bluuebunny/crossref_metadata_2025 huggingface dataset:
THE CONTROL OF THE STRENGTH OF THE CAFFEINE CONTRACTURE IN FROG ATRIAL TRABECULAE: AN ACTIVITY OF THE SODIUM‐CALCIUM EXCHANGE
Authors: Chapman R. A. , Tunstall J.
Published: December 2014

In frog atrial trabeculae low‐Na contractures and caffeine contractures evoked in Na‐poor solutions are increased by raising the external Ca concentration ([Ca]o), lowering the external Na concentration ([Na]o) or by tissue depolarization in K‐rich fluids. The source of activator Ca for the low‐Na and the caffeine contractures is probably different because Na‐withdrawal contractures are inhibited by Mn2+ but unaffected by local anaesthetics, while the caffeine contractures are potentiated by Mn2+ and inhibited by local anaesthetics. The spontaneous relaxation of the low‐Na contracture has a rate constant of 0·055 ± 0·009 s-1, at room temperature for any [Na]o, [Ca]o or external K concentration ([K]o). The spontaneous relaxation of the caffeine contracture in Na‐free fluid has a similar rate constant. However, the rate of spontaneous relaxation is increased if Na+ is present in the bathing medium and analysis of the results of experiments done in solutions with different [Na]o, [Ca]o or [K]o, suggests that two processes are involved in the reduction of the internal Ca concentration ([Ca]i) and the fall of tension. One, also responsible for the spontaneous relaxation of the low Na contracture, is dependent on metabolic energy and may be intracellular in origin. The other depends upon the activity of the sarcolemmal Na/Ca exchange, persists in the presence of metabolic inhibitors and is also activated during a low Na contracture when [Na]o is raised, or [Ca]o is lowered. The contractile response, of frog cardiac muscle to caffeine, would seem to be largely due to a release of Ca2+ from an intracellular store, but the strength of the resulting contracture depends upon a competition between the contractile proteins and the Na/Ca exchange for the released Ca2+.
THE DENSITY AND DISTRIBUTION OF CAPILLARIES AROUND A SYNOVIAL CAVITY
Authors: Knight A. D. , Levick J. R.
Published: December 2014

The interpretation of trans‐synovial fluxes requires a knowledge of the number of capillaries present around the joint cavity, and their depths below the surface of the joint lining. Measurements of capillary numbers, depths and dimensions were therefore carried out by light microscopy on synovial tissue sections from five rabbit knees. In addition the surface area of synovial tissue lining the joint was estimated, and the thickness of the synovium measured. Synovial capillary density was found to be uneven, with respect to both anatomical location in the joint cavity and depth below the synovial surface. The large area of synovium over areolar or adipose tissue was highly vascular (67000–83000 capillaries.cm−2 section; mean intercapillary distance 35–55, µm; 228–329 cm2 endothelium.cm−3 synovium). The small area of synovium over tendons was of very low vascularity (2000 capillaries.cm−2 section). From these data and a previous estimate of net filtration capacity, mean synovial endothelial conductivity was estimated as ∼ 16 x 10−7 cm.s−1.mmHg−1. The depth distribution of the capillaries was extremely skewed, with a sharp peak at 6–11 µm depth. The rapid decay in capillary density at depths 〉 6–11 µm was partly due to an uneven density of capillaries within the synovium itself; and partly due to a lower density in subsynovial tissues.

It was concluded that most synovium has a rich capillary bed which is very superficially located and that the depth of periarticular tissue which is effective in exchange processes with the joint cavity is less than 25 µm.
AN INVESTIGATION INTO SOME CEREBRAL MECHANISMS INVOLVED IN SCHEDULE‐INDUCED DRINKING IN THE PIG
Authors: Stephens D. B. , Ingram D. L. , Sharman D. F.
Published: December 2014

When pigs were fed small amounts at regular short intervals (5–10 min), drinking followed each ingestion. This resulted in a greatly increased total water intake (schedule‐induced polydipsia: s.i.p.). Injection of angiotensin II into the lateral cerebral ventricle of water‐replete pigs on normal feeding also produced a significant increase in water intake. Prior administration of the angiotensin II antagonist, saralasin, attenuated the dipsogenic effect of angiotensin II, but did not modify s.i.p. The tranquillizing drug, azaperone, had no effect on normal water intake and did not modify the response to angiotensin II. However, azaperone reduced the water intake of animals on scheduled feeding. From this, it was concluded that the increased drinking due to scheduled feeding did not involve the renin‐angiotensin system but it is tentatively suggested that it may involve central dopaminergic neuronal systems.
MANOMETRIC AND ELECTROMYOGRAPHIC OBSERVATIONS OF THE OESOPHAGUS OF SHEEP IN ERUCTATION, REGURGITATION AND SWALLOWING
Authors: Carr D. H. , Scott P. C. , Titchen D. A.
Published: December 2014

