bluuebunny/crossref_metadata_2025 huggingface dataset:
OVINE FETAL RESPONSE TO WATER DEPRIVATION: ASPECTS ON THE ROLE OF VASOPRESSIN
Authors: Herin Peter , Kim Jin K. , Schrier Robert W. , Meschia Giacomo , Battaglia Frederick C.
Published: December 2014

The effect of maternal hyperosmolality as created by an acute mannitol infusion was evaluated in eight chronic sheep preparations. Fetal osmotic and haemodynamic responses were compared to those achieved during an arginine vasopressin (AVP) infusion into the fetus (approximately 400 µU/(min kg)). To assess the AVP sensitivity of the fetal kidney the urine osmolality was determined. The activity of adenylate cyclase was measured in placental cotyledons as an indicator of AVP receptors affecting water permeability. The maternal mannitol infusion induced an increase in fetal serum AVP levels from 1·18 ± 0·25 up to 13·76 ± 2·1 pg/ml. During the fetal AVP infusion the AVP levels were approximately 22 pg/ml, somewhat higher when given concurrently with a mannitol infusion to the ewe (peak value: 26·13 ± 2·80 pg/ml). Fetal heart rate increased significantly during maternal hyperosmolality while this effect was blunted by exogenous AVP given to the fetus. The AVP infusion did not affect fetal or maternal serum osmolality. During the mannitol infusion fetal serum osmolality increased to peak values which were not significantly different whether or not AVP was infused into the fetus (from 298·0 ± 0·85 to 309·0 ± 0·90, and from 297·7 ± 1·47 to 307·9 ± 0·90 mosmol/kg, respectively). Similarly, there were no differences in the effect of mannitol infusion upon fetal urine osmolality with or without AVP infusion (increments: + 149·7 ± 34·12 and + 148·7 ± 31·30 mosmol/kg, respectively). Adenylate cyclase activity in the placenta was unchanged before and after AVP stimulation. The data suggest an unresponsiveness of placental water permeability to fetal AVP infusion. We also conclude that a maximal urine osmolality was reached already at AVP levels obtained after an osmotic maternal load whereas at AVP levels more than twice as high the cardiovascular effects were still AVP dose‐dependent.
THE EFFECT OF DIDS ON FLUID REABSORPTION FROM THE PROXIMAL CONVOLUTED TUBULE OF THE RAT: DEPENDENCE ON THE PRESENCE OF BICARBONATE
Authors: White S. J. , Greenwood S. L. , Green R.
Published: December 2014

The effects of the anion transport inhibitor DIDS (4,4'‐diisothiocyano‐stilbene‐2,2'‐ disulphonate) on fluid reabsorption by the rat proximal convoluted tubule were investigated by the stationary microperfusion (split‐drop) method. Addition of 10-5 mol l−1 DIDS to luminal and capillary perfusates in the presence of peritubular bicarbonate (25 mmol l−1) increased the reabsorptive half‐time (t½) from 35·1 ± 4·5 to 57·0 ± 6·2 s, corresponding to a decrease in fluid reabsorption (Jv) from 1·33 ± 0·06 to 0·89 ± 0·09 nl min−1 mm−1. Omission of bicarbonate per se from the peritubular capillaries reduced Jv to 0·41 ± 0·03 nl min−1 mm−1 and this reabsorptive flux was completely inhibited by the addition of 2 mmol l−1 NaCN to both the luminal and peritubular perfusates. In the absence of bicarbonate, the addition of DIDS at either 10−4 or 10−5 mol l−1 to both lumen and capillary perfusates had no significant effect on either t½ or Jv. These results show that the inhibitory action of DIDS on fluid reabsorption is dependent on the presence of bicarbonate. However, the proximal tubule also reabsorbs water in the absence of bicarbonate by a mechanism that is dependent on cellular metabolism, but is insensitive to DIDS at the concentrations used in this study.
OPTICAL MEASUREMENTS OF INTRACELLULAR pH IN INTACT ISOLATED MUSCLE FIBRES AND MUSCLE GROWTH CONES IN CULTURE
Authors: Gillespie J. I. , Ribchester R. R.
Published: December 2014

