bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relaxing effects of catecholamines on mammalian heart
Authors: Morad M. , Rolett E. L. 
Published: December 2014

1. The effect of catecholamines on the time course and amplitude of contraction and on KCl‐induced contractures has been studied in mammalian hearts.2. Marked and reproducible contractures could be obtained in mammalian ventricular trabeculae and papillary muscles after β‐adrenergic block with propanolol or if the hearts were depleted of their catecholamine stores by reserpine or by chemical denervation with 6‐hydroxydopamine.3. In neonatal hearts with lower endogenous catecholamine stores and poorly developed sarcoplasmic reticulum KCl contractures are easily produced.4. Catecholamines potentiate twitch tension and relax the contracture tension under all of the above circumstances.5. The relaxant effect of catecholamines is present during the time course of a twitch. This increased relaxation rate as well as the shortening of the time‐to‐peak of tension is independent of the variation in the duration of the action potential.6. The shortened relaxation time is present when the action potential is shortened with anodal repolarization or prolonged with cathodal depolarization (voltage‐clamp).7. The relaxant effect of catecholamines on the twitch is temperature and rate dependent. The effect is observed in the presence of high or low concentrations of calcium.8. The presence of catecholamines is necessary for full relaxation of mammalian heart muscle under high performance conditions or states of calcium overload.9. It is proposed that catecholamines exert their relaxant effect independent of their positive inotropic effect by stimulating the sequestering system (sarcoplasmic reticulum, mitochondria or sarcolemma) for calcium.
A compartmental analysis of 24Na kinetics in rat cerebrum, sciatic nerve and cerebrospinal fluid
Authors: Levin Victor , Patlak Clifford S. 
Published: December 2014

1. The kinetics of 24Na exchange in rat cerebrospinal fluid, brain and sciatic nerve were studied during steady‐state plasma isotope conditions. The entrance of 24Na into brain and sciatic nerve was found to fit a three compartmental model. Using newly derived equations for compartmental analysis, the first compartment 24Na space of brain was found to be about 22% and the second compartment space about 6%; the corresponding sciatic nerve spaces were 26 and 11%, respectively. In the discussion, arguments are presented that suggest that the first compartment is the extracellular space (ECS) and the second compartment is the intracellular space. The t½ for compartmental equilibration between plasma and brain ECS was 2 hr and from ECS to intracellular space 14 hr; in nerve the respective t½'s were ⅔ hr and 10 hr.2. A third compartment of 18% was found in sciatic nerve which was interpreted to be anatomically confined to the epi‐ and perineurium; in brain the corresponding space was 2% and was felt to be anatomically and kinetically an inactive closed compartment in parallel with the blood.3. There were two t½'s for plasma‐c.s.f. 24Na equilibration of less than 10 min and 2 hr.4. Profiles of brain, from cortex to ventricle, at 6 min, demonstrated a gradient of decreasing 24Na radioactivity from ventricle to cortex.
The role of the alkaline earth ions in anaphylactic histamine secretion
Authors: Foreman J. C. , Mongar J. L. 
Published: December 2014

1. Anaphylactic histamine release from rat peritoneal mast cells is dependent on the presence of calcium ions. Graded increase of histamine release occurs as the calcium ion concentration is raised from 0·1 to 1·0 m‐mole/l.2. Magnesium antagonizes the effect of calcium. The dissociation constant of the Mg‐receptor complex was found to be 9·4 m‐mole/l.3. Strontium will replace calcium ions in the activation of anaphylactic histamine release. Graded increase of histamine release occurs when the strontium ion concentration is raised from 1·0 to 10·0 m‐mole/l.4. Magnesium also antagonizes the effect of strontium. The dissociation constant of the magnesium‐receptor complex was found to be 11·0 m‐mole/l.5. The log concentration—effect curve for strontium has a greater maximum and steeper slope than the curve for calcium.6. Measurements of the interaction of calcium and strontium ions are in agreement with the hypothesis that strontium possesses a higher efficacy but a lower affinity than calcium, for the ‘calcium receptor’ in mast cells.7. Barium will replace calcium in the activation of anaphylactic histamine release.
The effects of peripheral and central nervous influences on gastric centre neuronal activity in sheep
Authors: Harding R. , Leek B. F. 
Published: December 2014

