bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pancreatic acinar cells: acetylcholine‐evoked electrical uncoupling and its ionic dependency
Authors: Iwatsuki N. , Petersen O. H. 
Published: December 2014

1. Isolated segments of mouse or rat pancreas were placed in a Perspex bath through which physiological saline solutions were circulated. Intracellular recordings from surface acini were made by inserting up to three separate micro‐electrodes into neighbouring cells within the same acinus. Through one of these electrodes current pulses could be injected. Electrical coupling between the cells could be continuously assessed. The acinus under investigation was stimulated by iontophoresis of ACh from an extracellular micropipette.2. During resting conditions all cells within an acinus were fully electrically coupled. A 5‐10 sec pulse of a relatively large iontophoretic ACh ejecting current, causing initially the well characterized surface cell membrane depolarization and resistance reduction, was followed by a marked electrical uncoupling of neighbouring cells. In some cases one cell was clearly being isolated equally from the two other cells impaled, in other cases the cell into which current pulses were injected was becoming more isolated from one of the neighbouring cells than from the other one.3. The ACh‐evoked electrical uncoupling was completely reversible and could be repeatedly observed in the same cell.4. The electrical uncoupling in response to short pulses of ACh (5‐10 sec) was not affected by even prolonged (up to 50 min) exposure to Ca‐free solution containing EGTA.5. ACh‐evoked uncoupling (short pulses) was not reduced about 5 min after introduction of Mn (2 m
M), Ni or Co (5 m
M). Mn thereafter gradually reduced and finally (after about half an hour) abolished the ACh‐evoked uncoupling. Ni and Co gradually enhanced the uncoupling response. The blocking effect of Mn on the ACh‐evoked uncoupling occurred much faster in the absence of superfusion fluid Ca.6. During a period of sustained ACh stimulation sustained electrical uncoupling was observed. If Ni or Co (5 m
M) was introduced during such a stimulatory period the cells recoupled. This effect of Ni and Co was immediate and fully reversible.7. The uncoupling responses to short pulses of ACh was not reduced immediately after replacing superfusion fluid Na by Tris at a time when the surface cell membrane depolarization and resistance reduction was already severely reduced. Thereafter a gradual slow reduction of the ACh‐evoked uncoupling was observed. This did not occur if Na was replaced by Li.8. It is concluded that the Ca needed to raise [Ca2+]i sufficiently to cause electrical uncoupling comes from the cells in cases of uncoupling evoked by short pulses of ACh, but from the external solution in cases of sustained uncoupling evoked by sustained stimulation of ACh.
Modification of visual response properties in the superior colliculus of the golden hamster following stroboscopic rearing
Authors: Chalupa Leo M. , Rhoades Robert W. 
Published: December 2014

1. Visual response properties of superior collicular neurones were investigated in golden hamsters reared from birth to adulthood in a stroboscopic environment.2. In comparison to normally reared animals, there was a marked decrease in the incidence of directionally selective cells in the colliculus of the strobe‐reared hamsters. This effect was apparent when directional selectivity was determined by either the null criterion or a statistical measure. The reduction in directionally selective cells was found in both superficial and the deep layers of the colliculus.3. Neurones in strobe‐reared hamsters also exhibited a different speed preference distribution from that obtained for normal animals, in that more cells in the restricted hamsters responded only to slow velocities, and less were broadly tuned with regard to the speed of moving stimuli.4. In addition to the effects obtained in dynamic response properties, there were also changes in the static response properties of superior collicular neurones. These were an increase in the proportion of cells whose responses were not affected by changing the size of a stationary flashed stimulus, and a concomitant decrease in the number of cells demonstrating either partial or complete suppression when the size of a flashed stimulus exceeded the boundaries of the receptive field activating region. Furthermore, while all cells which responded to stationary stimuli in normal animals yielded only phasic responses to stimulus onset and/or offset, in the strobe‐reared hamsters eight cells were encountered which responded in a sustained fashion to stationary spots.5. There was no indication of an increased responsivity in the restricted animals to strobe stimulation, even when a strobe rate identical to that employed in the rearing environment was employed.6. The results were interpreted as indicating a disruption of normal visual functional organization in the hamster's superior colliculus by an aberrant visual input during development.
The equilibrium between metarhodopsin I and metarhodopsin II in the isolated frog retina
Authors: Baumann Ch. 
Published: December 2014

