bluuebunny/crossref_metadata_2025 huggingface dataset:
AGE‐RELATED EFFECTS OF FATIGUE AND RECOVERY FROM FATIGUE IN RAT MEDIAL GASTROCNEMIUS MUSCLE
Authors: De Haan A. , Lodder M. A. N. , Sargeant A. J.
Published: December 2014

Force‐velocity, power‐velocity and unloaded shortening data were obtained from in situ medial gastrocnemius muscle‐tendon complexes (stimulated at 60 Hz) with intact circulation of mature male rats (∼ 125 days old). Measurements were carried out at the end of a long (15 s) contraction (fatigued muscles) or with a short (1 s) contraction either in the fresh state (fresh muscles) or in muscles which had recovered for 15 min after a long contraction. Compared to the fresh state fatigue reduced isometric force by 57%, maximal shortening velocity by ∼ 40% and maximal power output by 81%. These reductions were similar to data previously obtained with younger rats (40 days old). However, the velocity data of the muscles which had recovered for 15 min after a long contraction showed a greater reduction in the mature rats. This difference between the two age groups together with a difference in the changes in the initial parts of the isometric force‐time curves suggest an age‐dependent response of the fast‐fatigable fibre population of these mixed muscles. In a separate series of experiments the underlying mechanism of the recovery from fatigue was studied in a group of young rats. Fatigue was induced with five long (15 s) contractions (each at 5 min intervals). The recovery of isometric force and power output was monitored with short contractions which indicated a plateau of recovery but the absolute values were still reduced after 60 min (85 and 71% of pre‐fatigue values, respectively). Phosphocreatine concentration recovered rapidly, whereas the ATP concentration was still markedly reduced after 1 h of recovery. The time courses of recovery of inosine‐5'‐monophosphate (IMP) and lactate concentrations resembled those of force and power output. Thus it is possible that age‐dependent differences in IMP and/or lactate production may play a role in fatigue and recovery from fatigue.
EXTRACELLULAR MAGNESIUM REGULATES ACETYL‐CHOLINE‐EVOKED AMYLASE SECRETION AND CALCIUM MOBILIZATION IN RAT PANCREATIC ACINAR CELLS
Authors: Lennard Roger , Francis Leo P. , Singh Jaipaul
Published: December 2014

Application of ACh (10−6 M) to the isolated rat pancreas elicited large increases in amylase secretion, radiolabelled 45Ca influx and cytosolic free Ca2+ levels in zero and normal (1·1 mM) extracellular magnesium (Mg2+). Elevated (10 mM) Mg2+ significantly (P 〈 0·001) reduced the ACh‐induced amylase output and Ca2+ mobilization. Similarly, ACh (10−5 M) caused a transient increase in 45Ca efflux from pre‐loaded pancreatic segments in normal Mg2+ compared with the much reduced effect in elevated Mg2+. The results suggest that a modification in Mg2+ influences ACh‐evoked amylase secretion by regulating Ca2+ mobilization.
IONIC CHANNELS IN SYNAPTIC VESICLES: ARE THEY INVOLVED IN TRANSMITTER RELEASE?
Authors: Rahamimoff Rami , Yakir Nilly , DeRiemer Susan A. , Ginsburg Simona , Kaiserman Igor , Shapira Roy , Sakamann Bert , Stadler Herbert
Published: December 2014

Synaptic vesicles were isolated from the nerve terminals of Torpedo electric organ. After fusion, ‘giant’ vesicles were formed which could be examined by the patch clamp technique. One of the cationic channels, the P channel, shows a small preference for K+ compared to Na+ and has multiple conductance levels. Its rate of opening is voltage and calcium dependent. Fractal analysis of the P channels reveals that its behaviour does not seem to be fractal in nature. At voltages where only one conductance level is observed, fractal analysis shows at least one discrete open state and at least two discrete closed states. There are considerable similarities between the P channel and channels found in granules from the hypophysis. These channels resemble, in turn, the channels found in gap junctions. Therefore, it is not unwarranted to speculate that a gap‐junction‐like communication between the secretory vesicle and the extracellular space may occur during exocytosis.
POTASSIUM CHANNELS ACTIVATED BY SODIUM
Authors: Martin A. R. , Dryer S. E.
Published: December 2014

Na+‐activated K+ currents have been reported in snail neurones, crayfish giant motoneurones, cardiac myocytes, and in ganglion cells and brain stem cells from chick embryos. Such currents are seen in voltage‐clamp experiments, following depolarization‐induced Na+ influx. A variety of experiments have shown that the currents through the conductance pathways are indeed carried by K+ ions and that they are quantitatively dependent upon Na+ influx into the cells. Theoretical calculations indicate that such currents must make a substantial contribution to action potential repolarization. The conductances are activated by Li+ in invertebrate neurones, but not in the embryonic vertebrate neurones. Single‐channel recordings from vertebrate brain stem cells reveal channels with conductances of about 50 pS, activated by Na+ concentrations in the 10‐100 mM range.
SOME ASPECTS OF THE NEUROMUSCULAR SYSTEM OF ASCARIS
Authors: del Castillo José , Rivera Amelia , Solórzano Salbador , Serrato Jesus
Published: December 2014

1. The structure and physiological properties of the somatic neuromuscular system of the nematode Ascaris lumbricoides var. suum are discussed taking into account early work from this laboratory, the results of other workers, and experiments in progress.

2. Anatomically, the central feature of the somatic musculature is the presence of a specialized muscular, but not contractile, structure: the syncytium or sarcopile, formed by the terminal processes of the muscle cell arms that contact the nerve cord. In this region, they are electrically coupled to one another and form chemical synapses with the nerve fibres.

