bluuebunny/crossref_metadata_2025 huggingface dataset:
Calculation of the membrane potential in smooth muscle cells of the guinea‐pig's taenia coli by the Goldman equation
Authors: Casteels R.
Published: December 2014

1. The intracellular K+, Cl− and Na+ concentrations in the taenia coli cells of the guinea‐pig have been estimated from the total ion content or the extrapolated intracellular tracer content, the sorbitol space and the dry wt./wet wt. ratio.

2. The exchange of K+, Cl− and Na+ was studied by following the uptake and the efflux of these ions with radioactive isotopes. The following efflux values have been calculated: mK, 4 p‐mole.cm−2.sec−1; mCl, 8·4 p‐mole.cm−2.sec−1 and mNa, 7·2 p‐mole.cm−2.sec−1. These flux values agree well with the influx values, obtained under the same experimental conditions.

3. The slowness of diffusion in the extracellular space reduces the Na flux by about 2·5% and the K flux by about 30%. A correction factor of 1·3 has to be introduced to obtain the true K flux.

4. The values for the permeability constants calculated by the constant field assumptions are for PK, 11 × 10−8 cm/sec; PCl, 6·7 × 10−8 cm/sec and for PNa, 1·8 × 10−8 cm/sec. The introduction of these values and of the ion concentrations in the Goldman equation gives a resting potential of −37 mV.

5. One of the possible explanations for the discrepancy between the measured resting potential and the calculated one, is that the resting potential of these smooth muscle cells is partly a diffusion potential and partly due to the operation of an electrogenic Na pump.
The transient electric responses of the cochlea
Authors: Stopp Phyllis E.
Published: December 2014

1. DC responses were recorded from the cochleae of pigeons, cats and guinea‐pigs. In addition to the known summating potential, transients of the same polarity were observed at the onset and termination of the tonal stimulus.

2. These transients were most noticeable in the pigeon, being least in the guinea‐pig responses.

3. They could be modified by changing the rate of rise and fall of the stimulus envelope, but not by cutting the middle ear muscles.

4. Comparable effects were seen when the ear was directly driven by a mechanical stimulus.

5. With stimuli of long duration the off‐transient was usually masked by a slow potential of opposite polarity. This deflexion appears to be an afterpotential, rather than a mechanical transient, since it is dependent on the duration of the preceding stimulus.
Quantitative aspects of gain and latency in the cat retina
Authors: Cleland B. G. , Enroth‐Cugell Christina
Published: December 2014

1. The gain of the central response mechanism and the latency of the pure central response of on‐centre ganglion cells were studied by recording from single optic tract fibres the responses evoked by slow square‐wave stimuli applied against some steady background.

2. The concept of effective flux was introduced and defined: if any portion of a stimulus extends beyond Ricco's area of complete summation, then that stimulus has an actual flux, equal to the product of its area and luminance, but it also has an effective flux which is that fraction of its actual flux which equals the actual flux of another stimulus which, when it falls entirely within Ricco's area, evokes an isobolic pure central response or has the same adaptive effect upon the central response mechanism as the first stimulus.

3. The most significant finding was that when the cell responded with a pure central response to the incremental flux (the square wave) applied against a steady effective background flux, then the gain and the latency were functions exclusively of the sum of the two fluxes (the total flux), not of the incremental or background flux as such. This shows that the level of field adaptation of the central mechanism is reset within the latent period of the response to an incremental flux.

4. Increment sensitivity curves based on isobolic suprathreshold responses all had the same slope of 0·9, when the log of the incremental flux was plotted against the log of the total flux. A plot of log latency against log total effective flux had a slope of −0·1.

5. The stimulus—response relation derived from (3) and (4) was [Formula: see text] and [Formula: see text], where R is the response amplitude, Fet the total flux, ΔFe the incremental flux and K1 and K2 are constants.
Distance effects in human scotopic retinal interaction
Authors: Westheimer Gerald , Wiley R. W.
Published: December 2014

1. Using the threshold for a small, brief test flash as a measure, the effect of light stimulation of small adjacent retinal regions of the human retina was investigated during adaptation to a medium scotopic illuminance.

2. Within about ½° of the tested area, light causes a desensitization gradually decreasing with distance. Beyond that there is a sensitizing zone which in turn gives way to an outer desensitizing zone. The sign of these effects is reversed if the peripheral stimulus is a patch of darkness.

3. Evidence for non‐linearity of summation of individual patches was found. Occlusion of each other's sensitizing influence is observed if two regions are closely adjacent to each other.
The attenuation of rod signals by backgrounds
Authors: Alpern M. , Rushton W. A. H. , Torii S.
Published: December 2014

1. The paper which precedes this investigated the nerve interaction between two flashes, λ at centre (Fig. 1a) and ϕ on the surround region (but not on the centre). The size of the inhibitory nerve signal V generated by ϕ is given by V = ϕ(ϕ + σ), where σ is the semi‐saturation constant.

2. A former paper (Alpern & Rushton, 1967) had shown that when the flash ϕ falls upon a steady background θ, V suffers attenuation in the G‐box (Fig. 1b) down to the fraction θD/(θD + θ) where θD is the eigengrau or receptor noise. Thus, in general, the nerve signal N is given by [Formula: see text].

