bluuebunny/crossref_metadata_2025 huggingface dataset:
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.
Transcapillary exchange in the cat salivary gland during secretion, bradykinin infusion and after chronic duct ligation.
Authors: Mann G E , Smaje L H , Yudilevich D L
Published: December 2014

1. Capillary permeability‐surface area products for 86Rb, [51Cr]EDTA (mol. wt. 357), [57Co]cyanocobalamin (mol. wt. 1353) and [125I]insulin (approximate mol. wt. 6000) have been measured using the single‐circulation, multiple‐tracer dilution technique in the in situ perfused submandibular salivary gland during parasympathetic nerve stimulation, close‐arterial bradykinin infusion and following chronic duct ligation. 2. In glands with a natural blood supply, permeability‐surface area for 86Rb and [51Cr]EDTA increased during parasympathetic stimulation, but this was shown to be related to the concomitant increase in blood flow rather than to a change in capillary permeability or in surface area. 3. In glands perfused at constant flow, parasympathetic stimulation led to a decrease in permeability‐surface area for EDTA (‐19.1 +/‐ 5.2%, mean +/‐ S.E., n = 5, P less than 0.05) cyanocobalamin (‐12.3 +/‐ 6.0, n = 12, P less than 0.05), and insulin (‐15.3 +/‐ 4.8, n = 11, P less than 0.02). It is suggested that this may be the result of a redistribution of flow from the acinar microcirculation to a less permeable ductal vasculature. 4. Bradykinin infusion had no significant effect on permeability‐surface area for EDTA and cyanocobalamin in perfused glands. 5. In perfused glands, ligation of the submandibular duct for 3‐‐12 days reduced permeability‐surface area (ml.min‐1.g‐1) for [51Cr]EDTA from 5.26 +/‐ 0.60 (mean +/‐ S.E., n = 9) to 4.20 +/‐ 0.12 (n = 4, P less than 0.30), [57Co]cyanocobalamin from 3.22 +/‐ 0.12 (n = 48) to 2.02 +/‐ 0.08 (n = 15, P less than 0.001) and [125I]insulin from 1.52 +/‐ 0.07 (n = 39) to 0.72 +/‐ 0.23 (n = 11, P less than 0.001).
Microspectrophotometric demonstration of four classes of photoreceptor in an old world primate, Macaca fascicularis.
Authors: Bowmaker J K , Dartnall H J , Mollon J D
Published: December 2014

1. Microspectrophotometric measurements reveal four classes of photoreceptor in the retina of the cynomolgus monkey, Macaca fascicularis, which is known to possess colour vision similar to that of a normal human trichromat. 2. Although the eyes were removed in bright illumination, the densities of pigment were comparable to those we have measured in dark‐adapted rhesus retinae. 3. The mean wave‐lengths of peak sensitivity (lambda max) for the four classes of photoreceptor were 415, 500, 535 and 567 nm. 4. The band widths of the absorbance spectra decreased linearly as the wave‐number of peak sensitivity decreased. 5. If, by assuming a reasonable value for the axial density of the rod outer segment and correcting for lens absorption, a spectral sensitivity for human vision is reconstructed from the P500 pigment, it is found to be systematically broader than the CIE scotopic sensitivity function. 6. Given explicit assumptions, it is possible from the P535 and P567 pigments to reconstruct human psychophysical sensitivities that resemble the pi 4 and pi 5 mechanisms of W. S. Stiles. 7. Although the P415 pigment has a lambda max much shorter than that of the psychophysically measured blue mechanisms, the two spectral‐sensitivity functions are brought into proximity when the microspectrophotometric data are corrected for absorption by the optic media.
Persistent obesity in rats following a period of consumption of a mixed, high energy diet.
Authors: Rolls B J , Rowe E A , Turner R C
Published: December 2014