1. Rapid and slow changes in the absorbance of isolated frog retinae produced by exposure to brief flashes were studied at temperatures between 5 and 30 °C.2. Rapid changes observed at 475 nm consist of a transient increase of absorbance followed by an exponential decay to a new level of absorbance which is lower than before the flash exposure.3. The new level of absorbance determines the initial conditions of slow changes following the rapid ones. At higher temperatures, the loss of absorbance during the rapid changes is greater than at lower temperatures. Accordingly, the slow reactions start at lower levels of absorbance when the temperature is high.4. Quantitative analysis showed that the rapid reactions can be described in terms of two consecutive reactions followed by an equilibrium reaction: the light‐controlled formation of lumirhodopsin, decay of lumirhodopsin to metarhodopsin I, and the equilibrium reaction between the metarhodopsins I and II.5. The slow absorbance changes observed in the visible (λ = 480 nm) are due to metarhodopsin I and to metarhodopsin III. Metarhodopsin I decays during the early phase of slow reactions but can noticeably influence the kinetics at lower temperatures.6. The activation energy of the lumirhodopsin decay is 22.5 kcal/mole, that of the conversion of metarhodopsin I into metarhodopsin II is 30.1 kcal/mole. The entropy change associated with the metarhodopsin I‐II equilibrium amounts to +34 cal/mole. K.
Destruction of a single cell in the central nervous system of the leech as a means of analysing its connexions and functional role
Authors: Bowling D. , Nicholls J. , Parnas I. 
Published: December 2014

A method has been devised for killing an individual neurone in the
C.N.S. of the leech by injecting it with Pronase. The technique has been used to examine the role of individual sensory and motor cells involved in producing reflex movements.1. After a neurone was injected with Pronase, either in an intact animal or an isolated ganglion, its cell body lost its resting and action potentials. Some hours later the injected cell's axons in the periphery failed to conduct impulses. In the intact animal the cell body could no longer be discerned after a few weeks.2. To test for destruction of processes within the neuropile, cells were injected first with the enzyme horseradish peroxidase (HRP) and then several hours later with Pronase. Absence of the characteristic HRP reaction product indicated that Pronase had spread throughout the arborization of the cell.3. Injection of Pronase into one cell did not produce overt electrophysiological or anatomical changes in other cells in the ganglion including neurones that were originally electrically coupled to the killed cell.4. Evidence that an individual cell was the only motoneurone supplying particular muscles was provided by destruction of that cell in otherwise intact animals, which resulted in a characteristic motor deficit in the area supplied by the killed cell. Over a period of months, functional recovery of the affected muscles occurred by way of homologous cells in adjacent ganglia.5. A further application of the technique was to trace the connexion that a particular sensory neurone makes onto two motoneurones that are electrically coupled. Normally, the sensory neurone gives rise to excitatory potentials in both post‐synaptic cells. Synaptic potentials could still be recorded in one motor cell after the other had been destroyed by Pronase, indicating that synapses were made directly onto both of the motoneurones.
Fever and survival in rabbits infected with Pasteurella multocida
Authors: Kluger M. J. , Vaughn L. K. 
Published: December 2014

1. Fever and survival rate of New Zealand white rabbits, injected with two doses of live Pasteurella multocida, were compared to determine if the relation between fever and survival observed in reptiles is also seen in a mammal. Since it is known that fever is beneficial in infected reptiles, our experiments were viewed as an initial step in the investigation of a similar potentially beneficial effect in mammals.2. There was a statistically significant correlation between the fever magnitude and survival. As fever increased up to 2·25 °C, the survival rate increased. Fevers above this level were associated with a decreased survival rate.3. Antipyretic drugs were administered to half the rabbits. The drugs were ineffective in reducing the fevers produced by injections of large doses of bacteria. Rabbits infused with antipyretics had a decreased mortality rate. The decreased mortality rate may be due to some action of the drugs other than their antipyretic effect.4. In vitro growth of P. multocida at normal (39 °C) and febrile (42 °C) temperatures was not significantly different. This suggests that the increased survival rate associated with higher fevers was not due to a direct inhibition of the growth of the bacteria by the increased temperature. It may be due to an enhancement of some aspect of the rabbits' immunological defences.5. It remains to be determined whether fever causes a higher survival rate or whether fever is only correlated with survival rate.
Influence of rate of induction of hypoxia on the ventilatory response
Authors: Mahutte C. K. , Rebuck A. S. 
Published: December 2014

