bluuebunny/crossref_metadata_2025 huggingface dataset:
DEVELOPMENT OF SUBSTANCE P‐ AND VASOACTIVE INTESTINAL POLYPEPTIDE‐CONTAINING NEURONES IN THE RAT STOMACH
Authors: Ito Shigeo , Ohta Toshio , Kimura Atsuko , Ohga Akira
Published: December 2014

The ontogeny and distribution of nerve fibres containing immunoreactive substance P (SP) and vasoactive intestinal polypeptide (VIP) were studied in the fetal and neonatal rat stomach, using immunohistochemistry and radioimmunoassay. Dimly fluorescent SP‐ and VIP‐immunoreactive fibres began to appear in the myenteric plexus from embryonic day (ED) 17 and 18, respectively, and then in the circular muscle layer from ED 19. VIP‐immunoreactive fibres increased in the mucosal layer after birth but not SP‐immunoreactive fibres. Both immunoreactive fibres seemed to arise from intrinsic neurones in the stomach. SP and VIP were detectable from ED 15 and 18 in the rat stomach, respectively, by radioimmunoassay. The concentration of SP in the stomach increased until ED 18, but it tended to decrease somewhat thereafter. The concentration of VIP in the stomach increased throughout the period from ED 18 to 7 days post‐natal. The results suggest that the development of VIP‐containing neurones lags about 2 days behind that of SP‐containing neurones in the rat stomach.
‘PARALYTIC’ SECRETION AFTER PARASYMPATHECTOMY OF RABBIT SUBMANDIBULAR GLANDS INCLUDES A CHOLINERGIC COMPONENT
Authors: Garrett J. R. , Kyriacou K.
Published: December 2014

Chronic parasympathetic decentralization of submandibular glands in rabbits has been studied after 3 weeks, in acute experiments under urethane anaesthesia. A ‘paralytic’ secretion occurred from the supersensitive denervated glands and it was not attributable to an increase in the ‘spontaneous’ flow, that is present in normal glands. The ‘paralytic’ secretion was completely inhibited by atropine, after which a ‘spontaneous’ flow, that was similar to the contralateral glands, persisted. The α‐adrenergic blocker dihydroergotamine, when given before atropine, reduced the ‘paralytic’ secretion by 50‐75% but when this drug was given after atropine it had no additional effect. The β‐adrenergic blocker propanolol did not cause a reduction in the ‘paralytic’ secretion. Superior cervical ganglionectomy, in contrast, did not give rise to a significant ‘paralytic’ flow. The results suggest that acetylcholine, released spontaneously from terminals of postganglionic parasympathetic nerves, plays an essential part in the ‘paralytic’ secretion that occurs from rabbit submandibular glands after preganglionic denervation. Circulating catecholamines make a secondary contribution, acting synergistically with the acetylcholine on the supersensitive secretory cells.
TESTING THE HYPOTHESIS THAT CRYPT CELL HYPERPLASIA INHIBITS LACTASE EXPRESSION BY MOUSE JEJUNAL ENTEROCYTES
Authors: Smith M. W. , Lloyd S. , James P. S.
Published: December 2014

Lactase activity and crypt cell proliferation both increased significantly in mouse jejunal villi in the presence of the intestinal parasite Nematospiroides dubius. Comparisons are made between this result and others showing lactase activity to decline whenever crypt cell proliferation is increased.
CENTRALLY INJECTED ATRIAL NATRIURETIC FACTOR INHIBITS ANGIOTENSIN‐ AND OSMOTICALLY‐INDUCED DRINKING IN PIGS
Authors: Thornton S. N. , Baldwin B. A.
Published: December 2014

Atrial natriuretic factor 5‐28 (atriopeptin III, APIHI; 10 µg) injected into the cerebral ventricles of young pigs 5 min before injection of either angiotensin II (AII, 300 ng) or hypertonic NaCl (0·74 M) attenuated the subsequent drinking responses to these dipsogens although the latency to the response was not altered. The inhibition lasted for up to 4 days in the case of AII‐induced drinking but normal daily water intake was not disrupted. These findings suggest that in the pig APIII may play a role in the central regulation of drinking in response to AII and that it may have a long biological half‐life.
THYROID FUNCTION IN MALE ZUCKER RATS EXPOSED TO COLD
Authors: Whitaker E. M. , Robinson A. C. , Rayfield K. M. , Hervey G. R.
Published: December 2014

Non‐obese and obese Zucker rats were exposed to 6 °C for 20 days. At the end of the experiment thyroid stimulating hormone (TSH), circulating thyroid hormones, and the weights of the thyroid gland and a brown adipose tissue pad were measured. TSH and 3,5,3'‐triiodothyronine concentrations and brown adipose tissue weights increased in response to cold in both phenotypes but by larger amounts in obese rats. Free thyroxine was lower in obese rats. There appears to be no defect in thyroid function in congenitally obese rats exposed to cold, or in their ability to develop brown adipose tissue.
EFFLUX OF CHLORIDE FROM THE RAT LENS: INFLUENCE OF MEMBRANE POTENTIAL AND INTRACELLULAR ACIDIFICATION
Authors: Bassnett S. , Stewart S. , Duncan G. , Croghan P. C.
Published: December 2014

