bluuebunny/crossref_metadata_2025 huggingface dataset:
EFFECT OF HAEMORRHAGE ON PLASMA LYSINE VASOPRESSIN AND THE CARDIOVASCULAR RESPONSES TO VASOPRESSIN IN THE PIG FETUS
Authors: MacDonald Alastair A. , Forsling Mary L. , Ellendorff Franz , Beermann Ute
Published: December 2014

The effect of haemorrhage on plasma lysine vasopressin concentrations and the cardiovascular effects of intravenous injections of synthetic lysine vasopressin were studied in twenty‐four chronically catheterized pig fetuses aged between 81 and 114 d gestation (term = 114±1 d). Removal of 15‐20% of the estimated blood volume reduced mean arterial blood pressure and elevated plasma vasopressin concentrations above the mean basal value of 2·2±0·3 µ u./ml. The vasopressin concentration in plasma of fetuses younger than 104 d was insignificantly affected at 30 and 60 min after the bleed, whereas the corresponding values in older fetuses were raised by 12·7±7·2 µu./ml (d.f. = 7) and 16·0±6·0 µu./ml (d.f. = 7) respectively. The pituitary concentration of vasopressin was also greater towards the end of gestation. Plasma osmolality was unaffected by fetal blood loss. Maternal concentrations of vasopressin did not change from the basal values of 1·0±0·1 µu./ml (d.f. = 16). Injection of vasopressin raised fetal blood pressure and decreased heart rate. These results demonstrate that lysine vasopressin is present in the circulation of the pig fetus at 81 d (0·72 gestation), and that near term fetuses respond to haemorrhage more rapidly, and to a greater degree than younger fetuses.
AN EFFECT OF INJURY ON THERMOREGULATION IN MAN
Authors: Little R. A. , Stoner H. B. , Randall P. , Carlson G.
Published: December 2014

The effect of trauma on human thermoregulation has been studied using a behavioural test and the vascular response to cold exposure. It was confirmed, in controls, that a pleasurable temperature for the hand (Thand) depended on core temperature (Tc) to which it was negatively related. Shortly after moderately severe fractures in a leg this relationship was lost and in the patients the slope of this regression line was not significantly different from zero and they usually chose a Thand towards the upper end of the normal range irrespective of Tc. This effect was not imitated in controls by removing 500 ml blood but Thand was increased by occluding the circulation to one leg. Naloxone did not alter Thand in controls but when given in a suitable dose it reduced the rise in Thand during a short period of limb ischaemia. Immersing one hand and forearm in water at 17 °C reduced the blood flow through the contralateral forearm and hand. The reduction in flow was positively related to the initial rate of flow in both controls and injured but the slope of the regression line was significantly less after injury. It is concluded that thermoregulation is affected by trauma in man.
GALACTOSE TRANSPORT ACROSS RAT SMALL INTESTINE IN VIVO FOLLOWING DISTAL RESECTIONS OF VARYING EXTENTS
Authors: Bolufer J. , Delgado M. J. , Murillo F. , Murillo M. L.
Published: December 2014

The kinetics of D‐galactose absorption across rat small intestine in sham, 50 and 80% distal intestinal resected animals, have been studied under in vivo conditions. After 5 months post‐resection the total galactose absorption was increased. The relationship between total absorption of substrate and its concentration in the perfusate showed a non‐saturable component and a saturable one that can be inhibited by phloridzin, both in control and remnant intestine. The slope of the line that represents the non‐saturable component is greater in remnant duodenum and jejunum, indicating that the apparent mass‐transfer coefficient, K'D, was increased by distal resection. Non‐linear fitting of the saturable component data gave an apparent maximal galactose transport rate (J'max, nmol/cm2. min) of 134 ± 13 (sham), 132 ± 9 (50% resected), 139 ± 9 (80% resected) in duodenum and of 103 ± 11 (sham) and 106 ± 12 in jejunum. Apparent Michaelis constants (K'm, mM) of 12·1 ± 3·2 (sham), 12·3 ± 2·2 (50% resected) and 13·3 ± 2·2 (80% resected) in duodenum and of 11·6 ± 3·7 (sham) and 12·8 ± 3.7 (50% resected) in jejunum were found. Correction of the kinetic constants for the unstirred water layer (u.w.l.) effects showed that the differences between ‘real’ KD's of the experimental groups increased, whereas ‘real’ Km's did not significantly change. There were no significant differences in duodenal galactose absorption between 50 and 80% resected rats.
THE INFLUX OF ASCORBIC ACID INTO THE RAT'S BRAIN
Authors: Lam D. K. C. , Daniel P. M.
Published: December 2014

The influx of [14C]ascorbic acid into the rat's brain through the cerebral capillaries was measured by the steady‐state initial‐rate technique. Ascorbic acid was found to pass through the capillaries by a carrier‐mediated process and by simple diffusion. The carrier system was found to have an apparent Vmax of 1·2 nmol. min−1. g−1 of cerebral tissue and a Kt of 125 µM. The apparent constant of transfer, Kd, of the diffusional component was 0·98 µl. min−1. g−1. The contribution of the cerebral capillaries to the movement of ascorbic acid into the brain is discussed and was found to be the major route of entry into the brain for this vitamin.
HYPOTENSION‐INDUCED HYPOKALAEMIA IN SHEEP
Authors: Dallemagne Catherine , Cross R. B. , Law Sandra , Verschuer Louise , Wholohan Therese , Yesberg Nancy E.
Published: December 2014

