bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the function of myoepithelial cells in salivary glands
Authors: Emmelin N. , Gjörstrup P. 
Published: December 2014

1. In dogs under chloralose‐urethane anaesthesia the submaxillary duct was cannulated and connected either to an open outflow system, in which saliva displaced water, or to a closed pressure recording system.2. The secretory cells, which are supplied with β‐adrenoreceptors, were stimulated with isoprenaline, adrenaline or sympathetic nerve stimulation. Myoepithelial cells, supplied with α‐receptors, were activated with phenylephrine, adrenaline or sympathetic stimulation, and also with bradykinin. To abolish α‐receptor stimulating effects of adrenaline and sympathetic nerve stimulation, dihydroergotamine, phenoxybenzamine and phentolamine were used.3. When the secretory cells were activated alone, saliva flowed from the salivary duct, but the flow started late and only a moderately high pressure could be produced in the closed system. Saliva appeared much earlier in the duct when secretion was combined with myoepithelial contraction, and a much higher pressure could be built up in the duct system.4. It is concluded that rapid emptying of saliva in the mouth and a maintained flow at a high rate of the viscous saliva is promoted by contractions of the myoepithelial cells.
Differential release of acetylcholine from the hypothalamus and mesencephalon of the monkey during thermoregulation
Authors: Myers R. D. , Waller M. B. 
Published: December 2014

1. In unanaesthetized monkeys acclimated to primate chairs, 101 isolated sites in the hypothalamus and mesencephalon were perfused at a rate of 30–50 μl./min by means of push—pull cannulae. The perfusate, which contained an anticholinesterase, was assayed for acetylcholine (ACh) activity on the guinea‐pig ileum in the presence of neostigmine.2. The body temperature of each animal was monitored continuously during an experiment by colonic and brain thermistors. To alter the ambient temperature by 15–20° C, either a stream of warm air was passed over the monkey's trunk or containers of ice were placed in its chair chamber to cool the same region.3. Assays of the effluent revealed that the release of ACh varied according to the ambient temperature as follows: elevated only during cooling; elevated only during warming; elevated by both thermal stimuli; suppressed only by cooling; suppressed only by warming; suppressed by both thermal stimuli; elevated during cooling but suppressed by warming; and elevated by warming and suppressed by cooling.4. A composite anatomical ‘mapping’ of all perfusion sites revealed that in response to either peripheral cooling or warming, the output of ACh varied at only 36% of all sites anterior to the mid‐hypothalamic plane, but at 65% of those loci caudal to this coronal plane.5. In the anterior, preoptic area, cooling enhanced the output of ACh at 88% of the active releasing sites, whereas warming reduced the release of ACh at 80% of these perfusion loci. Posterior to this region, ACh release was elevated by cooling at about half of the active releasing sites, but lowered by warming at nearly every active perfusion locus. Within the mesencephalon, the ratio of the temperature‐induced change in ACh release was similar but in an opposite direction, since the level of ACh in the effluent collected from two out of three sites was augmented by cooling, but diminished by warming.6. These results provide additional evidence for the neurochemical model of Myers & Yaksh (1969), which suggests that a cholinergic pathway originating in the anterior, preoptic region transmits efferent signals for heat production. Further, within the posterior hypothalamic area as well as in the mesencephalon of the monkey, the characteristics of the ACh releasing sites reflect a function delegated primarily to heat gain, although evidence of a cholinergic pathway for the heat loss system is also presented.
The formation of synapses in reinnervated and cross‐reinnervated adult avian muscle
Authors: Bennett M. R. , Pettigrew A. G. , Taylor R. S. 
Published: December 2014