3. This formula had only been established for a moderate range of values. In this paper we use extreme values to explore the limits of its validity. We find the equation to be true over the entire intensity range where N is measurable.

4. Six different types of experiment have been performed to test various features of the equation. For instance, if log N is plotted against log ϕ for various fixed values of θ, the curve is always the same with simply a vertical shift. And the shift is equal to log(1 + θ/θD) for all values both of θ and of ϕ.

5. The most interesting curve is the plot of log ϕ against log θ for fixed N. This is similar to the Weber—Fechner increment threshold but the criterion is not that ϕ be strong enough to be detected, but strong enough to generate an N signal just sufficient to inhibit some fixed λ flash. These curves (below the onset of saturation) are all the same except for vertical separation, and prove that the condition for flash detection is that a fixed signal, N0, is generated of size 10−5 of the maximum signal obtainable (i.e. with ϕ large and θ zero).

6. With strong backgrounds the curves of (5) above exhibit a marked saturation of the Aguilar & Stiles’ type (1954). The family of curves each with a fixed N value shows a remarkable symmetry (Fig. 8) which in fact follows from the equation in (2) above. It has nothing to do with bleached pigment, but follows from the equation in (1) above. V there cannot exceed unity, thus when scaled by the G‐box below the criterion level, further increase in ϕ will not bring improvement.
Fat metabolism in brown adipose tissue in vivo
Authors: Hardman M. J. , Hull D.
Published: December 2014

1. Noradrenaline infusions (
I.V. for 30 min) in new‐born and 1‐week‐old unanaesthetized rabbits caused a rapid and sustained rise in oxygen consumption and an increase in blood glucose, free fatty acid and glycerol concentrations. Similar changes occurred in anaesthetized 1‐week‐old rabbits.

2. A simple direct method was used to measure the net exchange of metabolites across brown adipose tissue in anaesthetized young rabbits. It was found that the brown adipose tissue of rabbits reared from birth in a thermoneutral environment and studied when their next feed was due took glucose from and released fatty acids and glycerol into the circulation.

3. Similar rabbits kept unfed for a further 48 hr in a warm environment released fatty acids and glycerol from their brown adipose tissue at a far greater rate, but the rate of glucose uptake was reduced.

4. On the other hand the brown adipose tissue of rabbits kept unfed in a cold environment (20°C) took up circulating free fatty acids as well as glucose and did not release glycerol. The brown adipose tissue of these rabbits was depleted of fat.

5. The rate of blood flow through brown adipose tissue and the exchange of all three metabolites increased fourfold during noradrenaline infusion in the three groups of rabbits.

6. It is concluded (i) that brown adipose tissue releases significant amounts of fatty acids and glycerol into the circulation and that this contribution is greatly increased with noradrenaline infusion and presumably cold exposure, and (ii) that brown adipose tissue depleted of fat produces heat by drawing free fatty acids as well as glucose from the circulation.
Oscillation in the stretch reflex arc and the origin of the rhythmical, 8–12 c/s component of physiological tremor
Authors: Lippold O. C. J.
Published: December 2014

1. A brief downward, stepwise displacement applied to the outstretched finger gives rise to a train of approximately sinusoidal movements of it, lasting often more than 1 sec. The frequency of these waves is the same, in any one subject, as that of physiological tremor.

2. The oscillations are regular in form, and bear a constant phase relation to the applied displacement; they can be summated using an averaging computer (Biomac 1000) triggered by the mechanical stimulus.

3. The oscillations are altered in the same way as is physiological tremor by a number of factors. Cooling the arm before recording lowers the frequency, warming raises it, while the application of an arterial cuff decreases the amplitude and tends to elevate the frequency. These factors have effects of similar magnitude on both the oscillations and the tremor.

It thus appears highly likely that the waves produced by a mechanical input and physiological tremor waves are due to the same process, namely oscillation in an underdamped servo‐system.

4. The oscillation is not due simply to the mechanical, die‐away resonance of the finger, because bursts of muscle action potentials can be recorded in phase with the finger movements both in the wave train evoked by the mechanical displacement and during normal tremor.

5. It is concluded that physiological tremor in the 8–12 c/s band is due to oscillation in the stretch reflex servo‐loop.
The location of the chemoreceptor controlling gastric acid secretion during hypoglycaemia
Authors: Colin‐Jones D. G. , Himsworth R. L.
Published: December 2014

1. The injection of 2‐deoxy‐D‐glucose directly into the lateral hypothalamic area of rats, but not elsewhere, caused a prompt and sustained secretion of acid by the stomach at a rate comparable to that due to insulin hypoglycaemia.

2. Acid secretion provoked by such injections, like that resulting from hypoglycaemia, could be stopped by raising the plasma glucose concentration by the intravenous infusion of glucose.

3. Unilateral intrahypothalamic injection of 2‐deoxy‐D‐glucose activated both vagi for, although cutting one vagus reduced the secretion, division of both was necessary to abolish it.

4. Gastric acid secretion evoked by a systemic stimulus (insulin‐induced hypoglycaemia or intravenous 3‐O‐methylglucose) could be prevented by inactivating the lateral hypothalamic area on each side with phenol or lignocaine.