Plasma K+ was measured in Merino ewes during 50‐90 min periods of hypotension induced by sodium nitroprusside, isoprenaline, verapamil or nifedipine. Doses were adjusted to produce falls in systemic blood pressure of approximately 20 mmHg. All of these drugs caused decreases in plasma K+ which could not be attributed to increased urinary excretion of K+. In all cases plasma renin activity increased during the hypotension. Plasma aldosterone concentration which was measured in some sodium nitroprusside experiments also increased during the hypotension. However, enhancement of the plasma renin activity and plasma aldosterone concentration responses by prior sodium depletion of the sheep by furosemide administration or suppression of the plasma renin activity and plasma aldosterone concentration responses by prior salt loading did not influence the magnitude of the hypotension‐induced hypokalaemia.
THE EFFECT OF THE CORONARY VASCULAR WALL ON THE CHANGES IN THE CORONARY VASCULAR RESISTANCE DURING A SUDDEN REDUCTION AND RECOVERY OF THE AORTIC BLOOD PRESSURE
Authors: Gattullo D. , Losano G. , Soardo G. P. , Vacca G. , Linden R. J. , Mary D. A. S. G. , Rosettani E.
Published: December 2014

To demonstrate the effect of elastic and myogenic properties of the vessel wall on the mean coronary vascular resistance during ventricular diastole (m.d.c.r.), this resistance was assessed in twenty dogs anaesthetized with sodium pentobarbitone during a 10 s period of arterial haemorrhage and 20 s of recovery from this haemorrhage. In a first stage of the study ten dogs were investigated following sectioning of the vagal nerves in the neck, β‐blockade, and ligation of the carotid arteries. During haemorrhage and reduction in aortic blood pressure (A.B.P.) in these dogs, there was an initial rise (at 2 s after the start of the haemorrhage) in m.d.c.r. which quickly decreased to a value similar to that obtained during the control period. After the abrupt cessation of haemorrhage, and a rise in A.B.P., there was an initial decrease in m.d.c.r. which eventually increased to the control levels. In the second stage of study identical patterns of changes were obtained in a group of five dogs in which the cervical vagi were not sectioned and β‐blocking agents not given. In another group of five dogs, during infusion of dipyridamole to force maximal coronary vasodilation, the increase in m.d.c.r. was maintained throughout the period of haemorrhage and reduction in A.B.P., and m.d.c.r. did not decrease below the control values following the abrupt cessation of haemorrhage and a rise in A.B.P. The findings in the dogs without dipyridamole infusion suggested that the pattern of changes in m.d.c.r. was due to changes in the perfusion pressure and their effect on the elasticity and myogenic properties of the coronary vascular wall. This suggestion was supported in the second stage of the study, when the reductions in m.d.c.r. were abolished by forcing coronary vasodilation using the infusion of dipyridamole.
MOTILIN SECRETION AND THE MIGRATING MYOELECTRIC COMPLEX IN THE PIG
Authors: Rayner V. , Gregory P. , Goodall E. D. , Christofides N. D. , Bloom S. R.
Published: December 2014

The concentration of motilin in plasma from the abdominal aorta and the hepatic portal vein and the net portal motilin output varied with the phase of the migrating myoelectric complex (m.m.c.) in five of six pigs fasted for 17 h. Maximum concentrations and output occurred 9‐12 min before phase III in the duodenum or upper jejunum. In fed pigs m.m.c.s occurred and the first phase III in the duodenum occurred within 90 min of feeding. Both portal and arterial motilin concentrations were reduced after feeding and no longer varied with the phase of the m.m.c. Altered secretion of motilin after feeding did not appear to be associated with absorption of glucose as infusion of glucose (50 g/l, 10 ml/min) into the duodenum raised arterial and portal plasma glucose concentrations to post‐prandial levels yet motilin concentrations and output rates still varied with the phase of the m.m.c. Infusions of motilin (1 or 10 ng/kg.min) into the portal vein of 17 h fasted pigs did not induce an extra phase III or alter the duration of the m.m.c. Hydrochloric acid (100 mmol/l) infused into the duodenum of fasted pigs at 10‐21 ml/min increased the concentration of motilin in the portal blood but was without effect at 5 ml/min. Rapid injections of 50 ml hydrochloric acid into the duodenum also increased the portal motilin concentration. Hydrochloric acid infusion or injection did not alter the interval between phase IIIs. It is concluded that motilin secretion is a consequence of the m.m.c. or shows the same periodicity as the m.m.c. but that motilin is not an important factor in the initiation and control of the m.m.c. in the pig.
MEMBRANE CONDUCTANCE AND POTASSIUM PERMEABILITY OF THE RAT LENS
Authors: Bassnett S. , Duncan G. , Stewart Sophie , Croghan P. C. , Lucas Valerie A.
Published: December 2014

The membrane potential, electrical impedance and 86Rb+ efflux rate constants were measured in the rat lens perifused at 35°C. The membrane conductance was obtained from the difference between the magnitude of the impedance at low (〈 0·1 Hz) and high (〉 100 Hz) frequencies. Values of the rubidium permeability coefficients (PRb) were obtained from the rate constant and potential data. The values for the membrane potential and conductance in control solution (5 mM potassium) were ‐69·6 mV and 5·5 x 10−4 S respectively, while the computed permeability was 2·9 x 10−8 m.s−1. On perifusing with 35 mM potassium, the membrane depolarized by 25 mV and the conductance and rubidium permeability increased considerably. These increases could be blocked by quinine (0·3 mM), tetraethylammonium (30 mM) and 4‐aminopyridine (10 mM). The latter agent was more effective at alkaline pH (8·3). It is suggested that there are voltage‐gated potassium channels that are inhibited by these three agents. After the initial depolarization in high potassium, there was little further change in membrane potential with any of the inhibitors. All three agents, however, produced a marked depolarization when applied in control solution. This was accompanied by a decrease in conductance and rubidium permeability, suggesting that, in the rat lens, some voltage‐gated potassium channels are activated at the resting potential.
TRANSIENT CHANGES IN PERMEABILITY IN HeLa AND L CELLS DURING DETACHMENT FROM A SUBSTRATE
Authors: Lamb Joseph F. , Ogden Patricia H.
Published: December 2014