1. A study has been made of the formation of synapses in spontaneously reinnervated and cross‐reinnervated anterior latissimus dorsi (ALD) and posterior latissimus dorsi (PLD) muscles of adult fowls.2. Denervated ALD and PLD muscle fibres have a uniform and high sensitivity to iontophoretically applied acetylcholine (ACh). During early reinnervation the sensitivity distribution to ACh of the ALD muscle fibres begins to return to normal before synaptic potentials can be evoked. The normal ACh sensitivity distribution of PLD muscle fibres is also restored after reinnervation. After cross‐reinnervation of the ALD and PLD muscles the ACh sensitivity distribution of many of the muscle fibres is again restored to normal.3. Reinnervating and cross‐reinnervating ALD nerve terminals showed a greater than normal degree of facilitation of transmitter release when a test impulse was applied at various intervals after a conditioning impulse. Cross‐reinnervating PLD nerve terminals showed facilitation of transmitter release rather than the normal depression in a conditioning‐test impulse sequence.4. The distribution of nerve terminals over the surface of spontaneously reinnervated and cross‐reinnervated ALD and PLD muscle fibres has been determined from an examination of the sensitivity distribution to applied ACh, the graded versus all‐or‐none nature of the evoked potential and the distribution of cholinesterase stained synapses.5. The results suggest that the innervation pattern of individual ALD and PLD muscle fibres is restored both after spontaneous reinnervation and cross‐reinnervation.
Effects of muscle stretch on transmitter release at end‐plates of rat diaphragm and frog sartorius muscle
Authors: Turkanis S. A. 
Published: December 2014

1. Miniature end‐plate potentials (m.e.p.p.s) and end‐plate potentials were recorded intracellularly at neuromuscular junctions of the frog sartorius muscle and the rat diaphragm before, during and after muscle stretch.2. Stretch increased the frequency of the m.e.p.p.s and the mean quantum content (m) at end‐plates of the sartorius muscle.3. Stretch enhanced m.e.p.p. frequency of the sartorius muscle in normal Ringer solution as well as in solutions high in magnesium and low in calcium content. In addition, an increase in frequency occurred in the presence of tetrodotoxin and in the absence of neostigmine methylsulphate.4. The magnitude of the increase in m.e.p.p. frequency in the sartorius muscle was negatively correlated with the control frequency.5. In contrast to the above findings at sartorius end‐plates, muscle stretch did not affect the frequency of m.e.p.p.s or the m values at end‐plates of the rat diaphragm.
The hypothermic effect of tetrodotoxin in the unanaesthetized cat
Authors: Clark Wesley G. , Coldwell Barbara A. 
Published: December 2014

1. The hypothermic effect on unanaesthetized cats of tetrodotoxin injected
I.V. or into the lateral cerebral ventricle was examined.2. At an ambient temperature (Ta) of 22° C, tetrodotoxin given intraventricularly was over 400 times more potent in lowering body temperature (Tb) than when given
I.V. The magnitude of the hypothermia was dose‐dependent for both routes. Decreases in Tb as great as 6·8° C were induced by infusions or multiple injections of tetrodotoxin into the ventricle.3. Tetrodotoxin also lowered Tb at Ta = 13, 30 or 35° C. Tachypnoea, which lasted for longer durations and which became more intense the higher the Ta, accompanied development of hypothermia. Shivering was observed only during recovery from hypothermia at 13° C.4. During the tetrodotoxin‐induced hypothermia, animals were still able to regulate against environmental thermal stresses.5. EDTA disodium salt, leucocytic pyrogen and prostaglandin E1 antagonized the hypothermic effect of tetrodotoxin when they were administered during recovery from tetrodotoxin.6. Activation of heat‐loss mechanisms, and the absence of compensatory shivering during development of hypothermia after tetrodotoxin administration, plus lowering of Tb by tetrodotoxin at Ta above as well as below the thermoneutral temperature, indicate that lowering of the thermoregulatory set‐point is the mechanism by which centrally or peripherally administered tetrodotoxin lowers Tb. Further evidence for set‐point lowering after intraventricular administration of tetrodotoxin is provided by persistence of the ability to regulate against both heat and cold stresses during hypothermia. The possibility that the decrease in set‐point could be due to the well known action of tetrodotoxin to block transient increases in membrane sodium ion conductance is discussed in terms of a recent hypothesis regarding ionic control of the thermoregulatory set‐point.
Contrast perception and electrophysiological correlates
Authors: Fiorentini Adriana , Maffei L. 
Published: December 2014