The efflux of 36Cl− from perifused rat lenses consisted of two components: a fast (extracellular) component and a slow (cellular) component. The 36Cl− efflux rate constant of the cellular component was 5·7 x 10−3 min−1. The 36Cl− efflux was sensitive to changes in lens potential induced by treatment with high‐K+ solutions. The decrease in the 36Cl− efflux rate constant caused by high‐K+ solutions was consistent with the Goldman model, indicating that, under normal conditions, the majority of the 36Cl− efflux is by diffusion. The 36Cl− efflux rate constant corresponds to a Cl− permeability of 1·3 x 10−8 m s−1. The Cl− channel inhibitor anthracene‐9‐carboxylate (A‐9‐C), however, caused a relatively small reduction in the efflux rate constant. The anion‐exchange inhibitor 4‐acetamido‐4'‐isothiocyanatostilbene‐2,2'‐disulphonate (SITS) has little effect on the 36Cl− efflux under control conditions. Intracellular acidification, induced by pre‐treatment with NH4+, leads to a rapid stimulation of 36Cl− efflux. This increased 36Cl− efflux is blocked by SITS. Thus, it appears that at low intracellular pH (pHi), a normally quiescent, SITS‐sensitive, anion‐exchange mechanism is activated. The possible role of this exchange mechanism in regulating pHi is discussed.
EFFECTS OF LONG‐TERM STREPTOZOTOCIN DIABETES ON THE CONTRACTILE AND HISTOCHEMICAL PROPERTIES OF RAT MUSCLES
Authors: Cotter M. , Cameron N. E. , Lean D. R. , Robertson S.
Published: December 2014

Contractile and histochemical properties of soleus (a slow‐twitch muscle) and extensor digitorum longus (EDL, a fast‐twitch muscle) were studied in mature rats after 3 months of streptozotocin‐induced diabetes. Results were compared with age‐ and weight‐matched controls. Diabetes produced profound wasting of fast muscles and particularly of the fast glycolytic (FG) fibres. Slow muscle fibres, both within the mixed EDL and in soleus, were less atrophied. Strength performance of EDL was reduced by diabetes, but maintained in soleus. Diabetes was without effect on the time to peak tension (TTP) and half‐relaxation time (HRT) of EDL. However it produced profound slowing of soleus muscles, particularly of the relaxation phase. Part of the slowing effect of diabetes may be related to a histochemically demonstrable loss of fast oxidative glycolytic (FOG) fibres in soleus. Histochemical staining for the oxidative marker succinic dehydrogenase (SDH) revealed marked disruption of reaction product distribution in soleus, indicating an impairment of oxidative capacity.
THE EFFECTS OF PROLONGED EXPOSURE TO LOWERED AMBIENT TEMPERATURE ON THYROID ACTIVITY IN MATURE FEMALE RATS
Authors: Ibidapo I. I. , Sofola O. A.
Published: December 2014

The effects of prolonged exposure to lowered ambient temperature (18‐19 °C) for 6 weeks, on thyroid function, were studied in mature female rats. Exposure to cold resulted in a significant rise in serum thyrotrophin level but a fall in serum thyroxine. Radioactive iodine uptake by the thyroid gland was also depressed. Rectal temperature was reduced following cold exposure. Histological examination of the thyroid gland was suggestive of reduced glandular activity. Thus prolonged exposure to lowered ambient temperature leads to a reduction in thyroid gland activity which is accompanied by a lower body temperature.
VAGAL GASTRIC EFFERENT ACTIVITY AND ITS REFLEX CHANGES IN CONSCIOUS SHEEP
Authors: Dalal A. , Rousseau J. P. , Laplace J. P.
Published: December 2014

Electromyographical recordings from neck muscles reinnervated by the vagus nerve allowed monitoring of vagal output to the reticulo‐rumen in conscious sheep. The vagus nerve was sectioned below the nodose ganglion and its central end anastomosed with the peripheral end of the spinal accessory nerve, which innervates the trapezius and mastoido‐humeral muscles. Fifty‐three vagal efferent units recorded were identified and classified into seven distinguishable types on the basis of their temporal relationship with gastric movements. With respect to their patterns of discharge during the primary cycles type I to type V units were similar to units of the corresponding types described by Iggo & Leek (1967a) in anaesthetized sheep. Evidence for the hypothesis that each type of gastric unit innervates a distinct region of the reticulo‐rumen is strongest for types I and IV. Type I units which exhibited a bimodal pattern of discharge closely associated with reticular motility, are presumed to innervate the reticulum. Some of them, so‐called Ib because of their second burst with a long tail and their activity during the secondary cycles, are considered to activate the zone of attachment of the reticulum to the rumen. Type IV units which were active during the ruminal contractions of both primary and secondary cycles are considered to innervate the dorsal rumen. Discharges in these gastric units were observed when gastric motility was partially or totally abolished after administering autonomic blocking drugs for each unit tested (n = 25). They consisted of (i) a shortening of intervals between the onset of two successive bursts, and (ii) an increase in the duration of discharge and the number of potentials in the efferent units. As the abolition of gastric motility led to a decrease of gastric afferent input, these results suggest that the gastric centres are under a permanent inhibitory influence from the afferent drive.
THE PATTERN VISUAL EVOKED CORTICAL RESPONSE IN HUMAN AGEING
Authors: Morrison J. D. , Reilly J.
Published: December 2014

The N1, P1, N2 and P2 components of the pattern visual evoked response (PVER) have been recorded to the onset of presentation of a sinusoidal grating pattern of 3 and 8 cycles/deg in groups of young (15–34 years) and old (53–94 years) subjects. The negative components were taken to arise from striate cortex and the positive components from extrastriate cortex. For grating contrasts of 3–40%, the time‐to‐peak of the N1, P1 and N2 components, but not the P2 component, increased with age while the amplitude and rise time showed no consistent changes. Comparisons between 3 and 8 cycles/deg revealed a longer time‐to‐peak of N1 and P1 at 8 cycles/deg within the young group though not within the old group, i.e. an additional increment in the time‐to‐peak had occurred at 3 cycles/deg with ageing. This was also reflected for grating contrasts which were multiples of each individual's contrast threshold, irrespective of age. Now, the time‐to‐peak of N1, P1 and N2 was similar in young and old groups at 8 cycles/deg. At 3 cycles/deg, however, the time‐to‐peak was still longer in the old group, though the intervals between components were similar to those of the young group. This suggested the requirement for a further increment in contrast to make the time‐to‐peak similar, due to a selective loss of sensitivity in ageing within the low‐spatial‐frequency channels which are additionally sensitive to temporal modulation. Thus, it appeared that, by incrementing the stimulus contrast by the appropriate amount, the PVER of the old group could be made to resemble that of the young group. These results are consistent with the occurrence of neural changes during ageing in the retino‐geniculate pathway prior to the visual cortex.
VASOACTIVE INTESTINAL PEPTIDE CONTROL OF RENAL ADENYLATE CYCLASE: IN VITRO STUDIES OF CANINE RENAL MEMBRANES AND CULTURED CANINE RENAL EPITHELIAL (MDCK) CELLS
Authors: Griffiths N. M. , Simmons N. L. , Rugg E. L.
Published: December 2014