1. Adult male hooded rats which were offered a mixed, high energy diet for 90 days were hyperphagic and became significantly obese compared to chow‐fed control rats. Fasting plasma insulin and glucose levels were initially elevated in the experimental rats, but later in the 90 day period were similar to control levels. 2. When the high energy foods were withdrawn after 90 days and just chow was available, the obese rats maintained the elevated body weights. The obese rats were initially hypophagic, but chow intakes rapidly reached control levels. Plasma insulin and glucose levels were similar in both groups, suggesting that the persisting obesity may not be associated with altered insulin resistance. 3. Five weeks after withdrawal of the ‘fattening’ diet, half of the experimental rats were offered restricted access to chow for 27 days to reduce their weights to control levels. When the rats were again given free access to chow, they returned to the previously elevated weight. 4. Eighteen weeks after withdrawal of the ‘fattening’ diet, the experimental rats had significantly elevated body weights and fat stores. The elevated body weight was not simply due to increased growth because, although the experimental rats had slightly more lean body mass than the control rats, the increase in fat was not related to body size.
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.
The release of acetylcholine from post‐ganglionic cell bodies in response to depolarization.
Authors: Johnson D A , Pilar G
Published: December 2014

1. Acetylcholine (Ach) release from parasympathetic ganglia cell somata was investigated in denervated avian ciliary ganglia. Three days after the input to the ganglion (the oculomotor nerve) was sectioned, all presynaptic nerve terminals had degenerated. 2. Denervated ganglia were shown to contain endogenous ACh and to be capable of synthesizing [3H]ACh from [3H]choline added to the incubation medium. 3. In response to depolarization induced by incubation in 50 mM‐[K+]o, denervated ganglia released [3H]ACh into bath effluents in amounts approximately 15% of the non‐denervated contralateral control. This release was shown to be Ca2+ dependent in both intact and denervated ganglia. 4. Antidromic electrical stimulation of ciliary nerves also elicited [3H]ACh release. Nicotine (1 microgram/microliter.) depolarized denervated ciliary ganglion cells and evoked release of the transmitter and this release was antagonized by curare. 5. It is concluded that the ganglionic cell bodies sysnthesized ACh and released the transmitter in response to K+ depolarization, antidromic stimulation and cholinergic agonists, despite the lack of morphological specializations usually associated with stimulus‐induced release of neurotransmitter. The evidence suggests the existence of a mechanism of transmitter release which is Ca2+ dependent, probably from a cytoplasmic pool and therefore distinct from the usual vesicular release at the nerve terminal.
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.
The cat's vestibulo‐ocular reflex.
Authors: Donaghy M
Published: December 2014

1. The conscious cat's vestibulo‐ocular reflex (v.o.r.) has been studied using the electro‐oculogram to measure eye movements. A servomotor was used to rotate the head horizontally while the body remained stationary. 2. The frequency content of natural head movements in the cat has been determined by Fourier analysis. The fastest and most kinked head movement profiles contain frequency components of significant power extending up to 7‐10 Hz. 3. The transfer function of the v.o.r. slow‐phase response was measured in the frequency range 0.2‐7 Hz. At 1 Hz the average gain is 0.94 with a phase lead of 3 deg. At 7 Hz the gain has only fallen to 0.81 and the phase lag is 10 deg. This indicates that the v.o.r. can compensate to a considerable degree for the high‐frequency components of natural head movements. 4. Rotation of the body around a stationary head in the absence of vision does not produce a measurable neck‐ocular reflex. 5. The presence or absence of fast phases has no effect on the phase lead of the v.o.r. slow‐phase response at 0.2 Hz. 6. V.o.r. fast phases never occur more frequently than 4/sec. 7. Fast phases do not function merely to recentre the eyes once a slow phase has driven them to extreme orbital eccentricities. Instead, fast phases occur early on and serve to offset gaze in the same direction as the head movement.
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.
Phosphate fluxes in single muscle fibres of the spider crab, Maia squinado.
Authors: Caldwell P C , Lowe A G
Published: December 2014

1. The rates of influx and efflux of [32P]orthophosphate (Pi) have bben measured in single muscle fibres of the spider crab, Maia squinado. 2. Rates of influx of 32Pi from salines containing 0 . 11 to 0 . 37 mM‐Pi ranged from 0 . 11 to 0 . 41 p‐mole cm‐2 sec‐1. 3. After injection of [32P]orthophosphate there was an early rapid phase of 32P efflux which was maximal after about 5‐10 min, then a gradual decline until a low steady‐state efflux rate was established after about 100 min. The rate of decline of 32P efflux was similar to the rate of equilibration of injected 32Pi with arginine phosphate and ATP. 4. The steady‐state rate of 32P efflux was typically about 0 . 70 p‐mole cm‐2 sec‐1 when the sarcoplasmic Pi concentraion was 5 m‐mole kg‐1. Exposure of mucle fibres to conditions which caused contraction and increased the sarcoplasmic concentration of Pi also increased the rate of 32P efflux, which appeared to be linearly related to sarcoplasmic Pi concentration. 5. The results are compared with previous measurements of phosphate fluxes in nerve.
The monkey globus pallidus: neuronal discharge properties in relation to movement.
Authors: Iansek R , Porter R
Published: December 2014

