bluuebunny/crossref_metadata_2025 huggingface dataset:
Load compensating responses of human abdominal muscles
Authors: Lansing R. W. , Meyerink L.
Published: December 2014

1. We studied abdominal muscle responses to positive pressure loads applied suddenly to the external airway while subjects held a constant lung volume against steady pressure. The pre‐loading holding pressure was 6 cm H2O, and the loading pressures were 6 or 12 cm H2O lasting for 2 sec.

2. Surface electromyograms (e.m.g.) were recorded over the internal oblique, external oblique, and rectus abdominis muscles. The latency and pattern of the e.m.g. reactions were studied by measuring the raw record for each loading trial, and by averaging the rectified e.m.g. for many trials.

3. No responses were obtained if subjects were instructed not to respond to the loads. When instructed and trained to maintain their pre‐load position in spite of the load, a two‐phase compensatory response was found. The initial response (phase I) was 100‐300 msec in duration; it was followed by a continuous e.m.g. discharge (phase II) which continued to the offset of the pressure load. Subjects were also trained to make a single respiratory effort as quickly as possible after the load onset or after just an auditory stimulus. These were simple reaction time tasks of a traditional kind and the e.m.g. responses elicited were single, brief bursts.

4. For all subjects and experimental conditions the e.m.g. response of the internal oblique occurred first, followed by the external oblique and then the rectus abdominis. For the ‘maintain position’ task, phase I latencies (internal oblique) averaged 66‐90 msec for individual subjects, but for single trials with optimal conditions of practice and preparatory intervals these ranged from 42 to 110 msec with a third of the reactions occurring within 50‐60 msec.

5. The latencies for reaction time responses to loading were about 6 msec shorter than the phase I latencies. The latency distributions for the two types of responses were similar, and both were affected to the same degree by practice, and changing the length and variability of the preparatory interval. Because of these similarities we suggest that the phase I reaction was a learned response of a ‘simple reaction time’ type, and not comparable to late stretch reflexes such as the M2 of limb muscles.

6. Arm muscle responses to respiratory pressure changes were measured in three subjects under identical conditions used to obtain load reaction times of abdominal muscles. These simple reaction times averaged 61‐71 msec, and ranged from 42 to 97 msec. Therefore very short proprioceptive reaction times are not peculiar to the respiratory system, or to load perturbations of the responding muscle.

7. Mechanical adjustments of airway pressure and lung volume in response to loading are first expressed at the mouth about 90 msec after abdominal muscle activity begins. In the ‘maintain position’ task, the accuracy with which pressure and volume adjustments were made during the last 1.5 sec of the loading period approximated that reported in the literature for trained singers holding a tone using constant expiratory pressure.
Effects of histamine, high potassium and carbachol on 42K efflux from longitudinal muscle of guinea‐pig intestine
Authors: Bolton T. B. , Clark J. P.
Published: December 2014

1. Shortening and rate of loss of 42K were studied in strips of longitudinal muscle taken from guinea‐pig ileum.

2. Carbachol, histamine and raising the external potassium concentration, [K+]o, to 120 m
m in the presence of atropine caused equal maximal shortenings of the muscle, but unequal maximal increases in 42K efflux: maximal 42K effluxes obtainable in response to raised [K+]o and histamine were about ⅔ and ⅓ respectively of the maximal efflux in response to carbachol. In the absence of atropine the increase in 42K efflux produced by 120 m
m‐[K+]o was about 50% larger, probably because of the release of acetylcholine from nerve endings in the tissue.

3. If inhibitors of histamine metabolism were applied, or a H2‐receptor blocker (cimetidine), the maximum 42K efflux produced by histamine was not increased. An analogue of histamine reputed to resist metabolic degradation did not produce a larger increase in 42K efflux than histamine. The smaller maximal effect of histamine on 42K efflux than carbachol may be because it can open fewer ion channels in the smooth muscle membrane.

4. The ratio of the concentrations producing 50% maximal shortening and 50% maximal 42K efflux was about 1:1.3 for raised [K+]o but about 1:20 for histamine and carbachol. Depolarization by raising [K+]o appears to be less effective in causing tension development than similar depolarizations produced by carbachol or histamine.

5. The relative effects of carbachol, histamine and raised [K+]o were discussed in the light of their similar depolarizing actions. Increases in 42K efflux did not appear to be caused primarily either by contraction or by depolarization of the muscle. Access of the stimulant to cells and receptors other than those which are superficially situated was suggested as being an important factor in deciding the smaller increase in 42K efflux seen with some stimulants. Histamine receptors may be fewer in number than muscarinic receptors and less able in their activated form to open channels through which potassium ions can escape.
Effects of local anaesthetics on the relationship between charge movements and contractile thresholds in frog skeletal muscle.
Authors: Huang C L
Published: December 2014