Intracellular pH (pHi) has been measured in intact muscle fibres isolated from the mouse flexor digitorum brevis muscle, using the fluorescence of dicyanohydroquinone as an indicator. The pHi in fibres cultured from 1 to 14 days ranged from 7·0 to 8·1. With time in culture, isolated fibres developed growth cone‐like extensions from their ends. These ‘myocones’ were significantly more alkaline by 0·1‐0·2 pH units than the parent fibre. Cultured fibres regulated pHi in response to acid loading with an NH4Cl pulse with recovery rate constants of up to 0·8 pH units/min.
THE EFFECT OF LOW MUCOSAL pH ON SODIUM AND CHLORIDE MOVEMENT ACROSS THE ISOLATED RUMEN MUCOSA OF SHEEP
Authors: Gaebel G. , Martens H. , Bell M.
Published: December 2014

Isolated sheets of sheep rumen mucosa were studied in vitro by using the Ussing chamber technique. The pH of the mucosal solution was altered by adding HCl. Using 22Na and 36Cl unidirectional fluxes of sodium and chloride were measured across the short‐circuited and voltage‐clamped rumen mucosa at mucosal pH 7·4 and 5·5. Lowering mucosal pH to 5·5 caused a rapid decline in the short‐circuit current (Isc). The conductance (Gt) increased about 10 min after the drop in Isc. At pH 5·5, mucosal‐to‐serosal movement of Na+ and Cl‐ was decreased thus leading to a decreased net transport. These alterations were seen 30 min after mucosal acidification. They were intensified 120 min thereafter. Further studies showed that a clamped transmural potential difference (20 mV) influenced Na+ and Cl‐ transport only slightly more in acidified epithelia. Light and electron microscopy showed a swelling of the cells and especially of their mitochondria after acid exposure. These data indicate that lowering mucosal pH causes alterations in transepithelial Na+ and Cl‐ transport. We suggest a predominant effect on cellular transport mechanisms.
ESTIMATION OF THE PROJECTION FREQUENCIES OF SINGLE INHIBITORY INTERNEURONES TO MOTONEURONES IN THE CAT SPINAL CORD
Authors: Harrison P. J. , Riddell J. S.
Published: December 2014

An estimate has been deduced for the percentage of motoneurones in the lumbosacral spinal cord inhibited by single interneurones mediating group I non‐reciprocal inhibition. The estimate is derived from data for the percentage of interneurones discharged, and percentage of motoneurones inhibited, by the same group I afferents. These experimental data are compared with theoretical curves for the percentage of motoneurones in which inhibition would be expected following discharges in various numbers of interneurones, for different values of projection frequency. It is estimated that each interneurone projects to less than 5% of target motoneurones.
CONTROL OF GASTRIC EMPTYING IN THE PIG: INFLUENCE OF DUODENAL INFUSIONS OF GLUCOSE AND EMULSIFIED FAT
Authors: Gregory P. C. , McFadyen M. , Rayner D. V.
Published: December 2014

The influence of duodenal infusions of emulsified fat (20% Intralipid) and glucose (40%, w/v) on gastric emptying during the feeding period was studied in five pigs. Gastric emptying was measured by evacuation of gastric contents immediately the pigs had finished feeding in animals fitted with a gastric cannula and a duodenal catheter and fed a solid meal mixed with water. Infusions at various rates of Intralipid and glucose given either from the start of feeding or up to 30 min prior to feeding until the pigs had finished feeding inhibited gastric emptying of dry matter (DM) and liquids in a qualitatively similar but quantitatively different manner. With both infusions the rates of gastric emptying of DM and liquids were progressively reduced with pre‐infusions of 0, 10, 20 and 30 min. Slow infusions of Intralipid (2·3 and 4·6 ml/min) inhibited gastric emptying of DM and liquids to a greater extent than equicaloric infusions of glucose (3 and 6 ml/min), but faster infusions of Intralipid (6 ml/min) inhibited emptying less than equicaloric infusions of glucose (8 ml/min). When the DM emptied was converted into digestible energy (DE) there was no evidence that Intralipid inhibited gastric emptying calorically. In contrast the results showed that there was caloric regulation of gastric emptying with infusions of glucose begun at the start of feeding. There was a linear reduction in the rate of DM emptied with increase in the rate of glucose infusion (2‐8 ml/min) of 64·5 ± 4·8 g DM per MJ/min glucose infused, i.e. equivalent to a reduction of 0·98 ± 0·07 kJ/min DE emptied for each kJ/min glucose infused. These changes in gastric emptying with duodenal infusions of glucose and Intralipid mirror the changes previously observed in food intake following similar infusions, and the results are therefore compatible with control of gastric emptying being an important site of short‐term regulation of food intake in the pig.
THE CONTROL OF POTASSIUM (86Rb+) EFFLUX IN THE ISOLATED HUMAN SWEAT GLAND
Authors: Bovell Douglas L. , Elder Hugh Y. , Jenkinson David McEwan , Wilson Stuart M.
Published: December 2014