1. We have studied the influence of rate of induction of hypoxia on the duration of the phases of the respiratory cycle in seven conscious healthy subjects.2. Nine hypoxic procedures were performed on each subject, comprising three different rates of induction of hypoxia each at three different levels of PCO2. Ventilation vs. arterial O2 saturation plots were constructed and patterns of response were analysed in terms of ventilation vs. tidal volume and tidal volume vs. inspiratory duration (TI) and vs. expiratory duration (TE).3. The highest ventilatory responses were observed during steady‐state hypoxia when PCO2 was held at a level similar to the control mixed venous level; progressive hypoxia at this PCO2 failed to stimulate ventilation to comparable levels. The ventilatory response was not influenced by rate of induction of hypoxia when PCO2 was maintained at an end‐tidal PCO2 close to the control level.4. As tidal volume increased in response to hypoxia, TI and TE shortened. The progressive decrease in cycle duration occurred at all levels of PCO2 and at all rates of induction of hypoxia, but was most marked under eucapnic conditions during steady state.5. It is concluded that steady‐state hypoxia may produce a higher ventilatory response than progressive, non‐steady‐state hypoxia. Inspiratory time shortens as tidal volume increases irrespective of the rate of induction of hypoxia.
Variability of transmitter quanta released during incorporation of a false transmitter into cholinergic nerve terminals
Authors: Large W. A. , Rang H. P. 
Published: December 2014

1. Electrophysiological techniques have been used to investigate the variability of quanta released during various stages of the incorporation of acetylmonoethylcholine (AMECh) into the transmitter store at the neuromuscular junction.2. Stimulation of the rat phrenic nerve—diaphragm preparation at 3 Hz for 15‐25 min reduced the time constant of decay τm.e.p.c. of miniature end‐plate currents from 1·61 ± 0·08 (mean ±
S.E. of mean) msec to 1·32 ± 0·09 msec; this represents 45% replacement of acetylcholine (ACh) by AMECh. Total replacement of ACh was achieved by a further 30‐60 min stimulation which reduced τm.e.p.c. to 0·93 ± 0·06‐msec.3. At the intermediate stage of exchange, the coefficient of variation c.v.τ of τm.e.p.c. increased from the control value of 0·094 ± 0·005 to 0·154 ± 0·012. The latter value was less than the value (0·29) calculated for two distinct populations of quanta (i.e. pure ACh and pure AMECh quanta). Moreover, frequency distribution histograms of τm.e.p.c. did not reveal a bimodal distribution. Total replacement of ACh by AMECh achieved by the second period of stimulation decreased c.v.τ towards the control value.4. Pre‐incubation of muscles with MECh (to replace any stored choline) or stimulation in the presence of a cholinesterase inhibitor (to prevent ACh destruction and hence re‐uptake of choline) did not produce any greater degree of heterogeneity than was seen in the absence of these procedures.5. The increase in c.v.τ observed at the intermediate stage of replacement disappeared spontaneously with a half‐time of about 1 hr at 20 °C.6. These results are discussed in terms of the vesicle hypothesis.
Different mechanisms for neutral amino acid uptake by new‐born pig colon
Authors: Sepúlveda F. V. , Smith M. W. 
Published: December 2014