1. Previous findings show that the amplitude of the human visual potentials evoked by gratings alternating in phase at several c/s is linearly related to the logarithm of the grating contrast.2. Similar previous experiments on the cat have shown that both the amplitude of evoked potentials and the amplitude of the response of simple cortical cells to alternating gratings increase linearly with the logarithm of the contrast. No such relation is found for single neurones in the retina or in the lateral geniculate body.3. In this work the contrast of a grating is evaluated psychophysically by human subjects in a range of more than 10 times above threshold, using a binocular matching technique.4. The apparent contrast is found to increase linearly with the logarithm of the stimulus contrast.5. The conclusion is drawn that the linear relation between apparent contrast and the logarithm of the objective contrast might be the outcome of a process of elaboration that is carried out at the simple cell level.
A comparison of the effects of adenosine triphosphate with noradrenaline and with the inhibitory potential of the guinea‐pig taenia coli
Authors: Tomita T. , Watanabe Hisako 
Published: December 2014

1. The response of the smooth muscle of the guinea‐pig taenia coli to adenosine triphosphate (ATP) and related substances was compared with that to noradrenaline and dopamine. The effect of these substances on the inhibitory potential was investigated.2. ATP in concentration of 10−6‐10−5
M suppressed the spontaneous spike and relaxed the preparation. ATP in a concentration higher than 10−4
M hyperpolarized the membrane, reduced the membrane resistance and decreased the inhibitory potential.3. Effects of noradrenaline (5 × 10−6
M) and of dopamine (5 × 10−4
M) were similar to those of ATP (10−3
M). However, the effects of catecholamines were reduced in Cl‐deficient solution and blocked by phentolamine (3·5 × 10−6
M), while the effects of ATP were unaffected.4. A high concentration of phentolamine (3·5 × 10−4
M) almost abolished the inhibitory potential as well as the effects of ATP. The inhibitory potential and the effect of high concentration of ATP (10−3
M) were not impaired by imidazole (50 m
M).5. Adenosine diphosphate, adenosine monophosphate and adenosine produced effects essentially similar to those of ATP. However, their potency was less compared with ATP.6. These electrophysiological observations support the hypothesis that ATP may be the transmitter of the non‐adrenergic inhibitory nerves in the taenia coli. No evidence against the hypothesis was obtained.
The binding of acetylcholine to receptors and its removal from the synaptic cleft
Authors: Katz B. , Miledi R. 
Published: December 2014

1. Acetylcholine (ACh) noise and miniature end‐plate potentials were recorded with focal external micro‐electrodes.2. The effect of prostigmine on the time course of the ‘molecular’ and ‘quantal’ transmitter actions was studied. Prostigmine (10−6 g/ml.) has little or no effect on the duration of the molecular ‘gating action’, while it greatly prolongs the quantal conductance change.3. After inhibition of ACh hydrolysis, the removal of the transmitter from the synapse is generally too slow to be accounted for by free diffusion. It is suggested that diffusion is delayed by binding to post‐synaptic receptors. This is consistent with the finding that receptor blockage by curare or α‐bungarotoxin shortens as well as reduces quantal transmitter action.4. The correlated effects of the receptor‐blocking agents, on size and time course of the miniature end‐plate currents, were subjected to a simple analysis. Its result suggests that after inhibition of cholinesterase about two thrids of the quantal packet of ACh combines with post‐synaptic receptors.5. During focal external recording the effect of prostigmine on the time course of miniature end‐plate potentials can become exaggerated due to what appears to be a compression artifact which obstructs outward diffusion of the transmitter.
Kinetics of potassium transport across single distal tubules of rat kidney
Authors: de Mello‐Aires Margarida , Giebisch Gerhard , Malnic Gerhard , Curran Peter F. 
Published: December 2014

1. The transport of potassium across the distal tubular epithelium was studied in vivo in rats on a normal potassium intake and in rats in which distal tubular potassium secretion was either stimulated by potassium loading or the
I.V. administration of a 5% sodium bicarbonate solution or in which potassium secretion was suppressed by dietary deprivation of potassium or sodium.2. 42K was used to measure unidirectional fluxes across the luminal and peritubular cell membranes and to assess the magnitude of cellular potassium partaking in the transport process. This was accomplished by the simultaneous perfusion of the peritubular capillary network with 42K‐Ringer and of the distal tubular lumen with initially tracer‐free solution. From the steady‐state flux and the time course of tracer washout into the lumen after discontinuing the peritubular perfusion, unidirectional fluxes, rate coefficients of ion transfer and cellular transport pools could be measured.3. Transepithelial movement of potassium involves mixing with a variable cellular potassium transport pool. The latter is significantly elevated in conditions of enhanced distal tubular potassium secretion; cellular potassium labelling is reduced in conditions in which potassium secretion has been suppressed by potassium deprivation.4. Evidence is presented that changes in the peritubular transport pattern are primarily responsible for modifications of potassium translocation. Thus, stimulation of potassium secretion is associated with increased peritubular potassium uptake; a reduced potassium uptake across the peritubular cell membrane accounts for the fall in potassium secretion in potassium‐depleted animals. Whereas passive entry of potassium across the peritubular membrane is augmented in potassium‐loaded animals, the induction of metabolic alkalosis by the administration of 5% sodium bicarbonate stimulates active potassium uptake across the peritubular cell membrane. Sodium deprivation stimulates active reabsorptive transfer of potassium from the tubular lumen.
Analysis of Mauthner cell responses to iontophoretically delivered pulses of GABA, glycine and L‐glutamate
Authors: Diamond J. , Roper S. 
Published: December 2014