1. Responses of identified vagal reticulo‐ruminal motoneurones and gastric centre interneurones to changes in vagal afferent activity were examined in anaesthetized, decerebellate sheep.2. Procedures which reflexly modified the form of forestomach movements caused corresponding changes in the activities of motoneurones and Type A interneurones, whereas the activity patterns of Type B, and many Type C, interneurones were not affected.3. Distension of the pyloric region of the abomasum reduced the number of spikes in the periodic discharges of gastric centre neurones (motoneurones and Type A interneurones) with reticular activity, although the frequency of periods of activity was often increased. The afferent pathway for both effects was probably vagal.4. Unilateral vagotomy usually had little effect on the frequency and amplitude of forestomach movements, and did not influence the temporal relation between ipsilateral gastric centre discharges and the movements.5. Median division of the medulla oblongata only in the region between the gastric centres caused a loss of synchronization in the activities of the two centres, indicating the existence of commissural connexions at this level.6. Bilateral vagotomy abolished forestomach movements and motoneuronal activity, but rhythmic activity in gastric centre interneurones continued with a periodicity of approximately 1 min. This persisting periodic activity was unaffected by spinal section, but was not present after transection of the brain stem rostral to the medulla.7. Cyclical gastric centre activity could be elicited by reticular distension in preparations in which the medulla oblongata was isolated from higher regions of the brain, but, in contrast to many sheep in which the brain stem was intact, the existence of the activity was totally dependent upon peripheral afferent activity.8. The evidence indicates that medullary neurones responsible for periodic activation of vagal preganglionic reticulo‐ruminal motoneurones may be excited by either or by both vagal afferent fibres from the fore‐stomach or by descending, as yet unidentified, influences from the central nervous system.9. Possible roles for gastric centre interneurones in neural networks which control the periodic activation of motoneurones and which control the form of individual activity cycles are discussed.
The effect of carbohydrates on the intestinal potentials of Cryptochiton stelleri
Authors: Lawrence A. L. , Mailman D. S. , Puddy R. E. 
Published: December 2014

1. The effect of various monosaccharides on the potential difference across the intestine of the invertebrate, Cryptochiton stelleri, was studied using an everted sac technique.2.
D‐Glucose, when present in the mucosal solution, increased the transmural potential across the anterior intestine but had no effect on electrical potentials across the posterior intestine.3.
D‐Galactose, when present in the mucosal solution, increased the transmural potential across the posterior intestine but had no effect on electrical potentials across the anterior intestine.4.
D‐Fructose and
D‐mannose, metabolizable but non‐transported sugars, increased anterior intestinal potentials but not posterior intestinal potentials.5. 3‐O‐methylglucose, an actively transported (across the anterior intestine) but non‐metabolizable sugar, did not alter potentials across either the anterior or posterior intestine.6. The addition of
D‐glucose to the serosal solution increased anterior intestinal potentials, but the serosal addition of
D‐galactose did not affect posterior intestinal potentials.7. NaF, phlorizin and anoxia prevented the increase in potential across the anterior intestine and phlorizin (10−4 but not 10−6
M) and NaF but not anoxia prevented the increase in potential across the posterior intestine.8. It was suggested that the effect of glucose on anterior intestinal potentials was a metabolic effect, whereas the effect of galactose on posterior intestinal potentials was related to the active transport of that sugar from mucosa to serosa.
Absorption of palmitic, stearic and oleic acids in the sheep in the presence or absence of bile and/or pancreatic juice
Authors: Harrison F. A. , Leat W. M. F. 
Published: December 2014

