bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of distension of the pulmonary vein‐atrial junction on activity of left atrial receptors
Authors: Kidd C. , Ledsome J. R. , Linden R. J. 
Published: December 2014

1. In anaesthetized dogs, the activity from left atrial receptors with vagal afferent fibres has been examined during distension of small balloons in the pulmonary veins or the application of pulsatile pressures to an isolated perfused pouch of the left atrium.2. Eleven fibres were found in nineteen dogs. The receptors discharging into these fibres were located, post mortem, to the atrial endocardium and reasons are given for believing that these fibres were myelinated and the receptors were B or Intermediate.3. Distension of small balloons induced significant increases in the discharge of action potentials from the receptors, the increases were similar to those after infusions of saline or dextran.4. In the perfused pouch the ‘dynamic’ thresholds for pulsatile pressure were high as were the mean and pulsatile pressures required to induce bursts of action potentials similar to those observed from atrial receptors in the atrium of normal size. Restoration of the atrium to its normal size resulted in ‘dynamic’ thresholds and responses to changes in pressure within the normal range. The changes could be explained assuming the Laplace relationship.5. This evidence supports the conclusion from previous investigations in which these techniques were used, that the increase in discharge in atrial receptors with myelinated vagal fibres could be the cause of the increase in heart rate and urine flow.
Relation of potassium transport to oxidative metabolism in isolated brain capillaries
Authors: Goldstein Gary W. 
Published: December 2014

1. The uptake of K by a capillary suspension isolated from rat brain was studied with the radioactive analogue 86Rb.2. Rb uptake was dependent upon the presence of oxygen and could be markedly inhibited with ouabain.3. The ouabain sensitive Rb uptake was measured at varying external concentrations of K. Uptake of K (as 86Rb) was half‐maximal when the K concentration was 3·0 m
M. This in vitro affinity of the transport carrier for K is similar to that found in previous in vivo studies of K efflux from brain to blood.4. I propose that the ouabain sensitive K pump is located on the antiluminal plasma membrane of brain capillary endothelial cells and that this pump contributes to the maintenance of a constant concentration (i.e. 3 m
M) of K in brain interstitial fluid.5. Glucose and palmitate were tested as possible energy substrates for the support of active Rb uptake by isolated brain capillaries. The rate of Rb uptake increased 40% when 0·25 m
M‐palmitate was added to a capillary suspension containing 5 m
M‐glucose. This stimulation of Rb uptake could be blocked by 1 m
M‐4‐pentenoic acid, an inhibitor of fatty acid oxidation. In contrast, the fraction of Rb uptake supported by glucose was not altered by 4‐pentenoic acid.6. The rates of [U‐14C]glucose and [U‐14C]palmitate oxidation to CO2 were measured in isolated brain capillaries and compared to their oxidation by brain slices and synaptosomes. Palmitate was the source of 28% of the 14CO2 produced by the capillaries but only 0·5% of the 14CO2 produced by the brain slices and synaptosomes.7. It is concluded that brain capillaries are similar to renal tubules in their polar distribution of ouabain sensitive K transport carriers, dependence on oxidative metabolism for active ion transport, and use of fatty acids as energy substrates. These features may underlie the vulnerability of brain capillaries in several metabolic diseases that cause brain oedema.
Assessment of the pulmonary origin of bronchoconstrictor vagal tone
Authors: Jammes Y. , Mei N. 
Published: December 2014