3. The syncytium serves, primarily, as a nerve‐muscle manifold, or device which allows the neural control of the muscle fields with great economy in the amount of nervous tissue, numbers of chemical junctions and quantities of synaptic transmitters.

4. The structure of the syncytium is being studied with the scanning electron microscope. The results reveal the convergence of the arms on discrete sites as they approach the cords, as well as a longitudinal arrangement of the terminal processes as they course over the cords, at least in the posterior region of the animal.

5. The characteristics of the electrical coupling between the muscle cells are being investigated. A pattern has been observed that is dependent on the position of the cell pairs with respect to the longitudinal axis of the animal.

6. A study of signal propagation in the arms has revealed that the morphology of the muscle cells contributes to the extent and preferential direction of propagation.
THE NERVOUS CONTROL OF INTRALUMINAL PRESSURE IN THE VOMERONASAL ORGAN OF THE DOMESTIC RAM
Authors: Bland K. P. , Cottrell D. F.
Published: December 2014

In order to examine whether an aspiration mechanism exists in the vomeronasal organ (VNO) of the domestic ram, experiments were conducted in chloralose‐anaesthetized animals using acute electromanometry and electrophysiological techniques. Stimulation of the ipsilateral cervical sympathetic nerve activated a mechanism producing a negative (with respect to atmospheric pressure) intraluminal pressure which drew fluid into the VNO from the nasopalatine canal. The mechanism was under α‐adrenergic control and did not seem to involve the carotid blood supply. An ipsilateral increase in intraluminal pressure occurred following electrical excitation of the maxillary trigeminal innervation. Thus a mechanism was demonstrated in the ram for conveying odours to the putative olfactory receptors in the VNO.
PRE‐PYLORIC MECHANISMS REGULATING GASTRIC MOTOR FUNCTION IN THE CONSCIOUS DOG
Authors: Grundy D. , Hutson D. , Rudge L. J. , Scratcherd T.
Published: December 2014

Reflex mechanisms regulating gastric motor function were studied in four conscious dogs, whose stomachs had been surgically divided into separate corporal and antral pouches. Interactions between the corpus and antrum were investigated in fasted animals by balloon distension of each region. During the quiescent phase (phase I) of the migrating motor complex (MMC), distending the corpus with volumes greater than 80 ml resulted in contractions of the corpus, which persisted for as long as the distending stimulus was applied. This corporal distension also initiated antral contractions which were greater if the antrum was moderately distended and also greater with a larger corporal distending volume up to 300 ml. Graded 5 ml inflation of the antrum during the quiescent phase of the MMC stimulated antral contractions. This antral response to antral distension was augmented when the corpus was inflated but was only statistically significant with antral volumes below 25 ml. Distension of the antrum with volumes 〉 12·5 ml caused inhibition of corporal contractions during both the active phase of a migrating complex or when stimulated by corporal inflation. The degree of inhibition was proportional to the distending stimulus and was present for the duration of the applied distension. For antral volumes of 50 ml the inhibition persisted for a variable time after the stimulus was withdrawn. The inhibition of corporal activity by antral distension was still effective after blocking acid secretion with cimetidine (100 mg), which would eliminate spillage of acid into the jejunum as a cause of the inhibition. It is concluded that pre‐pyloric mechanisms co‐ordinate corporal and antral motor activity and would operate during gastric emptying to provide a controlled delivery of chyme to the duodenum.
MUSCLE TONE AROUND THE HUMAN KNEE IN PARAPLEGIA
Authors: Douglas A. J. , Walsh E. G. , Wright G. W. , Edmond P.
Published: December 2014

The thigh muscle tone of non‐injured subjects and complete injury paraplegics has been investigated using torques, generated by a printed motor, to move the knee. The dynamic measure of resonant frequency (related to stiffness) together with a static measure of stiffness have shown the legs of non‐injured subjects to respond non‐linearly to decreasing torques. However, the complete paraplegics' legs did not respond non‐linearly but showed constant resonant frequency and stiffness over the range of torques. Peak velocity at resonance (inversely related to damping) gradually increased with increasing torques in both groups. In addition, at a chosen baseline torque of 0·7 N m, resonant frequency and muscle stiffness were significantly lower and peak velocity significantly higher in the paraplegics compared to the non‐injured subjects. Contrary to expectations the thigh muscles in established, complete paraplegia showed a lack of tonic EMG activity. In addition, whilst phasic stretch responses were occasionally seen there was no tonic activity in relation to continued stretch. Since muscles atrophy after paralysis, the smaller muscle bulk may contribute to the lower muscle tone.
EVIDENCE FOR FUROSEMID E‐SENSITIVE Na+‐K+‐Cl#x2212; CO‐TRANSPORT IN LACTATING RAT MAMMARY TISSUE
Authors: Shennan D. B.
Published: December 2014

The transport of K+ (using 86Rb as tracer) by lactating rat mammary tissue slices has been studied in order to seek evidence for Na+‐K+‐Cl− co‐transport. Potassium transport was inhibited by furosemide; the locus of inhibition was at a site other than the Na+:K+ pump. Replacing medium Cl− with NO3 reduced the bidirectional movement of K+; moreover, furosemide was without effect in a Cl−‐free medium. Sodium replacement by N‐methyl‐D‐glucamine acted to reduce the loop diuretic‐sensitive component of K+ uptake whilst concomitantly increasing K+ influx via an ouabain‐and furosemide‐resistant pathway. Potassium efflux was found to be transiently stimulated by Na+ ions; this was attenuated by furosemide. Potassium egress was markedly increased via a furosemide‐insensitive pathway when salicylate was used to replace Cl−. The results are consistent with furosemide‐sensitive Na+‐K+‐Cl−co‐transport.
STOICHIOMETRY OF NET SODIUM AND POTASSIUM FLUXES MEDIATED BY THE Na‐K‐Cl CO‐TRANSPORT SYSTEM IN FERRET RED CELLS
Authors: Flatman Peter W.
Published: December 2014