5. It is concluded that there exists in the lateral hypothalamic area a chemoreceptor, responsive to a lack of metabolizable glucose, which can initiate and sustain the vagally mediated secretion of acid by the stomach.
The effects of nerve stimulation and hemicholinium on synaptic vesicles at the mammalian neuromuscular junction
Authors: Jones S. F. , Kwanbunbumpen Suthiwan
Published: December 2014

1. Electron micrographs of nerve terminals in rat phrenic nerve—diaphragm preparations have been studied. This has been done before and after prolonged nerve stimulation. The effectiveness of nerve stimulation has been monitored by intracellular micro‐electrode recordings from the muscle cells.

2. Characteristic changes in the form and distribution of the nerve terminal mitochondria were noted after nerve stimulation.

3. Synaptic vesicle numbers in the region of nerve terminal less than 1800 Å from the synaptic cleft were significantly greater in tissue taken 2 and 3 min after nerve stimulation, than in unstimulated preparations.

4. The long and short diameters of the synaptic vesicle profiles less than 1800 Å from the synaptic cleft were measured. Analysis of the distribution of the diameters indicated synaptic vesicles to be basically spherical structures. Estimates of synaptic vesicle volume were made from the measurements. Synaptic vesicle volume was significantly reduced in tissue taken 2 and 4 min following nerve stimulation.

5. If hemicholinium, a compound which inhibits acetylcholine synthesis, was present during the period of nerve stimulation, much greater reductions in synaptic vesicle volume occurred. Synaptic vesicle numbers in the region of nerve terminal less than 1800 Å from the synaptic cleft were also reduced, compared with unstimulated control preparations.

6. These results are regarded as support for the hypothesis that the synaptic vesicles in nerve terminals at the mammalian neuromuscular junction represent stores of the transmitter substance, acetylcholine.
Effect of asphyxia due to umbilical cord occlusion in the foetal lamb on leakage of liquid from the circulation and on permeability of lung capillaries to albumin
Authors: Adamson T. M. , Boyd R. D. H. , Hill June R. , Normand I. C. S. , Reynolds E. O. R. , Strang L. B.
Published: December 2014

1. Experiments were performed on foetal lambs, exteriorized at Caesarean section, to determine the effects of asphyxia on the leakage of liquid from the circulation and on the permeability of lung capillaries to albumin. Following a period of control observation (30–120 min) the foetus was asphyxiated by occlusion of the umbilical cord for 5‐10 min and then allowed to recover while observations were continued for a further 20–80 min.

2. Measurements were made of the lymph flow from the lungs, that had drained via the thoracic duct; of protein concentration in lymph and plasma; of arterial blood haematocrit, pH, PO2 and PCO2; and of arterial and left atrial pressures and heart rate. Human serum albumin labelled with 125I was infused intravenously during the control period and 125I count rates were followed in plasma and lymph throughout the experiment. Values for the transfer coefficient of albumin (Ė/V min−1, i.e. interstitial fluid clearance of albumin per unit of lung interstitial fluid volume) were determined during control, cord‐occlusion and post‐occlusion periods.

3. During cord occlusion arterial and left atrial pressure, haematocrit and plasma protein concentration all rose, returning to the control value by 20 min after release of cord occlusion. The haematocrit values indicated that about 9% of the blood volume was temporarily lost from the circulation. Lung lymph flow also increased, reaching a maximum in the 5 min period after release of occlusion and returning to the control level 15 min later. Values for Ė/V of albumin were at no time significantly different from those during the control period.

4. It was concluded that acute foetal asphyxia produced by umbilical cord occlusion caused an increased leakage of liquid from the circulation in general. This effect was temporary and was probably due to an increase in capillary pressure during cord occlusion. The asphyxia had no persistent effect on the permeability of lung capillaries to albumin.
Physiological and morphological identification of horizontal, bipolar and amacrine cells in goldfish retina
Authors: Kaneko Akimichi
Published: December 2014

1. Intracellular recordings were made from various types of cells in the isolated goldfish retina, and Procion Yellow was injected from the recording pipette in order to identify histologically the structure recorded. The dye diffused and stained the cell body and processes down to the fine branches.

2. S‐potentials were identified as coming from the external horizontal cells and from the internal horizontal cells. Both L‐ and C‐type S‐potentials were found in both regions, and no histological differences were seen in cells giving these two types of responses. S‐potentials recorded from the external horizontal cells showed less spatial summation than those recorded from the internal horizontal cells.

3. Bipolar cell responses consisted of sustained potentials associated with an antagonistic centre‐surround type receptive field (on‐centre, off‐surround or vice versa). Spike activity was not observed in bipolar cells.

4. Amacrine cells responded with transient depolarization both at the beginning and at the end of illumination. They sometimes showed spike activity. The amplitude of on‐ and off‐depolarization showed slight dependence on stimulus geometry but a distinct centre‐surround organization was not observed.
Effects of iontophoretically applied drugs on spinal interneurones of the lamprey
Authors: Martin A. R. , Wickelgren Warren O. , Berànek R.
Published: December 2014

1. Intracellular records were obtained from giant interneurones in the isolated spinal cord of the sea lamprey. The cells had a mean resting potential of about 75 mV and action potentials with overshoots of about 35 mV. Their input resistances, measured by passing polarizing currents through the recording pipette, were in the range 3‐7 MΩ.