1. In anaesthetized spontaneously breathing cats, the sensory component of the vagal nerves was sectioned at the level of nodose ganglion, using a method described previously (Mei, 1966; Mei & Dussardier, 1966).2. The strength of the Hering—Breuer reflex (inhibitory ratio, i.e. T1/T0) provided a test for effectiveness of section of vagal afferents, particularly respiratory afferents. On the other hand, by studying the cardiac and bronchomotor effects induced by electrical stimulation of the supranodose portion of the vagal nerve, it was possible to test the integrity of the efferent vagal component.3. Unilateral right sensory vagotomy was followed by a 29% reduction in total pulmonary resistance.4. Section of the contralateral sensory vagal component (sensory bivagotomy), produced a weak supplementary effect (total decrease of total pulmonary resistance: 31%).5. No additive bronchomotor effect could be observed after the bilateral section of efferent vagal fibres (total bivagotomy).6. In intact cats, blockade of the two vagal nerves by procaine induced a decrease in pulmonary resistance similar to those produced by the sensory bivagotomy (23%). This bronchodilatator effect was concomitant with a complete disappearance of the C wave of the compound vagal potential.7. Intravenous injection of phenyl diguanide, immediately after the blockade of the C vagal fibres by procaine did not modify bronchomotor tone. This result confirms that the C pulmonary afferents, which are activated by phenyl diguanide, are mainly involved in this mechanism.8. The pulmonary irritant receptors seem to play a minor role. In fact, the
I.V. administration of histamine under the same conditions, provides evidence that the corresponding neurones (small sized myelinated fibres) are potent during the procaine application.9. From these results, it appears that bronchoconstrictor vagal tone has an exclusive peripheral origin and that pulmonary endings, in particular those connected with non‐medullated fibres, are probably involved in this mechanism.
Surface tension induced by dipalmitoyl lecithin in vitro under physiological conditions
Authors: Barrow R. E. , Hills B. A. 
Published: December 2014

1. The surface tension of 161 films of DPL have been measured on a Langmuir trough using a Wilhelmy balance under conditions controlled to simulate the state of the alveolar lining in vivo.2. The parameters controlled were temperature (maintained at 37 °C), humidity (100% at 37 °C), surfactant concentrations (encompassing the best available estimates), area changes (consistent with normal respiration), frequency adaptation to continuous cycling and composition and pH of the aqueous hypophase.3. Simultaneously maintaining all of these parameters within the best estimates of physiological limits, the relationships between surface tension and surface area showed appreciable differences from previous studies, our results showing higher minimum values of surface tension, appreciably less change in surface tension with compression and far less hysteresis between surface tension and surface area.4. The higher minimum values are consistent with original estimates of alveolar surface tension made by von Neergaard, namely 35‐41 dyne cm−1.5. Although appreciably smaller than hitherto reported, the change in surface tension with change in area is still adequate to impart alveolar stability.6. The reversibility between surface tension and surface area under physiological conditions is discussed in connection with compliance hysteresis which is considered to be more dependent upon geometric irreversibility of the alveolar surface than upon any intrinsic property of the surfactant.
Influence of raising albumin concentration on renin release in isolated perfused rat kidneys
Authors: Fray John C. S. , Karuza Anthony S. 
Published: December 2014

1. Experiments were conducted in isolated perfused rat kidneys to determine the effect of raising perfusate albumin concentration on renin release.2. Raising albumin concentration in the perfusion fluid from 20 g/l. to 60 g/l. (high albumin concentration) increased renin release and renal perfusate flow rate. The effect was reversible.3. Ureteral occlusion did not prevent the rise in renin release and renal perfusate flow induced by high albumin concentration.4. Propranolol (0·28 m
M) did not block the renin release stimulated by high albumin concentration, but it inhibited the release stimulated by isoprenaline (2·43 μ
M).5. Clonidine (10 μ
M) and oxymetazoline (10 μ
M) constricted the renal vasculature and stimulated renin release during high perfusate albumin concentration providing perfusion pressure was kept constant.6. Low renal perfusion pressure (50 mmHg) and isoprenaline (2·43 μ
M) stimulated renin release in perfusion experiments with both 20 and 60 g/l., but the rate of renin release was substantially greater with 60 g/l.7. On the other hand, perfusion fluid deprived of calcium induced a greater increase in renin release in kidneys perfused with 20 g/l. than in those with 60 g/l.8. We conclude that high albumin concentration stimulates renin release in isolated perfused rat kidneys by a mechanism which does not involve the renal nerve, direct renal vasodilation or sodium excretion. High albumin concentration may increase the sensitivity of the kidney to acute stimulation by a mechanism involving calcium.
Responses of rod‐bipolar cells in the dark‐adapted retina of the dogfish, Scyliorhinus canicula
Authors: Ashmore J. F. , Falk G. 
Published: December 2014