Sweat glands, isolated from strips of human skin and pre‐loaded with 86Rb+, a marker of potassium transport, were superfused with physiological saline and rate constants for 86Rb+ efflux calculated. The rate of efflux during superfusion with Ca2+−free saline was lower than that measured in the presence of calcium (2·56 mM). Acetylcholine increased the rate of 86Rb+ efflux and this response could be resolved into two components: an initial transient phase which was Ca2+−independent and a slowly declining Ca2+−dependent phase. Adrenaline only caused a Ca2+−dependent increase in efflux. It is suggested that the potassium permeability of the secretory cells increases during activity.
THE EFFECTS OF CHANGES IN LEFT VENTRICULAR PRESSURE ON RESPIRATORY ACTIVITY IN ANAESTHETIZED DOGS
Authors: Crisp A. J. , Tutt S. M. , McGregor K. H. , Hainsworth R.
Published: December 2014

This study was undertaken to determine whether moderate increases in left ventricular systolic pressure in anaesthetized dogs result in changes in respiratory activity. Left ventricular systolic pressure was changed using a preparation in which the applied pressure did not distend the aortic arch and in which left atrial and carotid sinus pressures were held constant. The systemic circulation was perfused at constant flow and respiratory activity was assessed from the phrenic electroneurogram. Increases in aortic root and left ventricular systolic pressures resulted in a decrease in arterial perfusion pressure, no significant change in heart rate and a decrease in phrenic nerve activity. These responses differed from those to changes in carotid sinus pressure, which were decreases in perfusion pressure and heart rate but no significant steady‐state change in phrenic activity. Responses to changes in ventricular pressure were obtained to each small step between 16 and 28 kPa (120 and 210 mmHg). Following cervical vagotomy, changes in ventricular pressure resulted in neither respiratory nor vascular responses. These results indicate that left ventricular receptors may play a role in the control of respiration.
STUDIES ON THE CIRCULATION IN NORMOTENSIVE FEBRILE PATIENTS
Authors: Weinberg J. R. , Innes J. A. , Thomas K. , Tooke J. E. , Guz A.
Published: December 2014

Normotensive febrile patients were studied in a constant‐temperature room during stable fever, They were restudied later while afebrile and after heating the trunk. Finger and forearm blood flow were measured by venous occlusion plethysmography. The ability of cutaneous vessels to constrict on dependence of the limb was measured by laser Doppler flowmetry. The volume, velocity and acceleration of the blood in the ascending aorta were determined using pulsed Doppler ultrasound with a probe in the supra‐sternal notch; measurements of systolic time intervals were made. While febrile, patients had a tachycardia and shortened systolic ejection times; cardiac output and total peripheral resistance were unchanged on average as compared to when afebrile. There was no evidence of any change in left ventricular contractility during fever from measurements of the peak velocity, maximum acceleration of blood or from the systolic time intervals. As compared to when heated, febrile patients had a skin blood flow that was relatively reduced for their skin temperature and had preservation of postural vasoconstriction.
VASOPRESSIN V1‐RECEPTOR BLOCKADE LOWERS ARTERIAL BLOOD PRESSURE IN YOUNG CONSCIOUS LONG‐EVANS RATS
Authors: Obika L. F. O. , Laycock J. F.
Published: December 2014