The Na+ and K+ gradients of HeLa cells approach that of the medium during removal from a substrate with trypsin, but then recover during the next 15 min. The recovery is blocked by ouabain or the cold, but is unaffected by bumetanide. The effect is also obtained in cells which have no intercellular connexions, and in cells whose interior is made acid with CO2. Removal of cells with EDTA, pronase E and dispase has similar effects. It does not occur, or is greatly reduced, in cells already rounded up. Substances of molecular weight up to 5000 (e.g. inulin) also cross the cell membrane during this phase. We think that the effect is due to a transient increase in leakiness of the cell during rounding up, possibly due to the detachment of the ‘feet’ holding the cells onto the substrate. The transient increase in permeability of these cells may be a valuable method of introducing large molecules into them.
THE EFFECT OF LANTHANUM, QUERCETIN AND DINITROPHENOL ON CALCIUM‐EVOKED ELECTRICAL RESPONSES IN HAMSTER EGGS
Authors: Georgiou P. , Bountra C. , McNiven A. , House C. R.
Published: December 2014

At room temperature micro‐injections of calcium or strontium produced transient hyperpolarizations with an associated rise in input conductance. By contrast micro‐injections of potassium, barium, magnesium, cobalt or lanthanum did not produce hyperpolarizations. The reversal potential for the hyperpolarizing response was about ‐80 mV. Some responses to calcium injections appeared to suffer from an additional transient leak conductance generated by the injected current. In these cases the recovery of the potential and the conductance to normal values was prolonged. The reversal potential of this additional leak pathway was about ‐10 mV. Experiments designed to investigate the role of active calcium extrusion from the cells showed that extracellular lanthanum or quercetin caused a pronounced slowing of the recovery phase of the potential and conductance responses to calcium injection. The metabolic uncoupler dinitrophenol also prolonged the calcium‐evoked responses. The replacement of extracellular sodium by lithium or choline produced no alteration in the time course of the calcium‐evoked responses, thus suggesting that sodium‐calcium exchange exerts no rate control on the recovery phase of those responses.
STUDY OF THE RATE OF PASSAGE OF FOOD WITH CHROMIUM‐MORDANTED PLANT CELLS IN CHICKENS (GALLUS GALLUS)
Authors: Ferrando C. , Vergara P. , Jiménez M. , Goñalons E.
Published: December 2014

Thirty broilers 8‐10 weeks old were used to study the rate of food passage in chickens. Wheat bran and rice husks of three different sizes: more than 2 mm, between 1 and 1·5 mm, and less than 0·5 mm, mordanted with chromium, were used as markers. The suitability of these markers to study the rate of food passage in chickens and the possible influence of the size and hardness of the particle on the retention time was the objective of this study. Both T1, the time of first appearance of the marker, and Tm, the mean retention time, have been evaluated. Tm was a better parameter than T1 for studying transit time. Tm was longer with the biggest particles, especially with rice husk. The gizzard, with its grinding activity and pylorus, a selector of particle size, seems to be the transit regulator for solid particles in chickens. No chromium was found in the caecal contents of any case.
THE EFFECT OF CARBIMAZOLE ON GROWTH AND SEXUAL MATURITY IN THE PULLET
Authors: Shanawany M. M. , Morris T. R.
Published: December 2014

Carbimazole (100 mg/kg diet) was fed to pullets from 8 to 12 or from 12 to 16 weeks of age. Pullets fed carbimazole from 8 to 12 weeks of age matured about 12 d earlier and produced more eggs between 17 and 22 weeks of age. Their body weights and feed intake were significantly lower than those of normal birds. Feeding carbimazole from 12 to 16 weeks of age had no significant effect on the birds except during the course of treatment where their feed consumption was less than that of the controls.
COMPARISON OF PENICILLIN EPILEPTOGENESIS IN RAT SOMATOSENSORY AND MOTOR CORTEX
Authors: Holmes O. , Wallace M. N. , Campbell Angela M.
Published: December 2014

The relative sensitivities of somatosensory and motor areas of the cerebral cortex in penicillin epileptogenesis were compared in urethane‐anaesthetized rats. Penicillin was applied electro‐phoretically from a fluid‐filled micro‐electrode. Spontaneous focal interictal epileptiform discharges were detected by a nearby recording electrode. In motor cortex, every cortical layer was less sensitive in penicillin epileptogenesis than the corresponding layer in somatosensory cortex; epileptic spikes occurred later, were of lower amplitude and were less frequent. In motor cortex, the sensitive depth extended from the deep part of layer III to the upper part of layer V. It seemed possible that penicillin applied to motor cortex might be producing its effects by diffusing back to the sensitive somatosensory area. This was excluded by applying pencillin to motor cortex whilst recording from both somatosensory and motor areas and demonstrating that the spikes were found in motor but not in somatosensory cortex.
CATION TRANSPORT BY PANCREATIC β‐CELLS: EFFECT OF 4‐AMINOPYRIDINE ON 86Rb+ AND 45Ca2+ FLUXES
Authors: Boschero Antonio Carlos , Reis Luis Carlos , Dias Oneida , Delattre Edson , Gonçalves Antonio Ari
Published: December 2014

The effects of 4‐aminopyridine (4‐AP) on insulin release, glucose oxidation and 86Rb+ and 45Ca2+ fluxes of rat isolated islets were studied. 4‐AP (0·1 and 1·0 mM) did not alter the 86Rb+ fractional efflux. However, 10 mm 4‐AP significantly increased the 86Rb+ fractional efflux. 10 mM 4‐AP also reduced the insulin release from islets incubated over 90 min in the presence of both 6 and 16·7 mM glucose and from perifused islet in the presence of 16·7 mM glucose. 4‐AP (10 mM) only transiently increased the insulin release and the 45Ca2+ fractional efflux in the presence of 6 mM glucose. The 45Ca2+ fractional efflux was not changed when the islets were perifused at higher glucose concentration. At zero, 6 or 16·7 mM glucose, 4‐AP (10 mM) significantly increased the 45Ca2+ net uptake by islets incubated for 90 min. 10 mM 4‐AP significantly reduced the glucose oxidation of islets incubated for 120 min in the presence of 16·7 mM glucose. The effects of 10 mM 4‐AP on the dynamics of insulin release and 86Rb+ fractional efflux were poorly reversible. In conclusion, 4‐AP, at concentrations that did not alter the glucose metabolism, (0·1 and 1 mM), failed to affect the K+ permeability in β‐cells as judged by the measurements of 86Rb+ fractional efflux. At higher concentrations (10 mM) 4‐AP increased 86Rb+ efflux, decreased glucose metabolism and reduced insulin release.
VENOUS ADENOSINE CONTENT AND VASCULAR RESPONSES IN DOG HIND‐LIMB SKELETAL MUSCLES DURING TWITCH CONTRACTION
Authors: Ballard H. J. , Cotterrell D. , Karim F.
Published: December 2014