1. Charge movements to 10 mV steps at different potentials were studied in voltage‐clamped frog skeletal muscle fibres in isotonic solutions that minimized ionic currents, under different pharmacological conditions. The earliest onset of detectable mechanical movement (‘threshold’) was assessed visually under magnification. 2. Charge movements in isotonic solutions were similar to those reported in hypertonic solutions, under identical pulse procedures. 3. In the absence of local anaesthetics, threshold occurred at a mean membrane potential of ‐55 mV, after the movement of 4.0 nC/muF of non‐linear charge and when the membrane capacitance approximated values that corresponded to the onset of the ‘Qgamma’ charge movement component. 4. Lidocaine shifted the threshold in the hyperpolarizing direction to ‐62 mV, and reduced the amount of non‐linear charge needed to reach threshold to 1.4 nC/muF. 5. The presence of tetracaine shifted threshold in the depolarizing direction to ‐39 mV, and more than doubled the amount of non‐linear charge that had to move to reach threshold to 10.8 nC/muF. Much of this increase was attributed to the Qgamma component of charge movement. 6. It is concluded that more non‐linear charge is required to initiate mechanical movement when calcium release by sarcoplasmic reticulum is inhibited by tetracaine, whereas less charge is so required when calcium re‐uptake is being inhibited by lidocaine. Assuming earlier interpretations of the strength duration curve, this is consistent with charge movement preceding, rather than being a consequence of calcium release.
Effect of Escherichia coli heat‐stable enterotoxin, cholera toxin and theophylline on ion transport in porcine colon
Authors: Argenzio R. A. , Whipp S. C.
Published: December 2014

1. The effect of heat‐stable enterotoxin (ST) of Escherichia coli, cholera toxin (CT), and theophylline (a phosphodiesterase inhibitor) on ion and water transport was studied with an in vivo isolated loop system of the pig colon.

2. All three agents abolished net Na absorption as a result of a decrease in the lumen to blood Na flux alone. With all three agents, net Cl absorption was reduced, but not abolished, and net HCO3 secretion was elicited. Luminal pCO2 was reduced with CT and theophylline from that observed in normal Ringer alone.

3. Theophylline resulted in a prompt and sustained increase in both cyclic adenosine monophosphate (cyclic AMP) and cyclic guanosine monophosphate (cyclic GMP) levels in colonic mucosa studied in vitro. ST selectively elevated cyclic GMP, whereas CT selectively elevated cyclic AMP. These responses paralleled the time course and magnitude of response of the transepithelial electrical potential difference (ψLB) measured in vivo.

4. Ion replacement studies in the presence or absence of theophylline showed that in the absence of Na, Cl absorption was slightly reduced and HCO3 secretion was elicited; no further additive effects of theophylline in the absence of luminal Na were observed. In the absence of luminal Cl, net Na absorption was abolished and HCO3 was absorbed; theophylline resulted in significant net Na and HCO3 secretion. Theophylline also increased ψLB in the absence of either luminal Na or Cl.

5. Results suggest that in the presence of theophylline or enterotoxin, the coupled Na—H and Cl—HCO3 exchange processes that are normally responsible for at least half of the net NaCl absorption by this tissue are interrupted. Active HCO3 secretion is observed and Cl absorption under these conditions can be entirely explained as a consequence of ψLB. Thus, these studies indicate that the colon may participate in the production of diarrhoea of enterotoxigenic origin. They also suggest an important functional role of cyclic nucleotides in controlling the acidity and volume of colonic contents.
Extracellular recordings from oxytocin neurones during the expulsive phase of birth in unanaesthetized rats.
Authors: Summerlee A J
Published: December 2014

1. Extracellular electrical recordings were taken from nine antidromically identified paraventricular units in unanaesthetized, unrestrained rats. Neuronal activity was correlated with the observed events of parturition, i.e. abdominal contractions and delivery of young or placentae. 2. The level of spontaneous activity (0.15‐‐3.2 spikes s‐1) of all nine units began to increase 15 min before the first signs of abdominal contraction. This accelerated discharge (2‐‐5 fold increase over the background activity) was maintained throughout parturition (58‐‐93 min) and for up to 45 min after delivery of the last placenta. 3. All nine neurones displayed at 6‐‐14 s periods of even higher rate of discharge (10‐‐32 spikes s‐1) after forceful abdominal contractions. The peak firing rates within these periods of accelerated discharge decreased as labour progressed. 4. Four cells also showed a burst (5‐‐12 s) of high‐frequency activity 15‐‐28 s before delivery of either fetuses or placentae. These four units were later classified as oxytocinergic on the basis of their stereotyped activation 10‐‐12 s before reflex milk‐ejection. 5. The remaining five neurones which did not respond with a burst of high‐frequency discharge before delivery were classed as potential vasopressin‐producing cells. Four of these units displayed a phasic pattern of activity with periods of activity (5‐‐230 s) alternating with periods of silence (4‐‐31 s).
Surface potentials and sodium entry in frog skin epithelium.
Authors: Benos D , Latorre R , Reyes J
Published: December 2014

1. The effects which alterations in the surface potential of the apical membrane of isolated Rana catesbeiana skin have on Na entry were examined. 2. Changes in the external ionic strength have little effect upon the rate of Na transport across the frog skin epithelium. 3. Uranyl ion (UO2(2+), 2.5 mM) induces a +145 mV change in the surface potential of phosphatidylserine monolayers, and a +60mV change in the surface potential of monolayers made from phosphatidylcholine. 4. UO2(2+) inhibits the short‐circuit current (Isc) by a maximum of 20% in R. catesbeiana skin, while stimulating Isc by 40% in R. temporaria skin. Neither Isc stimulation nor inhibition by UO2(2+) can be seen in the presence of 10(‐4) M‐amiloride. 5. From points 1 and 2 above, we conclude that the surface charge density in the neighbourhood of the Na‐selective entry site located in the apical membrane is small (greater than 1e‐/600 A2). The results obtained using UO2(2+) suggest that Na entry is not affected by changes in the membrane surface potential.
Chloride transport and intracellular chloride activity in the presence of theophylline in Amphiuma small intestine.
Authors: White J F
Published: December 2014