1. The absorption of 3H‐ and 14C‐labelled palmitic, stearic and oleic acids under control conditions and in the absence of bile and/or pancreatic juice has been studied in sheep prepared with intestinal cannulae and reentrant fistulation of the thoracic lymph duct.2. Under control conditions the percentage recoveries in thoracic duct lymph of fatty acids introduced into the duodenum were: stearic acid 59·6 ± 3·2 (mean ±
S.E. of mean), palmitic acid 71·1 ± 1·2 and oleic acid 80·4 ± 1·9.3. At the peak of absorption over 90% of the radioactivity was located in the triglyceride fraction.4. It was calculated that between 1900 and 3800 ml. lymph containing up to 20 g lipid flowed daily from the thoracic duct. The major fatty acids of lymph triglycerides were C16:0 (26%), C18:0 (39%) and C18:1 (19%).5. In the absence of pancreatic juice, but in the presence of bile, the absorption of stearic, palmitic and oleic acids was 0·8, 4·–8·5 and 26% respectively of the dose injected into the duodenum. In the absence of bile but presence of pancreatic juice corresponding values were 0·1–0·5, 1·8 and 7·7%.6. In the absence of pancreatic juice the total lipid content of thoracic duct lymph fell from 800 to 80 mg% within 4 hr. When bile was also absent the lipid content of lymph fell further to 50 mg%.7. It is concluded that pancreatic juice functions in the lumen of the intestine probably through the production from biliary lecithin of the lysolecithin necessary for the optimum absorption of lipids.
A functional analysis of the components of the mesencephalic nucleus of the fifth nerve in the cat
Authors: Cody F. W. J. , Lee R. W. H. , Taylor A. 
Published: December 2014

1. The mesencephalic nucleus of the trigeminal nerve has been studied using extracellular micro‐electrode recording and the constituent cell types identified.2. Two types of unit were found, namely, muscle spindle first order afferents of ipsilateral jaw‐closing muscles and mechanoreceptor afferents of ipsilateral maxillary and mandibular teeth.3. No evidence was found for representation of extra‐ocular muscle stretch receptors, of temporo‐mandibular joint receptors or of tendon organs of jaw muscles.4. Spindle units of each of the jaw‐closing muscles were recorded in all parts of the nucleus and there was no evidence of their segregation according to muscle of origin.5. Attempts to classify spindle units by their dynamic response to ramp stretches, their following of high frequency vibration and their interspike interval variability at constant length gave no indication of two populations when fusimotor activity was suppressed.6. Following the injection of suxamethonium, however, units fell into two groups according to their dynamic index. Their behaviour resembled that described for primary and secondary spindle afferents. In data pooled from all of the jaw‐closing muscles there were approximately equal numbers of units in each group.
Nature and location of the receptors for salt‐gland secretion in the goose
Authors: Hanwell Ann , Linzell J. L. , Peaker M. 
Published: December 2014

1. The nature and location of the receptors which stimulate salt‐gland secretion in the goose have been investigated.2. The rapid injection of homologous blood (sufficient to raise the blood volume by 16 and 9%) into the right atrium failed to induce secretion. In contrast, hypertonic sucrose, Na2SO4 and LiCl initiated secretion.3. These results support the theory that osmoreceptors initiate secretion by detecting an increase in plasma tonicity.4. The minimal amount of hypertonic NaCl required to initiate secretion when infusions were made into a carotid artery or into various arteries and veins in the splanchnic region was not less than that required by an
I.V. route.5. Cross‐circulation and perfusion studies also showed that a raised [NaCl] in the blood perfusing the head was ineffective in evoking secretion and thus that plasma tonicity must be raised elsewhere in the body.6. Secretion in response to salt‐loading was abolished or prevented by cutting the vagus nerves or blocking them with local anaesthetic. Stimulation of the cephalic end of the cut vagi in an isolated, perfused decerebrate head induced secretion, indicating that the afferent fibres from the receptors to the
C.N.S. lie in the vagus nerves. Cutting the vagi below the heart, however, had no effect on the secretory response.7. Blocking nerves in the crop with local anaesthetic had no effect on secretion induced by salt‐loading but when local anaesthetic was injected into the pericardial sac, secretion decreased immediately, stopped, and recovered with a time course similar to that seen after blocking the vagus nerves.8. Section of the vagi in the neck abolished the tachycardia observed in response to the injection of hypertonic NaCl into the right atrium.9. As in other species, stimulation of the ‘secretory nerve’ induced secretion in anaesthetized or decerebrate geese.10. Hexamethonium given
I.V. or applied topically to the ‘secretory nerve ganglion’ blocked secretion in response to salt‐loading or to secretory nerve stimulation.11. It appears that the receptors for salt‐gland secretion are located in or near the heart and that afferent fibres from these receptors travel in the vagus nerves to the
C.N.S.12. A possible scheme of the secretory reflex which initiates and maintains salt‐gland activity is proposed.
The outer disinhibitory surround of the retinal ganglion cell receptive field
Authors: Ikeda Hisako , Wright M. J. 
Published: December 2014