In dogs anaesthetized with pentobarbitone sodium and chloralose and artificially ventilated, the skeletal muscles of a hind limb were vascularly and neurally isolated and perfused at a constant flow of 150% of the resting blood flow (5·8±0·3 ml.min−1. 100 g−1 muscle tissue, mean±S.E.M., n = 6) obtained after denervation of the limb. Electrical stimulation of the cut peripheral ends of the femoral and sciatic nerves for 20 min resulted in muscle contraction and a decrease in arterial perfusion pressure to a new steady level (59·7±8·6% decrease in vascular resistance) within 2 min; the pressure remained constant throughout the remaining 20 min. Similarly venous oxygen tension decreased from 38·2±1·3 (control) to 16·4±1·7 mmHg (n = 5) during contractions. The concentration of adenosine in arterial plasma did not change significantly during muscle contraction (122·5±28 nM, n = 8). However, the adenosine concentrations in venous plasma increased significantly (P 〈 0·05) from a control value of 94·8±33 nM (n = 8) to 256±82 nM (n = 8) after 10 min and 235±31 nM (n = 8) after 20 min of muscle contraction. During infusion of adenosine into the femoral artery to give a range of arterial plasma concentrations between 0·17 and 90 µM, 89·2±2·8% (n = 20) of the infused adenosine was removed (taken up by tissues) from the blood before it reached the vein. Infusion of adenosine caused dose‐dependent decreases in vascular resistance ranging between 7 and 79%; 5·58±1·50 µM adenosine caused a decrease in resistance of 36·1±7·1% (n = 10) and 51·7±7·4 µM adenosine caused a decrease of 51·2±4·1% (n = 9). Comparison of venous plasma adenosine concentrations during adenosine infusions with those seen during contractions suggests that the released adenosine can contribute about 60% of the total vasodilatation seen during contractions of the muscle. These results show that adenosine appears in the venous blood during muscle contraction and is likely to contribute to exercise hyperaemia.
EFFECTS OF PHOSPHOLIPASE OF ENHYDRINA SCHISTOSA VENOM ON NERVE, MOTOR END‐PLATE AND MUSCLE OF THE MOUSE
Authors: Brook G. A. , Torres L. F. , Gopalakrishnakone P. , Duchen L. W.
Published: December 2014

Phospholipase A2 from Enhydrina schistosa (sea snake) venom was administered intravenously or intramuscularly to mice. The effects on the contractile responses and neuromuscular transmission were studied in soleus (a slow‐twitch muscle) and extensor digitorum longus (e.d.l.‐a fast‐twitch muscle). These muscles were also studied by morphological methods which included light and electron microscopy and enzyme histochemistry. There was a rapid and irreversible reduction of resting membrane potentials of muscle fibres of soleus which then failed to contract in response to direct or indirect stimulation. The e.d.l. was less severely affected. Spontaneous and evoked release of transmitter remained detectable at almost all end‐plates tested and there was no apparent reduction in the sensitivity of the post‐synaptic membrane. Most muscle fibres of soleus but only about 50% of those in e.d.l. became necrotic, the histochemical fibre types 1 and 2A being affected. Electron microscopy showed that in the acute phase (up to 24 h) there were lesions of the plasmalemma and severe disorganization of the internal structure of muscle fibres. In contrast, motor nerve terminals remained intact as did myelinated axons in the intramuscular nerves. There was a transient increase in the number of omega‐shaped profiles in the axolemma and of coated vesicles in nerve terminals at 1‐3 h, but by 24 h motor nerve terminals were normal in appearance. In regenerated muscle, post‐synaptic folds at motor end‐plates were reduced in depth and number.
FLUID BALANCE IN FOOD‐DEPRIVED LACTATING GOATS DRINKING SALINE
Authors: Dahlborn Kristina
Published: December 2014

Fluid balance was studied in four lactating goats during two 3 week periods, which included 30 h periods of food deprivation. In one period the goats were given 0·9% NaCl to drink, and in the other they were given water. Prior to food deprivation, fluid intake and urinary flow were similar in the two groups, but urinary Na+ excretion was higher in the saline‐drinking goats. The plasma renin activity was depressed in saline‐drinking goats, while the plasma aldosterone concentration was the same both in saline‐drinking and water‐drinking animals. Food deprivation depressed fluid intake and urine flow in all goats, but the reduction was more pronounced in goats drinking saline. The urinary Na+ and K+ excretion also decreased, in both groups, as did plasma Na+ concentration and osmolality. The plasma protein concentration increased in both groups, indicating that hypovolaemia had developed. The renin‐angiotensin‐aldosterone system (r.a.a.s.) became activated in goats drinking water, but not in the group drinking saline. It is suggested that sodium retention may have attenuated the activation of the r.a.a.s. in the latter group. The results of this study show that hyponatraemic hypovolaemia develops during starvation in lactating goats, regardless of the sodium state of the animals. The possibility that the hyponatraemic hypovolaemia is secondary to an impeded Na+ and fluid absorption from the rumen reticulum is discussed.
RETROGRADE OESOPHAGEAL CONTRACTIONS IN THE DOG
Authors: Heywood L. H. , Wood A. K. W.
Published: December 2014