1. Simultaneous bidirectional tracer fluxes of 22Na and 36Cl were measured under short‐circuited conditions in isolated stripped segments of Amphiuma duodenum incubated in media containing Cl‐ and HCO3‐. 2. Theophylline (10 mM) increased the short‐circuit current (Isc), eliminated net Cl‐ absorption and elevated the residual flux by more than 50%. 3. Subsequent addition to acetazolamide lowered the Isc and reduced the residual flux. 4. Using double‐barreled Cl‐ specific micro‐electrodes the intracellular activity of Cl‐ averaged 27.1 mM in the presence of theophylline, consistent with active accumulation of Cl‐. 5. Theophylline depolarized the mucosal membrane of villus epithelial cells by an average of 6.9 mV. 6. The findings indicate that the inhibition of Cl‐ absorption by theophylline does not result from complete inhibition of mucosal Cl‐ uptake and provide evidence that HCO3‐ secretion is enhanced by theophylline.
Responses of cat corneal sensory receptors to mechanical and thermal stimulation.
Authors: Belmonte C , Giraldez F
Published: December 2014

1. The afferent responses evoked by mechanical and thermal stimulation of the cat cornea were recorded extracellularly from strands of long and mixed ciliary nerves under deep anaesthesia. 94% of the units studied (n = 53) responded consistently to both stimuli. 2. Conduction velocities, measured by electrical stimulation of the receptive field, corresponded to the lower range of the A‐delta fibre group (average = 5.4 m/sec). Receptive fields covered approximately a quadrant of the corneal surface and showed continuous sensitivity and overlapping. Units were silent in the absence of stimulation but an ongoing activity was commonly present after repeated mechanical and thermal stimulation. 3. Mechanical responses were evoked at low thresholds and consisted of a dynamic and static response that paralleled the amplitude of the stimulus. The pattern of the discharge was irregular and fatigue was easily developed by repeated stimulation. 4. Thresholds to heating were above 38 degrees C and the response increased monotonically with the temperature over the range from threshold to 50 degrees C. The heat response could be sensitized by repeated long suprathreshold stimulation while variable changes in the response were induced by briefer stimuli. Also depression was observed in some circumstances. A weak response to cooling was present in 50% of the units tested. 5. Damaging mechanical stimulation or the application of a strong acid solution evoked a vigorous response followed by an earlier discharge that persisted for hours. 6. The relation of these receptors to other polymodal nociceptors and corneal sensation is considered.
The activity of cerebellar neurones of an elasmobranch fish (Scyliorhinus canicula) during a reflex movement of a fin
Authors: Paul D. H. , Roberts B. L.
Published: December 2014

1. Response of neurones in the corpus cerebelli of Scyliorhinus canicula (Elasmobranchii) have been recorded in decerebrate unanaesthetized fish during the performance of pectoral fin reflexes (p.f.r.) evoked by electrical stimulation of the fins.

2. Of 421 single units recorded in the posterior dorsal quadrant of the corpus, 111 (26%) had their discharges modulated when the reflex was evoked; fifty nine were Purkinje (P) cells discharging single spikes, thirteen were P cells discharging complex responses, thirty‐six were stellate (S) cells and three were not positively identified.

3. The responses of fifty‐one units (thirty‐seven P cells and fourteen S cells) were analysed in detail. In thirty‐one of the P cells and all the S cells the initial response was excitatory, six P cells gave an inhibitory response only and a further three were inhibited after the initial excitation. Only one S cell had an inhibitory component in its response.

4. The discharges of the S cells completely overlapped the inhibitory responses of the P cells.

5. Only one cell (a P cell) was evoked at a latency shorter than that of the p.f.r. In one other P cell discharging single spikes spontaneously, the evoked response was a long latency (146 msec) complex response. Four other P cells discharged only complex responses but the pattern of their response to the p.f.r. was similar to that of P cells discharging single spikes only.

6. No cerebellar responses were evoked if the fin stimulus was below the threshold necessary to evoke a p.f.r. In curarized fish, unit responses were recorded that were qualitatively similar to those recorded in unparalysed fish.

7. These results suggest that (i) because of the long latency of the responses, the cerebellum is unlikely to have a role in the initiation of the p.f.r.; (ii) the responses during the p.f.r. were evoked via a mossy fibre‐parallel fibre pathway; (iii) the responses were correlated with motor activity rather than sensory input.
The energy liberation of frog skeletal muscle in tetanic contractions containing two periods of shortening.
Authors: Irving M , Woledge R C
Published: December 2014

1. Heat and work production have been measured in pairs of frog sartorius muscles undergoing two periods of rapid isovelocity shortening at 0 degrees C. The first (conditioning) shortening occurred in the sarcomere length range 2.70‐‐2.25 micrometer (as measured in resting muscles) and the second (test) shortening in the range 2.25‐‐2.10 micrometer. The shortening heat associated with the test shortening was obtained as the difference in heat production between pairs of tetani which were identical except for the presence of the test shortening. 2. The shortening heat associated with the test shortening was reduced when it was preceded by the conditioning shortening; with no interval between shortenings its value was 52 +/‐ 3% (mean +/‐ S.E. of mean, n = 6) of that without the conditioning shortening. As the interval between shortenings was increased the shortening heat became larger; its recovery was more than half complete with an interval of 0.3 sec. 3. The work produced in the test shortening was also reduced in tetani which contained the conditioning shortening; its dependence on the interval between shortenings was similar to that of the shortening heat.
High‐energy phosphate metabolism and energy liberation associated with rapid shortening in frog skeletal muscle
Authors: Homsher E. , Irving M. , Wallner A.
Published: December 2014

1. High‐energy phosphate metabolism and energy liberated as heat and work were measured in 3 sec tetani of frog sartorius muscles at 0 °C.