1. The intracellularly recorded responses of goldfish Mauthner neurones to iontophoretically applied pulses of amino acids have been analysed: their time courses have been compared with each other, and with those predicted from diffusion theory.2. The rise time of the response to GABA is slower than that to glycine or
L‐glutamate. The response curves of the latter substances were very similar, and unlike that of GABA were markedly affected by increasing the distance of pipette‐tip from the membrane. The results suggest that the time course of the responses to glycine and
L‐glutamate are determined mainly by free diffusion in the brain tissue (at least within about 200 μm of the cell), while that to GABA must be rate‐limited by other factors, e.g. drug‐receptor activation time.3. The possibility that the responses are influenced by some desensitizing process was investigated by applying a second (test) drug pulse during the response to a prior conditioning one. In the case of glycine and of
L‐glutamate there was no attenuation of the response to a second pulse at any time. With GABA, however, the second response was reduced during the period of the conditioning response; the reduction was progressively less marked the later the test pulse occurred. A similar effect with GABA was seen when glycine was used as the test pulse. The responses to long‐maintained drug pulses also indicated that for GABA, but not for glycine or glutamate, there seems to be some desensitizing process present.4. Calculated time courses of responses to brief pulses of glycine and of
L‐glutamate (based upon diffusion theory) differed somewhat from the observed curves, largely during the falling phase. However, when the calculations were based upon second‐order reactions (two molecules of drug per receptor) the diffusion model gave results very like the observed ones.5. Possible implications of these results for the role these three amino acids may have as neuro‐transmitters are mentioned.
Prostaglandin E1 fever induced in rabbits
Authors: Stitt J. T. 
Published: December 2014

1. Micro‐injections of prostaglandin E1 (PGE1) into the anterior hypothalamus of the rabbit produced fever which was nearly immediate in onset. The prostaglandin sensitive region appears to be identical to that described as being fever sensitive to leucocytic pyrogen.2. Micro‐injections of PGE1 into the posterior hypothalamus and midbrain reticular formation of the rabbit did not produce fever.3. The febrile response to PGE1 injected into the anterior hypothalamus was dose dependent over a range of 20–1000 ng.4. Ambient temperature influenced the thermoregulatory mechanism by which PGE1 fever evolved. In the cold, PGE1 fever was due to increased heat production while during heat exposure both evaporative and dry heat losses were reduced without significant changes in heat production. Vasoconstriction, confined mainly to the ears, was effective in producing fever in standard room environments (24–25° C) along with a small increase in heat production.5. The preoptic anterior hypothalamic area retained its thermosensitivity during PGE1 fever; heating this area attenuated, while cooling augmented the fever.6. The results support the view that PGE1 is a mediator of pyrogen induced fever.
Extra‐segmental reflexes derived from intercostal afferents: phrenic and laryngeal responses
Authors: Remmers John E. 
Published: December 2014