1. Mucosal amino acid uptake by pig proximal colon, measured independently for fourteen different amino acids each used at a concentration of 1 m
M, ranged from 0·6 to 8·6 n‐mole. cm−2. min−1 in the new‐born to 0 to 0·3 n‐mole. cm−2. min−1 in the 2‐day‐old animal. Long chain amino acids entered the mucosa of new‐born pig proximal colon much more readily than did short chain amino acids.2. Glycine was used extensively to inhibit the uptake of other neutral amino acids. The degree of maximal inhibition produced depended on the amino acid used. The relative inability of glycine to inhibit the uptake of long chain amino acids suggested that these compounds could cross the brush border on a carrier inaccessible to glycine. The glycine‐sensitive uptake remained more or less constant for all amino acids tested (1‐2 n‐mole.cm−2.min−1); the glycine‐insensitive uptake varied from 0 to 7 n‐mole.cm−2.min−1 (glycine and methionine respectively).3. It is suggested that at least two mechanisms exist for the entry of neutral amino acids into pig proximal colon, one showing specificity for hydrophobic amino acids and the other having broad specificity. The mechanism responsible for the uptake of long chain essential amino acids predominates over the less specific mechanism.4. These results are discussed in relation to previous work carried out on the rabbit ileum where two similar systems for neutral amino acid entry have been shown to be present. Both tissues transport hydrophobic amino acids on their own specific carrier at approximately the same rate; the ability of the pig colon to transport amino acids on the broad specificity carrier is eight times less than in the rabbit ileum. The possibility is raised that this system is subject to regulation.
Descending influences on the responses of spinocervical tract neurones to chemical stimulation of fine muscle afferents
Authors: Hong S. K. , Kniffki K.-D. , Mense S. , Schmidt R. F. , Wendisch Marion 
Published: December 2014

1. In cats, extracellular micro‐electrode recordings were made from axons of the spinocervical tract (s.c.t.) in both the decerebrate state and during cold block of the spinal cord (reversible spinal state) to examine the effects of intra‐arterial injection of algesic agents (bradykinin, potassium, 5‐hydroxytryptamine) into the gastrocnemius‐soleus (g.s.) muscle on the discharge behaviour of s.c.t. neurones.2. In the decerebrate state without cooling the spinal cord 13% of the cells (eleven out of eighty‐three) responded to intra‐arterial injection of bradykinin, 33% (twenty‐two out of sixty‐nine) to 5‐hydroxytryptamine, and 38% (thirty‐five out of ninety‐one) to potassium injection.3. The general time course and the latency of the responses of s.c.t. cells induced by injection of pain‐producing substances into the g.s. muscle reflect in many respects the activations of g.s. group III and group IV primary afferent units studied previously.4. For twenty‐seven s.c.t. neurones the period of recording was long enough to record the responses of the same cell to injections of algesic agents in both the decerebrate and the reversible spinal state. In the reversible spinal state 83% (nineteen out of twenty‐three) of the s.c.t. neurones tested with all the three substances responded to at least one of the algesic agents. In the decerebrate state the percentage was lower (39%).5. Reversible spinalization led not only to a significant increase in the number of s.c.t. neurones responding to the algesic agents used but also to an increase in the magnitude of the chemically induced responses.6. The mean latency of the responses of neurones that were activated in both preparations were shorter in the reversible spinal state than in the decerebrate state.7. Control experiments showed that the responses to bradykinin and potassium were entirely due to the nervous outflow from the g.s. muscle. In contrast, intra‐arterially applied 5‐hydroxytryptamine influenced the s.c.t. cells via unknown additional sites of action.8. The results indicate that muscular group III and/or group IV units excitable by algesic substances do project on to neurones of the spinocervical tract. Furthermore it is concluded that the responses of s.c.t. neurones to activation of fine muscle afferents by algesic agents are subject to a descending control similar to the well known descending modulation of their responsiveness to cutaneous input. Therefore, in addition to serving as a cutaneous pathway the spinocervical tract may take part in muscular nociception.
Relation between catecholamine‐induced cyclic AMP changes and hyperpolarization in isolated rat sympathetic ganglia
Authors: Kirby P. J. , Brown D. A. , Caulfield M. P. 
Published: December 2014