1. Responses to light were recorded from bipolar cells in the retina of the dogfish, Scyliorhinus canicula, under dark‐adapted conditions. The identity of the cells was confirmed by Procion Yellow staining.2. More than 95% of the bipolar cells sampled were of the type which depolarized to a spot of light. These are termed depolarizing bipolar cells. In most cells, illumination of the surround had little effect on the responses elicited from the central receptive field.3. The mean flash sensitivity of the depolarizing bipolar cells was 270 mV/Rh** (where Rh** signifies rhodopsin photoisomerization per rod for full field illumination).4. The mean flash sensitivity of horizontal cells under the same conditions was 8 mV/Rh**. In a limited sample of hyperpolarizing bipolar cells the highest flash sensitivity was 42 mV/Rh**.5. The high flash sensitivity of the depolarizing bipolar cells indicates a large voltage gain at its synapse with rods. On the assumption of a rod flash sensitivity of 2 mV/Rh** the mean gain at the synapse was 135, but for some cells the gain was in excess of 500.6. Responses of depolarizing bipolar cells to dim flashes could be approximated by the impulse response of a 12‐16 stage low‐pass filter, whereas horizontal cell responses could be fitted by a low‐pass filter of six sections. The implied filter at the rod‐bipolar cell synapse is tuned to the higher frequency components of rod signals, thereby improving temporal resolution in the rod pathway.7. Depolarizing bipolar cell responses to test flashes are reduced by weak background illumination (less than 0·1 Rh**/sec). This desensitization, which would not be expected to affect rod responses, could be explained by a shift in the operating point to a less sensitive region of the intensity—response curve as a result of the large depolarization elicited by the background.8. The results of current injection into the cell in darkness and during the response to light are consistent with the release by rod terminals of a transmitter which closes ionic channels in a conductance path having a reversal potential of ‐ 8 mV, transmitter release being suppressed by light.
Amygdala neurones: converging synaptic inputs produced by median eminence and medial preoptic area stimulations in rats
Authors: Hamamura Mitsuko , Yagi Kinji 
Published: December 2014

1. Amygdaloid afferent inputs from the median eminence and the medial preoptic area were studied electrophysiologically in urethane‐anaesthetized female rats.2. Stimulation of the surface of the median eminence produced orthodromic responses in about 80% of the forty‐seven amygdala units tested and about 65% of the responsive cells showed an excitation.3. Stimulation of the ipsilateral medial preoptic area orthodromically excited seventeen and inhibited twenty of the forty‐nine units tested.4. Stimulation of the contralateral medial preoptic area evoked orthodromic excitation in nine and inhibition in three of the twenty‐two units tested. These stimuli were ineffective for producing antidromically conducted impulses in the tested units.5. Sixteen of the thirty amygdala units tested for responses to both median eminence and ipsilateral medial preoptic area stimulation responded orthodromically with either excitation or inhibition. The latency of the response to median eminence stimulation was approximately equal to that of the response to ipsilateral preoptic area stimulation in four of these sixteen units.6. A characteristic bursting discharge was observed in eleven amygdala units during and after ipsilateral preoptic area stimulation. A transitory inhibition was evoked simultaneously with the bursting discharge in some units. Seven of the eleven units were also tested for median eminence stimulation, and a transitory excitation was observed in each of these units.7. These results suggest the existence of converging synaptic inputs both from tuberoinfundibular neurones and the ipsilateral medial preoptic area to certain amygdala neurones. They also demonstrate the existence of a specific neural pathway mediating a characteristic self‐sustained bursting discharge in some amygdala neurones after such stimulation.
Prostaglandin E levels in third ventricular cerebrospinal fluid of rabbits during fever and changes in body temperature
Authors: Bernheim H. A. , Gilbert T. M. , Stitt J. T. 
Published: December 2014