The bumetanide‐sensitive Na‐K‐Cl co‐transport system in ferret red cells produces net movement of lNa:1K. Tracer studies have misleadingly suggested a stoichiometry of 2Na:1K probably because the transporter mediates substantial Na‐Na exchange in these cells.
GROWTH AND SYNAPSE FORMATION BY IDENTIFIED LEECH NEURONES IN CULTURE: A REVIEW
Authors: Nicholls John G. , Hernandez Ubaldo Garcia
Published: December 2014

Within hours after identified neurones have been isolated from the CNS of the leech, they begin to sprout and to form synapses. Electrical recordings made by loose‐patch clamp show that the tip of the isolated neurone has distinct properties with a high density of sodium channels. Neurites grow out from this tip after about 30 min and continue to grow for the next few days. The extent of growth, the branching pattern and the distribution of calcium channels all depend critically upon the molecular composition of the substrate. The tip of the neurone also represents a preferred region for synapse formation. For example when the tips of two serotonin‐containing neuromodulatory neurones, the Retzius cells, are placed in contact, chemical synapses develop within about 6 h. These chemical synapses are bidirectional and become stronger over the next 2 days. Electrical synapses between the two Retzius cells develop more slowly and appear only after about 20 h. When the tip of one Retzius cell is apposed to the soma of another, chemical transmission develops more slowly. When other regions of these same cells are placed in contact, electrical transmission can appear before chemical. Together these results show that specialized areas of neuronal membrane are involved in neurite extension and in the formation of specific synaptic connections.
Gamma‐motoneurone discharge patterns during fictive locomotion in the decerebrate cat
Authors: Murphy PR , Hammond GR
Published: December 2014

Triceps surae gamma‐motoneurones were recorded during fictive locomotion in the paralysed high decerebrate cat. Two distinctive patterns of discharge were observed which were similar to those reported for static and dynamic gamma‐motoneurones during locomotion in the same preparation, but without paralysis (Murphy, Stein & Taylor, 1984). These results suggest that movement‐related afferent feedback is not essential for the generation of the basic patterns of static and dynamic gamma‐motoneurone activity during locomotion. The results are discussed in relation to the generation of alpha and gamma locomotor rhythms.
The distribution of substance P‐containing nerves to the rat small intestine
Authors: Amira S , Morrison JF , Rayfield KM
Published: December 2014

The concentrations of substance P‐like immunoreactivity (SPLI) were measured in mesenteric nerves and vessels of control rats and rats treated with capsaicin during the second day of life. The results showed that there was a significantly higher concentration of SPLI in the jejunum than in the terminal ileum, and that there was a loss of SPLI from these tissues following neonatal treatment with capsaicin. The results suggest that the substance P‐containing afferent innervation of the upper small intestine is greater than in the terminal ileum. The significance of these results to the Intensity or Summation hypothesis of visceral pain, and to the thresholds of visceral reflexes from different areas of the small intestine is discussed.
Water and sodium movements across the ruminal epithelium in fed and food‐deprived sheep
Authors: Holtenius K , Dahlborn K
Published: December 2014

Fluid and electrolyte movements across the ruminal epithelium of sheep were studied using the temporarily isolated rumen technique. The sheep were all subjected to the following treatments: (1) fed sheep (fed twice daily), after rumen emptying, received rumen contents from a fed sheep; (2) food‐deprived sheep (two meals were omitted), after rumen emptying, received rumen contents from a food‐deprived sheep; (3) fed sheep, after rumen emptying, received rumen contents from a food‐deprived sheep; and (4) food‐deprived sheep, after rumen emptying, received rumen contents from a fed sheep. Food deprivation led to an increased Na concentration of the rumen fluid while K and Cl concentrations, as well as osmolality, decreased. Plasma Na and osmolality decreased. During the 40 min after the rumen contents were exchanged no net movements of water occurred. Then the sheep were given an intraruminal load of saline which gave rise to a significant net absorption of fluid from the rumens of those sheep which had received rumen contents from fed sheep. The change in composition of the rumen contents after food deprivation impaired the absorption of Na and water from the rumen. Furthermore food deprivation reduced the Na absorptive function of the ruminal epithelium, but not the water permeability.
The effects of lower body negative pressure on baroreceptor responses in humans
Authors: Vukasovic JL , al-Timman JK , Hainsworth R
Published: December 2014

In healthy human subjects the immediate responses of pulse interval and the steady‐state responses of arterial blood pressure and cardiac output to changes in carotid sinus transmural pressure were determined before and during the application of a subatmospheric pressure to the lower part of the body. Increases in carotid sinus transmural pressure, effected by applications of subatmospheric pressure to the neck (neck suction) resulted in prolongation of pulse interval and decrease in blood pressure; opposite responses were obtained to application of a positive pressure (neck pressure). Application of lower body negative pressure resulted in a decrease in pulse interval (heart rate increase) but little change in blood pressure. During lower body negative pressure, the responses of pulse interval to neck pressure were reduced but those to neck suction were unaffected; the responses of blood pressure to neck suction were enhanced but those to neck pressure were unaffected. From experiments in which cardiac output was also determined, it was seen that lower body negative pressure reduced cardiac output, increased calculated total body vascular resistance and augmented the resistance response to neck suction although not to neck pressure. These results are compatible with the view that application of lower body negative pressure does not change the sensitivity of the baroreceptor reflex and that the changes in the responses are due to non‐linearities of the stimulus‐response curves.
An electrophysiological and anatomical study of afferents reaching the cerebellar uvula in the rabbit
Authors: Bradley DJ , Ghelarducci B , La Noce A , Paton JF , Spyer KM , Withington‐Wray DJ
Published: December 2014