Manometric and electromyographic recordings during eructation, swallowing and the regurgitation of rumination in sheep revealed variable oesophageal activity during eructation in contrast to the uniform pattern of oesophageal activity in swallowing and regurgitation. In eructation the passive increase in pressure of about 7–15 mmHg ‐ the filling phase ‐ associated with entry of gas into the oesophagus was commonly (in 96·6% of thirty eructations) terminated by contractions in the caudal thoracic oesophagus (c.t.o.). Eructation contractions were present in 73·3% of thirty eructations in a site 130 mm cranial to the c.t.o. and in 36·6% of thirty eructations in a site 260 mm cranial to the c.t.o. These contractions moved cranially at about 420 mm.s−1. In contrast during regurgitation the contractions of the oesophagus which moved cranially at about the same rate (410 mm.s−1) were characteristically more intense (47–64 mmHg) than eructation contractions (10–36 mmHg). Also in contrast to those in eructation, regurgitation contractions were invariably of each site of the oesophagus from which recordings were made. Secondary contractions of the caudal cervical and thoracic oesophagus which sometimes followed eructation were interpreted as serving as clearing contractions returning residual gas in the oesophagus to the stomach. These swept over the oesophagus at about 200 mm.s−1 and occurred without associated swallows. The variability of reactions of the oesophagus in eructation and differences in reactions of its different regions are discussed as arising from different degrees of sensitivity to, and stimulation by, gaseous distension of the oesophagus and stomach.
MONOSACCHARIDE TRANSPORT BY THE SMALL INTESTINE OF LEAN AND GENETICALLY OBESE (ob/ob) MICE
Authors: Morton A. P. , Hanson P. J.
Published: December 2014

The effect of the obese (ob/ob) genotype on monosaccharide transport in mouse small intestine has been examined, using several different methodologies, at various stages in the development of the syndrome. Evidence for an elevation of the total capacity of the small intestine for monosaccharide transport was found at 10, 20 and 40 weeks of age in obese mice by comparison with lean controls, the difference being most prominent at 20 weeks of age after the hyperphagic phase of the syndrome had ceased. No substantial alteration in transport, expressed per gram dry weight of intestine, either from luminal perfusion studies or from measurements of the kinetics of influx across the brush border was found in adult obese mice compared with lean controls. It is concluded that, in obese mice, the increased capacity of the intestine for monosaccharide transport compared with lean mice was due to increases in the total intestinal dry weight, and in the intestinal dry weight per centimetre, and not to changes in carrier activity per unit dry weight of intestine.
GESTATION‐DEPENDENT ASPECTS OF THE RESPONSE OF THE OVINE FETUS TO THE OSMOTIC STRESS INDUCED BY MATERNAL WATER DEPRIVATION
Authors: Bell R. J. , Congiu M. , Hardy K. J. , Wintour E. M.
Published: December 2014

Water deprivation was produced in pregnant sheep by withholding water for 24 h and then giving them 500 ml/d for the subsequent 3 d. All ewes bore chronically cannulated fetuses. Eleven experiments were performed in group I animals (gestation periods of 107–119 d at maximal stress) and eight experiments in group II (126–144 d of gestation). Measurements were made of maternal and fetal plasma osmolalities, fetal urine flow rate and osmolality, amniotic fluid osmolality and fetal plasma antidiuretic hormone (ADH) concentration. The experimental protocol produced a larger increment in maternal and fetal plasma osmolalities in group I than in group II (P 〈 0·025). For group I fetuses the relationship between plasma ADH concentration, [ADH] and plasma osmolality was log [ADH]= ‐4·50+0·0174 (osmol) which was significantly different from that for group II fetuses, log [ADHI = −10·46+0·0373 (osmol) (P 〈 0·02). Thus plasma [ADH] was significantly greater, at a given plasma osmolality, in older (group II) than younger (group I) fetuses. For a given value of fetal plasma [ADH] there was a greater reduction in fetal urine free water clearance in older than younger fetuses. Water deprivation of the ewe did disturb the composition of amniotic fluid and the trend in amniotic fluid osmolality followed the trend in fetal urinary osmolality.
COMPOSITION OF SECRETION FROM THE SUBMANDIBULAR SALIVARY GLAND IN THE RAT
Authors: Rigby M. , Templeton D.
Published: December 2014

The effects on the composition of rat submandibular saliva, of superimposing low frequency sympathetic nerve stimulation on parasympathetic nerve stimulation have been investigated. During continuous parasympathetic stimulation, additional sympathetic stimulation resulted in a frequency‐dependent rise of both protein and K+ concentrations. The threshold of frequency of stimulation for the protein response was 0·1 Hz and for the K+ response 0·Hz. The protein secretion is presumed to be acinar in origin whilst the K+ is believed to be secreted mainly by ducts other than the main excretory duct.
RENAL CONTROL OF PLASMA UREA LEVEL IN SHEEP: THE DIURETIC EFFECT OF UREA, POTASSIUM AND SODIUM CHLORIDE
Authors: Godwin I. R. , Williams V. J.
Published: December 2014

Two merino ewes were fed 800 and then 1000 g of lucerne chaff per day and renal responses and extracellular fluid volume (E.C.F.) were determined. Urine urea nitrogen, glomerular filtration rate (G.F.R.), urine volume, effective renal plasma flow (E.R.P.F.) and E.C.F. increased in both animals with the greater nitrogen intake. In a second experiment, five merino wethers and four merino ewes were infused intraruminally with increasing quantities of urea, whilst being fed a mainly roughage ration, and the above parameters were determined. No significant changes in G.F.R., E.R.P.F. or E.C.F. were noted. Urinary excretion maintained a linear response to nitrogen input until 20·6 g of urea nitrogen per day were infused. At this level of infusion, an increased fractional reabsorption of urea resulted in a large increase in plasma urea concentration, but when 500 mmol of NaCl or KCl were added to the infusate, urine urea nitrogen excretion increased from 10·4 to 11·4 and 11·9 g/d respectively and plasma urea concentration decreased from 68·0 to 35·2 and 37·3 mg nitrogen/100 ml. Urea clearance virtually trebled with both electrolyte infusions and E.C.F. and G.F.R. increased by aproximately 10 and 25% respectively. It is concluded that urea alone has limited diuretic ability and that the increased electrolyte content of higher protein dry roughage diets aids urine urea excretion by increasing G.F.R., and the urine flow rate by an osmotic diuretic effect.
THE ATRIAL RECEPTORS RESPONSIBLE FOR THE DECREASE IN PLASMA VASOPRESSIN CAUSED BY DISTENSION OF THE LEFT ATRIUM IN THE DOG
Authors: Bennett K. L. , Linden R. J. , Mary D. A. S. G.
Published: December 2014

