bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.