Stimulation of a medial region of the cerebellar uvula cortex produces sympathetically mediated cardiovascular effects in the decerebrate rabbit. In the present study the afferents to this cerebellar area have been determined using electrophysiological and neuroanatomical methods. Field potentials of prevalent mossy origin evoked by single‐shock stimulation of different peripheral nerves have been recorded from sublobules IXa and IXb. No response to vagus and aortic nerves stimulation has been found. A modulation of Purkinje cell discharge following natural vestibular stimulation has been found. A modulation of Purkinje cell discharge following natural vestibular stimulation has been recorded from sublobules IXb and IXc. The retrograde transport of horseradish peroxidase from the uvula cortex has revealed a widespread afferent input to this cerebellar region arising from brain stem reticular and sensory nuclei. On the basis of the results obtained, together with the results of experiments performed in conscious rabbits, contained in the following paper (Bradley, Ghelarducci, La Noce & Spyer, 1990), it is suggested that the uvula participates in co‐ordination of the visceral and somatic components of the alerting reaction in the rabbit.
Urea metabolism in sheep given conventional feeds or nourished by intragastric infusion
Authors: Whitelaw FG , Milne JS , Orskov ER , Stansfield R , Franklin MF
Published: December 2014

A comparison has been made of the kinetics of urea metabolism in sheep given conventional feeds or maintained wholly by intragastric infusions of volatile fatty acids, buffer, mineral and casein solutions. Daily nitrogen supply was 13.2 g/day in ‘fed’ sheep and 6.0 g/day in ‘infusion’ sheep. On each feeding system measurements were made at the basal (maintenance) level of intake and when the basal level was supplemented with infusions of urea into the abomasum (125 mmol/day) or into the rumen (300 mmol/day). Additional measurements were made when ammonium carbonate (100 mmol/day) was infused into the rumen, when cassava (150 g/day) was added to the diet of ‘fed’ sheep or when the input of casein to ‘infusion’ sheep was reduced by half. Urea kinetics were measured by means of a single intravenous injection of [14C]urea. Urea irreversible loss rate, urea pool size, urinary urea excretion, plasma urea concentrations and rumen ammonia concentrations were all significantly higher in sheep given conventional feeds than in those nourished by infusion but urea degradation in the gastrointestinal tract did not differ between the two methods of feeding. Regression analysis indicated only minor differences between the two feeding systems in the relationships between the various indices of urea metabolism. It is concluded that most of these findings can be attributed to differences in the quantity and nature of the nitrogen supplied in the basal diets and that the sheep nourished by infusion would be a suitable model for the study of factors involved in the control of urea recycling.
Inhibition of nitric oxide synthesis potentiates hypoxic vasoconstriction in isolated rat lungs
Authors: Robertson BE , Warren JB , Nye PC
Published: December 2014

We have investigated the influence of endogenous nitric oxide (NO) on the vascular resistance of isolated rat lungs by inhibiting its synthesis with the false substrate N‐monomethyl‐L‐arginine (L‐NMMA). When perfused with blood at constant flow the addition of L‐NMMA (10(‐3) M) did not affect pulmonary arterial pressure in hyperoxia but did increase the response to hypoxia (PO2 25‐35 mmHg) by 2.5 +/‐ 0.2 fold (mean +/‐ S.E.M.). The effect of L‐NMMA was reversed by 3 x 10(‐3) M‐L‐arginine, the true substrate for NO synthesis. Thus NO is an important pulmonary vasodilator but hypoxic vasoconstriction does not result from a reduction of its background release.
The effects of changes in laryngeal airway CO2 concentration on genioglossus muscle activity in the anaesthetized cat
Authors: Nolan P , Bradford A , O'Regan RG , McKeogh D
Published: December 2014

In the anaesthetized cat the larynx was isolated in situ, artificially ventilated and used to assess reflex effects exerted by respiration‐related laryngeal stimuli on genioglossus electromyographic activity (Gg EMG) and respiratory frequency (RF). Phasic Gg EMG was not observed when the larynx was unventilated but was evoked, with a concurrent decrease in RF, when negative pressures or oscillatory pressures similar to those of normal ventilation were applied to the larynx. Increases in laryngeal airway CO2 concentration also enhanced Gg EMG and reduced RF. All reflex effects were abolished by bilateral section of the superior laryngeal nerves. We propose that negative intralaryngeal pressure and CO2 may act together to restore pharyngeal patency during obstructive apnoea.
Unreliability of lithium clearance as a marker of proximal tubular function during haemorrhagic hypotension in the rat
Authors: Walter SJ , Shirley DG
Published: December 2014

Fractional lithium excretion (FELi) was measured before and after hypotensive haemorrhage (15 ml (kg body wt)‐1) in anaesthetized Brattleboro rats; simultaneously, micropuncture collections were made from late proximal convoluted tubules. Micropuncture data indicated that fractional reabsorption in the proximal convoluted tubules was not affected significantly by haemorrhage, whereas FELi fell from 0.25 +/‐ 0.02 (mean +/‐ S.E.M.; control period) to 0.03 +/‐ 0.01. In time‐control animals, no significant change in either variable was observed. These results suggest that lithium clearance is an unreliable marker of proximal tubular function during haemorrhagic hypotension.
A cultured human renal epithelioid cell line responsive to vasoactive intestinal peptide
Authors: Simmons NL
Published: December 2014