Vasoactive intestinal peptide (VIP) has been shown to stimulate adenylate cyclase activity in plasma membranes isolated from canine renal cortex, outer and inner medulla in vitro. Though related hormones such as glucagon also stimulate adenylate cyclase in these membrane preparations, it is likely that VIP interacts with specific VIP receptors since the VIP receptor antagonist, (4Cl‐D‐Phe6, Leu17)‐VIP, is capable of reducing the response to VIP, but not that to glucagon. Also binding of 125I‐VIP to cortical renal plasma membranes shows competition by unlabelled VIP, but not by glucagon. Strain 1 (and clone CL8lb cells derived from the established cultured dog kidney cell line, MDCK, have been shown also to respond selectively to VIP by an increase in adenylate cyclase activity and cyclic AMP accumulation in intact cells. A physiological correlate of VIP activation of adenylate cyclase has been sought by addition of VIP to reconstituted epithelial monolayers of strain 1 MDCK cells clamped in Ussing chambers. VIP addition to the basal‐lateral cell aspects generates an inward short‐circuit current that is sensitive to replacement of medium Cl− by NO3−, and to inhibition by the Cl− channel blocker, 3‐nitro‐2(3−phenylpropylamino)‐benzoic acid, consistent with VIP stimulation of transepithelial Cl− secretion.
THE EFFECT OF A CELL‐PERMEABLE DIACYLGLYCEROL ANALOGUE ON SINGLE Ca2+ (Ba2+) CHANNEL CURRENTS IN THE INSULIN‐SECRETING CELL LINE RINm5F
Authors: Velasco J. M. , Petersen O. H.
Published: December 2014

Depolarization evokes opening of single Ca2+ (Ba2+) channels of the ‘L’ type in the insulin‐secreting cell line RINm5F. Stimulation of the cells with the membrane‐permeable diacylglycerol analogue didecanoylglycerol (DC10; 5 µg/ml) markedly enhanced the proportion of time the channels spent in the open state during depolarizing voltage pulses. Similar effects have previously been demonstrated with glyceraldehyde stimulation and it therefore seems possible that carbohydrate‐evoked cellular Ca2+ uptake is mediated via protein kinase C activation.
ADULT RAT LUMBRICAL MUSCLE FIBRES ARE NOT POLYNEURONALLY INNERVATED
Authors: Chamberlain S. , Ridge R. M. A. P.
Published: December 2014

The existence of polyneuronal innervation in adult rat skeletal muscle reported by Taxt (1983) has been reinvestigated. The extent of polyneuronal innervation was measured by intracellular recording in cut muscle fibre preparations. Only fibres in which spontaneously occurring miniature end‐plate potentials were visible were tested for the presence of multiple inputs. Only one in sixty‐nine fibres penetrated was found to have more than one axonal input. High‐threshold, low‐amplitude end‐plate potentials were sought, but none was found. Thus we were unable to find any evidence for extensive polyneuronal innervation persisting in rats of 40 days of age.
DYE INJECTION CONFIRMS THE ELECTROPHYSIOLOGICAL IDENTIFICATION OF REGENERATING MUSCLE FIBRES IN THE RAT
Authors: Grubb B. D. , Harris J. B.
Published: December 2014

Microelectrodes were inserted at random into superficial fibres in rat regenerating soleus muscles. The fibres from which recordings of electrical properties were made were marked using the dye Lucifer Yellow CH and then processed for histological studies. It was shown that the microelectrodes had sampled small regenerating muscle fibres, and that random penetration does not select for any undamaged fibres that may be present.
STIMULATION OF OVINE PLACENTAL CALCIUM TRANSPORT BY PURIFIED NATURAL AND RECOMBINANT PARATHYROID HORMONE‐RELATED PROTEIN (PTHrP) PREPARATIONS
Authors: Abbas S. K. , Pickard D. W. , Care A. D. , Rodda C. P. , Martin T. J. , Heath J. A. , Caple I. W. , Hammonds R. G. , Woods W. I.
Published: December 2014

Perfusion in situ of the placenta of previously thyroparathyroidectomized fetal lambs has been used to compare the ability of various forms of parathyroid hormone‐related protein (PTHrP) to stimulate placental calcium transport. Whereas PTHrP (1–34) was without effect, PTHrP (1–141) was active but usually after a delay of up to 1 h, in common with the effect noted when using extracts of fetal parathyroid glands. In contrast, PTHrP (1–84) and PTHrP (1–108), tended to show a more rapid stimulatory action. It is suggested that post–translational processing of PTHrP (1–141) may occur as an activating step in the placenta in vivo.
ROLE OF CHLORIDE IN HYPERTONICITY‐INDUCED CONTRACTURES OF RAT SOLEUS MUSCLE
Authors: Bruton J. D.
Published: December 2014

The role of chloride in contractures induced in rat soleus muscle by mannitol‐, sucrose‐ or urea‐containing hypertonic solutions was investigated. Replacement of chloride with nitrate, sulphate or perchlorate reduced the amplitude of mannitol‐ and sucrose‐induced contractures, and the first phase of contractures induced by urea. Addition of 9‐anthracene carboxylic acid had similar effects. The presence of diazepam increased the amplitude of ‘hypertonic’ contractures. The results show that chloride is important in the development of hypertonic contractures.
THE EFFECTS OF INSULIN ON THE GROWTH RATE OF THE SHEEP FETUS DURING LATE GESTATION
Authors: Fowden Abigail L. , Hughes P. , Comline R. S.
Published: December 2014