2. Three contraction periods were studied: (a) shortening at near‐maximum velocity for 0.3 sec from sarcomere length 2.6 to 1.8 μm, beginning after 2 sec of isometric stimulation, (b) the 0.7 sec isometric period immediately following such rapid shortening, (c) the period from 2 to 3 sec in an isometric tetanus at sarcomere length 1.8 μm.

3. There were no significant changes in levels of ATP, ADP or AMP in any contraction period. The observed changes in inorganic phosphate and creatine levels indicated that the only significant reaction occurring was phosphocreatine splitting.

4. The mean rate of high‐energy phosphate splitting during rapid shortening, 0.48 ± 0.24 μmole/g.sec (mean ±
s.e. of mean, n = 29; ‘g’ refers to blotted muscle weight), was not significantly different from that in the 1 sec period in the isometric tetanus, 0.32 ± 0.11 μmole/g.sec (n = 17). The mean rate in the post‐shortening period, 0.71 ± 0.10 μmole/g.sec (n = 22), was greater than that in the 1 sec period in the isometric tetanus, and this difference is significant (P < 0.02, t test).

5. A large quantity of heat plus work was produced during the rapid shortening period, but less than half of this could be accounted for by simultaneous chemical reactions. The unexplained enthalpy production was 6.5 ± 2.6 mJ/g (mean ±
s.e. of mean). No significant unexplained enthalpy was produced in the 1 sec period in the isometric tetanus.

6. In the post‐shortening period the observed enthalpy was less, by 6.2 ± 2.6 mJ/g, than that expected from the simultaneous chemical reactions.

7. The results are interpreted in terms of an exothermic shift in the population of cross‐bridge states during rapid shortening. It is suggested that a relatively slow subsequent step prevents many of these cross‐bridges from completing the cycle and splitting ATP until after the end of shortening.
Pancreatic acinar cell function: measurement of intracellular ions and pH and their relation to secretion.
Authors: Preissler M , Williams J A
Published: December 2014

1. Isolated mouse pancreatic acini were used to investigate the effect of secretagogues on acinar cellular electrolytes and cell pH. The effect of changes in the acid‐base status of the incubation medium on acinar cellular electrolytes, cell pH and amylase release were also studied. 2. Carbachol at concentrations of 10(‐6) or 10(‐5) M was without any effect on the intracellular concentrations of total Na+, Na+ exchangeable with 22Na+, K+ and Cl‐, and did not influence cell pH as determined by the DMO method. 3. Changes in pHe achieved by varying the HCO3‐ concentrations at constant CO2, varying the CO2 concentration at constant HCO3‐ or by titration of a HCO3‐/CO2 free HEPES buffered medium did not influence intracellular electrolyte values. 4. pHi changed linearly with pHe by about 1.2 units/pHe unit change over the pHe range of 7.7‐‐6.5. pHi, however, did not change in response to a change in the CO2 tension when the HCO3‐ concentration was adjusted to keep pHe at 7.4. 5. Lowering pHe below 7.1 inhibited carbachol and CCK8‐stimulated amylase release. By contrast a decrease of pHe to 6.8 was without significant effect on basal and secretagogue increased 45Ca2+ efflux from pancreatic acini. 6. In conclusion the pH sensitivity of amylase release by acinar cells is probably related to changes in pHi. Since Ca2+ mobilization is not affected, the pH sensitive step is probably in the mechanism by which Ca2+ activates the release of zymogen granules contents by exocytosis.
Electrophysiological and freeze‐fracture studies of changes following denervation at frog neuromuscular junctions.
Authors: Ko C P
Published: December 2014

1. Changes which occur at frog neuromuscular junctions following denervation have been studied by combining intracellular recording and freeze‐fracture electron microscopy. 2. Shortly after nerve section, both neuromuscular transmission and intramembrane structures of neuromuscular junctions remain normal. 3. Later, neuromuscular transmission fails, beginning with the disappearance of end‐plate potentials (e.p.p.s) and followed by the disappearance of miniature end‐plate potentials (m.e.p.p.s). The frequency of m.e.p.p.s which persist after cessation of e.p.p.s is not increased dramatically in K+‐rich or hypertonic solutions. 4. Concomitant with the changes of transmission are changes in intramembrane structures. The first sign of these changes in disruption of active zones, which become disorganized, fragmented or vanish. Nerve terminals then disintegrate and eventually are engulfed by Schwann cells. 5. When neuromuscular transmission has failed completely, former sites of the neuromuscular junction are occupied by Schwann cells. These cells develop transverse ridges which lie opposed to junctional folds, just like active zones of nerve terminals. However, the ridges on Schwann cells do not contain organized rows of particles or clusters of any synaptic organelles, even at later stages when Schwann cell m.e.p.p.s commence. 6. It is suggested that the failure of e.p.p.s involves at least an impairment of the transmitter release mechanism at the nerve terminal, which is probably associated with the disruption of active zones. The cessation of m.e.p.p.s is thought to be caused by the engulfment of terminals by Schwann cells.
Inhibitory interactions between colonic and vesical afferents in the micturition reflex of the cat.
Authors: Floyd K , McMahon S B , Morrison J F
Published: December 2014