In dogs anaesthetized with chloralose, the effects of cooling the cervical vagi on the reflex decrease in plasma concentration of vasopressin, caused by distension of a large balloon in the lumen of the left atrium, were examined. Distension of the balloon in ten dogs with the vagi at 37°C resulted in a decrease in plasma concentration of vasopressin and, as before, an increase in urine flow. The responses were not significantly affected by cooling to 16·18 °C but were abolished at 9 °C. At 16–18 °C the increase in activity in myelinated vagal afferent fibres is largely unchanged and at 9 °C is abolished (Kappagoda, Linden & Sivananthan, 1979; Sivananthan, Kappagoda & Linden, 1981). It is concluded that the decrease in plasma concentration of vasopressin during distension of the left atrium is mediated by the Paintal‐type atrial receptors with myelinated vagal afferent fibres.
EPITHELIAL CELL VOLUME REGULATION IN HYPOTONIC FLUIDS: STUDIES USING A MODEL TISSUE CULTURE RENAL EPITHELIAL CELL SYSTEM
Authors: Simmons N. L.
Published: December 2014

The cultured renal epithelial cell line MDCK has been used in a study of cell volume regulation, emphasis being placed upon cell swelling in hypotonic media. MDCK cell volume was measured directly by electronic cell sizing using a Coulter counter in MDCK cell suspensions; this method gave comparable values for cell water when compared with those obtained using an intracellular space marker [14C]3‐O‐methyl glucose. MDCK cells behaved as perfect osmometers when suspended in hypertonic fluid (cell shrinkage). Cellular swelling in hypotonic media, in certain conditions, was found to be less than expected for an ideal osmometer. Non‐ideal swelling was found to be the result of a substantial loss of intracellular K+ (Cl‐) due to a specific increase in membrane K+ permeability. The membane channel mediating the increased net K+ loss was separate, by pharmacological identity, from the Na+‐K+ pump, the diuretic‐sensitive co‐transport system and a Gardos‐type channel inhibited by quinine. A role for increased Ca2+ influx mediating the increased K+ permeability is suggested by results from hypotonic exposure in nominally Ca2+‐free solutions.
EFFECT OF THE SERUM CONCENTRATION OF THE GROWTH MEDIUM ON THE SODIUM PUMP SITE DENSITY OF CULTURED HeLa CELLS
Authors: Aiton J. F. , Lamb J. F.
Published: December 2014

The density of sodium pump sites in the plasma membrane of cultured HeLa cells has been measured as a function of the serum concentration of the cell growth medium. Growth in media containing increased concentrations of serum (from 1 to 20% v/v) leads to an increase in sodium pump site numbers (as measured by the specific binding of [3H]ouabain) and pump activity ( as measured by the ouabain‐sensitive 86Rb influx). Time‐course studies show that (1) new sodium pump sites first appear some 3–6 h after transfer to medium containing an elevated serum concentration and (2) the serum‐mediated increase in new sodium pump sites is completely abolished by the protein synthesis inhibitors, cycloheximide and actinomycin D. These results suggest that de novo protein synthesis is required for the development of the serum response. Preliminary characterization of the serum factor responsible for initiating the synthesis of new sodium pump sites indicates that the activity is associated with a high molecular weight serum fraction (> 50000). The different types of interaction seen between the serum effect and other experimental manoeuvres which initiate the synthesis of new pump sites (growth in low‐K+ medium, growth in Li+ medium and pre‐treatment with exogenous ATP) suggest that there may be more than one pathway for the control of sodium pump site synthesis in cultured HeLa cells.
CONTROL OF CULTURED EPITHELIAL (MDCK) CELL TRANSPORT FUNCTION: IDENTIFICATION OF A β‐ADRENOCEPTOR COUPLED TO ADENYLATE CYCLASE
Authors: Rugg E. L. , Simmons N. L.
Published: December 2014

A catecholamine‐sensitive adenylate cyclase activity was observed in cell homogenates of cultured renal epithelial (MDCK) cells. 10 µM isoprenaline gave a 2·85‐fold increase in adenylate cyclase activity above basal levels. A series of adrenoceptor agonists gave a relative ptoency series of isoprenaline 〉 adrenaline 〉 noradrenaline (K⅓ values of 1·9 x 10−7, 1·6 x 10−6 and 1·9 x l0−5 M respectively), consistent with activation of a β‐adrenoceptor. Intracellular accumulation of cyclic AMP was also stimulated by 10 βM isoprenaline, peak values being observed after 2 min, followed by a decline to lower maintained levels. The phosphodiesterase inhibitor isobutylmethylzanthine (1 mM) augmented isoprenaline‐stimulated cyclic AMP accumulation. In epithelial preparations of MDCK cells grown upon Millipore filters and mounted in Ussing chambers isoprenaline was only effective in elevating intracellular cyclic AMP contents when applied to the basal cell surfaces. Direct measurement of β‐adrenoceptor density and subtype was determined by (±)−3−[125I]iodocyanopindolol binding to MDCK cell homogenates. Binding consisted ofa saturable component (Vmax = 14·9 fmol/mg cell protein) of high molar affinity (Kd = 10·8 pM) and a non‐saturable component which showed a linear dependence on iodocyanopindolol concentration. In addition to the high‐affinity binding site, dissociation kinetics revealed a low‐affinity component (Kd = 450 pM) comprising 24% of saturable binding. Competition of (±)−3−[125I]iodocyanopindolol binding with β‐adrenoceptor agonists and antagonists was entirely consistent with the existence of a β2‐adrenoceptor. Examination of various MDCK cultures and clones revealed the existence of MDCK cultures whose adenylate cyclase activity was unresponsive to catecholamine stimulation; this correlated with a reduced or undetectable level of (±)−3−[125I]iodocyanopindolol binding. The control of transepithelial chloride transport in MDCK epithelia by catecholamines is discussed.
FINE STRUCTURE OF PRIMARY AFFERENT AXON TERMINALS PROJECTING FROM RAPIDLY ADAPTING MECHANORECEPTORS OF THE TOE AND FOOT PADS OF THE CAT
Authors: Maxwell D. J. , Bannatyne B. A. , Brown A. G. , Fyffe R. E. W.
Published: December 2014