2. Iontophoretic ejection of γ‐aminobutyric acid (GABA) from a micropipette placed near the surface of a cell resulted in a slight hyperpolarization, accompanied by a marked reduction in input resistance. The reversal point for the potential change was about 5 mV greater than the resting membrane potential.

3. Iontophoretic application of
L‐glutamate to the cells produced a depolarization with a decrease in input resistance much smaller than that accompanying a GABA potential of similar amplitude. The action potential amplitude was reduced by
L‐glutamate application. The reversal potential could not be determined accurately but appeared to be near zero membrane potential.

4. Glutamate application produced, in addition, a burst of inhibitory synaptic potentials in the cell, presumably by depolarizing either inhibitory presynaptic nerve terminals or nearby inhibitory cell bodies.

5. Acetylcholine (ACh) produced no detectable change in membrane resistance or potential.

6. Application of the three drugs to first‐order sensory cells in the spinal cord had no effect on their membrane properties.
The frequency of nerve impulses in single carotid body chemoreceptor afferent fibres recorded in vivo with intact circulation
Authors: Biscoe T. J. , Purves M. J. , Sampson S. R.
Published: December 2014

1. The responses of single afferent fibres of carotid body chemoreceptors to independent changes in arterial O2 and CO2 tensions and pH were studied in the cat in vivo.

2. The response curve obtained relating chemoreceptor activity to changes in arterial PO2 was similar to an hyperbola; the frequency of nerve impulses at first decreased rapidly as the Pa,O2 was raised and then more slowly. The arterial PO2 at which the slow decrease was reached varied among the different fibres; the mean level was 190 mm Hg (
S.D. ± 40 mm Hg).

3. Single chemoreceptor afferent fibres continued to discharge even when the arterial PO2 was more than 600 mm Hg.

4. The discharges of single chemoreceptor afferent fibres increased both with increasing Pa,CO2 at constant pH and Pa,O2, and with increasing arterial H+ at constant Pa,CO2 and Pa,O2.

5. It is concluded that single carotid body chemoreceptor afferent fibres of the cat can be activated in vivo by an increase in either arterial H+ or arterial PCO2 as well as by a decrease in arterial PO2.
The ontogenesis of haematoencephalic cation transport processes in the rhesus monkey
Authors: Bito L. Z. , Myers R. E.
Published: December 2014

1. This investigation was undertaken to determine the time course of development of cation transport processes between blood and the extracellular fluid compartments of the central nervous system (
C.N.S.) of the foetal rhesus monkey. The development of concentration gradients within the cerebrospinal fluid (c.s.f.) system was also studied in an attempt to gain information on regional variations in transport activities.

2. Cerebrospinal fluid samples were obtained from the lateral ventricle, the cisterna magna, the cortical subarachnoid space and the lumbar region of the spinal subarachnoid space of adult monkeys. Foetal c.s.f. samples were obtained from the cisterna magna and the frontal region of the cortical subarachnoid space. Blood samples were taken within 3‐10 min of the c.s.f. samples. The concentration of K, Mg and Ca were determined on appropriately diluted samples by atomic absorption spectrophotometry.

3. The concentrations of K, Mg, and Ca in the plasma and c.s.f.s of the adult monkey are similar to those of other mammalian species. The c.s.f./blood concentration gradients of these cations are in the same direction but generally of greater magnitude than those in non‐primate mammals. The indicated [Mg] in the extracellular fluid of the adult monkey's cerebral cortex is high (more than 2 m‐equiv/kg H2O) and the [K] is low (less than 2 m‐equiv/kg H2O).

4. Accumulation of Mg into the c.s.f. system against a concentration gradient is evident in the earliest foetuses studied (50 days of intrauterine life) and by the second half of gestation the concentration gradients of this cation are similar to that of the adult.

5. In the second trimester foetus, the [K] in the cisternal fluid is near the plasma ultrafiltrate level. It then decreases gradually throughout the remainder of gestation, approximating the adult value at birth.

6. The very low [K] typical of the adult cortical subarachnoid fluid is observed by the sixth month following birth but not during foetal life or within the first few weeks of post‐natal life. This indicates that the transport processes at the cortical region of the haematoencephalic interphase do not fully develop until well after birth.

7. It is concluded that the various transport processes responsible for the elaboration and maintenance of adult type of K, Ca and Mg concentrations within the extracellular fluid compartments of the monkey
C.N.S. do not develop at the same time. This temporal dissociation provides strong evidence against any direct association or coupling between the haematoencephalic K and Mg transport systems.

8. Existence of normal cation concentration gradients between c.s.f. and blood may serve as a criterion for the normality of the (foetal) blood—brain barrier.
Luteinizing hormone releasing factor in rat hypophysial portal blood collected during electrical stimulation of the hypothalamus
Authors: Harris G. W. , Ruf K. B.
Published: December 2014

1. Ovulation was induced in Nembutal‐blocked pro‐oestrous rats by electrical stimulation of the hypothalamus.

2. The same type of electrical stimulation was applied during the collection of hypophysial portal blood.

3. Pooled hypophysial portal plasma from donors in pro‐oestrus, oestrus and met‐oestrus was assayed for ovarian ascorbic acid depleting (OAAD) activity.