1. In anaesthetized cats in which the only intact autonomic pathways innervating the colon and bladder were in the pelvis nerves, distension of the colon resulted in a graded inhibition of spontaneous bladder motility, and a decrease in the reflexly evoked waves of activity in the vesical branches of the pelvic nerves. 2. Electrical stimulation with voltages sufficient to excite only the myelinated fibres in the colonic branches of the pelvic nerve caused inhibition of spontaneous bladder motility, an increase in micturition threshold, and a reduction in the reflexly evoked waves of activity in the vesical efferents of the pelvic nerve. 3. The results demonstrate that the pelvic nerve afferent inflow from the colon produces a marked central inhibitory influence on the micturition reflex.
Opposing effects of hypothalamic cooling on threshold and sensitivity of metabolic response to body cooling in rabbits.
Authors: Inomoto T , Mercer J B , Simon E
Published: December 2014

1. Extrahypothalamic thermosensitivity at normal (39 degrees C) and lowered (33.8 degrees C) hypothalamic clamp temperatures has been measured in cold exposed rabbits equipped with chronically implanted hypothalamic perfusion thermodes. The animals were subjected to body core cooling by means of cold perfused thermodes placed in the colon. 2. At lowered hypothalamic temperature the threshold core temperature for increased metabolic heat production due to body core cooling was significantly increased as compared to that at normal hypothalamic temperature. However, the slope of the response relating increased metabolic rate to body core temperature was significantly reduced. 3. The experimental results compare well with those predicted from a mathematical model, which takes into account the effect of temperature on synaptic transmission of afferent information in the hypothalamus.
The role of buffer anions and protons in secretion by the rabbit mandibular salivary gland.
Authors: Case R M , Conigrave A D , Favaloro E J , Novak I , Thompson C H , Young J A
Published: December 2014

1. The role of extracellular HCO3‐ and H+ in the formation of primary saliva and its subsequent modification by the glandular ducts has been investigated in the isolated perfused mandibular salivary gland of the rabbit. 2. Variation of extracellular HCO3‐ concentration between 12.5 and 50.0 mmol/l was without effect on salivary flow rate or on Na+ and K+ excretion, even though salivary HCO3‐ (and Cl‐) content altered with changes in the extracellular concentration of the two anions. 3. Complete replacement of perfusate HCO3‐ by Cl‐ reduced fluid secretion by 34% and almost abolished ductal Na+ absorption. However, when extracellular pH was controlled by replacing HCO3‐ with the hydrophilic HEPES buffer, fluid secretion but not ductal Na+ absorption was restored to normal. 4. Complete replacement of exogenous HCO3‐ with acetate increased fluid secretion by 110% and also stimulated ductal Na+ absorption. This effect did not appear to be related to changes in cell pH and remains unexplained. Acetate entered the saliva in concentrations comparable to those seen for HCO3‐ in control experiments. 5. Salivary secretion showed an almost linear dependence on extracellular pH, rising from 14% of control (pH 7.4) levels at pH 6.2 to 130% at pH 7.8. Ductal Na+ absorption showed similar pH dependence. 6. Carbonic anhydrase inhibitors did not affect fluid secretion rates (except when supramaximal doses of ACh were used to evoke secretion) but they did cause a large reduction in salivary HCO3‐ output. In glands perfused with acetate rather than HCO3‐, carbonic anhydrase inhibitors had no effect on excretion of fluid, acetate or metabolically derived HCO3‐. Duct perfusion studies suggested that the effect of the inhibitors on HCO3‐ output was at the site of primary secretion rather than at the ductal site of HCO3‐ transport.
Effect of prolactin on urinary excretion and renal haemodynamics in conscious rats.
Authors: Bliss D J , Lote C J
Published: December 2014

1. Conscious rats received a saline infusion (5.8 ml . hr‐1) via a tail vein, for a 6 hr period. For the final 2 hr of this infusion period, prolactin (7.1 microgram (100 g body wt.)‐1 . hr‐1) was incorporated in the infusate. A control group of animals continued to receive saline alone. 2. In the first hour of prolactin administration (in comparison with the control group), urine flow, sodium output and osmolal output were all significantly reduced (P less than 0.02); there was also a reduction (P less than 0.05) in renal plasma flow (p‐amino‐hippurate clearance), but the filtration fraction did not alter. The changes in urinary excretion, and in renal haemodynamics, did not persist for the second hour of prolactin administration, but there was a sustained increase in body fluid volume. 3. It is possible that altered renal haemodynamics are responsible for the reduced urinary water and solute excretion which occurs during acute prolactin administration.
Further observations on the suppression of fever in rabbits by intracerebral action of anisomycin.
Authors: Cranston W I , Hellon R F , Townsend Y
Published: December 2014

1. Anisomycin has been given into the cerebral ventricles of rabbits. The inhibitory action of a range of doses on fever and on [14C]leucine incorporation into hypothalamic protein has been studied. 2. Fever was far less sensitive to inhibition by anisomycin than was incorporation of [14C]leucine. The dose‐‐response curves showed a general similarity in shape, which would be compatible with the hypothesis that protein synthesis may be necessary for the production of fever. 3. A comparison was made of the effects of giving anisomycin into the cerebral ventricles 0, 30 or 60 min after the intraventricular injection of leucocyte pyrogen. Anisomycin inhibited fever to some extent even when given 60 min after leucocyte pyrogen. This suggests that if protein synthesis is involved in fever, it may continue at least into the early phase of rising temperature, but probably not to any significant extent after the plateau has been reached.
Inhibition, by trichothecene antibiotics, of brain protein synthesis and fever in rabbits.
Authors: Cannon M , Cranston W I , Hellon R F , Townsend Y
Published: December 2014