A permanently transformed cell line derived from human embryo renal cortical cells (HEK293) has been investigated for the retention of renal‐specific properties. The cell line is epithelioid in growth on plastic, and transmission electron microscopy demonstrates the formation of apical zonae occludentes. There is no prominent brush‐border. The response of HEK293 cell adenylate cyclase is noteworthy for the response to vasoactive intestinal peptide (half‐maximal activation at 0.9 nM). The HEK adenylate cyclase response to VIP is specific, with related peptides such as glucagon and secretin being ineffective. The response to VIP is competitively antagonized by the VIP receptor antagonist (4Cl‐D‐Phe6,Leu17)‐VIP.
Effects of selective blood and tissue heating on blood flow in the dog hindlimb
Authors: McMeeken JM , Bell C
Published: December 2014

This study investigated the effects of independent and combined heating of blood and tissue to 40‐44 degrees C on femoral blood flow in the hindlimb of the anaesthetized dog. An increase in arterial blood temperature by means of an extracorporeal circuit increased femoral vascular resistance. An increase in limb tissue temperature, induced by external hot packs, decreased femoral vascular resistance. These responses occurred both before and after sympathetic blockade. Neither blood heating nor tissue heating affected the hyperaemic response to exercise. When blood and tissue heating were combined, femoral vascular resistance remained unaffected. We conclude that changes in blood temperature do not contribute to the hyperaemic effect of limb warming and that exercise combined with limb warming is no more effective as a therapeutic tool for promoting limb flow than exercise alone.
Effects of microwave irradiation on blood flow in the dog hindlimb
Authors: McMeeken JM , Bell C
Published: December 2014

Physiotherapeutic doses of microwave irradiation to the hindlimb of the anaesthetized dog increased the temperature in the underlying skin and muscle by 5‐6 degrees C and, after a latency of 2‐8 min, heart rate, blood pressure and femoral conductance all increased. The conductance increase was predominantly in the paw. At this time plasma catecholamine levels were elevated above resting values. At the conclusion of irradiation, heart rate and blood pressure rapidly returned to basal levels, but there was a sustained increase in femoral conductance which was mainly in the leg. The results are discussed in terms of the likely mechanisms underlying the effects of microwave irradiation on limb blood flow and compared with those obtained with direct heating of arterial blood and limb tissue in the accompanying paper.
The effect of loop diuretics on fluid reabsorption from the rat proximal convoluted tubule
Authors: Greenwood SL , White SJ , Green R
Published: December 2014

The effects of the ‘loop diuretics’ bumetanide, furosemide and piretanide on fluid reabsorption from the rat proximal convoluted tubule have been tested to assess whether a Na(+)‐Cl‐ cotransport mechanism can support fluid reabsorption from this nephron segment. Proximal convoluted tubules were perfused in vivo at 25 nl min‐1 with chloride Ringer solutions containing [3H]inulin. Fluid reabsorptive rate (Jv) was 2.05 +/‐ 0.07 nl mm‐1 min‐1 (n = 115) from control chloride Ringer. Bumetanide at 10(‐6) and 10(‐5) M reduced Jv by about 40%. Bumetanide at 10(‐7) M, furosemide (10(‐4) and 10(‐5) M) and piretanide (10(‐4) and 10(‐5) M) had no effect on Jv. At 10(‐3) M, furosemide and piretanide reduced Jv by about 45%. The results show that luminal application of loop diuretics lowers fluid reabsorption from the proximal convoluted tubule and the order of potency for inhibiting reabsorption is bumetanide greater than furosemide identical to piretanide. The specificity of the loop diuretics at their effective concentrations needs to be confirmed, however, before attribution of a role for Na(+)‐Cl‐ co‐transport in the support of proximal tubule fluid reabsorption.
Exocrine pancreatic function during cold blockade of the vagus in chronic experiments on calves
Authors: Zabielski R , Podgurniak P , Pierzynowski SG , Barej W
Published: December 2014

Four calves were prepared surgically to investigate the exocrine pancreatic function in chronic experiments. Cooling devices were implanted on both vagi for temporary, reversible, thermal blockade of the conductivity in the nerves. Cooling of the vagi caused significant decreases of volume, total protein content and trypsin activity in pancreatic juice. All of these variables recovered to the control level immediately after the cooling. Results presented indicate an important role of vagally driven information on the exocrine pancreatic secretion in calves.
Endometrial electrogenic ion secretion in the rat is modulated by prostaglandins
Authors: Sebkhi A , Levin RJ
Published: December 2014

In the isolated rat uterus, maximal increases in endometrial electrogenic ion secretion produced by luminal prostaglandins (PGs) E1, E2 and F1, and measured as the short‐circuit current (Isc), displayed bell‐shaped dose‐response curves. PGE1 was the most potent and PGF1 the least. The dose‐response relationships for the decrease in resistance were curvilinear for PGE1 and PGF1 but bell shaped for PGE2. PGF1 was the most potent at inhibiting the increase in Isc induced by serosal adrenaline but not in inhibiting the fall in tissue resistance. The electrogenic ion secretion of rat endometrium is modulated by prostaglandins via a mechanism also influenced by adrenaline.
Effects of exercise intensity on absorption of ingested fluids in man
Authors: Maughan RJ , Leiper JB , McGaw BA
Published: December 2014