1. Recordings were made of the natural discharges of 388 pallidal neurones in awake, free‐to‐move monkeys in order to describe the discharge properties of such neurones in relation to normal movement performance. 2. Of the 388 neurones, 156 discharged only in association with one direction of movement of the forelimb about a specific joint. If that movement was not taking place the neurone would not discharge. 3. All joints and directions of movement for the upper limb were represented by clusters of cells within the pallidal population. 4. Twenty‐nine per cent of neurones co‐varied with movement of both contralateral and ipsilateral limb for the same direction of movement about a given joint; distal movements were represented with similar frequency to proximal movements in this group. 5. Afferent information provided by natural stimulation of peripheral receptors did not directly influence either the discharging or non‐discharging pallidal neurones. 6. Movement related neurones were regionally organized and were found in the posterior part of the pallidum.
Variation in the isometric maintenance heat rate with muscle length near that of maximum tension in frog striated muscle.
Authors: Aubert X , Gilbert S H
Published: December 2014

1. Tension and heat rate were measured as a function of muscle length in the range 0.75‐‐1.25 lO in 10‐sec isometric tetani in frog striated muscle at 0 degrees C in seven experiments. lO was defined as the length at which maximal tension was developed. 2. The length at which the stable maintenance heat rate (hB) was maximal was 7‐‐16% lO shorter than the length at which tension was maximal (Pmax). 3. The range of hB at the length at which tension was maximal was 0.82‐0.97 times the maximum value of hB. 4. For equal values of tension of 0.9 Pmax on each side of lO, hB was almost 40% greater at the shorter muscle length. 5. The results show that h(B) varies considerably with muscle length near lO, where tension varies little, and imply that tension is not the sole determinant of energy liberation in this little region.
Effects of denervation and botulinum toxin on muscle sensitivity to acetylcholine and acceptance of foreign innervation in the frog.
Authors: Antony M T , Tonge D A
Published: December 2014

1. The effects of denervation and local paralysis produced by botulinum toxin (type D) on the sensitivity of skeletal muscle to ACh and its ability to accept innervation by an implanted foreign nerve were investigated in the frog. 2. Denervated muscles developed supersensitivity to ACh within 2 weeks and became extensively innervated by an implanted foreign nerve after about 4 weeks. 3. Chronic electrical stimulation of denervated muscles (50 Hz for 1 sec every 60 sec) did not prevent the development of supersensitivity. 4. Muscles paralysed by botulinum toxin did not usually develop supersensitivity to ACh until after 2‐3 months and the extra‐junctional sensitivity of individual fibres was generally less than after denervation. Significant innervation of the paralysed muscles by an implanted foreign nerve did not occur until after 2‐3 months. 5. The results suggest that in the frog nerves are able to control muscle sensitivity to ACh and to prevent innervation by foreign nerves by some mechanism other than muscle activity. Prolonged inactivity seems to result in some development of extra‐junctional sensitivity and acceptance of foreign innervation.
Milk yield, suckling behaviour and milk ejection in the lactating rat nursing litters of different sizes.
Authors: Russell J A
Published: December 2014