Young, conscious Long‐Evans rats had significantly higher basal mean arterial blood pressure than age‐matched Brattleboro rats with hereditary hypothalamic diabetes insipidus, and an intravenous injection of a specific vasopressin V1‐receptor blocker significantly decreased the mean arterial pressure in the former animals only. The basal heart rate, which was significantly higher in the Brattleboro rats than in the Long‐Evans rats, was unaffected by the vasopressin antagonist in either strain. These results indicate that vasopressin may be important in maintaining normal blood pressure in young rats.
A COMPARISON OF THE EFFECTS OF ORAL AND INTRAVENOUS GLUCOSE ADMINISTRATION ON RENAL CALCIUM EXCRETION IN THE RAT
Authors: Singh H. J. , Garland H. O.
Published: December 2014

Standard renal clearance techniques were used to compare the effects of oral and intravenous glucose administration on renal calcium handling in the rat. A significant (P 〈 0·01) calciuric response was evident in both groups following glucose loading. The maximal effect in the oral group, however, was slightly delayed. The increased urinary calcium excretion in both groups was the result of a reduction in fractional calcium reabsorption. The filtered load of calcium was unchanged. The response was also independent of changes in urinary sodium output, urine flow rate and glycosuria. The role of insulin in the response remains unclear.
ENHANCED DEVELOPMENT OF STRIATED MYOFIBRILS IN XENOPUS MYOBLASTS CULTURED IN AN APPLIED ELECTRIC FIELD
Authors: Dover P. J. , McCaig C. D.
Published: December 2014

Cultured myoblasts from Xenopus laevis differentiating in a DC electric field (∼100 mV/mm) had more microfilaments, more striated myofibrils and an increased Z‐disc diameter than myoblasts in control cultures.
RESISTANCE TO ACID OF CANINE KIDNEY (MDCK) AND HUMAN COLONIC (T84) AND ILEO‐CAECAL (HCT–8) ADENO‐CARCINOMA EPITHELIAL CELL MONOLAYERS IN VITRO
Authors: Chan A. B. , Allen C. N. , Simmons N. L. , Hirst B. H. , Parsons M. E.
Published: December 2014

Monolayers of canine kidney (MDCK) and human lower intestinal (T84 and HCT‐8) cell lines generated significant transepithelial electrical resistance (700–5000 Ω cm2). Electrical integrity was maintained upon acidification of the apical and/or basolateral surfaces to pH 3·0, and this was associated with increased transepithelial electrical resistance, and generation of a potential difference at pH 〈 4·5. These results indicate that resistance to acid is a general phenomenon of epithelial layers, and that monolayers of epithelial cells, including those of human origin, are a homogeneous and simple model for studying epithelial barrier function in vitro.
THE RAT DISTAL ILEUM HAS A REDUCED ABSORPTIVE AND SECRETORY CAPACITY COMPARED WITH PROXIMAL ILEUM ‐ IS IT TO FACILITATE ITS CHEMOSENSING FUNCTION?
Authors: Young A. , Levin R. J.
Published: December 2014

Compared with the proximal ileum, the distal ileum in rat has a greatly reduced capacity for electrogenic ion secretion induced by secretagogues and for electrogenic, sodium‐linked glucose transfer assessed in vitro. Similarly, in vivo, there is a great reduction in distal ileal basal fluid absorption and secretagogue‐activated fluid secretion compared with proximal ileal values. This reduced absorptive and secretory capacity of the distal ileum would allow minimal changes in the concentrations of the luminal contents, facilitating its putative role as final chemosensor of the luminal contents of the small intestine.
THE DISTRIBUTION OF β‐ADRENOCEPTORS IN HUMAN CERVIX
Authors: Whitaker E. M. , Nimmo A. J. , Morrison J. F. B. , Griffin N. R. , Wells M.
Published: December 2014

The distribution of βadrenoceptors in sections of human cervix taken at the proliferative phase of the menstrual cycle was studied using light‐microscopic autoradiography. The radioligand [125I]iodo‐cyanopindolol (125ICYP) was used to identify specific binding sites. Moderate density of labelling by 125ICYP was seen over smooth muscle and blood vessels. The most intense labelling, however, was seen over glands and surface columnar epithelium. The association of β‐adrenoceptors with glands and surface columnar epithelium suggests a possible adrenergic regulation of secretory function in the cervix.
METABOLISM AND INACTIVATION OF GASTRIN RELEASING PEPTIDE BY ENDOPEPTIDASE‐24.11 IN THE DOG
Authors: Bunnett N. W. , Turner A. J. , Debas H. T.
Published: December 2014