Two Pacinian corpuscle afferents and two rapidly adapting afferents from Krause corpuscles were intra‐axonally labelled with horseradish peroxidase in the lumbosacral enlargement of the cat's spinal cord. Tissue was prepared for combined light and electron microscopical analysis. Boutons from both classes of afferent had similar ultrastructural appearances. They both formed from one to three synaptic junctions with dendritic shafts and spines and received axo‐axonic synapses. In addition, both categories of bouton were seen to be presynaptic to structures interpreted as vesicle‐containing dendrites. It is concluded that both types of afferent fibre are subject to presynaptic control and that they synapse with dorsal horn neurones which are possibly interneurones involved in primary afferent depolarization and post‐synaptic dorsal column neurones.
UREA SECRETION INTO THE COLON OF SHEEP AND GOAT
Authors: Engelhardt W. v. , Hinderer S. , Rechkemmer G. , Becker G.
Published: December 2014

Total urea entry rate into the body pool and urea hydrolysis rate (transfer of endogenous urea into the total gastrointestinal (g.i.) tract) were obtained after single intravenous injections of [14C]urea and from renal urea excretion in sheep and goat. Secretion of endogenous urea into the colon was estimated from the appearance of urea N in the temporarily isolated and perfused colon. Rate of urea secretion ino the colon was rather small (0·10‐0·31 mmol. h−1). It was only 0·3‐1·1% of urea entry rate, or 0·4‐7% of urea hydrolysis rate. Urea secretion into the colon increased linearly with increase of plasma urea concentration. Dietary conditions and short‐chain fatty acid concentrations in colonic contents had no significant effect on the permeability of the colonic epithelium for urea.
COMPOSITION AND VOLUME OF FLUID SWALLOWED BY FETAL SHEEP
Authors: Harding R. , Bocking A. D. , Sigger J. N. , Wickham P. J. D.
Published: December 2014

Oesophageal cannulations were performed in seven fetal sheep between 109 and 128 d of gestation. Fluid swallowed by the fetuses was collected externally and periodically returned to the fetal stomach by a peristaltic pump. The volume of fluid swallowed daily was calculated from the movement of water in a parallel pump circuit. Samples of oesophageal fluid were removed from the collection bag at the same time as tracheal and amniotic fluid samples. Oesophageal fluid was very viscous and was usually intermediate in colour between tracheal and amniotic fluids. After reduction of viscosity by dithiothreitol, the compositions of the three fluids were analysed. Mean concentrations of Na+, Cl− and protein, and mean osmolarity of oesophageal fluid, were intermediate between values obtained in tracheal and amniotic fluids. [K+] was often greater in oesophageal fluid than would be expected by the relative contribution of tracheal and amniotic fluids as indicated by [Na+] and [Cl−] in the three fluids. It is suggested that the high viscosity of oesophageal fluid and its relatively high [K+] may result from fetal salivary secretions. Ionic concentrations in individual sets of samples show that the proportions of tracheal and amniotic fluids swallowed by the fetus are variable from day to day. The mean daily volumes of fluid swallowed by the seven fetuses ranged from 98 to 577 ml, and are in agreement with previously published data.
FINE STRUCTURE OF PRIMARY AFFERENT AXON TERMINALS OF SLOWLY ADAPTING CUTANEOUS RECEPTORS IN THE CAT
Authors: Bannatyne B. A. , Maxwell D. J. , Fyffe R. E. W. , Brown A. G.
Published: December 2014

Three slowly adapting type I and two slowly adapting type II afferent fibres from the lumbosacral cord of the cat were intra‐axonally labelled with horseradish peroxidase and processed for light and electron microscopy. Terminals from both types of afferent exhibited similar ultrastructural features in that both formed contacts with one to five post‐synaptic profiles, including dendritic shafts and spine heads, some of which contained vesicles. The stained axons were themselves post‐synaptic in axo‐axonic synapses. Maximum diameters of slowly adapting boutons and the dendritic shafts on which they terminated were measured. The present results indicate that there is considerable overlap in the morphological characteristics studied for all large myelinated cutaneous afferent boutons. It is not possible therefore to distinguish between these on ultrastructural grounds alone.
BLOOD FLOW AND ABSORPTION FROM THE RUMEN
Authors: Dobson A.
Published: December 2014

Blood flow to the ruminoreticular epithelium varies cyclically with feeding. Within this range the absorption of rapidly penetrating solutes will be dependent on the blood flow. For HTO absorption, the most satisfactory model suggests the involvement of a countercurrent exchanger behind the epithelium. The consequences of this arrangement are presented, and are qualitatively consistent with known effects of solute absorption on net water movement. The control mechanisms for net water absorption are not fully identified. The observed blood flows in the splanchnic region raise interesting questions of functional changes in the omasum and fat.
ELECTROPHYSIOLOGICAL STUDY OF VAGAL AFFERENT AND EFFERENT UNITS IN CONSCIOUS SHEEP
Authors: Rousseau J. P.
Published: December 2014