The effects of insulin on fetal growth rates were investigated by measuring crown‐rump length (CRL) chronically in sheep fetuses before and after pancreatectomy, sham operation or pancreatectomy accompanied by insulin‐replacement treatment. Pancreatectomy of the fetus produced hypoinsulinaemia and reduced the daily and total increments in CRL by 40‐50% over the last 20‐30 days of gestation. The growth rate fell immediately after pancreatectomy and remained low throughout the rest of gestation. In contrast to the sham‐operated fetus no pre‐partum decline in the growth rate was observed in the pancreatectomized animal. The body weight, limb lengths and actual CRL at delivery were also significantly less after pancreatectomy than in the sham‐operated animals. When fetal insulin levels were maintained after pancreatectomy by exogenous insulin infusion, the daily and total increments in CRL and the body size at delivery were restored to their normal values. Raising insulin levels above normal in the pancreatectomized fetus did not lead to additional fetal growth. When the data from all the fetuses were combined irrespective of treatment, there were significant positive correlations between the plasma insulin concentration in utero and the mean daily increment in CRL after treatment and between the former value and the body weight at delivery. These observations demonstrate that insulin is a major determinant of the growth rate in utero and that it is required throughout late gestation for the normal growth and development of the sheep fetus. They also indicate that insulin deficiency is probably the primary cause of the growth retardation observed after fetal pancreatectomy.
THE EFFECTS OF ACUTE AND CHRONIC EXPOSURE TO ETHANOL ON GLUCOSE UPTAKE BY RAT JEJUNAL BRUSH‐BORDER MEMBRANE VESICLES
Authors: Al-Balool Fawzia , Debnam E. S.
Published: December 2014

Rats were pair‐fed for 28‐32 days a nutritionally adequate liquid control diet or an isocaloric diet containing ethanol (5 % v/v). Brush‐border membrane vesicles were prepared from jejunal mucosa and Na+‐dependent D‐glucose accumulation was measured using sugar concentrations of 0·2‐1·0 mmol l−1. In separate experiments the effects of acute ethanol exposure on glucose uptake by vesicles prepared from chow‐fed rats were determined. Chronic ethanol ingestion enhanced Na+‐gradient‐dependent glucose uptake. In contrast, incubation of vesicles with alcohol (4 % v/v). reduced active uptake of the sugar.
EFFECT OF THE CESSATION OF AN INFUSION OF VASOPRESSIN IN ACUTELY HYPOPHYSECTOMIZED ANAESTHETIZED DOGS
Authors: Bennett K. L. , Linden R. J.
Published: December 2014

Stimulation of left atrial receptors in dogs anaesthetized with chloralose results in a reflex diuresis and a small decrease in the plasma concentration of vasopressin. It has been suggested that this diuretic response is solely mediated by the antidiuretic hormone, vasopressin (Gauer & Henry, 1976; Ledsome, 1985). The present investigation was designed to determine how these anaesthetized dogs, which are thought to be insensitive to changes in plasma vasopressin, respond to small decreases in plasma vasopressin similar to those observed during stimulation of left atrial receptors. In the event it was shown for the first time that it is possible to obtain a water diuresis in an anaesthetized animal in response to a small fall in the concentration of plasma vasopressin. In order to produce changes in plasma vasopressin similar to those seen during stimulation of left atrial receptors the pituitary gland was removed and an intravenous infusion of arginine vasopressin was given in eleven dogs anaesthetized with chloralose; a small decrease in plasma vasopressin was then produced by replacing the vasopressin with an infusion of saline for 30 min. A decrease in the plasma concentration of 1·29 pg cm−3 from a control concentration of 1‐85 pg cm−3 resulted in a 96·7% increase in urine flow. The fall in concentration of vasopressin consequent upon stimulation of atrial receptors could, therefore, explain the water diuresis in the anaesthetized dog preparation. However, it is argued that results from the previous papers, in one of which a humorally mediated diuresis was obtained without the involvement of vasopressin, suggest that vasopressin may not be solely responsible for the diuretic response from the left atrial receptors; it may act as a ‘trigger’ which allows another (diuretic) substance to act.
ROLE OF 1,25‐(OH)2D3 DURING PREGNANCY; STUDIES WITH PIGS SUFFERING FROM PSEUDO‐ VITAMIN D‐DEFICIENCY RICKETS, TYPE I
Authors: Lachenmaier‐Currle Ute , Breves G. , Harmeyer J.
Published: December 2014

Biochemical parameters of Ca homeostasis in fetal and maternal plasma and placental transfer of Ca, Pi and vitamin D metabolites were measured during pregnancy and at parturition. Control pigs and pigs with inherited pseudo‐vitamin D‐deficiency rickets, type I (PVDR), which are devoid of renal calcitriol production, were used. Although sows with PVDR normally require treatment with massive doses of vitamin D at intervals of 4 weeks to stabilize Ca and Pi concentrations in plasma, these plasma parameters tended to normalize during the first 3 months of pregnancy when the vitamin D treatment was discontinued about 4 weeks before conception. In homozygote sows plasma calcitriol concentrations remained unphysio‐logically low and the 25OHD3 concentrations increased steadily during pregnancy reaching higher levels than those found in control sows. Despite hypocalcaemia and hypophosphataemia of the homozygote sows at term, fetal Ca and Pi concentrations were normal. This demonstrated a higher feto‐maternal concentration gradient in PVDR pigs than in control pigs. It is concluded that maintenance of Ca and Pi homeostasis of the feto‐maternal system, including active transplacental transport in pigs, is at least partly independant from calcitriol.
CHLORIDE‐BICARBONATE EXCHANGE IN ISOLATED RAT PANCREATIC ACINI
Authors: Gillespie J. I. , Hedley Claire , Greenwell J. R. , Argent B. E.
Published: December 2014