1. To test further the hypothesis that brain protein synthesis is necessary for fever, three structurally similar trichothecene antibiotics were injected into the cerebral ventricles of rabbits. They were 3,15‐diacetoxy‐12‐hydroxytrichothec‐9‐ene (DAHT), 3,15‐didesacetyl‐calonectrin (DDAC) and T‐2 toxin. Their actions on hypothalamic incorporation of [14C]leucine and fever were compared. 2. DDAC (60 micrograms) and T‐2 toxin (10 micrograms) strongly inhibited leucine incorporation and fever. DAHT (60 micrograms) did not diminish fever and had a smaller effect upon leucine incorporation. 3. The findings strengthen considerably earlier suggestions that brain protein synthesis is an essential step in pyrogenesis.
On the quantal release of endogenous glutamate from the crayfish neuromuscular junction.
Authors: Kawagoe R , Onodera K , Takeuchi A
Published: December 2014

1. The abdominal slow flexor muscle was isolated from the crayfish (Cambarus clarkii) and placed in 150 microliters. Harreveld solution. The concentrations of glutamate and aspartate in this solution were measured by mass fragmentography. 2. Application of black widow spider venom (BWSV) produced a marked increase in the frequency of miniature excitatory post‐synaptic potentials (m.e.p.s.p.s). During the high frequency discharge of m.e.p.s.p.s, the glutamate content in the solution was significantly increased. There was an approximately linear relationship between the increase in the glutamate efflux produced by BWSV and the variance of the membrane potential fluctuation during high frequency discharge of m.e.p.s.p.s. 3. In most cases, the efflux of aspartate during control rest periods was smaller than that of glutamate. During the discharge of m.e.p.s.p.s produced by BWSV, the increase in the aspartate efflux was very small compared to glutamate. 4. Nerve stimulation caused a significant increase in the efflux of glutamate, but the change in the aspartate efflux was very small and not significant. 5. Application of methylene blue increased the frequency of m.e.p.s.p.s and glutamate efflux, but little, if any, increase was found in aspartate efflux. 6. It is concluded that glutamate is preferentially released from nerve terminals in a quantal fashion.
Gallamine triethiodide‐induced modifications of sodium conductance in Myxicola giant axons.
Authors: Schauf C L , Smith K J
Published: December 2014

1. Internal gallamine triethiodide (Flaxedil) modifies Na+ channel kinetics in Myxicola axons but does not alter K+ conductance. The drug has no effect externally. 2. Gallamine initially increases the leakage‐conductance, but this effect completely reverses within 30 min despite the maintained presence of drug. 3. During step depolarizations to membrane potentials less than ‐10 mV, gallamine slows the rate of Na+ inactivation, but all channels which have opened can still inactivate. During depolarizations to more positive potentials, gallamine‐modified Na+ currents show a biphasic decline, and at VM greater than ‐10 mV, Na+ inactivation is incomplete as evidenced by the large Na+ tail currents which follow pulses sufficiently long to have allowed complete inactivation of normal Na+ channels. The tail currents are slower than normal Na+ tails, and exhibit a pronounced hook. With gallamine, the fraction of Na+ channels which do not inactivate increases sigmoidally over the range 0 mV to +80 mV. 4. For VM greater than ENa, gallamine almost completely blocks outward Na+ currents. The block is determined by the direction of Na+ current, rather than the absolute membrane potential. 5. Gallamine has no effect upon the rate of Na+ channel activation, the maximum Na+ conductance, the steady‐state Na+ inactivation curve, or the rate of development or removal of inactivation by prepulses. 6. Gallamine eliminated physiological immobilization of intramembrane charge movements (QOFF and QON) and does not itself induce immobilization. Thus, in the presence of gallamine, QOFF following long pulses is the same as QOFF following short pulses.
Chemical transmission between individual Retzius and sensory neurones of the leech in culture.
Authors: Fuchs P A , Henderson L P , Nicholls J G
Published: December 2014

1. Chemical synaptic transmission develops between individual identified neurones dissected from leech ganglia and maintained in culture. Impulses in Retzius cells give rise to hyperpolarizing synaptic potentials in pressure (P) sensory cells. In suitable medium the potentials develop by 3 days and can be observed for more than 3 weeks. 2. The synaptic potentials occur after a synaptic delay, exhibit facilitation and depression and are reversed by hyperpolarization. The blocking effects of reduced calcium and raised magnesium concentrations in the bathing fluid provide additional evidence for the chemical nature of transmission. 3. An increase in chloride conductance is involved in the generation of the synaptic potential in the P cell. With high intracellular Cl in the post‐synaptic cell, the synaptic potentials become reversed and amplified. The amplitudes of these reversed responses range from 1 to 20 mV with a falling phase lasting for seconds. 4. Changes in the membrane potential of the presynaptic cell that modify the amplitude and duration of the action potential influence the efficacy of transmission. In addition, impulses in Retzius cells initiated from hyperpolarized values of membrane potential evoke smaller synaptic potentials in the P cells than impulses arising from a depolarized level. 5. With neurones placed directly next to one another in the dish, maintained depolarization of the presynaptic Retzius cell in the absence of conducted action potentials gives rise to slow synaptic potentials in the P cells. In some pairs, the response in the P cell consists of a marked increase in ‘noise’. 6. Injection of horseradish peroxidase into the Retzius cell reveals neurites with distinctive varicosities growing over the P cell.
The effect of extracellular calcium deprivation on amylase secretion and 45Ca efflux from rat pancreas
Authors: Argent B. E. , Case R. M. , Hirst Frances C.
Published: December 2014

1. The role of extracellular Ca2+ in pancreatic enzyme secretion and 45Ca efflux evoked by acetylcholine (ACh) and caerulein has been assessed in the incubated, uncinate pancreas of young rats.

