. It is concluded that Hammond's theory of the partition of nutrients is confirmed, so far as mother and conceptuses are concerned, in the rat.
Further study of the role of calcium in synaptic transmission
Authors: Katz B. , Miledi R.
Published: December 2014

1. The effect of calcium on synaptic transmission has been studied by intracellular recording of pre‐ and post‐synaptic potential changes in the stellate ganglion of the squid.

2. For a given presynaptic ‘input’ (propagated spike, or local depolarizing pulse after tetrodotoxin treatment), the post‐synaptic response increases with external calcium concentration [Ca]o in a highly non‐linear fashion, indicating that transmitter output varies with more than the second power of [Ca]o over a certain concentration range.
Enzymic and physiological studies on normal and disused developing fast and slow cat muscles
Authors: Mann William S. , Salafsky B.
Published: December 2014

1. Contraction time (CT), ½ relaxation time (½ RT), maximum twitch‐tetanus tensions and the activity of two glycolytic enzymes (aldolase, pyruvic kinase) and two oxidative enzymes (malic and isocitric dehydrogenase) was studied in anterior tibialis (AT) and soleus (SOL) muscles from birth to 18 weeks of age.

2. One hind leg of each of six kittens was casted at birth and the above parameters were examined in both casted and contralateral AT and SOL at 18 weeks of age.

3. Differentiation of the contraction properties in normal developing fast muscle (AT) was closely paralleled by a marked elevation in glycolytic enzyme activity. Oxidative enzymic activity in AT and SOL was relatively unchanged from birth to 18 weeks of age, as was glycolytic activity in SOL.

4. Disuse, due to immobilization, produced atrophy in AT and SOL muscles at 18 weeks of age. The CT of the casted SOL was slightly quicker than normal while the CT of the AT was unchanged. The glycolytic and oxidative enzymic activity in both casted muscles was generally unchanged but the contralateral AT had higher glycolytic activity than normal muscles.