bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.