Crossed‐nerve anastomoses were performed to record activity of vagal efferents and afferents during regurgitation and eructation in conscious sheep. Following anastomoses of the central end of a vagus nerve to the peripheral end of a phrenic nerve, discharges in units of the diaphragm reinnervated by vagal efferent neurones were associated with contractions of the caudal oesophagus and of the rumen. During regurgitation in the course of rumination, discharges in oesophageal efferents consisted of a characteristic pattern of two bursts in a constant association with the additional phase of the reticular contraction and the more forceful inspiratory effort. Discharges in two types of units bore a temporal relation with the motor gastric cyles. Early units are interpreted as innervating pillars of the rumen and late units its dorsal wall. Regular patterns of discharge were recorded during successive A sequences of rumen contractions. In contrast, there was a variability of pattern of activity of efferents during B sequences: a constant time relationship was not observed between discharges of both types of units. During B sequences accompanied by eructation, the most characteristic pattern in gastric and oesophageal units had the following features: the impulses in the early units increased in frequency, outlasted the discharge in the late units by 1 s and ended when a brief discharge was recorded in an oesophageal unit at the time of eructation. It is suggested from the patterns of discharge observed in both gastric and oesophageal efferents that the orderly sequence which achieves regurgitation and eructation results from the central co‐ordination of efferent output.

Following anastomoses of the central root of the nodose ganglion to the peripheral end of the accessory nerve, discharges in units of the mastoido‐humeral muscle reinnervated by vagal afferent axons were associated with contractions of the oesophagus and movements of the larynx during swallowing and regurgitation. Discharges in oesophageal afferents coming from the caudal oesophagus were coincident with discharges observed in the vagal efferent fibres innervating this part of the oesophagus. Afferents from the pharynx and the larynx were active at the same time as the nasopharynx and the glottis were demonstrated to be closed. Thus the major characteristic of the afferents the traffic of which has been recorded in cross‐sutured sheep in the course of rumination is that their discharges are occurring at the same time as motor events are developing. It has been concluded that in the complex motor events during regurgitation there is a significant afferent input which contributes to the central nervous regulation of their course at any time.
POST‐NATAL CHANGE AND REGIONAL VARIATION OF THE RESPONSE OF THE VAS DEFERENS OF NEW‐BORN RATS TO AUTONOMIC DRUGS
Authors: Chiu‐Wei Yen‐Fun , Kasuya Yutaka , Watanabe Minoru
Published: December 2014

The vas deferens isolated from rats of different ages (11–60 d old) was bisected to provide an epididymal and a prostatic half. The contractile responses of both halves to potassium ions, adrenergic agents (noradrenaline, isoprenaline and tyramine), cholinergic agents (acetylcholine, methacholine and tetramethylammonium), histamine and serotonin were measured. The response to 150 mM potassium, which was regarded as an approximate measure of full contractility of the preparation, increased in parallel with the organ weight. Most of the agonists could induce the full contractility in both halves until 3–4 weeks of age, but thereafter they could produce only smaller responses than the full contractility in either or both halves, resulting in a differentiation of the halves in the response to agonists. A regional variation of the post‐natal development of α‐adrenergic, muscarinic and nicotinic responses is discussed.
MECHANICAL FACTORS REGULATING GASTRIC EMPTYING OF VISCOUS NUTRIENT MEALS IN DOGS
Authors: Keinke Oliver , Schemann Michael , Ehrlein Hans‐Jörg
Published: December 2014

The aim of this study was to determine the mechanisms controlling gastric emptying of viscous meals. In four conscious dogs the antral, pyloric and duodenal activities were recorded with strain‐gauge transducers and induction coils during gastric evacuation of an inert cellulose meal and of four nutrient meals containing mannitol, casein, glucose or oleic acid. Gastric emptying and the internal pyloric and duodenal diameters were measured from radiographs. The nutrients delayed gastric emptying and diminished to a various extent the antral and duodenal motility as well as the pyloric opening. The motility gradient between antral and duodenal activity showed no relationship to the emptying delay. The duodenal lumen was reduced and the propulsive contractions of the duodenum decreased while the segmental activity increased. The findings suggest that gastric emptying is controlled by (1) the depth of the antral waves, (2) the pyloric opening, (3) the receptive relaxation of the duodenum and (4) the type of the duodenal contractions. By contrast the sequence of the terminal antral contraction and the pyloric closure, as well as the co‐ordination between pyloric and duodenal contractions, played no important role in regulating gastric emptying.
EVIDENCE THAT ENTERIC CHOLINERGIC NEURONES PROJECT ORALLY IN THE INTESTINAL NERVE OF THE CHICKEN
Authors: Hodgkiss J. P.
Published: December 2014