1. The quantitative relationship between the suckling stimulus and several suckling‐dependent variables was studied in lactating rats. 2. The intensity of the suckling stimulus, measured as the product of duration and number of pups suckling was in proportion to litter size for litters of one, ten or twenty‐two pups. 3. Pups in the litters of ten grew fastest. Single‐pup litters grew most slowly, some not at all. Litter weight gain, corrected for inevitable losses, was used to estimate milk yield. Total milk yield was greater for litters of twenty‐two to twenty‐four pups than for litters of ten pups only in the first week. Milk yield for single pups was up to 7% of the yield for ten pups. Milk yield per mammary gland sucked was similar for the larger litters but less for single pups. 4. The number of milk ejections, measured as pup stretch reactions, in observation periods of 225 min, was similar for litters of ten and twenty‐two to twenty‐four pups, but less for single‐pup litters. 5. The suckling stimulus applied by single‐pup litters inhibited ovarian growth less effectively than did the stimulus applied by larger litters. 6. There was no change in serum osmolality during lactation. 7. It is concluded that litters of ten or twenty‐two to twenty‐four pups applied suckling stimuli of different intensities, but these had similar effects on the daily secretion rate of oxytocin, milk production and suppression of ovarian growth. Single‐pup litters were less effective.
The effects of tetraethylammonium and cobalt ions on responses to extrinsic current in toad rods.
Authors: Fain G L , Quandt F N
Published: December 2014

1. Double‐barrel micropipettes were used to pass pulses of current in darkness into single rods in the isolated, perfused retina of the toad, Bufo marinus. 2. In normal Ringer solution, current pulses evoked non‐linear changes in membrane potential which varied as a function of current amplitude and of time. Responses to currents of both polarities showed slow relaxations toward the base line during the pulse, and the steady‐state I‐V curve exhibited a prominent outward rectification. 3. In Ringer containing 12 mM‐TEA, the slow relaxation of voltage during outward current pulses was diminished, and the outward rectification was markedly reduced. In contrast Co2+, at a concentration in excess of that required to block Ca2+ spikes in rods, increased the receptor input resistance but did not reduce either the amplitude of the slow relaxation or the extent of outward rectification. 4. These experiments indicated that the outward rectification of rods is predominantly due to a conductance which is gated by voltage rather than by entry of Ca2+. 5. Long‐lasting after‐potentials followed the termination of outward current pulses. In normal Ringer the after‐potentials were hyperpolarizing and were accompanied by an increase in input conductance. In TEA, the afterpotentials were depolarizing and were also accompanied by an increase in input conductance. The after‐depolarizations in TEA were enhanced by Sr2+ and blocked by Co2+. These experiments suggest that the hyperpolarizing and depolarizing afterpotentials are produced by different mechanisms, the hyperpolarizing by an increase in K+ conductance, and the depolarizing by an increase in Ca2+ conductance.
The action of isoprenaline on the smooth muscle of the guinea‐pig taenia coli.
Authors: Bülbring E , den Hertog A
Published: December 2014

1. The beta‐action of catecholamines on the smooth muscle of guinea‐pig taenia coli was investigated by observing the effects of isoprenaline (2 X 10(‐8)‐7.2 X 10(‐6) M) in the presence of an alpha‐blocker, phentolamine (6.3 X 10(‐6) M). Electrical and mechanical activity were recorded with the double sucrose gap method. Calcium and potassium fluxes were determined using the 45Ca and 42K isotopes. 2. Isoprenaline suppressed spontaneous spike generation, reduced the size of evoked phasic contractions, and caused a small hyperpolarization of the membrane without change in membrane resistance. These effects were abolished by a beta‐blocker, propranolol (6.8 X 10(‐6) M). 3. The hyperpolarization induced by isoprenaline was smaller in quiescent, nonstimulated muscle than in active, frequently stimulated preparations. It occurred with the same time course as the reduction in the size of evoked phasic contractions. Both effects were dose dependent and reached a maximum at 7.2 X 10(‐7) M‐isoprenaline. 4. Hyperpolarization by direct current application did not reduce the size of evoked phasic contractions until excitation threshold was reached. In the presence of isoprenaline, repolarization of the membrane to its original level by depolarizing current application did not restore the reduced phasic contractions to their original size. 5. The slopes of the current‐voltage relation in the absence and presence of isoprenaline were parallel, confirming the absence of a change in membrane resistance. Isoprenaline also did not affect membrane resistance when applied in the modified ionic environments used. 6. In different external K concentrations (0.60‐29.5 mM) the relationship between the size of the electrotonic potential and the magnitude of the isoprenaline‐induced hyperpolarization was linear. A similar, direct relation was seen between isoprenaline hyperpolarization and membrane resistance when the latter was increased by lowering external chloride to 13.3 mM. 7. Excess Cao (7.5 mM) hyperpolarized the membrane and reduced membrane resistance, but the hyperpolarization by isoprenaline was larger than in normal solution, being inversely related to the membrane resistance. The hyperpolarization was directly related to the external Ca concentration, suggesting that the magnitude of the response to the beta‐action might depend on the cytoplasmic Ca concentration. 8. In low external Na (18 mM‐Nao) the beta‐action was scarcely affected. Complete replacement of Na with choline increased membrane resistance, muscle tone and phasic contractions; in this condition the effects of isoprenaline were abolished. 9. When the Na pump was blocked by exposure to zero K, to ouabain, or to both simultaneously, isoprenaline remained highly effective. However, prolonged exposure to ouabain abolished the beta‐action. 10. Isoprenaline (1.4 X 10(‐6) M) increased 45Ca efflux by about 20%, while 45Ca influx was not changed, and 42K efflux remained constant. 11...
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.
A calcium‐readmission response recorded from Nauphoeta salivary gland acinar cells.
Authors: Ginsborg B L , House C R , Mitchell M R
Published: December 2014