1. A method was devised to sample cerebrospinal fluid (c.s.f.) from the third ventricle of conscious rabbits.2. Levels of PGE were measured in c.s.f. withdrawn from the third ventricle of rabbits exposed to a variety of manipulations of both brain and body core temperatures which mimicked various facets of fever in these animals. These results were compared to the levels of PGE in the c.s.f. of the same rabbits made febrile by
I.V. injections of endogenous pyrogen.3. Levels of PGE in ventricular c.s.f. remained unaltered at 2‐3 ng/ml. during exposure to cold, hyperthermia due to heat exposure, hypothalamic cooling or hypothalamic heating, whereas during fever produced by endogenous pyrogen, they rose to an average of 11‐12 ng/ml. Furthermore, a significant positive correlation was established between the level of PGE measured in the c.s.f. and the subsequent height of the fever produced by the pyrogen.4. Since production of PGE within the brain is not caused by changes in the brain or body temperatures which are comparable to those observed during fever, and yet greater than fivefold increases in the PGE levels in c.s.f. are produced by
I.V. injections of endogenous pyrogen, it is concluded that PGE production in the brain is involved in the pathogenesis of fever.
Rat supraoptic neurones: the effects of locally applied hypertonic saline
Authors: Leng G. 
Published: December 2014

1. Extracellular action potentials were recorded from supraoptic neurones in lactating, urethane‐anaesthetized rats. A microtap was used to apply a very small volume (about 10−7 ml.) of hypertonic saline (1‐4
M‐NaCl) to the immediate neighbourhood of these units over about 1 min.2. Twenty‐five of twenty‐seven supraoptic neurones were excited by this local osmotic stimulus. The response of individual units was reversible and repeatable. Microtap applications of isotonic saline to supraoptic neurones were without observed effect.3. Continuously firing supraoptic neurones responded to hypertonic saline with a smooth acceleration in firing rate. Phasic neurones showed an increase in the over‐all level of activity, and in particular, a prolongation of the active phases. Slow, irregularly firing cells responded either with a smooth acceleration in firing rate, or with phasic behaviour.4. The response to local hypertonic saline appears to be reasonably specific to the supraoptic nucleus. Of thirty‐five neurones recorded close to the supraoptic nucleus but which were not antidromically activated from stimulation of the neural stalk, only nine responded to the local application of hypertonic saline.5. Similarities between the manner of response of supraoptic neurones to local application of hypertonic saline and the manner of their response to systemic increases in the osmotic pressure of blood plasma support the hypothesis that supraoptic neurones are osmosensitive.
The electrical basis for contraction and relaxation in canine fundal smooth muscle
Authors: Morgan Kathleen G. , Muir T. C. , Szurszewski J. H. 
Published: December 2014

1. Mechanical and intracellular electrical activities were recorded simultaneously from canine fundal and antral smooth muscle preparations.2. Most fundal preparations displayed no spontaneous electrical or mechanical activity. The tissue had a space constant of 1·5 mm and a time constant of 189 msec and showed outward rectification in response to depolarizing current.3. Transmural nerve stimulation of fundal preparations demonstrated the presence of cholinergic excitatory and non‐cholinergic, non‐adrenergic inhibitory neural inputs to the tissue. The cholinergic nerve response consisted of a small, graded depolarization accompanied by a slow graded contraction; the inhibitory nerve response consisted of a graded hyperpolarization accompanied by a slow relaxation.4. The excitatory fundal nerve response was abolished or greatly diminished by D600 and Mn2+. D600 and Mn2+ also decreased basal tone. The inhibitory nerve response was unaffected by either agent.5. The excitatory nerve response in the fundus was contrasted with the excitatory nerve response in the antrum. In the fundus, stimulation of cholinergic motor nerves produced a depolarization which always produced a contraction. In the antrum, stimulation of cholinergic motor nerves between action potentials produced graded depolarizations of antral cells; however, there were no associated contractions. Stimulation of cholinergic motor nerves during spontaneous action potentials increased the amplitude and duration of the plateau phase of the action potential; this was associated with an augmentation of the spontaneous contractions.6. Voltage—tension curves were determined for antral and fundal preparations using K+ depolarization as a means of controlling membrane potential. Antral preparations displayed a voltage threshold for contraction at a membrane potential approximately 30 m V positive to the resting potential. In cntrast, fundal resting potentials were at or more positive than their voltage thresholds.7. These differences in electromechanical coupling provide an explanation for the marked differences in the responses of fundal and antral smooth muscles to nerve stimulation and account for their physiologic function in vivo.
Influence of the sympatho‐adrenal system and somatostatin on the secretion of insulin in the rat
Authors: Ahrén B. , Järhult J. , Lundquist I. 
Published: December 2014