The intestinal nerve of the chicken, which runs almost the whole length of the small and large intestine, was studied in vitro, using suction electrodes for stimulation and recording. Lengths of nerve with side branches intact in the region of the ileum and rectum were used. The spike discharges that were evoked by supramaximal stimulation of a side branch were recorded at oral and aboral ends of the main nerve trunk. Exposure of the preparation to hexamethonium (550 µM) reversibly abolished or greatly reduced the amplitude of the largest component of the evoked oral response in eighteen experiments, but was without effect on the evoked aboral response in ten experiments. No evidence of a nicotinic cholinergic component to the evoked aboral response was obtained at distances up to 12·5 mm along the nerve. There was also no evidence for a projection of post‐ganglionic neurones along the stimulated side branch. The mean conduction velocity of the preganglionic nerve fibres was 0·25 ± 0·02 m.s‐1 while that for the post‐ganglionic nerve fibres was 0·66 ± 0·11 m.s‐1. These results suggest that both groups of nerve fibres are non‐myelinated. 8‐16 d after side branch transection, stimulation of the side branch evoked no oral response in five experiments and a hexamethonium‐insensitive response in seven others. In a further four experiments a hexamethonium‐sensitive component was seen, but it constituted only a small part of the evoked oral response. It is postulated that transection results in the degeneration of cholinergic nerves in the intestinal nerve. The results suggest that enteric cholinergic nerves form part of a pathway which projects orally along the ileal and rectal segments of the intestinal nerve.
ELECTROPHYSIOLOGICAL EVIDENCE FOR THE INHIBITION OF POTASSIUM PERMEABILITY IN PANCREATIC β‐CELLS BY GLIBENCLAMIDE
Authors: Ferrer Rosa , Atwater Illani , Croghan P. C. , Rojas E. , Omer E. M. , Gonçalves A. A.
Published: December 2014

The effects of glibenclamide on the electrical activity of the β‐cells of the islets of Langerhans of normal mice have been investigated in the absence and presence of glucose (11·1 mM). Glibenclamide depolarized the cell membrane and this has been interpreted in terms of an increase in the ratio of the Na+ and K+ permeabilities, PNa/ PK. This ratio increased from 0·05 to 0·24 in the presence of 4 µM glibenclamide and zero glucose. The input resistance of the β‐cells also increased. These observations indicate a decrease in K+ permeability. The effect is only slowly reversed after removal of glibenclamide. Uncouplers of oxidative phosphorylation do not reverse the depolarization induced by glibenclamide. It is suggested that glibenclamide is acting directly to inhibit the [Ca2+]i‐gated K+ permeability in the β‐cell membrane.
SPONTANEOUS [3H]NORADRENALINE RELEASE FROM THE MAIN PULMONARY ARTERY OF THE RABBIT INDUCED BY SODIUM‐PUMP INHIBITION
Authors: Török Tamás L. , Salamon Zsuzsanna , Nguyen Tinh Thi , Magyar Kálmán
Published: December 2014

Inhibition of Na pump either by ouabain (10−4 M) or by K removal increased the [3H]noradrenaline ([3H]NA) release from the isolated main pulmonary artery of the rabbit in the presence of neuronal (cocaine, 3 x 10−5 M) and extraneuronal (corticosterone, 5 x 1O−5 M) uptake blockers. The ouabain‐evoked [3H]NA release began after a delay of about 30 min and peaked after 66 min of ouabain application. Both times were shortened by omission of K from the external medium. About 90% of ouabain‐evoked [3H]NA release proved to be external Ca concentration ([Ca]o) dependent and the peak effect was delayed by about 80 min in Ca‐free (+1 mM EGTA) solution. In the presence of external Ca (2·5 mM) the [3H]NA‐releasing effect of ‘K‐free’ treatment was much less pronounced than that of 10‐4 M ouabain, the initial delay in transmitter release was shorter (10‐15 min) and the peak effect developed earlier (at 42 min). On readmission of K the [3H]NA release recovered quickly to the original value. Ca removal did not antagonize the transmitter release observed in K‐free solution, but the peak release was delayed by about 90 min. A low concentration of ouabain (10‐5 M) failed to produce transmitter release in the presence of normal external K, but markedly increased the release in K‐free solution. The release was much bigger than the sum of their separate effects, and the rate of rise was faster than when 10–4 M ouabain was applied in normal solution. Excess Ca (7·5; 15 mM) inhibited the [3H]NA release observed in K‐free solution. 7·5 mM‐Ca also delayed the transmitter‐releasing action of 10−4 M ouabain, an effect antagonized by omission of K from the external medium. The mitochondrial uncoupler carbonyl cyanide m‐chlorophenylhydrazone (CCCP, 10−5 M) significantly increased the [3H]NA release in Ca‐free, 1 mM EGTA‐containing solution, and enhanced the effects of ouabain (10−4 M). The Ca ionophore A23187 (10−5 M) also significantly increased the [3H]NA release in the absence of external Ca and in the presence of 1 mM EGTA. Again, in the presence of A23187 the effects of 10−4 M ouabain in releasing neurotransmitter were enhanced. When CCCP and A23187 were applied together in Ca‐free, EGTA solution the [3H]NA releasing action of ouabain was still apparent. Veratridine (10−4 M) enhanced the transmitter release in the absence of external Ca in a tetrodotoxin (TTX)‐sensitive manner. After veratridine treatment the action of ouabain was totally abolished. However, in the presence of TTX (10−7 and 3 x 10−7 M) which by itself significantly inhibited the veratridine‐evoked transmitter release the action of ouabain persisted. It is suggested that excess Ca, like external K, inhibits the transmitter‐releasing effect of Na‐pump inhibition, furthermore that in the absence of external Ca the ouabain‐evoked transmitter release is the result of Ca release from internal stores rather than Na‐pump inhibition per se.
MOTILIN AND MIGRATING MYOELECTRIC COMPLEXES IN THE PIG AND THE DOG
Authors: Borody T. J. , Byrnes D. J. , Titchen D. A.
Published: December 2014