1. There is an outer disinhibitory zone surrounding the classical inhibitory surround of the retinal ganglion cell receptive field.2. The disinhibitory surround is strong and narrow in ‘sustained’ cells but weak and laterally spread in ‘transient’ cells.3. The disinhibitory surround can be demonstrated using a black spot as a probing stimulus as well as by a white spot, and is therefore not an artifact of scattered light.4. Stimulation with a light spot in the disinhibitory zone gives an increase in firing to ‘stimulus on’ in on‐centre cells and to ‘stimulus off’ in off‐centre cells.5. The disinhibitory surround may be revealed by plotting the latency of the first spike discharge following stimulation against position in the receptive field. The disinhibitory zone shows a decrease in latency to the centre‐type stimulus.6. The disinhibitory surround may be revealed by plotting the threshold intensity of a spot against position in the receptive field. It is thus a feature of the sensitivity gradients of both ‘transient’ and ‘sustained’ cells.7. Using two spots, one at the centre of the receptive field and the other at varying distances from the receptive field centre, dynamic interactions between the centre, inhibitory and disinhibitory zones are demonstrated. A spot presented in the disinhibitory zone causes an enhancement of the centre response when flashing in phase with the centre spot, while it causes inhibition of the centre response when presented 180° out of phase.8. A scheme for the anatomical basis of the disinhibitory surround is proposed, and the relation of disinhibition to the spatial transfer characteristics of the visual pathways is discussed.
Properties and distribution of peripherally evoked presynaptic hyperpolarization in cat lumbar spinal cord
Authors: Mendell Lorne 
Published: December 2014

1. The action of peripheral nerve volleys on the polarization of presynaptic terminals of inactive sensory fibres in cat lumbar spinal cord has been investigated by recording (a) the dorsal root potential (DRP), (b) intracellular changes in polarization of single preterminal axons (PAD or PAH), and (c) changes in excitability of populations of preterminal axons.2. Presynaptic hyperpolarization (positive DRP‐PAH) can be evoked by stimulation of muscle group III afferents as well as by volleys in cutaneous Aβ, Aδ and C afferents. These volleys can also produce presynaptic depolarization (negative DRP‐PAD).3. The positive DRP is observed in the decerebrate state and increases in amplitude following spinalization.4. Picrotoxin blocks the positive DRP at the same dosages required to block the negative DRP. Test negative DRPs are depressed during a conditioning positive DRP. These results are used to support earlier suggestions that the positive DRP results from inhibition of interneurones mediating the negative DRP.5. Trains of group III stimuli at 20/sec evoke a steady positive DRP. Trains of the same intensity at 200/sec evoke a phasic negative DRP. This frequency dependence is observed for PAD and PAH in single sensory axons.6. The DRPs recorded from different dorsal root filaments in response to a given stimulus vary widely in the ratio of negative to positive DRP.7. Intracellular recording from single axons reveals that the same stimuli evoke widely varying ratios of PAD and PAH.8. Stimulation of FRA evokes PAH > PAD in PBST group I afferents, PAD > PAH in sural A fibres and intermediate effects in G‐S group I units.9. It is suggested that activation of flexor reflex afferents may selectively potentiate the synaptic efficacy of large muscle afferents mediating the flexor reflex rather than large skin afferents or large afferents from extensor muscles.
Oligopeptidases of brush border membranes of rat small intestinal mucosal cells
Authors: Fujita M. , Parsons D. S. , Wojnarowska Fenella 
Published: December 2014

1. The properties of peptidases located in the brush borders of rat small intestinal mucosal cells have been investigated using a new method for the assay of peptidase activity. In this method amino acids produced by hydrolysis of peptides are oxidized by ophidian
L‐amino acid oxidase and the hydrogen peroxide produced during reoxidation of the reduced enzyme is estimated spectrophotometrically.2. 10–20% of the total cellular peptidase activity and 50% of the leucylnaphthylamidase (LNAase) activity were found to be tightly bound to the brush borders and to possess different substrate specificity from the supernatant peptidase activity.3. Evidence from kinetic and competition studies indicates the presence of more than one peptidase in the brush borders. The peptidases exhibit pH optima of 8·0–8·5, are inhibited by EDTA, but are not usually activated by divalent metal ions. The brush border peptidases hydrolyse di‐ and tripeptides, some oligopeptides, leucinamide and leucyl‐β‐naphthylamine. On the basis of the Michaelis constants, these substrates differ in their affinities for the enzymes.4. It is proposed that the brush border peptidases serve an analogous function in the terminal stages of protein digestion to that of the disaccharidases in the case of carbohydrate digestion and absorption.
Carbamino compounds of haemoglobin in human adult and foetal blood
Authors: Bauer C. , Schröder E. 
Published: December 2014