1. Phrenic and recurrent laryngeal efferent responses were evoked by brief tetani or single shocks to the cut external intercostal nerves of anaesthetized cats. The reflexes derived from middle thoracic segments (T5 and 6) were compared with those emanating from caudal thoracic segments (T9 and 10).2. During inspiration, middle intercostal nerve stimulation transiently inhibited the spontaneous discharge in both efferent neurograms, whereas stimulation of caudal intercostal nerves facilitated phrenic discharge and usually inhibited recurrent laryngeal activity.3. During expiration, stimulation at either thoracic level enhanced recurrent laryngeal discharge while provoking little or no phrenic response.4. Superficial lesions of the lateral cervical cord, ipsilateral to the stimulus sites, above or below the phrenic outflow, eliminated all reflex responses except the phrenic response to caudal thoracic stimuli. Similarly, in the spinal animal, middle intercostal afferents could not be shown to decrease phrenic excitability. Caudal intercostal afferents cause phrenic excitation by a spinal reflex.5. Group I afferents of the mid‐thoracic segments and group II afferents of the caudal thoracic segments initiate these extra‐segmental reflexes.6. The recurrent laryngeal responses manifest, for the most part, changes in the discharge of fibres innervating the posterior cricoarytenoid muscle. The responses fit the overall pattern of response to middle intercostal nerve stimulation, namely, inhibition of inspiratory muscles and excitation of expiratory muscles. Intercostal afferent stimulation also activated the laryngeal adductor muscles.7. The results support the view that intercostal mechanoreceptors initiate an array of extra‐segmental respiratory reflexes, including spinal and supraspinal arcs. The simplest way to account for the various responses to stimulation of middle intercostal afferents is to postulate a reflex involving supraspinal respiratory neurones.8. The observed reflexogenic differences correlate with anatomical differences between the middle and caudal ribs. Possible functional implications of this relationship are discussed.
Rubidium influx into rat skeletal muscles in relation to electrical activity
Authors: Kernan R. P. , McDermott Mary 
Published: December 2014

1. Rates of 86Rb influx were compared in vivo over 2, 4 and 6 hr periods in various tonic and phasic muscles of rat following its
I.P. injection.During the 2 hr period its influx rate into soleus was about 4 times that of the vastus with the EDL muscles at an intermediate rate. Uptake by diaphragm was fastest reaching equilibrium within 2 hr.2. Unilateral section of the sciatic nerve 48 hr before 86Rb injection reduced isotope uptake into soleus to about 50% of its contralateral control muscle over a 4 hr period. In EDL muscles on the other hand nerve section increased influx by about 75% of control in conscious rats and more than doubled influx in anaesthetized rats.3. Tenotomy of soleus reduced 86Rb influx to 40% of control, but tenotomy in EDL was without effect in influx.4. Uptake of urea into muscles within 5 min of its
I.V. injection was used to determine the possibility of muscle blood flow determining 86Rb influx. Accumulation of urea was not significantly different in control and denervated EDL muscles nor between soleus and vastus muscles in anaesthetized rats, so it seems unlikely that blood flow is important here.5. Membrane depolarization in response to addition of 30 m
M rubidium to external bathing fluid was greater in the case of denervated than in control EDL muscles which was in keeping with the greater 86Rb influx seen in the former muscles. The ouabain sensitivity of rubidium‐induced depolarization in the denervated EDL muscles would suggest, however, that rubidium enters the fibres actively.
The respiratory effects in man of altering the time profile of alveolar carbon dioxide and oxygen within each respiratory cycle
Authors: Cunningham D. J. C. , Howson M. G. , Pearson S. B. 
Published: December 2014

1. Breathing hypoxic gas through an external dead space (ca. 1200 c.c.) stimulated ventilation disproportionately. A loop (ca. 250 c.c.) in the inspiratory pathway reduced the effect.2. The alveolar time patterns of PCO2 and PO2 characteristic of tube breathing with or without the loop have been simulated in moderate hypoxia by changing the composition of inspired gas at selected intervals after the beginning of inspiration.3. Supplying CO2‐free gas in late inspiration usually stimulated ventilation, but less than did real tube breathing. Supplying CO2‐free gas early in inspiration usually depressed ventilation. The difference between the ‘CO2‐free late’ and ‘CO2‐free early’ effects was 20% of the control ventilation (P < 0·001), i.e. was nearly the same as between the effects of real tube breathing without and with the loop.4. Tube‐like PA, O2 time patterns had no effects.5. A—a PCO2 and PO2 gradients remained constant throughout.6. The V̇E, f and VT relations were unaltered in tube breathing.7. The respiratory system can discriminate between small differences in time patterns of PA, CO2 but not of PA, O2; the signal is amplified by steady hypoxia. The arterial chemoreceptors are probably responsible for these effects.