4. Electrical stimulation of the hypothalamus increased the OAAD activity, believed to be due to luteinizing hormone releasing factor (LRF), in pro‐oestrus and met‐oestrus, but not in oestrus.

5. It is concluded that the hypothalamic nerve fibres responsible for releasing LRF into the hypophysial portal vessels are depleted of their store of this releasing factor, or are refractory to electrical stimulation, during oestrus.
Changes in the blood volume of the rabbit with age
Authors: Little R. A.
Published: December 2014

1. The changes in blood haemoglobin concentration, great vessel haematocrit value, red cell volume, plasma volume and total blood volume have been studied in rabbits from birth to 4 months of life.

2. The plasma volumes were measured with [131I]human serum albumin and/or rabbit serum [14C]albumin. Red cell volumes were measured with [51Cr]‐rabbit red blood cells. Blood volumes were also calculated from carbon clearance curves.

3. The haemoglobin concentration and the great vessel haematocrit value fell during the first 11 days of life. The great vessel haematocrit value was then not significantly different from the value at 4 months; whereas the haemoglobin concentration fell further until 22 days, when it started to rise towards the concentration at 4 months.

4. The true plasma volume could not be accurately measured during the first 48 hr of life by the injection of labelled albumin since it rapidly equilibrated with an extravascular albumin space. As the ratio of the whole body haematocrit to the great vessel haematocrit (Fcells) did not appear to change with age the plasma volume at this time was best obtained by calculation from the red volume and corrected great vessel haematocrit.

5. The blood volume fell significantly during the first 4 months of life due to significant falls in the red cell and plasma volumes.
The effect of temperature in the range 0–35° C on the resting tension of frog's muscle
Authors: Hill D. K.
Published: December 2014

1. It has long been known that a resting muscle shows a reversible ‘rubber‐like’ response to a change of temperature: it develops tension when warmed and this reverses on cooling. It was recently shown (Hill, 1968) that part of the resting tension is due to a weak interaction between the sliding filaments, and it was suggested that the rubber‐like tension might be caused by the same process rather than by some inert structural component. Further information on this point has now been obtained from some observations on the effect of temperature on isometric tension at temperatures not far below the level (28–35° C) at which a heat contracture is produced.

2. The temperature of a frog's sartorius was changed by moving it up and down in a vessel containing Ringer solution at two different temperatures. The temperature in one part was maintained constant in the range 0–20° C and in the other at 5‐35° C. The changes was 90% complete in 12 sec.

3. From 0° up to about 23° C the tension developed per 1° C rise of temperature (ΔP/ΔT) is almost constant, but as the temperature approaches the level at which a heat contracture appears the value of ΔP/ΔT rises steeply. This behaviour indicates that the tension in question has an ‘active’ rather than a ‘passive’ origin, and this view is supported by other evidence from experiments with muscles in hypertonic solutions, described in the next paper.

4. It was found that the temperature at which a muscle goes into a heat contracture depends on the length at which it is set; the critical temperature is lower in an extended muscle. A shortened muscle at a temperature not far below the critical value will therefore produce a contracture when it is stretched.
Comparison of the reflex vasomotor responses to separate and combined stimulation of the carotid sinus and aortic arch baroreceptors by pulsatile and non‐pulsatile pressures in the dog
Authors: James Jennifer E. Angell , Daly M. de Burgh
Published: December 2014

1. In the anaesthetized dog the carotid sinuses and aortic arch were isolated from the circulation and separately perfused with blood by a method which enabled the mean pressure, pulse pressure and pulse frequency to be varied independently in each vasosensory area. The systemic circulation was perfused at constant blood flow by means of a pump and the systemic venous blood was oxygenated by an extracorporeal isolated pump‐perfused donor lung preparation.

2. When the vasosensory areas were perfused at non‐pulsatile pressures within the normal physiological range of mean pressures, the reflex reduction in systemic vascular resistance produced by a given rise in mean carotid sinus pressure was significantly greater than that resulting from the same rise of aortic arch pressure.

3. On the other hand, when the vasosensory areas were perfused at normal pulsatile pressures and within the normal physiological range of mean pressures, there was no difference in the size of the reflex vascular responses elicited by the same rise in mean pressure in the carotid sinuses and in the aortic arch.

4. Whereas the vasomotor responses elicited reflexly by changes in mean carotid sinus pressure are modified by alterations in pulse pressure, those evoked by the aortic arch baroreceptors through changes of mean pressure are only weakly affected by modifications in pulse pressure. Evidence for this was obtained from single stepwise changes of mean pressure in each vasosensory area during pulsatile and non‐pulsatile perfusion, and from curves relating the mean pressure in the carotid sinuses or aortic arch and systemic arterial perfusion pressure.

5. The vasomotor response elicited by combined stimulation of the carotid sinus and aortic arch baroreceptors was greater than either response resulting from their separate stimulation.

6. When the mean perfusion pressures in the two vasosensory areas are changed together, the curve relating mean pressure to systemic arterial pressure during pulsatile perfusion of the areas is considerably flatter than that for non‐pulsatile perfusion.