1. When cockroach salivary glands are exposed to bathing solutions without added calcium, reintroduction of calcium causes the acinar cells to hyperpolarize. The effect ('readmission response') may be very prolonged if the conditioning solution contains 5 mM‐cobalt. 2. Evidence is presented against the possibility that the readmission response is mediated by transmitter released from the salivary nerves. 3. The readmission response is shown to reflect an increase in potassium conductance.
Multiple actions of 5‐hydroxytryptamine on myenteric neurones of the guinea‐pig ileum.
Authors: Johnson S M , Katayama Y , North R A
Published: December 2014

1. Intracellular recordings were made from neurones lying within ganglia isolated from the myenteric plexus of the guinea‐pig ileum. 2. 5‐hydroxytryptamine (5‐HT) (200 nM‐10 microM) was applied to 160 neurones by adding it to the perfusing solution. Depolarizations were observed in 27% of neurones, and were more likely to be observed in S‐cells. Hyperpolarizations were observed in 30% of neurones, and were more likely to be seen in AH cells. 52% of neurones were unaffected. 2. 5‐HT was applied to 104 neurones by micro‐electrophoresis from an electrode with its tip placed close to the soma membrane. Depolarizations were observed in 35% of cells, and hyperpolarizations 13%; 10% of neurones showed biphasic responses in membrane potential and the remaining cells were unaffected. 4. The depolarizing responses to 5‐HT were associated with an increase in neuronal input resistance and were probably due to inactivation of the membrane potassium conductance. The responses declined in amplitude during prolonged or repeated applications of 5‐HT. 5. The hyperpolarizing responses to 5‐HT were associated with a fall in neuronal input resistance and were probably due to activation of the membrane potassium conductance. These responses persisted throughout the duration of application of 5‐HT and did not show marked tachyphylaxis. The hyperpolarizing responses were reversibly abolished by calcium‐free solutions. 6. The depolarizing responses to 5‐HT may underlie the release of acetylcholine caused by 5‐HT in the guinea‐pig ileum. The hyperpolarizing responses may contribute to the inhibition of the peristaltic reflex which has been observed when 5‐HT is applied to the serosal aspect of the intestine.
Barium and strontium can substitute for calcium in noradrenaline output induced by excess potassium in the guinea‐pig.
Authors: Nakazato Y , Onoda Y
Published: December 2014

1. The ability of Ba2+ and Sr2+ to substitute for Ca2+ in the noradrenaline output induced by excess K+ was examined using isolated guinea‐pig vas deferens. 2. When the vas deferens was repeatedly exposed to excess K+ (60 mM) at 40 min intervals, the noradrenaline output increased at least three‐fold in incubation medium which contained either Ca2+, Ba2+ or Sr2+. The response decreased on repetition. The order of effectiveness was roughly Ba2+ > Ca2+ > Sr2+. 3. In the absence of excess K+, these cations had no significant stimulating effect on the noradrenaline output even when added after exposure to Ca2+‐free solution. 4. As the concentration of divalent cation was increased from 0.2 to 2.5 mM the noradrenaline output induced by excess K+ increased. The maximum noradrenaline output was achieved at a divalent cation concentration of 2.5 mM and was 29.56 +/‐ 3.52, 15.02 +/‐ 1.12 and 7.45 +/‐ 0.84 (mean +/‐ S.E. of mean) n‐mole/g per hr in the presence of either Ba2+, Ca2+ or Sr2+, respectively. Further increase in the concentration of the cations reduced the response. 5. The addition of either Sr2+ (2 mM) or Ca2+ (1 mM) to a solution containing various concentrations of Ba2+ facilitated the K+‐induced increase in the noradrenaline output when the Ba2+ concentration was low, but inhibited release of noradrenaline when higher concentrations of Ba2+ were used. The addition of Sr2+ (1 mM) to Ca2+‐containing solutions had a similar effect. 6. Mg2+ competitively inhibited the K+‐induced increase in the noradrenaline output in the presence of either Ba2+ or Sr2+ and blocked that in the presence of CA2+. 7. The results indicate that both Ba2+ and Sr2+ can substitute for Ca2+ in the cations act though the same site at some stage in the process of K+‐induced transmitter release.
Ephaptic transmission between single nerve fibres in the spinal nerve roots of dystrophic mice.
Authors: Rasminsky M
Published: December 2014