1. The carbamate (HbCO2) concentration in oxygenated and deoxygenated human adult and foetal red blood cells was estimated at a constant pressure of carbon dioxide (PCO2 = 40 mm Hg) and various pH values of the serum. The Donnan ratio for chloride and bicarbonate ions was used to calculate the bicarbonate concentration in the red cells. With this figure the carbamate concentration was calculated as follows:[HbCO2] = [Total CO2] — [HCO−3] — [dissolved CO2].2. At a given pH value in the red cell deoxygenated foetal red cells contain more HbCO2 than deoxygenated adult ones. Upon oxygenation (at constant pH) HbCO2 drops in both types of erythrocytes to lower values than in deoxygenated cells. The fraction of ‘oxylabile carbamate’ (−ΔHbCO2/ΔHbO2) at a red cell pH of 7·2 and a PCO2 of 40 mm Hg is 0·117 in foetal and 0·081 in adult erythrocytes.3. From the fraction of moles carbamate formed per Hb monomer (moles CO2/mole Hbi) K′c and K′z, the apparent carbamate equilibrium constants were calculated which can be used to estimate the carbamate concentration in normal adult and foetal blood.4. The first apparent dissociation constant of carbonic acid is significantly higher in oxygenated (−log10K′1 = pK′1 = 6·10) than in deoxygenated (pK′1 = 6·12) adult red cells, whereas in foetal red cells the difference is smaller and statistically not significant.5. For a given set of physiological conditions in arterial and mixed venous blood in respect to oxygen saturation, PCO2 and pH, the fractional contribution of carbamino compounds of haemoglobin to the amount of carbon dioxide which is exchanged during the respiratory cycle was computed on the basis of the present results and found to be 10·5% in adult and 19% in foetal blood.
Transmitter release from insect excitatory motor nerve terminals
Authors: Usherwood P. N. R. 
Published: December 2014

1. Intracellular and extracellular electrodes were used to study spontaneous and impulse‐linked release of transmitter at locust retractor unguis nerve‐muscle synapses.2. At most extracellular recording sites the amplitude distributions of the excitatory post‐synaptic potentials (e.p.s.p.s) were apparently non‐Poisson. However, interpretation of these amplitude distributions was complicated by the effect on the extracellular recordings of the complex structural organization of the retractor unguis nerve terminal with its spatially distinct transmitter release sites extending over distances of 15–30 μm.3. The spontaneous miniature excitatory post‐synaptic potentials (min e.p.s.p.s) did not occur at random intervals, bursts of min e.p.s.p.s being frequently recorded. As a result the spontaneous release of transmitter rarely approximated a Poisson process.4. For a period of at least 390 msec following a conditioning nerve impulse a test e.p.s.p. was facilitated and the probability of spontaneous transmitter release was enhanced. A large primary phase of facilitation of impulse‐linked and spontaneous release was invariably followed by one or more secondary phases of smaller magnitude.
Intra‐axonal transport and turnover of neurohypophysial hormones in the rat
Authors: Jones C. W. , Pickering B. T. 
Published: December 2014

1. The specific radioactivities of isotopically pure oxytocin and vasopressin prepared from the neural lobe of the pituitary gland have been measured at various times after an intracisternal injection of [3H]tyrosine.2. Radioactive hormone began to appear in the gland 1–2 hr after the injection which suggests an intra‐axonal transport velocity of 1–2 mm/hr.3. From 7 days onwards the specific radioactivity of each hormone declined exponentially with the same rate constant and a half‐life of about 13 days.4. If the decline in radioactivity can be equated with the release of the hormones, the rates of secretion for the male rat in water balance are 18·7 m‐u./day for oxytocin and 28·9 m‐u./day for vasopressin.5. Calculation from the secretion rates gave steady‐state plasma concentrations of about 3 μu./ml. for each hormone.