7. Increasing the pulse pressure in the carotid sinuses or aortic arch caused a decrease in systemic vascular resistance, the response elicited from the carotid sinuses being the larger.

8. Altering the phase angle between the pulse pressure waves in the carotid sinuses and aortic arch had no effect on systemic vascular resistance.

9. In both vasosensory areas, increasing the pulse frequency caused a reduction in systemic vascular resistance.
The site of action of nerves in the pulmonary vascular bed in the dog
Authors: Daly I. de Burgh , Ramsay D. J. , Waaler B. A.
Published: December 2014

1. The effects of stimulation of the thoracic vagosympathetic nerve or upper thoracic sympathetic chain on the pulmonary vascular resistance have been studied in atropinized, isolated, ventilated lung lobes under various conditions of pulmonary circulation perfusion. Throughout the nerve‐stimulation tests bronchial circulation perfusion was maintained or temporarily interrupted.

2. The pulmonary vascular resistance increase evoked by nerve stimulation (a) occurred in the absence of tidal air changes; (b) did not consistently differ during predominantly ‘sluice’ and ‘non‐sluice’ conditions of pulmonary circulation perfusion; (c) was approximately one and a half times greater during constant pressure than during constant volume inflow perfusion of the pulmonary circulation; and (d) was greater during reverse than during forward perfusion.

3. In lung lobes perfused in either direction at constant volume inflow nerve stimulation produced an increase in inflow pressure and a diminution in total lung blood volume reflected by a temporary increase in blood outflow.

4. In lung lobes in which neither the pulmonary nor the bronchial circulations were perfused and the capillaries were completely blocked by high intratracheal pressures, thus isolating the pulmonary arterial system from the venous system, nerve stimulation produced a diminution in the blood volume of both systems.

5. Nerve stimulation produced a rise in bronchial arterial pressure in the absence of pulmonary circulation perfusion.

6. Further evidence is adduced that pulmonary vasomotor nerve responses do not depend upon the transfer of transmitter substances from the bronchial to the pulmonary circulation.

7. The possible significance of these observations in relation to the site of action of pulmonary vasomotor nerves is discussed.
PO2, PCO2 and pH levels in the umbilical and uterine blood of the mare and ewe
Authors: Comline R. S. , Silver Marian
Published: December 2014

1. Foetal and maternal blood gas tensions and pH levels have been investigated in the mare and the ewe during late pregnancy under a number of experimental conditions.

2. Observations were made on anaesthetized animals with the foetus in utero. Simultaneous blood samples were withdrawn from a maternal artery and uterine vein, and from the two umbilical vessels, through catheters inserted at the beginning of each experiment.

3. At normal maternal arterial PO2 (80–110 mm Hg) the umbilical venous PO2 of the foal was very high (49 mm Hg) and the PO2 in the umbilical artery (33 mm Hg) was similar to that in the umbilical vein of the lamb (34 mm Hg).

4. The PO2 difference between the umbilical and uterine venous blood was 17 mm Hg in the ewe but only 4 mm Hg in the mare. The corresponding PCO2 gradients were about one quarter of those for oxygen in both species.

5. When the maternal arterial PO2 was raised above 100 mm Hg both uterine venous and umbilical PO2 increased in the mare, and the gradient between the uterine vein and umbilical vein was reversed, whereas little change occurred in the corresponding vessels of the ewe.

6. Alterations in maternal arterial PCO2 were associated with concomitant changes in the blood in the other three vessels but in both species the PCO2 difference between uterine and umbilical venous blood appeared to remain constant.

7. Foetal blood pH levels followed those of the mother if the changes in the maternal blood were of respiratory origin. The effects of prolonged changes in maternal pH on foetal levels were investigated in the ewe. Foetal pH remained unchanged during maternal alkalaemia (pH 7·7) induced by Na2CO3 infusions, but increased during a similar rise in maternal pH induced by hyperventilation.

8. The present observations have been compared with findings on the conscious animal and possible explanations for the differences between the two species are discussed.
The mechanism of the cardio‐acceleration elicited by electrical stimulation of the parahypoglossal area in the cat
Authors: Calaresu F. R. , Henry J. L.
Published: December 2014

1. In chloralosed and in decerebrated cats localized electrical stimulation of a discrete parahypoglossal area (including the nucleus intercalatus and a discrete neighbouring region ventrolateral to the hypoglossal nucleus) elicited cardio‐acceleration and arterial hypertension, either singly or together.

2. The cardio‐acceleratory response was decreased by intravenous administration of propranolol (2 mg/kg). In another group of experiments the response was abolished by acute bilateral cervical vagotomy but it was observed to return partially when stimulation was applied one or more hours after vagotomy. The hypertensive response was not affected by propranolol or by vagotomy.

3. Evoked electrical activity with a latency of 3‐10 msec was recorded from pre‐ and post‐ganglionic sympathetic cardio‐acceleratory nerves during stimulation of this region.