1. The effect of catecholamines on cyclic adenosine 3′5′‐monophosphate (cyclic AMP) production in isolated rat superior cervical ganglia has been measured under experimental conditions in which they also produce ganglion hyperpolarization.2. (±)Isoprenaline (1 μ
M) increased cyclic AMP levels by 8‐100 times after 15 min incubation at 25 °C. Half‐maximal stimulation occurred at about 0.03 μ
M. This was due to stimulation of β‐receptors, since it was prevented by 1 μ
M‐propranolol but not by 1 μ
M‐phentolamine.3. The α‐agonists phenylephrine (100 μ
M), dopamine (100 μ
M) and clonidine (1 μ
M) did not produce a detectable increase in ganglionic cyclic AMP. Dopamine (100 μ
M) was also ineffective at 37 °C in the presence of 10 m
M‐theophylline.4. Exogenous cyclic AMP (0.01‐1 m
M) hyperpolarized the ganglion. This effect was replicated by other adenosine compounds, most effectively by adenosine and by adenosine 5′‐monophosphate, and was antagonized by theophylline. Dibutyryl cyclic AMP was weaker than cyclic AMP.5. Neither theophylline nor the non‐xanthine phosphodiesterase inhibitor, Ro 20‐1724, enhanced the hyperpolarizing actions of noradrenaline or dopamine.6. Since catecholamine‐induced hyperpolarization of the isolated rat ganglion is induced via α‐receptors, whereas cyclic AMP‐production is induced via β‐receptors, it is concluded that cyclic AMP is unlikely to mediate the hyperpolarization. The effect of exogenous cyclic AMP may be due to an action on external adenosine‐receptors.
Selective response of rat peripheral sympathetic nervous system to various stimuli
Authors: Ulus I. H. , Wurtman R. J. 
Published: December 2014

1. We utilized the induction of tyrosine hydroxylase, a catecholamine‐synthesizing enzyme, in sympathetic ganglia and adrenal medullae to explore the central and peripheral mechanisms through which choline, various environmental stresses, and drugs that alter blood pressure or central neurotransmission affect various portions of the sympathetic nervous system. Animals received each treatment chronically, and enzyme activity was measured in the superior cervical, stellate, and coeliac ganglia and in the adrenal medullae.2. Choline administration increased tyrosine hydroxylase activity in all four tissues, probably by increasing the release of acetylcholine from preganglionic sympathetic neurones that synapse on catecholamine‐producing ganglion and chromaffin cells; carbachol and nicotine had similar effects.3. Insulin enhanced tyrosine hydroxylase activity primarily in the coeliac ganglion and the adrenal medullae, but not in the superior cervical ganglia.4. Reserpine and phenoxybenzamine increased the activity of the enzyme in all four tissues.5. Prolonged exposure to a cold environment increased enzyme activity in all four tissues, but especially in the stellate and coeliac ganglia; forced swimming affected tyrosine hydroxylase only in these two ganglia.6. Several drugs known to modify central neurotransmission were found to increase tyrosine hydroxylase activity in some portions of the sympathetic nervous system but not in others. 5,7‐Dihydroxytryptamine, which destroys terminals of serotoninergic neurones, enhanced enzyme activity in all four tissues, but primarily in the coeliac ganglion and adrenal medullae. ET‐495 (a dopaminergic agonist),
D‐amphetamine, and morphine induced tyrosine hydroxylase activity in the adrenal medullae and the coeliac ganglion, but not in the superior cervical ganglia. Oxotremorine, a centrally acting muscarinic agonist, increased tyrosine hydroxylase activity only in the adrenal medullae; its effect was not blocked by methylatropine, a peripheral muscarinic blocker.7. These data indicate that specific neurones in the central nervous system, which utilize specific neurotransmitters and which are differentially affected by drugs and environmental inputs, selectively influence the outflows through the various zones of the sympathetic nervous system.
The properties of bovine lens membranes measured by a conventional double‐chamber method
Authors: Delamere N. A. , Duncan G. 
Published: December 2014

1. When the bovine lens was mounted in a divided chamber, an asymmetry potential of 4·3 mV (anterior face positive) was measured across the lens and values of 0·48 and 0·60 were obtained for PNa/PK of the anterior and posterior faces respectively.2. The half‐times for the depolarization of the anterior and posterior face potentials on increasing the external K concentration were 20 and 14 min respectively compared to less than 2 min for the corresponding change determined previously from the totally immersed lens.3. The electrical resistance of the anterior surface was significantly smaller than that of the posterior and both resistances were much smaller than the value previously obtained from the bovine lens immersed in solution.4. The K permeability of the anterior surface, measured by 42K efflux experiments, was greater than the value for the posterior surface and both were again very much higher than the value obtained for the totally immersed lens.5. The discrepancies between the present double‐chamber preparation and the data obtained previously can be explained if it is assumed that the capsule provides a short‐circuit pathway between the chamber port and the lens membranes. As the capsule is thicker at the anterior face, the short circuit there would be greater and this may explain many previously observed ‘asymmetry’ properties for the lens.