Plasma 2H accumulation was measured in six male volunteers after ingestion of drinks containing trace amounts of 2H2O. Subjects fasted overnight and remained seated at rest or exercised on a cycle ergometer at 42, 61 or 80% of their maximum oxygen uptake (VO2, max). The rate of plasma 2H accumulation was faster at rest than during exercise at 61 or 80% of VO2, max (P less than 0.05), and was faster at 42 and 61% than at 80% of VO2, max (P less than 0.05). The time to peak plasma 2H concentration was longer during exercise than at rest. This suggests that strenuous exercise may reduce the availability of fluid ingested during exercise.
Biodynamics of the ankle in spastic children‐‐effect of chronic stretching of the calf musculature
Authors: Walsh EG , Wright GW , Brown K , Bell E
Published: December 2014

The biodynamics of the feet of spastic children have been studied by estimating the resonant frequency using a printed motor to supply rhythmic torques. Changes induced when the muscles have been stretched by casting for four weeks are trivial or absent. The position of the feet, however, after the procedure became more nearly normal.
Amylin‐amide: a new bone‐conserving peptide from the pancreas
Authors: Zaidi M , Datta HK , Bevis PJ , Wimalawansa SJ , MacIntyre I
Published: December 2014

Amylin‐amide is a new member of the family of peptides encoded by the calcitonin multigene complex. In the present study, we have compared directly, the hypocalcaemic potency and duration of action of human amylin‐amide and human calcitonin in an in vivo rat bioassay and an in vitro osteoclast bone resorption assay. Amylin‐amide was found to have a potency approximately 40‐fold lower than human calcitonin, whilst both peptides followed the same time course. This suggests that amylin‐amide is the most potent non‐calcitonin hypocalcaemic peptide so far reported. An important physiological implication follows. It would seem that amylin‐amide can play a central role in the maintenance of the skeleton by virtue of its inhibitory influence on osteoclastic function.
Vasoactive intestinal peptide stimulation of adenylate cyclase activity in isolated rabbit renal arterial microvessels
Authors: Griffiths NM , Simmons NL
Published: December 2014

Vasoactive intestinal peptide (VIP) at a concentration of 1 microM stimulates adenylate cyclase (AC) in isolated rabbit renal preglomerular arterial vessels by 3.9 +/‐ 1.3 fold (n = 6) over basal values. A comparable stimulation of AC was observed with prostaglandin E1. Half‐maximal VIP‐stimulated activity was observed at 7.2 +/‐ 3.5 nM (n = 6), which was increased to 17.4 +/‐ 4.4 nM by 10 microM‐(4Cl‐D‐Phe6,Leu17)VIP, a VIP‐receptor antagonist.
Rectal electrogenic secretion‐‐is it a putative indicator of intestinal secretory status induced by nutritional deprivation in the rat?
Authors: Levin RJ , Parker AJ
Published: December 2014

Intestinal secretion is enhanced by starvation in rats. The rectum from fed and 3‐day‐starved rats generates a basal electrogenic ion transfer (short‐circuit current) in vitro which is mainly electrogenic Na+ absorption (amiloride‐sensitive, 66‐71%) with a small component of electrogenic chloride secretion (furosemide‐sensitive, 14‐22%). Bethanechol, a muscarinic agonist, caused an increase in the short‐circuit current (mainly furosemide‐sensitive chloride secretion) and potential difference in rectums from both fed and starved rats but the respective values for the starved animals were 100% and 64% greater. In starvation, the rat rectum is an indicator of intestinal secretory status. The result warrants investigation of human rectal electrogenic secretion in nutritional deprivation.
The effect on intestinal disaccharidase activity of feeding galactose to growing rats
Authors: Tadesse K
Published: December 2014

The effect of supplementation of the diet with galactose on the age‐related decline of intestinal lactase activity was investigated in 108 growing rats. Starting from 14 days of age, the rats were divided into two groups and fed with chow, and with fluid either as tap water or 5% galactose solution. At 14 days the specific lactase activity was 112.8 +/‐ 3.2 mumol min‐1 (g protein)‐1, which decreased to less than 10% of this value at maturity. Galactose supplementation did not prevent the decline. The increase of maltase, sucrase and trehalase was also unaffected. The result suggests that galactose plays no significant role in the regulation of disaccharidase activities in the rat.
Development of chronic secondary epileptic foci following intrahippocampal injection of tetanus toxin in the rat
Authors: Jefferys JG , Empson RM
Published: December 2014

It is known that injecting a minute dose of tetanus toxin into rat hippocampus leads to a chronic epileptic syndrome. Here we describe the development of secondary, ‘mirror’ epileptic foci in the hippocampus contralateral to a single injection of the toxin (12 mouse LD50). This was detected in slices in vitro prepared 6 to 56 days after injection, both as evoked after‐discharges and as spontaneous synchronous bursts that were mainly restricted to subregions CA3b and c.
Intracellular free magnesium and its regulation, studied in isolated ferret ventricular muscle with ion‐selective microelectrodes
Authors: Buri A , McGuigan JA
Published: December 2014