2. In a medium containing 2·5 × 10−3
m‐Ca2+, the maximal rates of amylase secretion evoked by optimal doses of each secretagogue were similar. However, the time courses of amylase release during prolonged stimulation of the gland were different.

3. The time course of amylase secretion in response to an optimal dose of ACh (10−5
m) was characterized by an initial rapid increase followed by a slow sustained rise. For caerulein (10−8
m), an initial rapid rise was followed either by a plateau or slight decline in the rate of amylase secretion.

4. Both secretagogues produced similar increases in the rate coefficient of 45Ca efflux from the gland.

5. With supra‐optimal doses of the secretagogues, amylase secretion, but not the rate coefficient of 45Ca efflux, was depressed.

6. Reducing the extracellular Ca2+ concentration did not have a marked effect on basal amylase secretion but inhibited the action of both secretagogues. When the Ca2+ concentration was 10−6
m or lower, these inhibitory effects were irreversible. Amylase secretion stimulated by ACh was more sensitive to extracellular Ca2+ deprivation than that stimulated by caerulein, the concentration required for half‐maximal secretion being about 9‐fold greater for ACh.

7. Decreasing the extracellular Ca2+ concentration increased both the basal and stimulated rate coefficients of 45Ca efflux.

8. Our results support the hypothesis that pancreatic enzyme secretagogues act by releasing bound Ca2+ from sites within the acinar cell. Furthermore, they suggest that the site utilized by ACh is more amenable to depletion, via changes in extracellular Ca2+ concentration, than that employed by caerulein.
Inputs to testosterone‐sensitive stria terminalis neurones in the rat brain and the effects of castration.
Authors: Kendrick K M
Published: December 2014

1. The inputs to cortico‐medial amygdala neurones which project directly to the area of the medial preoptic/anterior hypothalamic junction were studied electrophysiologically in urethane anaesthetized male rats. 2. In experiments with fifteen male rats it was found that none of these neurones was responsive to electrical stimulation of the ipsilateral olfactory bulb or accessory olfactory bulb or odour stimulation. 3. Experiments with four rats showed that electrical stimulation of the lateral portion of the contralateral fimbria excited 81% of these cortico‐medial amygdala neurones. Their typical response to stimulation of the contralateral fimbria was a single action potential followed by an inhibitory period (20‐100 ms). 4. Analysis of the polarity of evoked waves in the amygdala suggested that the fimbria input terminated in the basolateral nucleus of the amygdala and that this nucleus subsequently projected to the cortico‐medial amygdala. The fimbria input was found to be contralateral in origin, crossing the mid line in the anterior fornical commissure. 5. In a further experiment 118 identified cortico‐medial amygdala neurones were recorded from twelve rats (six gonadally intact and six castrated). Castration significantly decreased the percentage of these neurones responding to stimulation of the ipsilateral fimbria (20 vs. 97%) and lengthened post‐excitatory inhibitory periods. 6. Results are discussed with respect to the initial finding by Kendrick & Drewett (1979) of testosterone‐sensitive absolute refractory periods in cortico‐medial amygdala neurones.
Uptake of adenosine and release of adenine derivatives in mammalian non‐myelinated nerve fibres at rest and during activity
Authors: Maire J. C. , Medilanski J. , Straub R. W.
Published: December 2014

1. Influx of adenosine into rabbit non‐myelinated nerve fibres was measured using [2‐3H]adenosine. The uptake of radioactivity increased linearly with duration of incubation for up to 60 min and adenosine concentration up to 200 μ
m. The uptake at different adenosine concentrations showed a saturable component with a half‐maximal activation at 17·1 μ
m and a linear part.

2. The radioactivity taken up was rapidly incorporated into AMP, ADP and ATP. Isotopic equilibrium between the nucleotides was achieved within 15 min.

3. The uptake of 3H from 0·2 μ
m‐adenosine was almost completely inhibited by addition of 200 μ
m‐adenosine and to a similar extent by 200 μ
m‐tubercidin and AMP; a 70% inhibition was found with ATP and ADP; α, β methylene‐ADP had no effect.

4. ATP, ADP and AMP added to the extracellular medium of a desheathed vagus were slowly hydrolysed.

5. In preparations loaded with [2‐3H]adenosine and then washed with adenosine and label‐free solution there was a steady efflux of radioactivity amounting to 0·18 × 10−3/min. Addition of adenosine or tubercidin transiently increased the efflux.

6. Electrical stimulation caused an extra release of radioactivity. The extra fractional loss was 21·8 × 10−6/impulse in preparations that had rested for several hours; it decreased to 2·3 × 10−6/impulse when stimulation was applied after a 30 min rest.

7. The radioactivity of the resting efflux and of the extra efflux after stimulation was found mostly in inosine and hypoxanthine; adenosine and adenine accounted for only 3%, and the nucleotides for less than 1% of the efflux.