1. Ephaptic transmission was observed between spontaneously active single nerve fibres in the spinal nerve roots of dystrophic mice. 2. In the five ephaptically interacting pairs of fibres studied in detail, the conduction velocities in the exciting fibres were < 1 m/sec and the conduction velocities in the excited fibres were 2‐10 m/sec in the immediate vicinity of the ephapses at 26‐28 degrees C. 3. Membrane current analysis suggested that conduction was continuous in the exciting fibres. In some cases conduction away from the ephapse in the excited fibre was saltatory in at least one and possibly in both directions of transmission. 4. It is concluded that in at least some cases the direction of ephaptic transmission is from bare axon to myelinated axon. 5. Transmission time across the ephapses, measured as the interval between peaks of inward membrane current in exciting and excited fibres, was less than or equal to microseconds‐240 microseconds. 6. Ephaptic transmission is not necessarily contingent upon the direction of propagation of the impulse in the exciting fibre. 7. Ephaptic transmission between two fibres can remain stable at frequencies of at least 70 Hz. 8. There may be multiple sites of spontaneous ectopic excitation in single dystrophic mouse spinal root axons. An impulse traversing a site of ectopic excitation may incite a subsequent burst of impulses to arise from that site following a delay of more than 100 msec.
The mechanism of the increase in glomerular filtration rate in the twelve‐day pregnant rat.
Authors: Baylis C
Published: December 2014

1. Whole kidney and micropuncture techniques were employed to investigate the determinants of glomerular ultrafiltration in virgin and 12‐day pregnant rats. 2. A significant increase in whole kidney glomerular filtration rate (g.f.r.) and superficial cortical single nephron g.f.r. was noted in pregnant rats compared to virgins. 3. Increases in whole kidney and glomerular plasma flow rate also occurred in pregnancy which were in proportion to the increase in rate of filtration. No differences were noted in the hydrostatic and oncotic pressures which influence formation of glomerular ultrafiltrate in the superficial nephron population. 4. Reduction in arterial haematocrit and no change in mean red cell volume indicate that a plasma volume expansion has occurred by day 12 of pregnancy in the rat. 5. It is concluded that the increased g.f.r. seen in 12‐day pregnant rats is exclusively the result of an increase in renal plasma flow rate (r.p.f.) since the other determinants of glomerular ultrafiltration are unaffected by pregnancy. The plasma volume expansion which also occurs must be, at least in part, responsible for the increase in r.p.f.
Thermoregulatory and rhythm‐generating mechanisms governing the sudomotor and vasoconstrictor outflow in human cutaneous nerves.
Authors: Bini G , Hagbarth K E , Hynninen P , Wallin B G
Published: December 2014