4. These findings demonstrate the existence of a discrete medullary area which controls heart rate by activation of a sympathetic pathway and inhibition of a parasympathetic pathway.
Contributions of the sodium pump and ionic gradients to the membrane potential of a molluscan neurone
Authors: Gorman A. L. F. , Marmor M. F.
Published: December 2014

1. The membrane potential of the gastro‐oesophageal giant neurone of the marine mollusc, Anisodoris nobilis, was examined during changes of temperature and of the ionic medium.

2. The response of the membrane potential to rapid changes in the external K concentration was prompt, stable, and reversible up to 200 m
M‐K, and was independent of the external Cl concentration.

3. Warming the cell produced a prompt hyperpolarization that was approximately 10 times greater than predicted by the Nernst or constant field equations. Electrogenic activity of the Na—K exchange pump was shown to be responsible for this effect.

4. At temperatures below 5° C, the relationship between the membrane potential and the external K concentration could be predicted by a constant field equation.

5. At temperatures above 5° C, the membrane potential could not be predicted by the constant field equation except after inhibition of the electrogenic Na pump with ouabain or the reduction of internal Na.

6. Inhibition of the electrogenic Na pump by low external K concentrations was dependent upon the external Na concentration.

7. It is concluded that the membrane potential is the sum of ionic and metabolic components, and that the behaviour of the ionic component can be predicted by a constant field type equation.
The glycogenolytic response to stimulation of the splanchnic nerves in adrenalectomized calves
Authors: Edwards A. V. , Silver Marian
Published: December 2014

1. The effects of stimulation of the peripheral ends of one or both splanchnic nerves have been investigated in adrenalectomized calves at different ages.

2. During the first 24 hr after birth unilateral splanchnic nerve stimulation led to a prompt rise in the plasma glucose concentration and this response was more than doubled when both nerves were stimulated simultaneously. Under these latter conditions hyperglycaemia was found to be associated with a measurable loss of glycogen from the liver.

3. Both the glycogenolytic and hyperglycaemic effects of splanchnic stimulation became more pronounced with age; at 5 weeks of age liver glycogen was depleted by approximately 2/3 and plasma glucose raised by about 200 mg/100 ml. after stimulation of the right splanchnic nerve for 9 min.

4. Splanchnic stimulation also caused a rise in mean arterial blood pressure and haematocrit during the period of stimulation at all ages studied; the rise in haematocrit was greatest in the oldest animals.

5. The hyperglycaemic response to splanchnic stimulation persisted after pancreatectomy and was also demonstrated in calves in which the whole of the portal effluent blood flow was collected during splanchnic stimulation. The plasma from blood collected in this way had no apparent hyperglycaemic effect when infused into a branch of the mesenteric vein in recipient calves.

6. In adrenalectomized calves in which the liver had been partially denervated before stimulation both the hyperglycaemic and the glycogenolytic responses were substantially reduced, although the rise in haematocrit was unaffected, during stimulation of both splanchnic nerves.

7. It is concluded that glycogenolysis occurs in the liver as a result of stimulation via the hepatic innervation in the new‐born calf and that this response increases with age during the first few weeks after birth.
Mechanism of action of pyrogen
Authors: Feldberg W. , Saxena P. N.
Published: December 2014

1. In unanaesthetized rabbits the cerebral ventricles were perfused for 30–75 min from left lateral ventricle to cisterna magna with solutions of different composition, whilst rectal temperature was continuously recorded.

2. Temperature did not rise during the perfusion when the perfusing fluid consisted of artificial c.s.f.; it did rise, however, when the perfusing fluid consisted merely of a 0·9% sodium chloride solution.

3. Temperature fell, though not in all rabbits, during the perfusion when the calcium in the perfusing fluid was increased from 1·25 m
M, the concentration in c.s.f. to 5 m
M.

4. Magnesium chloride had only a weak action, in comparison to calcium, in preventing the rise produced during perfusion with 0·9% sodium chloride solution. In a concentration of 1·25 m
M it had no effect, but in a concentration of 5 m
M it delayed and greatly reduced the rise.

5. Temperature did not rise during perfusion with an isotonic sucrose solution.

6. The rise in temperature produced by an intravenous injection of leucocyte pyrogen was not prevented when the injection was made during a perfusion with artificial c.s.f., but it was prevented when the calcium concentration in the perfusing fluid was raised to 5 m
M or when the perfusing fluid consisted of isotonic sucrose solution. Again, magnesium had only a weak action in comparison to calcium.

7. These results support the theory put forward recently (Feldberg, Myers & Veale, 1970) that the constancy of temperature depends upon the physiological balance of sodium and calcium ions in the anterior hypothalamus, that the calcium ions act as a kind of ‘brake’ preventing the sodium ions from exerting their temperature raising effect, and that pyrogen acts by removing the ‘calcium brake’, the pyrogen fever thus being a sodium fever.
Persistence of the cardio‐inhibitory response to brain stem ischaemia after destruction of the area postrema and the dorsal vagal nuclei
Authors: Borison Herbert L. , Domjan Daniel
Published: December 2014

1. In anaesthetized cats, in which the carotid arterial bifurcation had been denervated and the spinal cord transected at the cervical level, reversible bradycardia mediated by the vagus nerves was elicited by temporary arrest of the cranial circulation. Methoxamine was infused intravenously to maintain peripheral vascular resistance, and artificial ventilation was given to avert systemic asphyxia.