We have measured the intracellular pH (pHi) of single isolated rat pancreatic acini using the fluorescent dye dicyano‐hydroquinone (DCH). Steady‐state pHi was unaffected by either acetylcholine (10, µM), caerulein (10 nM) or secretin (1 nM), or by the anion exchange inhibitor DIDS (1 mM) and only changed by 0·32 units when extracellular pH was varied over the range from 6·8 to 8·4. However, replacing extracellular chloride with gluconate, such that the final bath chloride concentration was less than 20 mm, caused a marked alkalinization of pHi to a new steady‐state value. The rate of pHi alkalinization under these conditions was bicarbonate‐ dependent, blocked by pre‐incubation of the acini with 1 mM‐DIDS, but unaffected by removal of extracellular sodium. These observations are consistent with the presence of a Cl−‐HCO3− exchanger on rat pancreatic acinar cells. Since DIDS had no effect on steady‐state pHi the anion exchanger is unlikely to play a role in pHi regulation. However, rat pancreatic acini secrete a NaCl‐rich fluid and the Cl−‐HCO3- exchanger might function in parallel with Na+‐H+ exchangers to provide a mechanism for chloride accumulation across the basolateral membrane of the acinar cells.
Thixotropy in frog single muscle fibres
Authors: Lakie M , Robson LG
Published: December 2014

The thixotropic properties of single muscle fibres have been investigated. The effect is larger than in whole muscle and although the time course of stiffness recovery is generally similar, there is an indication that two phases may be involved. Rigor, induced chemically, eliminates thixotropic behaviour.
Direct and indirect contractile responses of the human vas deferens and actions of noradrenaline and of calcium antagonists
Authors: Smith IC , Bray M
Published: December 2014

Contractile responses of the isolated human vas deferens, obtained from vasectomy operations, were measured. Large single electrical shocks gave a twitch response with short latency (0.36 s) which was insensitive to prazosin (5 microM) or TTX (0.2 microM) and was thus identified as due to direct muscle stimulation. A train of 100 low intensity shocks gave a response with a longer latency (1.9 s) which was substantially sensitive to both prazosin and TTX; we assume this response is dominated by an indirect nerve‐induced contraction. Relaxations, presumably caused by activation of circular muscle, were recorded from regions of some preparations both by direct and indirect stimulation. Noradrenaline (10‐20 microM) induced a tonic contracture, spontaneous contractions and a large potentiation of the response to direct stimulation‐‐but not to indirect stimulation implying a strong presynaptic inhibition. Noradrenaline also speeded the relaxation from contractions. Verapamil (1‐100 microM) and nifedipine had no effect on the direct responses but verapamil (10 microM) inhibited the indirect response. Calcium removal prevented most, and 5 mM‐EDTA all, of the direct response. However, even with EDTA, noradrenaline was able to support spontaneous and stimulus‐induced contractions. Thus contraction of the vas, though sustained by external calcium, does not appear to directly depend on it.
Effective pulmonary flow, aortic flow and cardiac output: in vitro and in vivo comparisons in the dog
Authors: Franks PJ , Hooper RH , Humphries RG , Jones PR , O'Connor SE
Published: December 2014

This paper presents data on the measurement of aortic flow (Qa) using an electromagnetic flowmeter and the measurement of pulmonary blood flow (Qep) using a single‐breath technique employing freon‐22 as the soluble marker gas. The purpose was to assess the potential of a single‐breath technique (using freon) as an effective way to estimate cardiac output (Q) non‐invasively. The electromagnetic flowmeter was calibrated in vitro in an isolated heart‐aorta preparation by collection of the ejected blood volume, thereby giving an absolute calibration of the Qa measurement. Using anaesthetized beagles Qa was measured immediately preceding (Qa,mean) and during (Qa,inst) measurement of Qep. These measurements were made before and after I.V. bolus doses of nifedipine used to increase cardiac output so as to measure a range of flows. The Qa was disturbed by the respiratory manoeuvre imposed as part of the single‐breath technique, rising, falling and rising again as the lung volume was reduced, increasing with the test gas and reducing again, typically giving Qep = 1.39 +/‐ 0.13 l min−1, Qa,mean = 1.35 +/‐ 0.15 l min−1 and Qa,inst = 1.33 +/‐ 0.17 l min−1 (+/‐ S.D., n = 7 in each case). The standard deviations include interanimal variation as well as technique errors. Regression analysis of Qep on Qa,mean gave the highest correlation (r = 0.75) and the lowest coefficient of variation (11.7%), the values being 0.69 and 14.0% respectively for Qep on Qa,inst. These compare favourably with equivalent values for alternative methods reported in the literature, the strict calibration giving confidence that the single‐breath technique provides data closely related to the aortic flow found prior to the respiratory manoeuvre, i.e. the undisturbed cardiac output.
Phenylbiguanide not phenyldiguanide is used to evoke the pulmonary chemoreflex in anaesthetized rabbits
Authors: Kay IS , Armstrong DJ
Published: December 2014

The pulmonary chemoreflexes evoked by phenylbiguanide (PBG), phenyldiguanide (PDG), phenylguanidine (PG) and 5‐hydroxytryptamine (5‐HT) have been investigated in the pentobarbitone‐anaesthetized rabbit. The rank order of potency was 5‐HT greater than PBG greater than PG greater than PDG. The responses evoked by all agonists were antagonized by pre‐treatment with the selective 5‐HT3 receptor antagonist MDL 72222, suggesting that their reflex effects are mediated by 5‐HT3 receptors located on pulmonary vagal afferents. Furthermore, considering the low potency and long injection response time of PDG compared to PBG, we conclude that previous workers have used PBG and not PDG to identify non‐myelinated pulmonary vagal afferents and to evoke the pulmonary chemoreflex.
Neurones in the dorsal motor vagal nucleus of the cat with non‐myelinated axons projecting to the heart and lungs
Authors: Ford TW , Bennett JA , Kidd C , McWilliam PN
Published: December 2014