Intracellular free magnesium ([Mg2+]i) was measured in isolated ferret papillary muscles using ion‐selective microelectrodes filled with the new magnesium sensor ETH 5214. This new sensor, unlike its predecessor ETH 1117, does not react to marked changes in K+, Na+ or pH. Reducing Ca2+ from 20 microM to around 10 nM also did not affect the response so these electrodes are ideally suited to study intracellular Mg2+ and its regulation. The mean value for the [Mg2+]i from thirty‐two experiments (forty‐two impalements) was 0.85 mM, confirming previous estimates from this laboratory. Intracellular Mg2+ is not passively distributed and the possibility that Mg2+ is transported out of the cell by a Na(+)‐Mg2+ exchanger was investigated. An increase in [Mg2+]o caused an increase in [Mg2+]i, as did stepwise reduction in the [Na+]o. However, this increase in [Mg2+]i on Na+ reduction also occurred in Mg2(+)‐free solution suggesting that the increase in [Mg2+]i was due to the increase in intracellular Ca2+ on Na+ reduction. Moreover, increasing [Na+]i by strophanthidin did not change the [Mg2+]i and on increasing [Mg2+]o there was no reduction in the [Na+]i. Blocking ATP production lead to small increases in the [Mg2+]i. These results are not consistent with a Na(+)‐Mg2+ exchanger as being the main outward transport mechanism for Mg2+ in this tissue.
Adaptation of the mechanisms controlling gastric motility following chronic vagotomy in the ferret
Authors: Andrews PL , Bingham S
Published: December 2014

Changes in gastric motility were studied in the urethane‐anaesthetized ferret following acute or chronic (3 weeks) vagotomy. The stomach was divided into the corpus and antrum and the effects of vagotomy on tone, frequency and contraction amplitude were investigated separately in the two gastric regions. In the corpus tone is kept at low levels by vagal activation of nonadrenergic, non‐cholinergic (NANC) inhibitory neurones and also tonic sympathetic inhibition of intramural cholinergic activity. Frequency of contractions is also low due to tonic inhibition of cholinergic neurones by the vagus but not the sympathetic nervous system. There appears to be little vagal involvement in contraction amplitude but there is sympathetic inhibition of this parameter again via inhibition of cholinergic neurones. In the antrum there is no vagally driven inhibition of tone but a sympathetic inhibition of cholinergic neurones tends to reduce tone in the intact animal. Frequency of contractions does not appear to be extrinsically modulated. The vagus is tonically excitatory with regard to contraction amplitude in the antrum whereas the sympathetic nervous system is inhibitory, again via inhibition of cholinergic neurones. After chronic vagotomy some adaptation appears to take place within the surviving control systems in both the corpus and the antrum. Changes in cholinergic function have been suggested previously and are corroborated in this study. In addition novel alterations in intrinsic NANC systems and the remaining sympathetic innervation have been demonstrated in both regions of the stomach which tended to reduce the effects of vagotomy and return values for the parameters measured toward those observed in intact animals. The contribution of the cholinergic, adrenergic and NANC neurotransmitter systems to the post‐vagotomy motility patterns differed in the corpus and antrum.
Forskolin but not isoprenaline increases sodium current from frog cardiac myocytes
Authors: Bonvallet R , Lemtiri-Chlieh F , Rougier O
Published: December 2014

The effect of forskolin on sodium current (INa) was studied in enzymatically dispersed frog atrial myocytes. The single pipette patch‐clamp technique was used, with a low external sodium concentration. Forskolin (0.5 microM) increased INa at all potentials between ‐50 and +30 mV. The forskolin‐induced increase of INa was mimicked by 1,9‐dideoxyforskolin (0.5 microM) but not by isoprenaline (2 microM). These results suggest that forskolin can modulate INa through a mechanism that does not involve the production of cyclic AMP.
Sympathetic stimulation causes increased output of lymphocytes from the popliteal node in anaesthetized sheep
Authors: McHale NG , Thornbury KD
Published: December 2014

Stimulation of the lumbar sympathetic chain at a frequency of 4 Hz caused a threefold increase in the lymphocyte output in efferent lymph from the popliteal node in anaesthetized sheep. The increase was accounted for by a rise in both lymph flow and lymphocyte count. Intra‐arterial infusion of phentolamine (10 micrograms kg‐1 min‐1) abolished the nerve‐mediated increases in flow and cell count.
Mechanism of electrically silent Na and Cl transport across the rumen epithelium of sheep
Authors: Martens H , Gabel G , Strozyk B
Published: December 2014

This study was designed to study the mechanism of electroneutral Na and Cl transport across the isolated rumen epithelium of sheep. Net sodium transport (5.75 +/‐ 0.35 microequiv cm‐2 h‐1) was significantly higher than the short‐circuit current (0.95 +/‐ 0.08 microequiv cm‐2 h‐1). Both, net sodium and net chloride transport were markedly reduced by replacement of chloride, bicarbonate and sodium, respectively, but were not changed by the absence of mucosal potassium. Net sodium and net chloride absorption was significantly decreased by 1.0 mM‐amiloride. Mucosal addition of bumetanide, furosemide, hydrochlorothiazide or low concentrations of amiloride (less than 0.1 mM) did not change sodium fluxes. These results provide compelling evidence consistent with the presence of Na‐H exchange as the predominant electroneutral mechanism for transepithelial sodium movement. The ion replacement studies and data from literature suggest that the Na‐H exchange is working in parallel with a Cl‐HCO3 exchange although luminal addition of DIDS (4,4'diisothiocyanatostilbene‐2,2'‐disulphonate, 1 mM) did not significantly influence Cl transport.
Calcitonin gene‐related peptide inhibits exocrine secretion from the rat pancreas by a neurally mediated mechanism
Authors: Bunnett NW , Mulvihill SJ , Debas HT
Published: December 2014