The purpose of this investigation was to examine the metabolism and inactivation of gastrin releasing peptide 10 (GRP10) by endopeptidase‐24.11 prepared from the stomach wall. GRP10 was metabolized in vitro by gastric endopeptidase‐24.11. The metabolites were purified by high‐pressure liquid chromatography and identified as (1‐8) GRP10 and (9‐10) GRP10 by amino acid analysis, indicating hydrolysis of the His8‐Leu9 bond. The intravenous administration of GRP10 to conscious dogs stimulated gastrin release, gastric acid secretion, pancreatic protein secretion and pancreatic bicarbonate secretion. Incubation of GRP10 with endopeptidase‐24.11 significantly diminished the biological activity of the digests compared to control digests containing heat‐inactivated enzyme. This effect was abolished by the enzyme inhibitor phosphoramidon. It is concluded that endopeptidase‐24.11 from the stomach metabolizes and inactivates GRP10.
THE INFLUENCE OF LEFT VENTRICULAR PRESSURE ON THE VASCULAR RESPONSES TO CHANGES IN CAROTID SINUS PRESSURE IN ANAESTHETIZED DOGS
Authors: Vukasovic J. L. , Tutt S. M. , Crisp A. J. , Hainsworth R.
Published: December 2014

The aim of this study was to determine whether the degree of stimulation of left ventricular receptors influenced the sensitivity of the carotid sinus baroreceptor reflex. In anaesthetized dogs, the stimulus to left ventricular receptors was changed by changing aortic root and hence ventricular systolic pressure, using a preparation in which the applied pressure did not distend the aortic arch and in which left atrial pressure was controlled. A large step increase in either carotid or left ventricular pressure resulted in vasodilatation both in a perfused hindlimb and in the remainder of the systemic circulation and resulted in a reduction in the response to a change in pressure in the other area. The stimulus‐response curves, relating limb and systemic perfusion pressures to small step changes in carotid sinus pressure, were displaced downwards at high left ventricular pressures. However, the curves remained parallel indicating the absence of an interactive effect. These results indicate that the vascular responses to changes in carotid and ventricular pressures show simple additive summation.
CO‐CULTURE OF DISSOCIATED HIPPOCAMPAL AND SYMPATHETIC CELLS FROM THE NEONATAL RAT
Authors: Johnson Mark D. , Potter David D.
Published: December 2014

When sympathetic neurones, obtained from superior cervical ganglia of postnatal rats, were grown in microcultures with cells of the postnatal hippocampal formation for 6‐44 days, about 70% of the sympathetic neurones formed functional synapses on themselves or a neighbouring sympathetic neurone. In all forty‐four cases in which hexamethonium (0·5‐1 mM) was applied it strongly or completely blocked the synaptic interaction. This indicates that the synaptic interaction was cholinergic and raises the possibility that the denervated cells of the hippocampal formation induced the cholinergic function in the co‐cultured sympathetic neurones.
A COMPARISON BETWEEN CHANGES IN RAT PAROTID PROTEIN COMPOSITION 1 AND 12 WEEKS FOLLOWING SURGICAL SYMPATHECTOMY
Authors: Proctor G. B. , Asking B.
Published: December 2014

One week after surgical sympathectomy the amylase and protein concentrations of parotid glands were increased by 250 and 51% respectively. Whilst these concentration changes had partly returned to normal after 12 weeks, major differences still remained in the protein composition of parotid glands. Anion‐exchahge chromatography showed that proline‐rich pr6teins were progressively reduced and that the relative proportions of other proteins changed variably. These results indicate that normal synthesis of proline‐rich proteins requires on‐going stimulation of the cells via the sympathetic nerve. In the absence of sympathetic nerve activity there was initially an increased synthesis of amylase which theh returned towards normal.
THE MODULATION OF FORCE IN ISOLATED RAT EGTATREATED ANOCOCCYGEUS MUSCLE BY PHOSPHATE, CYCLIC AMP AND NORADRENALINE
Authors: Crichton C. A. , SMITH G. L. , Miller D. J. , McGrath J. C.
Published: December 2014