Associations between migrating myoelectric complexes (m.m.c.s) and peak plasma motilin concentrations were confirmed in the dog fasted 18 h and shown not to be present in pigs fasted 3–4 h. Infusions of both natural porcine and synthetic 13‐Nle‐motilin failed to induce m.m.c.s in the pig. It was confirmed that motilin infusions stimulated the premature appearance of m.m.c.s in the dog whether motilin remained within, or exceeded, its normal plasma values. Immunoneutralization by intravenous administration of rabbit antimotilin serum was without effect on naturally occurring m.m.c.s in the dog and the pig. In the dog, antimotilin serum blocked production of m.m.c.s by exogenous motilin for 7–10 d post‐immunoneutralization. It is suggested that there are both: (i) species differences in associations of m.m.c.s and plasma motilin concentration, and (ii) an independence of m.m.c.s from plasma motilin even in the dog in which normally exogenous motilin can produce m.m.c.s.
CONTROL OF STOMACH MOTILITY IN THE LLAMA (LAMA GUANACOE F. GLAMA)
Authors: Gregory P. C. , Heller R. , Engelhardt W. V.
Published: December 2014

Manometric and electromyographic recordings of stomach motility were made in five conscious llamas to investigate the influence of distension of the stomach compartments, of temporary cervical vagal blockade and the influence of atropine, acetylcholine and adrenaline. The frequency of A‐contractions was slowed by distension of the canal joining compartment 2 (C2) and compartment 3 (C3), or of the proximal region of C3, and either increased and/or reduced by distension of the distal region of C3 or the hind stomach. The number of B‐contractions in a cycle was increased according to the degree of distension of the cranial sac of compartment 1 (C1). B‐contractions were also induced by distension of the canal or proximal region of C3 and were inhibited by distension of the distal region of C3 or the hind stomach. Contractions of C3 were not influenced by distension of C1 or C2 but were inhibited by distension of the canal, while distension within C3 caused a local excitation and an inhibition both proximal and distal to the point of stimulation. The hind stomach was only affected by local stimuli. Temporary vagal blockade abolished all contractions of C1, C2, the canal and C3, but had little effect on the motility of the hind stomach. Infusion of atropine (0·01 mg/kg), acetylcholine (7–33 µg/kg.min) and adrenaline (0·3 µg/kg.min) inhibited motility in all stomach compartments except the hind stomach where acetylcholine was stimulatory. It is concluded that while the hind stomach may have intrinsic motility, the contractions of C1, C2, the canal and C3 of the llama stomach are dependent upon a vagal motor nerve supply and that the pattern of contractions observed is regulated at least partially according to the individual degree of distension of each of the stomach compartments.
ACTIONS OF GABA AND ETHYLENEDIAMINE ON CA1 PYRAMIDAL NEURONES OF THE RAT HIPPOCAMPUS
Authors: Blaxter T. J. , Cottrell G. A.
Published: December 2014

The effects of locally applied γ‐aminobutyric acid (GABA) and ethylenediamine were examined and compared on CA1 pyramidal neurones in slice preparations of rat hippocampus using intracellular voltage recording techniques. Each substance produced both depolarization and hyperpolarization of the dendrites; the cell body responded with hyperpolarization alone. Ion substitution experiments suggest that the depolarizing responses of the dendrites were Cl− dependent and the hyperpolarizing responses of the cell body were dependent on Cl−, which suggests that the Cl− potential (ECl) is different in the dendrites compared with the cell body. The hyperpolarizing responses of the dendrites were dependent on K+. Dendritic depolarizing responses to GABA and ethylenediamine were antagonized by bicuculline and picrotoxin whereas the dendritic hyperpolarizing response was unaffected. The hyperpolarizing responses of the cell body were more difficult to study but it appeared that they were reduced by both bicuculline and picrotoxin. The benzodiazepines flurazepam and diazepam potentiated the dendritic depolarizing responses to GABA and ethylenediamine. It also had this effect on the hyperpolarizing response of the cell body but not on the hyperpolarizing response of the dendrites.
MILK ACCUMULATION AND SECRETION IN THE RABBIT
Authors: Calvert D. T. , Knight C. H. , Peaker M.
Published: December 2014

Over the 24 h period after suckling, total mammary‐gland weight increased linearly indicating no reduction in the rate of milk secretion during the relatively long interval between sucklings in the rabbit. Thus, storage capacity is matched to the long storage period. Beyond 24 h in the absence of suckling at 24 h, the rate of milk accumulation declined rapidly. This decline was not prevented by the administration of ovine prolactin or by permitting suckling of sealed teats at 24 h. During the decline in secretory rate after 24 h, milk [Na] and [Cl] increased while [K] and [lactose] decreased, as in other species. It is concluded that the decrease in secretory rate after cessation of suckling is not caused by lack of hormonal stimulation; it is suggested that mammary distension caused by accumulation of milk is responsible.
THE EFFECTS OF FEEDING EITHER ROUGHAGE OR CONCENTRATE DIETS ON SALIVARY PHOSPHORUS SECRETION, NET INTESTINAL PHOSPHORUS ABSORPTION AND URINARY PHOSPHORUS EXCRETION IN THE SHEEP
Authors: Scott D. , Buchan W.
Published: December 2014

Mature sheep fitted with rumen and duodenal cannulae were fed either a hay or a concentrate diet and the effects on salivary phosphorus secretion, net intestinal phosphorous absorption and pathway for phosphorous excretion were examined. Route of excretion was markedly affected by diet with urine phosphorus levels being much higher and faecal levels lower when the concentrate diet was fed. This difference was not due to differences in phosphorus intake nor could it be related to differences in either plasma phosphorus levels or net intestinal phosphorus absorption. Salivary phosphorus secretion and renal tubular reabsorptive efficiency for phosphorus were, however, both lower when the concentrate diet was fed. The significance of these effects of diet in relation to the control of phosphorus balance in ruminants is discussed.
CHARACTERIZATION OF A CATION CHANNEL ON THE APICAL SURFACE OF THE FROG LENS EPITHELIUM
Authors: Jacob T. J. C. , Bangham J. A. , Duncan G.
Published: December 2014