Retrograde oesophageal contractions were observed by simultaneous radiography and electromyography during naturally occurring post‐prandial eructations in six dogs. The contractions progressed cranially at 85 ± 16 cm s−1 (S.E.M., n = 50) displacing, to the mouth, gastric gas which had previously passed into and distended the thoracic part of the oesophagus for 304 ± 22 ms (S.E.M., n = 30). Ninety per cent (n = 100) of retrograde oesophageal contractions were followed immediately by a slower aboral contraction (17·1 ± 0·02 cm s−1; S.E.M., n = 15). This appears to be the first description of naturally occurring retrograde oesophageal contractions in a non‐ruminant animal.
NON‐ADRENERGIC, NON‐CHOLINERGIC SALIVARY SECRETION IN THE FERRET
Authors: Ekström J. , MÅnsson B. , Olgart L. , Tobin G.
Published: December 2014

Secretion of parotid and submandibular saliva evoked by electrical stimulation of the parasympathetic nerves occurred in the presence of adrenergic and cholinergic blocking agents. The ‘atropine‐resistant’ response amounted to about 30% in the submandibular gland and to about 5% in the parotid gland as compared to the response before administration of antimuscarinic agents. The ‘atropine‐resistant’ secretion was found at relatively high frequencies, and the latency between the start of the stimulation and the onset of secretion was long. Upon long‐lasting stimulation the ‘atropine‐resistant’ secretion decreased rapidly and markedly. The tachykinins substance P (SP) and substance K, injected i.v., evoked flow of saliva from both glands. Given singly, exogenous vasoactive intestinal peptide (VIP) caused no salivary flow. However, it enhanced the tachykinin‐evoked secretory response. The response to SP was also enhanced when i.v. injections of this peptide were combined with nerve stimulation, even at subthreshold frequencies for secretion, in the presence of the autonomic receptor blockers. Both tachykinins and VIP are putative transmitters involved in mediating the ‘atropine‐resistant’ secretory response.
TRANSIENT EXCITATORY RESPONSES TO SUSTAINED STIMULATION OF INTRAMURAL NERVES IN ISOLATED BOVINE LYMPHATIC VESSELS
Authors: McHale N. G. , Allen J. M. , McCarron J. G.
Published: December 2014

Spontaneous isometric contractions were measured in 2 cm segments of bovine mesenteric lymphatics. Field stimulation at 4 Hz was applied for a 20 min period. This caused a threefold increase in contraction frequency initially but the response faded rapidly so that, within 6 min of the beginning of stimulation, contraction frequency had returned to a value which was not significantly different from control. In contrast to the effect on frequency 3H efflux from vessels pre‐loaded with [3H]noradrenaline was maintained at a value significantly higher than control for the entire stimulation period. The fade in response to exogenous noradrenaline was similar to that seen with field stimulation but with a slightly slower time course. Vessels desensitized with noradrenaline showed a greatly diminished response to field stimulation but responded normally to other agonists. Increasing the extracellular KCI concentration to 18 mM also caused a threefold increase in contraction frequency but, unlike the response to noradrenaline and field stimulation, this was maintained for the 20 min period during which [K+]o was raised. The results suggest that the adrenoceptors on lymphatic smooth muscle exhibit very rapid homologous desensitization.
MAGNESIUM ABSORPTION FROM THE TEMPORARILY ISOLATED RUMEN OF SHEEP: NO EFFECT OF HYPER‐ OR HYPOMAGNESAEMIA
Authors: Martens H. , Stossel Eva‐Maria
Published: December 2014

The net absorption of magnesium from the temporarily isolated rumen of sheep was measured at different plasma magnesium concentrations. In the first series of experiments, the plasma magnesium concentration was raised from 0·89 ± 0·11 to 1·97 ± 027 mmol l−1 by intravenous infusion of MgCl2 immediately before measurement of magnesium absorption. In a second series absorption of magnesium was studied over 20 h after the beginning of a continuous intravenous infusion of magnesium, which led to hypermagnesaemic levels of 2·78 ± 0·59 mmol l−1. In the third series sheep were fed a magnesium‐deficient diet which caused a significant decrease of plasma magnesium concentration from 0·96 ± 0·06 to 0·50 ± 0·06 mmol 1−1. Neither hyper‐ nor hypomagnesaemia changed net absorption of magnesium from the rumen of sheep. It is concluded that the active ttansport of magnesium from the rumen was not influenced by the plasma magnesium concentration and that any passive and paracellular movement of magnesium through the rumen wall must have been negligibly small under the conditions of these experiments.
AN IMMUNOFLUORESCENT STUDY OF INSULIN‐, GLUCAGON‐, PANCREATIC POLYPEPTIDE‐ AND SOMATOSTATIN‐CONTAINING CELLS IN THE EARLY OVINE FETAL PANCREAS
Authors: Reddy S. , Bibby N. J. , Elliott R. B.
Published: December 2014

Using antisera to insulin, glucagon, pancreatic polypeptide (PP) and somatostatin, the localization and cellular distribution of the four hormones were investigated in the sheep fetal pancreas of day 40‐45 gestation by immunofluorescence. All four hormones were immuno‐ localized at this early gestational period. The endocrine cell types had a characteristic distribution and were present in different numbers. Insulin and glucagon immunoreactive cells were seen in larger numbers compared to fetal PP and somatostatin cells and were located either in the developing islets or as single scattered cells in the epithelium of the embryonic ductules. These cells became more confined to the developing islets at later stages of gestation. In the pancreas of day 40‐45 fetuses PP cells were less numerous than glucagon and insulin cells while somatostatin cells were seen rarely. However, PP and somatostatin cells became more numerous at later stages of gestation. Our studies demonstrate the presence of insulin, glucagon, PP and somatostatin within distinct cell types in the early sheep fetal pancreas.
THE EFFECTS OF EXERCISE AND SUBJECT AGE ON PULSED DOPPLER MEASUREMENTS OF LEFT VENTRICULAR EJECTION IN NORMAL MAN
Authors: Innes J. A. , Simon T. D. , Murphy K. , Guz A.
Published: December 2014