Saponin treatment is commonly used to permeabilize the surface membrane of muscle cells. Incubation of isolated rat anococcygeus for 4 h in a low Ca2+ and low Mg2+ solution resulted in the muscle responding to Ca2+, phosphate and cyclic AMP in a similar way to a saponin‐treated muscle. However, unlike saponin‐treated preparations, the maximal calcium‐activated force was stable for many hours and the addition of noradrenaline caused contracture. These properties would permit this preparation to be used to study aspects of receptor‐mediated excitation‐contraction coupling.
A COMPARISON OF CONTRACTILE FUNCTION IN LARGE AND SMALL PULMONARY ARTERIAL VESSELS OF THE RAT
Authors: Leach Richard M. , Twort Charles H. C. , Cameron Ian R. , Ward Jeremy P. T.
Published: December 2014

The contractile function of rat pulmonary arterial vessels, ranging in internal diameter from 100 to 2000 µm, was studied in vitro using a small vessel myograph. It was found that vessels with a diameter of 200‐400 µm produced considerably more force for a given intervention than those either smaller (〈100‐2000 µm) or larger (400‐2000 µm). It is suggested that these vessels may play an important role in the generation of pulmonary vascular resistance.
THE AUTORADIOGRAPHIC LOCALIZATION OF CALCITONIN GENE‐RELATED PEPTIDE AND SUBSTANCE P RECEPTORS IN HUMAN FALLOPIAN TUBE
Authors: Nimmo Alan J. , Whitaker Elaine M. , Carstairs Jill R. , Morrison John F. B.
Published: December 2014

The binding of [125I] humancalcitonin gene‐related peptide (hCGRP) and [125I]Bolton‐Hunter‐labelled substance P (BH‐SP) to human fallopian tube tissue sections was characterized and the respective binding sites were localized by light‐microscopic autoradiography. The hCGRP binding sites were associated with the muscularis, lamina propria and vascular smooth muscle, the latter being the most intensely labelled. BH‐SP binding sites were associated only with blood vessels. This labelling was intense, and appeared to be restricted to the vascular endothelium. These results suggest that calcitonin gene‐related peptide and substance P may act together to regulate local blood flow and plasma extravasation.
TOLBUTAMIDE REVERSES HYPOXIC PULMONARY VASOCONSTRICTION IN ISOLATED RAT LUNGS
Authors: Robertson B. E. , Paterson D. J. , Peers C. , Nye P. C. G.
Published: December 2014

We have investigated the effects of tolbutamide on the hypoxic vasoconstriction of isolated, perfused rat lungs. We did this because lowered ATP may link hypoxia and constriction, and tolbutamide mimics the effects of ATP in other tissues by blocking ATP‐sensitive potassium (ATP‐K) channels. Pulmonary vasoconstriction, induced by lowering the oxygen of the gas ventilating the lungs from 95 to 2 %, was always reduced or abolished by tolbutamide (1·7 x 10−4‐8·5 x 10−3 M). High concentrations (greater than or equal to 10−3 M) of diazoxide, a drug that opens ATP‐K channels, dramatically constricted the pulmonary vasculature and this effect was also reversed by tolbutamide. The opening of ATP‐K channels may therefore underlie hypoxic pulmonary vasoconstriction.
RECEPTOR‐CONTROLLED CALCIUM DISCHARGE IN FROG HEART CELLS
Authors: Niedergerke R. , Page S.
Published: December 2014

A brief account is given of previous work concerned with the effects which ATP (P2‐‘purinergic’) and α‐adrenaline receptors have on the activity of the sarcoplasmic reticulum (SR) in frog heart atrial cells. More recent experiments made with single atrial trabeculae are also described which suggest, among other things, that ATP and α‐adrenaline receptors both facilitate the process by which an action potential induces SR calcium discharge in atrial heart cells. The facilitatory effect involved is considerable; at high (≥ 2 µM) ATP doses, SR calcium discharge seems to be increased about 14‐fold and, quite possibly, more than this. Results obtained with different levels of [Ca2+]o during ATP action suggest that the process of calcium‐induced calcium release plays little part in the facilitatory process. Its putative mechanism is briefly discussed.
Pulmonary shunting by the bronchial artery in the anaesthetized horse
Authors: Gleed RD , Dobson A , Hackett RP
Published: December 2014