2. The bradycardia persisted in cats subjected to one or more of the following acute surgical procedures: left vagotomy, mid‐collicular decerebration, decerebellation, bulbar transections at the acoustic striae and inferior fovea, and destruction of the area postrema and the underlying dorsal vagal nuclei. Ischaemia‐induced bradycardia was invariably abolished after bilateral vagotomy or the administration of atropine.

3. Bradycardia could not be elicited by electrical stimulation of the dorsal vagal nuclei, but was evoked by stimulation of deep structures in the vicinity of the nucleus ambiguus even after destruction of the dorsal vagal nuclei.

4. Simultaneous application of ischaemia and electrical stimulation of the medullary cardio‐decelerator locus produced convergent occlusion of the vagal response. The effect of ischaemia was inhibited by stimulation of a neighbouring region in the medial reticular formation. These interactions indicate that an interneuronal link is involved in the mechanism of ischaemia‐induced bradycardia.

5. It is concluded that the cardio‐decelerator response to ischaemia is initiated upstream to the primary efferent vagal motor neurones and that the cardio‐inhibitory fibres do not originate in the dorsal vagal nuclei.
The carotid body in the duck and the consequences of its denervation upon the cardiac responses to immersion
Authors: Jones D. R. , Purves M. J.
Published: December 2014

1. The anatomy of the carotid body and its afferent nerve supply was studied in the duck and a method of denervating the carotid body which ensures a satisfactory post‐operative course is described.

2. The effect of denervating the carotid body upon the cardiac response to immersion of the head in water was studied in ten ducks which at the time of the test were unanaesthetized.

3. When the nerves were intact, immersion of the head caused a fall in heart rate after a latent period of between 1 and 9 sec to an average of 24% of the resting rate after 30 sec. Simultaneous measurement of arterial oxygen tension (Pa, O2) in the brachiocephalic artery showed a rapid initial fall during the initial 10 sec from control levels, 93–103 mm Hg, to between 42 and 47 mm Hg, followed by a gradual fall of 3‐5 mm Hg for each subsequent 30 sec period of submergence.

4. Following carotid body denervation, the latent period before heart rate started to fall was no different from control but the average fall in heart rate was now to 90% of the resting rate and brachiocephalic Pa. O2 continued to fall steadily during submergence reaching levels of between 10 and 21 mm Hg by the end of the second minute.

5. Stimulation of the central end of branches of the IXth (glossopharyngeal) nerve supplying the glottis caused apnoea and bradycardia.

6. It is concluded that apnoea and bradycardia during submergence in the duck is initiated reflexly from receptors in the nares, pharynx and glottis but that the profound degree of bradycardia and mechanisms which maintain a relatively high Pa, O2 are regulated by peripheral chemoreceptor activity.
Inotropic changes in the left ventricle: the effect of changes in heart rate, aortic pressure and end‐diastolic pressure
Authors: Furnival C. M. , Linden R. J. , Snow H. M.
Published: December 2014

1. Under conditions where heart rate, mean aortic pressure and enddiastolic pressure in the left ventricle are held constant, the intravenous infusion of isoprenaline is accompanied by large changes in dP/dt max in the left ventricle.

2. Under similar conditions, during stepwise increments in the rate of infusion of isoprenaline the changes in dP/dt max (measured at a constant paced heart rate) were proportional to changes in the free (intrinsic) heart rate. It is concluded that dP/dt max is a quantitative index of inotropic changes in the left ventricle.

3. In comparison to dP/dt max, three other variables which have been used to indicate inotropic changes in the heart (peak pressure in the left ventricle, duration of systole and stroke work at constant end‐diastolic pressure), were shown to be unreliable indices of inotropic changes.

4. Using dP/dt max to indicate inotropic changes, alteration in the heart rate while mean aortic pressure and end‐diastolic pressure in the left ventricle were held constant, and in mean aortic pressure while heart rate ane end‐diastolic pressure in the left ventricle were held constant, were each shown to be accompanied by small inotropic changes in the heart.

5. Under similar conditions, changes in end‐diastolic pressure in the left ventricle alone were not accompanied by inotropic changes as indicated by dP/dt max.
Interaction between heart rate and calcium concentration in the control of contractile strength of the frog heart
Authors: Chapman R. A. , Niedergerke R.
Published: December 2014

1. The changes in twitch tension during the ascending and descending staircase of the frog heart have been examined under various experimental conditions including the hypodynamic and prehypodynamic state.

2. The descending staircase resembles the tension change after reduction of external calcium concentration in showing two consecutive phases, an initial rapid and later slow phase of tension decline.

3. The time course of the ascending staircase depends on the condition of the heart; it is slow after, and rapid before, development of the hypodynamic state. It is also rapid when elicited after conditioning periods of increased heart rate.

4. The tension transients in response to brief concentration steps of external calcium concentration were examined at various levels of heart rate. The results indicate that at high heart rates the sensitivity of heart cells to external calcium is increased.

5. The results are interpreted along the lines of a previous hypothesis relating tension development to the cooperative action of two intracellular calcium compounds. The additional assumption is made that an intermediary exists which facilitates calcium movements in heart cells to an extent depending on the level of heart rate.