1. Recordings of multiunit sympathetic activity were made from human nerve fascicles supplying hairy and glabrous skin of the extremities in healthy subjects exposed to different ambient temperatures. Sudomotor and vasomotor events accompanying the neural activity were monitored by simultaneous recordings of electrodermal and pulse plethysmographic events (Pleth) in the neural innervation zones. 2. By exposing the subject to warm (43 degrees C) or cold (15 degrees C) environments, it was possible to obtain a selective activation of either the sudomotor or the vasoconstrictor neural system, respectively, with suppression of spontaneous activity in the other system. 3. Bursts of both vasoconstrictor and sudomotor nerve activity were found to occur at certain preferred intervals which were integer multiples of a period of about 0 . 6 sec (100 cycles/min). With high sudomotor or vasoconstrictor tone the 100 cycles/min rhythm was prominent but with decreasing tone slower subharmonic rhythms prevailed. Respiratory rhythms were also discerned as well as slower rhythms attributable to oscillatory tendencies in thermoregulatory servos. 4. Vasoconstrictor bursts had longer mean duration than sudomotor bursts, a finding attributed to a slower conduction velocity of vasoconstrictor as compared to sudomotor impulses. 5. With increasing incidence of bursts transient electrodermal or plethysmographic responses following individual bursts merged, and thus the fast neural rhythms were not discernible in either the electrodermal or Pleth traces. Given increments in firing rate of nerves produced less additional vasoconstriction at high than at low firing rates. The rhythm generating mechanisms may help to restrict rates of individual fibres to the low range which provides high gain in the neuroeffector transfer functions.
Suppression of sprouted synapses in axolotl muscle by transplanted foreign nerves.
Authors: Wigston D J
Published: December 2014

1. The supracoracoideus (s.c.) muscle of the axolotl shoulder is innervated by two nerves, the anterior and posterior s.c. nerves. The posterior nerve was induced to make synapses outside its normal territory in the muscle by removing a segment of the anterior nerve. Intracellular recording indicated that the efficacy of transmission from posterior nerve terminals outside their normal territory increased over several weeks prior to the return of the anterior nerve. 2. The anterior nerve reinnervated its muscle by 40‐50 days after the operation, and quickly made synapses throughout the muscle. The posterior nerve territory subsequently returned to its original size and location over 3‐6 months. 3. Transplantation of either of two completely foreign nerves into s.c. muscles with enlarged posterior nerve territories resulted in a similar return of the posterior nerve territory to its normal size when anterior nerve regeneration was prevented. 4. These results suggest that the advantage which newly regenerated native nerves have over sprouted foreign nerves is not the quality of ‘nativeness’ but rather the smaller number of synapses they support. In this view, sprouted nerves compete less effectively because they initially support more synapses per neurone than regenerating nerves.
Selective depression of excitatory amino acid induced depolarizations by magnesium ions in isolated spinal cord preparations.
Authors: Ault B , Evans R H , Francis A A , Oakes D J , Watkins J C
Published: December 2014

1. The depressant actions of Mg2+ and a range of other divalent ions on synaptic excitation and on responses produced by excitatory amino acids and other putative transmitters have been investigated in hemisected isolated spinal cords of frogs and neonatal rats. Some comparative studies were also made using the rat isolated superior cervical ganglion. 2. At concentrations above 10 microM, Mg2+ selectively antagonized N‐methyl‐D‐aspartate (NMDA)‐induced motoneurone depolarization as recorded from ventral roots of tetrodotoxin‐blocked spinal cords. Depolarization evoked by quisqualate (unaffected by 20 mM‐Mg2+) was resistant to the depressant action of these ions, while depolarizations evoked by other excitant amino acids were depressed to intermediate degrees. 3. Mn2+, Co2+ and Ni2+ had qualitatively similar actions to Mg2+; Mn2+ was somewhat less potent and Co2+ and Ni2+ more potent than Mg2+. The alkaline earth metal ions, Ca2+, Sr2+ and Ba2+, had very weak Mg2+‐like actions. Ca2+ and Mg2+ acted additively in depressing amino acid‐induced responses. 4. Mg2+ also depressed motoneurone responses evoked by noradrenaline, substance P and carbachol in the neonatal rat isolated spinal cord. However, none of these effects were as marked as the depression of NMDA‐induced responses by Mg2+ in this preparation. Mg2+ did not depress motoneurone depolarization produced by 5‐HT in the rat spinal cord or the depolarizing action of GABA on primary afferent terminals of the isolated frog spinal cord. 5. At concentrations producing marked depression of NMDA‐induced responses, Mg2+ also depressed synaptic transmission in spinal cords in the absence of an effect on ganglionic transmission. At the same concentrations, Mn2+, Co2+ and Ni2+ depressed synaptic transmission in both preparations. 6. From the similarity in action between Mg2+ and the D‐alpha‐aminoadipate group of NMDA antagonists, it is suggested that the central depressant action of low concentrations of Mg2+ involves predominantly a postsynaptically mediated interference with the action of an excitatory amino acid transmitter.
Pancreatic endocrine responses to stimulation of the peripheral ends of the splanchnic nerves in the conscious adrenalectomized calf.
Authors: Bloom S R , Edwards A V
Published: December 2014