Pulsed Doppler measurements of ascending aortic blood velocity and acceleration were made in a group of normal subjects on exercise. The aims of the study were: (1) to document the normal response to exercise and its variability at various ages as a baseline for future studies in abnormal subjects, and (2) to investigate the accuracy and reproducibility of these non‐invasive measurements. Doppler measurements were related to oxygen consumption in normal subjects aged between 22 and 69 years, during a submaximal 4 min incremental cycle exercise protocol. Computer‐aided ensemble averaging of digital spectral data was used to reduce the effects of noise and respiratory variations in the signals. The mean relationship between cardiac output (Q) and oxygen consumption (VO2) was Q = 5·75 VO2 + 4·22 1 min−1, r = 0·84 in subjects aged under 45 years, compared to Q = 6·16 VO2 + 3·87 1 min−1, r = 0·65 in older subjects; this difference was not significant. These values are slmilar to those previously described in invasive studies. There was a wide range of individual responses especially in the older subjects. These inter‐subject differences probably reflect true physiological differences between subjects rather than methodological errors because they were consistent on repeated testing in the same individual, similar differences occurred in heart‐rate responses between individuals where Doppler errors do not apply, and inter‐subject variability of similar magnitude was found in comparable studies using invasive methods. Peak velocity (PV) rose from 73±10 cm s−1 at a VO2 of 0·4 1 min−1 to 101±11 cm s−1 at a VO2 of 1·2 1 min−1 in subjects aged under 45 years; corresponding values in the older subjects were significantly lower at 48±12 and 64±10 cm s−1 respectively. Maximum acceleration was also significantly higher at rest and on exercise in subjects under 45 years compared to older subjects. Despite these differences, stroke volume and cardiac output responses showed no significant age dependence, suggesting that differences in ejection velocity are due to increasing aortic cross‐sectional area with age. The wide variety of individual responses found suggests an underlying variability in the arteriovenous oxygen difference on exercise between subjects.
THE EFFECT OF HIGH‐FREQUENCY VENTILATION ON PATTERN OF BREATHING OF ANAESTHETIZED RABBITS
Authors: Davies A. , Dutia M. B. , Price R. F.
Published: December 2014

The lungs of anaesthetized rabbits were ventilated with a frequency of 30 Hz and a displacement of 5 ml. High‐frequency ventilation (HFV) was superimposed on static inflation or deflation pressures of 2·5 and 5 cmH2O and was maintained for 10 s. Changes in pattern of breathing in response to this procedure were recorded before and during block of pulmonary stretch receptors by SO2. With lung stretch receptors intact apnoea or extended duration of expiration demonstrated the predominant role of pulmonary stretch receptors in the response to HFV. Block of stretch receptors exposed effects of other pulmonary afferents, presumably rapidly adapting receptors, during HFV, and demonstrated the influence of their sustained stimulation on pattern of breathing as augmented breaths and the reduction of duration of expiration. High‐frequency ventilation may represent a useful experimental method of stimulating rapidly adapting receptors.
STUDIES ON THE INFLAMMATORY RESPONSE DURING INVOLUTION OF THE OVINE MAMMARY GLAND
Authors: Colditz I. G.
Published: December 2014

Cessation of lactation, initiated by the removal of lambs from their mothers, induced an inflammatory response with elevated numbers of neutrophil leucocytes in mammary secretions being detected within 16 h. Leucocyte numbers were still elevated 7 d later. Infusion of whole milk into non‐lactating glands caused no change in leucocyte numbers after 24 h. Involution secretions, however, had the capacity to induce an inflammatory response when infused into non‐lactating glands. Daily infusion of endotoxin (100 ng) into non‐lactating glands resulted in a marked attenuation of the inflammatory response. Such desensitization did not accompany reinfusion of involution secretion. Responses to involution secretion were enhanced in glands desensitized to endotoxin. The failure of desensitization to develop in glands receiving repeated infusions of involution secretion and the lack of cross‐desensitization between involution secretion and endotoxin indicate that a novel mediator of inflammation may be produced during mammary involution in sheep.
ATROPINE‐RESISTANT SECRETORY RESPONSES OF THE OVINE PAROTID GLAND TO REFLEX AND DIRECT PARASYMPATHETIC STIMULATION
Authors: Reid A. M. , Titchen D. A.
Published: December 2014

A study was made of mechanisms involved in the parasympathetic control, especially of protein concentration in, and also flow, of ovine parotid secretion. The effects of distension of the caudal thoracic oesophagus were characterized in four anaesthetized sheep each with a unilateral chronic superior cervical sympathetic ganglionectomy. Oesophageal distension produced increases in both the flow and protein concentration of saliva from the control glands similar to that from the sympathectomized glands indicating the response was mediated by the parasympathetic innervation. Atropine, in doses which completely abolished increases in flow and protein concentration produced by bethanechol infusion, reduced, but did not abolish, the responses to oesophageal distension providing evidence of non‐cholinergic transmission. Electrical stimulation of the parotid (parasympathetic, postganglionic) nerve during atropinization produced ca. 70% increases in flow and ca. 100% increases in protein concentration of parotid saliva thus giving further evidence of such a mechanism. Intracarotid infusion of vasoactive intestinal polypeptide (VIP) evoked responses with similarities to those observed with oesophageal distension and nerve stimulation during atropinization. This observation adds to other evidence indicating that VIP acts as a parasympathetic neurotransmitter involved in the control of salivary secretion.
SYNAPTIC CONTACTS BETWEEN GLUTAMIC ACID DECARBOXYLASE‐IMMUNOREACTIVE BOUTONS AND POSTSYNAPTIC DORSAL COLUMN NEURONES IN THE SPINAL CORD OF THE CAT
Authors: Maxwell D. J.
Published: December 2014