The properties of a single conductance pathway of the apical (fibre‐facing) surface of the frog lens epithelium are reported. Using the patch‐clamp technique (Hamill, Marty, Neher, Sakmann & Sigworth, 1981), the most common single‐channel currents had an amplitude of 1·9 pA, the mean open time 2·1 ms and a conductance of 25 pS. One open‐state time constant (to = 3·3 ms) and two closed‐state time constants (τc1 = 0·9 ms, τc2 = 23·1 ms) were resolved. The channel current and the mean open time were both increased when Ca2+ was removed from the external solution and the open time distribution was no longer fitted by a single exponential. Multiple‐channel events in cell‐attached patches containing two or more identical channels were distributed in a binomial fashion and the probability that an individual channel was open, obtained by fitting the binomial distribution, was 0·039. The channel was found to have a Na+:K+ selectivity ratio of 3:1. When Ca2+ was removed from the pipette solution the probability that an individual channel was open increased to 0·137 and the Na+:K+ selectivity ratio increased to 4:1. Channel activity was observed in the presence of tetrodotoxin (10−6 M) in the bathing medium and the pipette solution but was abolished by internal perfusion of the patch pipette with 0·5 x 10−4 M amiloride. This apical conductance pathway is identified as an amiloride‐sensitive cation channel. These channels are clustered in groups on the apical membrane, spontaneously active at the resting potential and with the possibility of altering their Na+:K+ selectivity. They represent a distinct type of channel, that differ from nerve and muscle Na+ channels in their manner of activation, but do share some common features with both Na+ and Ca2+ channels in excitable cells.
SPECIFIC EFFECTS OF THORACIC VAGOTOMY ON THE ELECTRICAL ACTIVITY OF THE GASTRIC ANTRUM AND PYLORUS IN RABBITS
Authors: Deloof Sylvie , Rousseau J. P.
Published: December 2014

The electrical activity of the antrum and the pylorus was recorded in rabbits, with chronically implanted electrodes. Effects of food intake were studied before and after bilateral vagotomy (b.v.), ventral vagotomy (v.v.) or dorsal vagotomy (d.v.) performed just above the diaphragm. In fasted animals, the electrical activity was characterized by bursts of potentials at a frequency of 1·93±0·09/min, initiated 45 mm or 20 mm from the pylorus in the greater and the lesser curvature respectively. The velocity of propagation of the bursts increased from 5‐6 mm/s in the proximal antrum to 12‐25 mm/s in the last 10 mm of the antrum along the greater curvature and from 2‐4 mm/s to 5‐15 mm/s along the lesser curvature. Feeding led to a rapid increase in the frequency of both antral and pyloric bursts up to 4·01±0·10/min, lasting 30‐60 min after a large meal but only 15 min when the amount of food was restricted. The behaviour of the rabbits was not significantly affected by bilateral or ventral vagotomy. In contrast, dorsal vagotomy resulted in a drastic decrease of food intake. The mean frequency (fo) of bursts before meals was significantly reduced after vagotomy in v.v. animals (1·49±0·1/min, P 〈 0·02) and in d.v. animals (1·34±0·08/min, P 〈 0·001) but not in b.v. or sham‐operated rabbits. For the first 3 d after surgery, the frequency (f) of bursts during the 30 min after the beginning of meals was significantly different from fo and reduced relative to f before nerve sections (1·9 ±0·11/min and 2·32±0·20/min respectively in b.v. and v.v. animals). In sham‐operated animals, the value of f was closely similar to f before surgery. The effects of meals on the frequency of bursts were again similar to the effects in intact animals within 4‐6 d for v.v. animals and 6‐9 d for b.v. animals. In the pylorus, a different pattern for electrical activity, which consisted of trains of spikes at a frequency of 0·3/s, was superimposed on the bursts and was most marked in d.v. animals. The spiking activity was not affected by atropine, phentolamine or propranolol. The role of the vagus nerve in the motile responses of the antrum to food intake is discussed. These results indicate the existence of a non‐cholinergic, non‐adrenergic innervation of the pylorus which is involved in the opening of the sphincter and appears to be mediated by the dorsal vagal trunk.
THORACIC OESOPHAGEAL MOTOR ACTIVITY DURING ERUCTATION IN SHEEP
Authors: Heywood L. H. , Wood A. K. W.
Published: December 2014

Concurrent radiographic and electromyographic observations were made in sheep during naturally occurring eructations. The radiographic field extended from the base of the heart to the cranial region of the rumen. Electromyographic recording was from two sites on the caudal thoracic oesophagus within 20‐70 mm of the diaphragm. Passage of gas from the rumen into the oesophagus was followed by passive gaseous distension of the caudal thoracic oesophagus for period of 540‐2860 ms (n = 80), at the end of which there was both electromyographic and radiographic evidence of oesophageal contraction. The pattern of radiographic change was indicative of a cranially progressing contraction of the thoracic oesophagus. Movements of the diaphragm observed radiographically during ventilation ceased (at the end of expiration), or became shallower, during the period of oesophageal distension. This resulted in a varying degree of interruption of the rhythm of ventilation. The first inspiration marking a return of ventilation to its former character was deeper than normal. The events during eructation were essentially similar whether the animals were eating, ruminating, or doing neither. When swallowing occurred during eructation it appeared to continue normally, interrupting the train of oesophageal reactions in eructation. Gas sometimes entered the caudal thoracic oesophagus after a mixing contraction of the reticulo‐rumen but it was returned to the stomach by a caudally moving oesophageal contraction.