1. Certain effects of stimulation of the peripheral ends of both splanchnic nerves have been investigated in unanaesthetized calves, given appropriate adrenal steroid replacement therapy. 2. Splanchnic nerve stimulation at frequencies within the physiological range produced prompt rises in the concentration of glucose, pancreatic glucagon and pancreatic polypeptide in the arterial plasma. These responses were followed by a rapid rise in plasma insulin concentration when the stimulus was terminated. The extent of this rise was related to the plasma glucose concentration at that precise point in time. 3. Stimulation at all frequencies tested had no effect on the concentration of vasoactive intestinal peptide in lymph collected from the intestinal duct. 4. The results are discussed in relation to those obtained in previous studies in anaesthetized calves of the same age.
Amylase release from dissociated mouse pancreatic acinar cells stimulated by glucagon: effect of membrane stabilizers.
Authors: Singh M
Published: December 2014

1. The effect of membrane stabilizers and cytochalasin‐B on amylase secretion, basal and induced by ionophore A23187, CCK‐PZ, bethanechol and glucagon, was studied in dissociated mouse pancreatic acinar cells. 2. Cytochalasin‐B did not affect basal or secretagogue‐stimulated amylase secretion. 3. Membrane stabilizers [thymol (10(‐7)‐10(‐4) M), chlorpromazine (10(‐7)‐10(‐4) M) and propranolol (10(‐7)‐10(‐5) M) did not alter basal release of amylase. At higher concentrations of thymol (10(‐3) M), chlorpromazine (10(‐3) M) and propranolol (10(‐4) M), dissociated acinar cells were lysed as indicated by an increase in release of lactic dehydrogenase (LDH). 4. Ionophore A23187, CCK‐PZ (maximal effective concentrations, 0.01 u. ml.‐1), bethanechol (maximal effective concentrations, 10(‐4) M) and glucagon increased amylase secretion in a dose‐dependent fashion. Concentrations of CCK‐PZ and bethanechol beyond optimal levels decreased amylase secretion. Concentrations of ionophore A23187 and glucagon when tested beyond 10(‐6) M and 10(‐4) M respectively increased the release of LDH. In concentrations that were non‐toxic, membrane stabilizers blocked the stimulating effect of cholecystokinin‐pancreozymin and bethanechol on amylase secretion but did not alter the response to A23187 and glucagon. 5. Unlike bethanechol, glucagon neither increased the uptake of 45Ca nor did it alter the release of 45Ca from cells previously loaded with 45CaCl2. 6. These data provide evidence that stimulus‐secretion coupling in dissociated pancreatic acinar cells is basically similar to cells in situ. The effect of glucagon is consistent with the model in which hormone‐dependent mobilization of Ca2+ from intra‐ or extracellular sources is bypassed leading to digestive enzyme secretion.
Changes in the perception of inspiratory resistive loads during partial curarization.
Authors: Campbell E J , Gandevia S C , Killian K J , Mahutte C K , Rigg J R
Published: December 2014

1. The ability of normal subjects to estimate the magnitude of resistive loads and to detect resistive loads was determined using standard psychophysical techniques. The experiments were repeated during maintained partial neuromuscular blockade with D‐tubocurarine. 2. During curarization the ability to detect the presence of a small inspiratory resistive load was not significantly impaired. This finding is consistent with the view that changes in the usual breath‐by‐breath relation between pressure and flow mediate detection. 3. The size of resistive loads was over‐estimated during partial curarization. Subjects thus placed more reliance on sensing the increased motor command required during curarization than on alternative peripheral signals related to pressure, flow or resistance. 4. The exponent for the power function relating the perceived magnitude of a resistive load to its actual size (Stevens, 1957) was reduced during partial neuromuscular blockade. 5. These results suggest that detection of resistive loads depends upon sensing apparent information arising from an unexpected pressure‐flow disturbance but that estimation of the size of an added load depends, in part, on sensing the outgoing motor command.