8. Adenosine added to the external medium of a desheathed nerve was slowly deaminated.

9. It is concluded that inosine and hypoxanthine found in the effluent from desheathed vagus nerve trunk result from release of these compounds from nerve fibres and not from extracellular breakdown of released ATP or adenosine.

10. Electrical activity in non‐myelinated nerve fibres of the nerve trunk thus causes the release of metabolites (inosine and hypoxanthine) together with small amounts of adenosine and adenine, while release of ATP and other nucleotides is almost completely absent.
Acute changes in the composition of milk during the ovulatory menstrual cycle in lactating women.
Authors: Hartmann P E , Prosser C G
Published: December 2014

1. Breast milk composition was followed for a period of 28 days in five women during lactational amenorrhea and in another two who were taking oral contraceptives. The milk composition was also studied in two women during an anovulatory menstrual cycle and in six women during an ovulatory menstrual cycle. Samples of milk were collected from each breast at each feed for each day of the study. 2. Two acute changes, the first 5‐6 days before and the second 6‐7 days after ovulation, occurred in the milk composition during the ovulatory menstrual cycle. At both times there was an increase in Na and Cl concentrations from (mean +/‐ S.E. of mean) 4.6 +/‐ 0.2 mM and 11.1 +/‐ 0.2 mM to 10.1 +/‐ 0.9 mM and 22.0 +/‐ 0.9 mM respectively and a decrease in lactose and K concentrations from 7.8 +/‐ 0.2 g/100 ml. and 13.6 +/‐ 0.4 mM to 6.0 +/‐ 0.2 g/100 ml. and 10.2 +/‐ 0.5 mM respectively. The mean duration of the first change was 28 hr and the second was 32 hr. The concentrations of lactose, Cl, K and Na remained relatively constant during lactational amenorrhea, anovulatory menstrual cycles and for those women taking oral contraceptives. 3. These observations indicate that an increase in the permeability of the mammary epithelium was elicited by changes related to ovulation. It is suggested that the first acute change in the breast milk composition may be associated with the final stages of follicle maturation and the second with the regression of the corpus luteum during the ovulatory menstrual cycle.
Effects of cholinergic drugs on receptive field properties of rabbit retinal ganglion cells
Authors: Ariel M. , Daw N. W.
Published: December 2014

1. Retinal ganglion cells were recorded extracellularly from the rabbit's eye in situ to study the effects of cholinergic drugs on receptive field properties. Physostigmine, an acetylcholinesterase inhibitor, and nicotine increased the spontaneous activity of nearly all retinal ganglion cell types. The effectiveness of physostigmine was roughly correlated with the neurone's inherent level of spontaneous activity. Brisk cells, having high rates of spontaneous firing, showed large increases in their maintained discharge, whereas sluggish cells, with few or no spontaneous spikes, showed small and sometimes transient increases in spontaneous activity during physostigmine.

2. The sensitivity of ganglion cells to spots of optimal size and position did not change substantially during the infusion of physostigmine. However, the responsiveness to light (number of spikes per stimulus above the spontaneous level) increased. This effect occurred with sluggish and more complex cells, rarely with brisk cells.

3. Another effect of physostigmine on sluggish and more complex cells was to make these cells ‘on—off’. The additional response to the inappropriate change in contrast had a long latency and lacked an initial transient burst.

4. Complex receptive field properties such as orientation sensitivity, radial grating inhibition, speed tuning and size specificity were also examined. These inhibitory properties were still present during infusion of physostigmine and, in most cases, the trigger feature of each cell type remained.

5. These results are consistent with pharmacological results on ACh release from the retina. There appear to be two types of release of ACh, having their most powerful influences on separate classes of cells. One release (transient), occurs at light onset and offset and acts primarily on sluggish and more complex ganglion cells; the other release (tonic) is not light‐modulated and acts primarily on brisk cells. A wiring diagram for the ACh cells is suggested.
Eye position signals in the flocculus of the monkey during smooth‐pursuit eye movements
Authors: Noda Hiroharu , Warabi Tateo
Published: December 2014

1. Discharges of Purkinje cells and mossy fibres were recorded from the flocculus of monkeys trained to fixate a small visual target and to track the target when it moved slowly.

2. Discharges of Purkinje cells changed tonically with shifts of gaze. Firing rates were linearly related to eye positions for either the entire or more than half the eye‐position range in 12·6% of Purkinje cells tested (76/603 units).

3. The eye position‐related activity (position component) was observable in these cells also during smooth‐pursuit eye movements. It was typically seen during slow eye movements (velocities less than 10 deg/s) but became undetectable during high velocity movements (faster than 50 deg/s).

4. The position component became prominent when smooth pursuit was executed at the preferred loci of the individual cells. In the majority of the cells tested at their preferred loci, the position component was observable to a relatively high frequency, such as 0·5 Hz (± 10 deg; peak velocity 31 deg/s).

5. Forty‐five mossy fibre units showed saccade‐related bursts and position‐related intersaccadic tonic activity during steady eye position. In each unit, the position component was found only during fixations within a specific range of eye positions. During fixations outside these regions, all position‐related mossy fibres were completely silent.

6. During sinusoidal smooth‐pursuit eye movements, the mossy fibres also displayed cyclic modulations in activity. All fibres discharged with eye movements in one direction and were silent during eye movements in the other direction.

7. Saccade‐related bursts from mossy fibres led the onset of saccades, ranging from 0 to 19 ms with a mean lead‐time of 6·9 ms. This observation negates the possibility that the position‐related signals might represent proprioceptive impulses from the stretch receptors of the extraocular muscle.