Extracellular recordings were made from ninety‐four single motoneurones in the dorsal motor vagal nucleus of chloralose‐anaesthetized or decerebrate cats. Fifty‐five neurones had axons in cardiac vagal branches and thirty‐nine had axons in pulmonary vagal branches; the conduction velocities of the axons were in the C fibre range, i.e. the axons were non‐myelinated. The neurons exhibited little or no spontaneous activity. Excitatory and inhibitory synaptic inputs were demonstrated by electrical stimulation of the vagus nerve or its branches. Twenty‐four neurones were tested by carotid sinus distension but only one was excited. Iontophoretic excitation of neurones projecting to cardiac vagal branches had no effect on heart rate. The properties of these neurones and their possible functions are discussed and contrasted with those of cardiac and pulmonary vagal motoneurones in the nucleus ambiguus.
5‐Hydroxytryptamine mediates the post‐embolic increase in respiratory rate in anaesthetized rabbits
Authors: Armstrong DJ , Kay IS
Published: December 2014

The effect of the neuronal 5‐HT3 receptor antagonist MDL 72222 has been investigated on the reflex tachypnoeic response to pulmonary embolism in pentobarbitone‐anaesthetized rabbits. Pre‐treatment with MDL 72222 (640 micrograms kg‐1, 5 min prior to embolization) significantly attenuated the reflex tachypnoeic response associated with the injection of emboli. MDL 72222 had no effect on the bradycardia associated with embolization; however, it significantly reduced the decrease in arterial blood pressure and converted the decrease in tidal volume seen in pulmonary embolism to an increase. Furthermore, MDL 72222 had no effect on the decrease in circulating platelet count associated with embolization. The data suggest that 5‐hydroxytryptamine is of primary importance in mediating the post‐embolic increase in respiratory rate seen in this model of pulmonary embolism.
The influence of bicycle exercise, with or without hand immersion in cold water, on forearm sweating in young and middle‐aged women
Authors: Cable NT , Green JH
Published: December 2014

Forearm sweat production rate (SPR) and external auditory meatal temperature (TEAM) were examined in five young and five middle‐aged women in response to intermittent exercise, on three separate occasions. The first experiment was a control study, while in the second study the left hand was immersed in cold water at the onset of sweating during each exercise bout, and in the third study this immersion was accompanied by venous occlusion of the upper left arm. TEAM increased by 0.5 degrees C during exercise with no significant differences between the groups on any occasion. The young women displayed a greater peak SPR during exercise in the control than the middle‐aged women (52.5 +/‐ 23.9 vs. 16.7 +/‐ 6.5 mg cm2 h‐1, P less than 0.001). With hand immersion, peak SPR was depressed to 14.0 +/‐ 4.6 mg cm2 h‐1 (P less than 0.001) in the young women and to 13.1 +/‐ 4.5 mg cm2 h‐1 in the middle‐aged (P less than 0.05). With hand immersion and venous occlusion the peak SPR in young women increased (43.0 +/‐ 9.2 mg cm2 h‐1). In the older women SPR was 14.9 +/‐ 6.1 mg cm2 h‐1, which was not different from either control or cold‐immersed values. Thus, forearm SPR during low‐intensity intermittent exercise is greater in young compared with middle‐aged women, despite similar changes in TEAM. The response to hand immersion in cold water was more marked in the young subjects.
Catecholamine release from bovine chromaffin cells: the role of sodium‐calcium exchange in ouabain‐evoked release
Authors: Torok TL , Powis DA
Published: December 2014

Spontaneous catecholamine (CA) release from bovine chromaffin cells maintained in primary tissue culture has been measured after pre‐loading the cells with [3H]noradrenaline. Ouabain inhibited 86Rb+ uptake and increased 3H release in a concentration‐dependent manner during a 60 min incubation period. Low external Na+ (5 mM: Li+ substitution) also increased 3H release. Whereas the 3H‐releasing action of ouabain was maintained, the Li(+)‐evoked release decreased with time. The effects of both ouabain and low Na+ solution on 3H release were completely inhibited by removal of Ca2+ from the external medium even though in Ca2(+)‐free solution ouabain further inhibited 86Rb+ uptake into the cells. Readmission of Ca2+ to Na(+)‐loaded cells (10‐4 M‐ouabain in Ca2(+)‐free‐1 mM‐EGTA solution for 60 min) markedly increased the release of 3H. In the additional presence of diphenylhydantoin (DPH, 10‐4 M) 3H release was significantly less on Ca2+ readmission. The 3H release from Na(+)‐loaded cells was proportional to the concentration of Ca2+ readmitted. The 3H release was further increased from Na(+)‐loaded cells in response to Ca2+ readmission when [Na+]o was lowered from 149 to 5 mM (Li+, choline+, Tris+ or sucrose substitution) though Li+ was less effective than the other Na+ substitutes. Potassium removal from the external medium significantly inhibited the 3H release evoked by Ca2+ readmission to Na(+)‐loaded cells, even when [Ca2+]o was greater than normal (7.5 mM) or if Ca2+ was readmitted in low [Na+]o solution. Rb+, Cs+ or Li+ could substitute for K+ with the order of potency: Rb+ greater than or equal to K+ greater than Cs+ greater than Li+. A slight increase of external K+ (10.8 mM) potentiated the 3H release from Na(+)‐loaded cells on Ca2+ readmission, but a higher concentration of K+ (149.4 mM) had the opposite action. The data is consistent with the hypothesis that ouabain‐evoked CA release from bovine chromaffin cells is, in part, a consequence of an internal Na(+)‐dependent Ca2+ influx. The evidence also suggests that there is Na(+)‐Ca2+ competition at the external arm of the exchanger together with a monovalent cation activation site.
Ammonia absorption from the isolated reticulo‐rumen of sheep
Authors: Bodeker D , Winkler A , Holler H
Published: December 2014