The mechanism by which calcitonin gene‐related peptide (CGRP) inhibits exocrine secretion from the rat pancreas was examined in the isolated, vascularly perfused pancreas and in vitro using freshly isolated pancreatic acini. CGRP (10(‐10)‐10(‐7) M) inhibited the volume and protein output from the perfused pancreas, stimulated by a mixture of the cholecystokinin octapeptide CCK8 (10(‐10) M) and secretin (10(‐8) M). The inhibition by CGRP was dose related and maximal at 10(‐8) M (P less than 0.05). CGRP (10(‐8) M) failed to inhibit amylase secretion from isolated pancreatic acini, stimulated by graded concentrations of CCK8 (10(‐13)‐10(‐8) M). This implies an indirect mechanism of inhibition. The mechanism of inhibition was investigated in the isolated, vascularly perfused pancreas using tetrodotoxin, atropine and hexamethonium (all 10(‐7) M). Tetrodotoxin and atropine but not hexamethonium prevented the inhibition of volume and protein secretion by CGRP (10(‐8) M) (P less than 0.05). Tetrodotoxin, atropine and hexamethonium were without effect on exocrine secretion stimulated by CCK8 and secretin (controls). These results indicate that CGRP inhibits pancreatic exocrine secretion by an indirect, neurally mediated mechanism involving cholinergic‐muscarinic transmission.
Turnover of hyaluronan in synovial joints: elimination of labelled hyaluronan from the knee joint of the rabbit
Authors: Brown TJ , Laurent UB , Fraser
Published: December 2014

After the injection of [3H]acetyl‐labelled hyaluronan into normal rabbit knee joints, about 90% of its isotope content was ultimately accounted for as 3H2O. The rate of elimination of hyaluronan from synovial fluid was therefore estimated from changes in the level of 3H2O in plasma. The half‐life of plasma 3H2O was 6.2 days (S.D. 0.7). As estimated from its metabolism to 3H2O, the mean intrasynovial half‐life of [3H]hyaluronan of high molecular weight (modal relative molecular mass (Mr) greater than 6.0 x 10(6) was 13.2 h (range 11‐15.5 h; n = 4); an otherwise identical preparation of low molecular weight (modal Mr 0.09 x 10(6] exhibited a mean half‐life of 10.2 h (range 7.8‐13.5 h; n = 4). The difference between the two groups was significant (P = 0.029). Both estimates were nevertheless close to those determined by others in the same species for injected proteoglycans (Mr 2.5 x 10(6), t1/2 = 12 h) and for endogenous hyaluronan calculated from changes in concentration during intravenous infusion of fluid under anaesthesia (t1/2 = 16 h). The similarity suggests that hyaluronan and proteoglycan are removed from synovial fluid by a common pathway with limited dependence on their molecular dimensions and concentrations.
Calcitonin gene‐related peptide promotes transient radiocalcium uptake into chick bone in vivo
Authors: Ancill AK , Bascal ZA , Whitaker G , Dacke CG
Published: December 2014

We have examined the in vivo effects in chicks of intravenously injected chicken (c‐) and rat (r‐) calcitonin gene‐related peptides (CGRP) on uptake into bone of a simultaneously administered 45Ca label. Both peptides caused transient (10 min) increases in 45Ca uptake into a variety of bone types. In dose‐response experiments at 10 min, CGRP doses of 0.26‐1.04 nmol/100 g body wt were found to give maximal responses. These were well developed in chicks fasted for 22 h but absent in those which were continuously fed. This contrasts with the hypercalcaemic effect of CGRP which is apparent in fed rather than fasted chicks.
Intracellular sodium activity in papillary muscle from diabetic rat hearts
Authors: Lagadic-Gossmann D , Feuvray D
Published: December 2014

In quiescent papillary muscles isolated from hearts of rats with streptozotocin‐induced diabetes resting intracellular sodium activity (aiNa) was about 56% greater than in muscles from controls. An intracellular acid load induced by the NH4+ method caused a rise in aiNa whose maximum amplitude was similar in both groups of muscles. However, the half‐time to maximum amplitude was increased by about 56% in diabetic muscles. These results are consistent with a diabetes‐induced decrease in the activity of the sarcolemmal Na(+)‐H+ exchange.
Plasma clearance of emulsified triolein in conscious rats: effects of phosphatidylcholine species, cholesterol content and emulsion surface physical state
Authors: Clark SB , Derksen A , Small DM
Published: December 2014

In vivo clearance of an emulsified triglyceride from rat plasma is strongly influenced by the phosphatidylcholine molecular species and the cholesterol content of the emulsion. Chylomicron‐sized, glycerol‐tri[9,10‐3H]oleate (triolein)‐sonicated emulsions containing 2‐3 or 9‐14 mol% unesterified cholesterol and specific phosphatidylcholines (egg, dimyristoyl, dipalmitoyl, distearoyl) were prepared above the phospholipid gel‐‐‐‐liquid crystalline transition temperatures and injected intravenously into awake, non‐fasting rats in bolus doses of 1‐3 mg lipid. The emulsified triolein was cleared from plasma both by lipolysis during circulation and by uptake of emulsion particles or their remnants into tissues. Increasing the cholesterol content greatly accelerated particle clearance from plasma when emulsions were made with mixed‐chain (egg) phosphatidylcholine, but prolonged their circulation time when the emulsions contained saturated phosphatidylcholines. The relative amounts cleared by reticuloendothelial versus liver parenchymal cells were influenced both by the cholesterol content and the phosphatidylcholine species of the emulsions. Significant triolein lipolysis in plasma occurred only with egg or dimyristoyl phosphatidylcholine emulsions containing 2‐3% cholesterol and this lipolysis was blocked by increasing the cholesterol content. No lipolysis occurred when emulsions contained dipalmitoyl or distearoyl phosphatidylcholine, irrespective of cholesterol content.