In the quietly standing horse the bronchial arterial blood flow is low, 0.1–0.2% of the pulmonary arterial flow. In horses anaesthetized with halothane, the bronchial arterial flow is reduced by a greater fraction than that in the pulmonary artery. Thus the shunting through the bronchial circulation is decreased about 3‐fold by anaesthesia, and cannot, therefore, contribute significantly to the increased alveolar‐arterial gradient seen in dorsal recumbency. The results indicate bronchial vasoconstriction under anaesthesia.
Contribution of lymph formation in the popliteal node to efferent lymph flow following stimulation of the sympathetic chain in the sheep
Authors: Thornbury KD , McHale NG , McGeown JG
Published: December 2014

Lymph flow and contraction frequency were measured in popliteal efferent lymphatics. Stimulation of the ipsilateral sympathetic chain resulted in an approximate threefold increase in lymph flow, while contraction frequency increased 28% (n = 6). Occlusion of the metatarsal afferent lymphatics with a pneumatic cuff reduced efferent flow from 18 to 4 microliters/min after 25 min (n = 5), indicating that approximately 80% of popliteal efferent lymph is derived from the foot. After occlusion of the afferent lymphatics, sympathetic stimulation failed to increase efferent lymph flow significantly, while efferent contraction frequency still showed a significant rise. It is concluded that lymph formation in the popliteal node does not contribute to the rise in efferent lymph flow following sympathetic stimulation.
Effects of muscle thixotropy on afferent activity in the hindlimb of the rat
Authors: Warner JE , Wiegner AW
Published: December 2014

The increase with time of the stiffness of resting muscle and its effect on afferent nerve activity arising within the muscle were investigated in the leg of the anaesthetized rat. Nerve activity was recorded from the branch of the tibial nerve innervating the gastrocnemius muscle. A sinusoidal torque from a motor coaxial with the ankle produced small (less than 0.25 deg) oscillations of the resting foot that were interrupted by several cycles of a much larger amplitude displacement. After the perturbation, the same small torque caused larger (greater than 0.40 deg) oscillations, demonstrating a reduction in the resting or short‐range stiffness of muscles acting at the joint. Turning off the torque for 30 s allowed the stiffness to return to its enhanced level. Afferent nerve activity in response to the small torque was greater following the perturbation, reflecting the larger oscillations. We conclude that thixotropic stiffening of muscles at rest reduces postural displacements produced by small torques as well as the quantity of afferent signals converging on the central nervous system from these events.
Hepatic branch vagotomy attenuates the feeding response to 2‐deoxy‐D‐glucose in rats
Authors: Delprete E , Scharrer E
Published: December 2014

The effect of hepatic branch vagotomy on the feeding response induced in rats by intraperitoneally injected 2‐deoxy‐D‐glucose (2‐DG) was tested. Injections were given 1 h after onset of the dark phase, and immediately [corrected] after the rats had ingested a meal. 2‐DG produced a smaller feeding response in hepatic branch‐vagotomized rats compared with that in sham‐vagotomized rats. This finding suggests that hepatic glucoreceptors with vagal afferent fibres are involved in the feeding response to glucose deprivation.
Respiratory responses of domestic fowl to hyperthermia following selective air sac occlusions
Authors: Brackenbury JH , Amaku JA
Published: December 2014

Ventilation together with blood and respiratory gas tensions were measured in adult domestic fowl under normothermic and hyperthermic conditions, following bilateral occlusion of the cranial and caudal thoracic air sacs (series I) or the cranial and caudal thoracic plus the abdominal air sacs (series II). Series I birds showed no significant differences from controls. Both control and experimental animals displayed a typical thermal polypnoea combined with mild hypocapnaemia. A larger drop in PCO2 was demonstrated in the clavicular sac than in the blood, possibly indicating partial failure of inspiratory valving at the ventrobronchi. However, there was no evidence of any effect of thoracic air sac occlusion on inspiratory airflow valving in the palaeopulmo. Series II birds were strongly hypercapnaemic/hypoxaemic in normothermic conditions, with a normal minute volume, but a faster, shallower breathing pattern. During hyperthermia they increased minute ventilation 3‐fold, as in control animals, and blood gas tensions were almost restored to normal. Again, there was no evidence that experimental reduction in air sac capacity, in this case up to 70% of the total, had any effect on inspiratory airflow valving in the palaeopulmo, although inevitably in this case airflow in the neopulmo was abolished.
Lack of interaction between adenosine‐induced vasodilatation and carotid baroreflex‐induced changes in sympathetic activity in dog hindlimb artery
Authors: Ballard HJ , Karim F
Published: December 2014