In fistulated sheep (50‐60 kg live weight) the absorption of ammonia from the reticulo‐rumen in vivo was studied applying the technique of the temporarily isolated and washed reticulo‐rumen. It was found that, at ammonia concentrations between 3 and 18 mM, ammonia efflux and ammonia net absorption were linearly related to the ammonia concentration in the artificial rumen fluid, whereas influx of ammonia nitrogen from endogenous sources remained almost constant. When the concentration of unionized NH3 was changed at the ratio 1:10:76 by varying the pH from 5.8 to 6.8 and 7.7, ammonia net absorption did not reflect the concentration ratio of unionized NH3, indicating either flux of NH4+ ions or titration of NH4+ to NH3 at the absorptive surface. In the experiments with buffer solutions without ammonium salts and extended over 2 h, ammonia concentrations in the artificial rumen fluid increased due to endogenous nitrogen influx and reached levels far beyond the expected plateau concentration of about 2 mM. Labelling of the N pool in the isolated organ by 15N showed that ammonia efflux had almost ceased in these experiments. It is argued that as yet unidentified changes have taken place in the artificial rumen fluid during the experiment, but there is some reason to believe that volatile fatty acid (VFA) absorption was affecting ammonia absorption.
Abnormal expression of dipeptidylpeptidase IV activity in enterocyte brush‐border membranes of children suffering from coeliac disease
Authors: Smith MW , Phillips AD
Published: December 2014

Dipeptidylpeptidase IV (DPP IV) activity has been shown cytochemically to decrease significantly in enterocytes of children suffering from coeliac disease. This decrease is due to a halving of the time available for enterocytes to express DPP IV in their brush‐border membranes during development. This effect is compared with previous results showing coeliac disease to inhibit disaccharidase activities selectively.
The relationship between left atrial pressure and atrial receptor discharge in dogs and cats with different body weights
Authors: Hicks MN , Linden RJ , Mary DA
Published: December 2014

The diuretic response to distension of a large balloon in the left atrium and the increase in discharge of atrial receptors for a given increment in left atrial pressure have been found to be greater in dogs with a high blood volume than in dogs with a low blood volume. To determine whether atrial size may influence atrial receptor discharge, a group of cats and two groups of dogs with different body weights were examined under anaesthesia with alpha‐chloralose. The relationship between atrial receptor discharge and left atrial pressure was determined in twenty‐six fibres from seven cats, thirty‐seven fibres from eight small dogs weighing less than 15 kg and twenty‐five fibres from five large dogs weighing more than 25 kg. The slope of the relationship between the increase in atrial receptor activity and increments in left atrial pressure was shown to be significantly greater in the large dogs than in the small dogs, and the slopes in dogs were greater than in cats. The size of the atria was greater in larger dogs than small, and both those groups had atria larger than those of the cats. These findings indicate that the response of an increase in atrial receptor discharge to the same increment in left atrial pressure was greater in large animals than small and that this difference is possibly due to the different atrial size.
Mechanism of action of magnesium on acetylcholine‐evoked secretory responses in isolated rat pancreas
Authors: Francis LP , Lennard R , Singh J
Published: December 2014

This study investigates the effects of magnesium (Mg2+) on acetylcholine (ACh)‐evoked secretory responses and calcium (Ca2+) mobilization in the isolated rat pancreas. ACh induced marked dose‐dependent increases in total protein output and amylase release from superfused pancreatic segments in zero, normal (1 x 1 mM) and elevated (10 mM) extracellular Mg2+. Elevated Mg2+ attenuated the ACh‐evoked secretory responses compared to zero and normal Mg2+. In the absence of extracellular Ca2+, but presence of 1 mM‐EGTA (ethylene glycol bis(beta‐aminoethylether)‐N,N,N',N''‐tetraacetic acid), ACh elicited a small transient release of protein from pancreatic segments compared to a larger and more sustained secretion in the absence of both Ca2+ and Mg2+. Incubation of pancreatic segments with 45Ca2+ resulted in time‐dependent uptake with maximum influx of 45Ca2+ occurring after 20 min of incubation period. ACh stimulated markedly the 45Ca2+ uptake compared to control tissues. In elevated extracellular Mg2+ the ACh‐induced 45Ca2+ influx was significantly (P less than 0.001) reduced compared to zero and normal Mg2+. ACh also evoked dose‐dependent increases in cytosolic free Ca2+ concentrations ([Ca2+]i) in pancreatic acinar cells loaded with the fluorescent dye Fura‐2 AM. In elevated Mg2+ the ACh‐induced cytosolic [Ca2+]i was significantly (P less than 0.001) reduced compared to zero and normal Mg2+. These results indicate that Mg2+ can influence ACh‐evoked secretory responses possibly by controlling both Ca2+ influx and release in pancreatic acinar cells.
Fetal magnesium homeostasis in the sheep
Authors: Barri M , Abbas SK , Pickard DW , Hammonds RG , Wood WI , Caple IW , Martin TJ , Care AD
Published: December 2014

The fetal plasma magnesium concentration exceeds that of the mother but the difference is small compared to that of ionized calcium concentration. Although not fully independent of changes in maternal magnesaemia, fetal magnesaemia showed a high degree of autonomy during both hypermagnesaemic and hypomagnesaemic changes induced in the ewe. As with calcium, the placental gradient is reversed after fetal thyroparathyroidectomy (TXPTX) with thyroxine replacement. During perfusion in situ of the placenta from such TXPTX fetuses isolated from the fetus itself, a stable positive placental gradient of magnesium concentration could be re‐established between the perfusing blood and the maternal circulation. As with calcium, this gradient could be increased by fetal calf parathyroid extract, parathyroid hormone‐related protein (PTHrP 1‐141), PTHrP (1‐84) but not by PTHrP (1‐34). It was concluded that a mid‐molecule portion of PTHrP can stimulate a putative placental pump which is responsible for the gradients of both calcium ions and magnesium across the ovine placenta.
The effect of a hindgut fermentation on urea metabolism in sheep nourished by intragastric infusion
Authors: Oncuer A , Milne JS , Whitelaw FG
Published: December 2014