Neurones with axons ascending the dorsal columns were retrogradely labelled with horseradish peroxidase in the lumbosacral spinal cords of adult cats. Sections, containing labelled neurones, were processed immunocytochemically using an antibody for glutamic acid decarboxylase, the enzyme responsible for the synthesis of γ‐aminobutyric acid (GABA). Thirteen retrogradely labelled cells were observed to receive an average of five contacts each from immunoreactive structures. Ultrastructural investigation revealed that immunolabelled structures were boutons and that some of them were presynaptic to labelled cells. It is concluded that GABA probably mediates at least some of the postsynaptic inhibitory responses which have been recorded from these neurones.
THE EFFECTS OF TWO CALCIUM ANTAGONISTS (NIFEDIPINE AND VERAPAMIL) ON RENAL FUNCTION IN SHEEP
Authors: Verschuer Louise , Yesberg Nancy E. , Henderson Myrna , Dallemagne Catherine , Cross R. B.
Published: December 2014

The effects of the calcium antagonists, nifedipine and verapamil, were measured in five conscious Merino ewes at a dose rate of 0·5 µg min−1 kg−1 for 60 min. Nifedipine caused a significant fall in mean arterial blood pressure (MABP) and central venous pressure (CVP) and an increase in heart rate (HR). There was no significant effect on renal vascular resistance (RVR) but, with the fall in MABP, renal plasma flow (RPF) decreased. There was a significant rise in glomerular filtration rate (GFR) and a small rise in filtration fraction (FF). Solute excretion, urine osmolality and solute‐free water reabsorption (Tc, H2O) increased and urine flow (V) decreased. Plasma potassium (PK) and osmolality (Posm) decreased. Verapamil produced a similar fall in MABP and also had similar effects on the other parameters, except that in this case RVR was significantly reduced and there were significant increases in RPF and GFR. The rise in GFR which occurred regardless of the change in RPF, can account for the increase in solute excretion, although an effect of the calcium antagonists on tubular function cannot be excluded.
THE TRANSFER OF ZINC ACROSS THE TERM DUALLY PERFUSED HUMAN PLACENTAL LOBULE
Authors: Page K. R. , Todd A. , Abramovich D. R. , Aggett P. J. , Dacke C. G.
Published: December 2014

Net zinc transfer between fetal and maternal circulation has been described in the in vitro perfused lobule of the human term placenta. The transfer results in a 3 µM differential between fetal and maternal perfusates which is comparable to estimated values in vivo. Tissue zinc concentration is more than 10 times perfusate concentration and is correlated with zinc flux across the fetal borders of the lobule. Open‐circuit studies on net transport of zinc, and upon flow of 65Zn relative to tritiated water (3H2O), indicate these fluxes depend upon the non‐protein‐bound (free) zinc gradient across the fetal‐facing membranes. On the other hand movement across the maternal surface is not related to diffusion gradients of free zinc and is either independent of, or inversely related to, the level of tissue zinc. It is concluded that the uptake of zinc from the maternal perfusate may be coupled to metabolism, whereas its transfer to fetal circulation is linked to the level of free zinc in the tissue.
GLUCOSE UPTAKE AND IRON ABSORPTION BY AN ISOLATED, VASCULARLY AND LUMINALLY PERFUSED PREPARATION OF RAT SMALL INTESTINE
Authors: Davies N. T. , Coppen D. E.
Published: December 2014

Some characteristics of an isolated vascularly and luminally perfused rat intestinal preparation are described. Over 60 to 90 min perfusion, the vascular perfusion medium (VPM) ‘arterial’ pressure remained stable and between animals it varied between 22 and 47 mmHg while the VPM flow rate remained constant at 1·3 ml/min. Hypersecretion, as monitored by changes in the concentration of phenol red in the luminal perfusion medium (LPM), did not generally occur. Histological examination of the tissue post‐perfusion showed that normal morphology was retained for at least 1 h. Total glucose uptake ranged between 85 and 155, µmol/(g dry wt.h) with greater uptake from the VPM than the LPM. Approximately 50% of the glucose taken up by the intestine appeared as lactate in the perfusion media, most of which was released to the VPM. The addition of phloridzin (5 x 10−4 M) to the LPM significantly reduced the uptake of glucose from the LPM and its transfer to the VPM. Iron absorption was studied by adding FeCl2 (with 59Fe and ascorbate, 100 µg/ml) to the LPM to give a final concentration of 10‐100 µg iron/ml. The appearance of iron in the VPM was investigated over a period of 1 h. At the two lowest concentrations (10 and 25 µg/ml) there was a lag of 20‐40 min before iron appeared in the VPM. At the higher doses (50 and 100 µg/ml) the lag was 10 min. During the final 20 min the appearance of iron in the VPM plateaued to dose‐dependent constant rates. The ratio of the specific radioactivity of 59Fe in the two perfusates (LPM:VPM) was unity when the initial iron concentration was 25 µg/ml or above. At the lowest dose (10 µg/ml) this ratio was 2·5 indicating that during transfer, iron taken up from the LPM had mixed with a small labile endogenous iron pool. Both amounts of iron retained by the intestinal tissue and transferred to the VPM increased exponentially with increasing luminal iron dose. The amount of iron retained by the tissue was always greater than that transferred to the VPM.
FLUX OF CALCIUM ACROSS THE SHEEP RUMEN WALL IN VIVO AND IN VITRO
Authors: Höller H. , Breves G. , Gerdes Herta , Kocabatmaz M.
Published: December 2014