1. The effects of somatostatin on insulin secretion in anaesthetized rats subjected to different manipulations of the sympatho‐adrenal system have been investigated.2. Somatostatin (0·1 μg/min) inhibited the secretion of insulin in intact rats both in the basal state and after inducing an enhanced insulin release by infusion of the α‐adrenoceptor‐blocker phentolamine.3. Combined surgical splanchnicotomy and adrenalectomy caused an increase in the basal plasma insulin concentration. Somatostatin (0·1 μg/min) inhibited basal insulin release also in these rats. After infusion of phentolamine, however, the dose of somatostatin had to be raised five fold (0·5 μg/min) to achieve a comparable inhibition of insulin release. On the other hand, a similar rate of insulin secretion induced by glucose in intact rats could be inhibited by the lower dose of somatostatin.4. Administration of the β‐adrenoceptor‐blocking agent propranolol to splanchnicotomized—adrenalectomized rats lowered basal insulin secretion to the same level as seen in intact rats. In these β‐adrenoceptor‐blocked rats somatostatin (0·1 μg/min) inhibited insulin release both in the presence and absence of α‐adrenoceptor blockade.5. Rats subjected to chemical sympathectomy through pre‐treatment with 6‐hydroxydopamine together with adrenalectomy displayed plasma insulin concentrations slightly above the normal range, but the values were much lower than in splanchnicotomized—adrenalectomized rats. Infusion of phentolamine to the chemically sympathectomized rats did not further increase insulin secretion, and somatostatin (0·1 μg/min) depressed insulin release both in the absence and presence of α‐adrenoceptor blockade.6. It is suggested that an inhibitory tone exerted by the splanchnic nerves modulates the basal insulin secretion in the rat. Somatostatin and the sympathoadrenal system show a complex interaction on the insulin cells in that the sensitivity to somatostatin in splanchnicotomized—adrenalectomized rats with intact β‐adrenoceptors is decreased in the presence of the α‐adrenoceptor‐blocker phentolamine. The exact mechanism behind this decreased sensitivity remains unclear.
Effects from fine muscle and cutaneous afferents on spinal locomotion in cats
Authors: Kniffki K.-D. , Schomburg E. D. , Steffens H. 
Published: December 2014

1. The effects of chemically activated fine muscle afferents (groups III and IV) and electrically activated cutaneous afferents on motoneuronal discharges were studied before and during fictive locomotion induced pharmacologically by
i.v. administration of nialamide and
l‐DOPA in high spinal cats. Efferent activity was recorded simultaneously from nerve filaments to ipsi‐ and contralateral extensor and flexor muscles. In addition, intracellular recordings were made from lumbar α‐motoneurones.2. After nialamide but before treatment with
l‐DOPA, in some cases, transient locomotor‐like discharges were induced by an increased activity in fine muscle afferents. The response pattern in nerves to both hind limbs could be different showing e.g. only transient alternating activity between knee flexor and extensor of one limb but not of the other one.3. Treatment with
l‐DOPA did not always cause fictive locomotion. Often not all motoneurone pools showed rhythmic activity. In these cases stimulation of group III and IV muscle afferents usually caused transient periodic activity. In cases with apparent rhythmic activity, algesic stimulation of the gastrocnemius—soleus muscle caused an accentuation of the rhythm by a more abrupt transition from the active phase to the non‐active interval. Again, the response patterns on both sides were not uniform in all cases.4. A second type of response to activation of fine muscle afferents had a quite different character: the rhythmic activity was more or less completely overridden by a strong transient tonic hyperactivity or the rhythm was transiently blocked. These phenomena did not occur in the same way in all nerves.5. Electrical stimulation of cutaneous nerves of the hind limb generally induced the same response pattern as chemical stimulation of the group III and IV muscle afferents. The effects varied depending on the stimulus strength and the nerve.6. The results revealed that cutaneous and fine muscle afferents not only have similar functions in the reflex control of a limb but also in evocation and modulation of locomotion. Therefore, it is assumed that both types of afferents may serve together as a peripheral feed‐back to the spinal locomotor centre.