Four female sheep nourished wholly by infusions of volatile fatty acids, buffer and minerals into the rumen and casein into the abomasum were given, in addition, infusions of fermentable carbohydrates into the terminal ileum. The ileal infusions consisted of (1) water alone, (2) 25 g starch + 50 g cellulose, and (3) 50 g starch + 50 g cellulose. Measurement of nutrient digestibility and nitrogen retention were made over 5 days and the kinetics of urea metabolism were measured over 24 h by means of a single injection of [14C]urea. Endogenous urinary nitrogen excretion was measured over a subsequent 5 days when casein was omitted from the infusion mixtures. Increases in hindgut fermentation resulted in a significant increase in faecal nitrogen excretion (P less than 0.01) and a corresponding reduction in urinary urea nitrogen excretion (P less than 0.05). The ileal infusions did not significantly affect urea irreversible loss rate or urea pool size and were also without effect on plasma urea or rumen ammonia concentrations. Urea degradation in the gastrointestinal tract increased by about 2 g/day in progressing from lowest to highest level of hindgut infusion but differences between treatments were not statistically significant. Endogenous urinary nitrogen excretion was not affected by hindgut fermentation and averaged 206 mg N/(kg0.75 day) over the three treatment groups. Faecal nitrogen excretion however increased progressively with increase in ileal infusions (P less than 0.05) and was similar to that seen when nitrogen input was adequate. It is concluded that changes in hindgut fermentation can alter the partition of nitrogen excretion between faeces and urine but the quantities involved are small relative to the total exchange of urea across the digestive tract. The rumen appears to be an important site of urea degradation even when microbial fermentation is absent.
The effect of surgical anaesthesia on antral motility in the ferret
Authors: Grundy D
Published: December 2014

Gastric motility was recorded from ferrets chronically prepared with an antral strain gauge. In fasted animals, antral motility showed cycles of activity and quiescence typical of the migrating motor complex (MMC) with a period of 44.7 +/‐ 6.1 min (n = 4). Anaesthesia with pentobarbitone sodium (50 mg/kg) disrupted this interdigestive motor pattern which returned along with recovery from anaesthesia. The first cycle of antral motility occurred 119 +/‐ 23.9 min after the onset of anaesthesia and thereafter continued to cycle at the pre‐anaesthetic interval. The recovery was unaffected by treatment with guanethidine (2 mg/kg) or naloxone (1.25 mg/kg) but all motility was prevented with atropine (100 micrograms/kg). Following chronic truncal vagotomy cycles of antral activity persisted during pentobarbitone anaesthesia. With prolonged anaesthesia with ethyl carbamate (1300 mg/kg) there was no return to antral cycling but instead continuous low amplitude regular contractions were present. The lack of MMC activity in acute experiments is thus a consequence of the anaesthesia and not the surgical interventions.
Dissociation between plasma concentrations of thyroxine and insulin‐like growth factor‐I
Authors: Dauncey MJ , Morovat A , Rudd BT , Shakespear RA
Published: December 2014

The relation between plasma concentrations of thyroxine (T4) and insulin‐like growth factor‐I (IGF‐I) has been examined in young, growing pigs under controlled conditions of energy intake. Compared with euthyroid controls, plasma levels of IGF‐I were significantly elevated (P less than 0.005) both in hypothyroid animals on the same food intake and in hyperthyroid animals on double the food intake. There was however no increase in IGF‐I in a hyperthyroid group on the control level of intake. Contrary to previous reports in which energy intake was not controlled, it is concluded that there is no simple correlation between plasma concentrations of T4 and IGF‐I.
Dietary salt‐loading attenuates endothelium‐dependent relaxation in response to histamine but not to acetylcholine in rat aortic rings
Authors: Obiefuna PC , Sofola OA , Ebeigbe AB
Published: December 2014

Endothelium‐dependent relaxation in response to histamine and ACh has been studied on precontracted aortic rings from control and salt‐loaded Sprague‐Dawley rats. Both ACh and histamine caused relaxation of the noradrenaline‐induced precontraction only in the presence of the endothelium. The relaxation response to ACh in rings from control and salt‐loaded rats did not differ significantly whereas histamine‐induced relaxation was significantly attenuated in aortae from salt‐loaded rats. The results suggest that salt‐induced hypertension is associated with impairment of endothelium‐dependent relaxation to histamine but not to ACh.
The length, width and volume of isolated rat and ferret ventricular myocytes during twitch contractions and changes in osmotic strength
Authors: Boyett MR , Frampton JE , Kirby MS
Published: December 2014

The length and width of rat and ferret ventricular myocytes have been measured using a linear photodiode array; the volume of the myocytes has been calculated based on the assumption that the cells were elliptical cylinders. During a twitch contraction, there was a decrease in cell length, but no significant change in the calculated cell volume, because the cells increased in width. Inotropic interventions not only resulted in a greater shortening of the cell during each contraction, but also a greater increase in cell width. Changes in cell length, width and volume on changing the osmotic strength of the bathing solution have also been investigated. The increase in volume in hypotonic solution, and the decrease in hypertonic solution, were the result of changes in the cell width; there were no significant changes in the cell length. It is concluded from the latter experiment that the lateral compliance of a cell is greater than its longitudinal compliance, and, therefore, during a twitch contraction, when the cell shortens, the displacement of the cell contents from the two ends of the cell and the expansion of the cell laterally will not act as a large force to oppose shortening.