Experiments were carried out in vivo and in vitro to study the flux of Ca2+ across the sheep rumen wall. Buffer solutions with five different Ca2+, concentrations in the range 0·2‐3·6 mmol l−1 were introduced into the isolated, emptied and washed reticulo‐rumen for 1 h to determine Ca2+ net flux. Phosphate concentrations were either kept constant at 8 mmol l−1, or varied so as to maintain a constant phosphate/Ca2+ ratio of 2:1. Under both conditions there was a Ca2+ net secretion into the rumen at Ca2+ concentrations below approximately 1 mmol l−1 whereas Ca2+ net absorption occurred at higher Ca2+ concentrations and linearly increased with increasing Ca2+ concentrations. When phosphate concentrations were reduced to 4·3 and 0·6 mmol l−1 (Ca2+, 3 mmol l−1) Ca2+ net absorption was reduced by about 50% and completely abolished, respectively. The unidirectional (mucosal‐to‐serosal or serosal‐to‐mucosal) Ca fluxes in vitro, JCams and JCasm, were measured in Ussing chambers with computer‐controlled voltage clamp. Under short‐circuit current conditions (Ca2+ and phosphate, 2 mmol l−1) there was a significant net flux of Ca2+ from the mucosal to the serosal side. This net flux of Ca2+ was abolished when ouabain was added to the serosal solution, indicating that the unidirectional Ca2+ flux JCams and, hence, the net flux of Ca2+ was dependent upon active Na+ transport accomplished by the Na, K‐ATPase system. Under voltage clamp conditions, the net flux of Ca2+ was greatly increased at a potential difference PD = ‐25 mV (serosa negative) but disappeared at PD = +25 mV (serosa positive). Analysis of the unidirectional Ca2+ fluxes JCams and JCasm under varying potential differences indicated that both Ca2+ fluxes consisted of a PD‐dependent and a PD‐independent component. The results show that the reticulo‐rumen participates in Ca2+ absorption in sheep.
ACETYLCHOLINE‐EVOKED POTASSIUM AND SODIUM TRANSPORT IN RAT LACRIMAL SEGMENTS: EVIDENCE FOR A SODIUM‐CHLORIDE CO‐TRANSPORT SYSTEM
Authors: Singh Jaipaul
Published: December 2014

An investigation was made of the effects of acetylcholine (ACh) on transmembrane movements of potassium (K+) and sodium (Na+) in isolated segments of rat lacrimal glands. ACh elicited dose‐dependent and transient increases in K+ concentration in the effluent (K+ release). The ACh‐induced K+ outflow was unaffected by either pre‐treatment of lacrimal segments with loop diuretics (frusemide, piretanide and bumetanide, all 10−4 M) or replacement of chloride (Cl−) in the physiological salt solution with nitrate (NO3−). In contrast, ACh caused a significant (P 〈 0·001) reduction in Na+ concentration in the effluent (Na+ uptake). The ACh‐evoked Na+ uptake was sensitive to loop diuretics and Cl− removal. Pre‐treatment of tissue with ouabain (10−3 M) resulted in a marked sustained K+ release. ACh produced a further increase in K+ efflux in the continuing presence of ouabain. Incubation of the tissue with 10 mM‐tetraethylammonium (TEA) resulted in an uptake of K+. The results suggest the presence of a diuretic‐sensitive Na+‐Cl− co‐transport system in lacrimal acinar cell membranes.
HYDROSTATIC PRESSURE ENHANCES BARORECEPTOR REFLEXES IN THE RAT
Authors: Bowser-Riley F. , Kidd C.
Published: December 2014

The effects of increased hydrostatic pressure on baroreceptor reflexes in the decerebrate rat have been investigated. Baroreceptor ‘sensitivity’ was assessed from the relationship between cardiac interval and systolic blood pressure following infusion of phenylephrine to animals exposed to increases in hydrostatic pressure (1‐30 bar) with helium. Resting heart rate and systolic blood pressure were reduced and the ‘sensitivity’ of the baroreflex heart rate response was significantly increased by exposure to pressure. This enhancement of cardiovascular reflex function, elicited by moderate increases in hydrostatic pressure may, in part, be centrally mediated.
A COMPARISON OF THE DISTRIBUTION OF SUBSTANCE P AND CALCITONIN GENE‐RELATED PEPTIDE RECEPTORS IN THE RAT BLADDER
Authors: Nimmo Alan J. , Morrison John F. B. , Whitaker Elaine M.
Published: December 2014

Binding of [125I]Bolton‐Hunter labelled substance P (BH‐SP) and [125I]human α‐calcitonin gene‐related peptide (hαCGRP) to rat bladder tissue sections was characterized and the respective binding sites localized by light‐microscopic autoradiography. BH‐SP binding sites were localized to epithelium, blood vessels and smooth muscle while hCGRP binding sites were present only over the epithelium. These results suggest that the range of biological actions of substance P and calcitonin gene‐related peptide, which may be co‐released from the same afferent terminals, might be determined by the different distributions of their respective receptors.
RECOVERY FROM IMMOBILIZATION‐INDUCED ATROPHY OF RABBIT SOLEUS MUSCLES CAN BE ACCELERATED BY CHRONIC LOW‐FREQUENCY STIMULATION
Authors: Cotter Mary , Barry Jacqueline , Cameron Norman
Published: December 2014

Immobilization of rabbit soleus muscles with an ankle joint angle of 90° led to gross degeneration after 2 weeks. Natural recovery in the subsequent 2 weeks had little effect on the mean area of soleus fibres, although there were signs of regeneration. However chronic low‐frequency activation of soleus muscles by nerve stimulation greatly accelerated recovery, producing muscle fibres of normal areas and with characteristics of maturity.
REFLEX RESPONSES OF VAGAL EFFERENT FIBRES INFLUENCED BY GASTROINTESTINAL MECHANORECEPTORS TO ELECTRICAL AFFERENT STIMULATION IN THE ANAESTHETIZED FERRET
Authors: Blackshaw L. A. , Grundy D.
Published: December 2014

Activity was recorded from 188 vagal efferent fibres, 90 % of which showed responses to distension of the stomach and duodenum. Of thirty fibres tested with single‐shock vagal stimulation, reflex action potentials were evoked in fifteen, ranging in latency from 39 to 318 ms. Responses at short latency showed little latency‐jitter and high response‐probability, and those at long latency showed opposite characteristics. This suggests that two pathways are present in the central organization of vagal reflexes to the gut.