In anaesthetized dogs, a hindlimb was vascularly isolated and perfused at a constant flow rate of 7.7 +/‐ 1.9 ml min‐1 100 g‐1 (mean +/‐ S.E.M.; n = 5) through the femoral artery. The carotid sinuses were isolated and perfused at high (greater than 145 mmHg) or low (less than 75 mmHg) pressure to enable reflex sympathetic tone on the hindlimb vessels to be controlled. Both vagi were sectioned in the neck and mean aortic blood pressure was held constant by connection of the aorta to a reservoir. The responses to infusion of three doses of adenosine at high and low carotid sinus pressures were not significantly different: infusion of 0.60 +/‐ 0.16 microM‐adenosine reduced femoral arterial perfusion pressure (FAPP) by 11.6 +/‐ 3.2% (n = 6) at high carotid sinus pressure and by 12.6 +/‐ 5.1% (n = 4) at low carotid sinus pressure, while 4.71 +/‐ 0.49 microM‐adenosine reduced FAPP by 20.8 +/‐ 4.8% (n = 6) at high carotid sinus pressure and by 20.7 +/‐ 4.8% (n = 6) at low carotid sinus pressure; 50.1 +/‐ 7.3 microM‐adenosine reduced FAPP by 36.7 +/‐ 5.5% (n = 6) at high carotid sinus pressure and by 27.7 +/‐ 7.8% (n = 5) at low carotid sinus pressure.(ABSTRACT TRUNCATED AT 250 WORDS)
Measurement of plasma osteocalcin in sheep: assessment of circadian variation, the effects of age and nutritional status and the response to perturbation of the adrenocortical axis
Authors: Corlett SC , Couch M , Care AD , Sykes AR
Published: December 2014

An assay for plasma osteocalcin (BGP) in ruminants is described. Satisfactory cross‐reaction was obtained for bovine BGP in several species, namely ovine, cervine, caprine and human. Sample stability at room temperature, after freezing and thawing and after lyophilization and reconstitution is described. Sheep of both sexes have been used throughout and no significant sex effect has been noted. A series of experiments showed a lack of circadian rhythm of plasma BGP concentration in sheep. Plasma BGP values from sheep ranging in age from 0.25 to 7 years fell exponentially from 300 ng/ml at 0.25 years to approximately 50 ng/ml at 1.25 years of age where it remained until the end of the study at 7 years. Long‐term administration of adrenocorticotrophic hormone (ACTH) depressed plasma BGP concentrations, although plasma BGP levels were not affected sufficiently by short‐term administration of ACTH to increase plasma cortisol concentrations 10‐fold during a period of 4 h. It was confirmed that dietary phosphate deficiency depressed plasma BPG concentrations. It is concluded that neither circadian variation nor the short‐term stress of handling and bleeding untrained animals need be considered in sampling sheep for measurement of plasma BGP concentration and that the change with age reflected the pattern of development of skeletal maturity in sheep. Values in both growing and mature sheep were at least 6 times higher than in human subjects, which may reflect the 10‐fold higher skeletal growth rate in sheep than in humans. This high skeletal activity in sheep may have been selected for in the development of highly productive breeds.
Behavioural thermoregulation in mice: effects of low doses of general anaesthetics of different potency
Authors: Pertwee RG , Marshall NR , Macdonald AG
Published: December 2014

Chloroform, monochlorodifluoromethane and nitrous oxide produced dose‐related decreases in the rectal temperatures of mice allowed to choose between a warm and a cool environment. The doses used were subanaesthetic, respectively 0.0013‐0.004, 0.028‐0.085 and 0.25‐0.5 atm. The hypothermia (up to 3.6 degrees C) was usually associated with significant reductions in time spent in the warm. The log dose‐hypothermic response plots were approximately parallel and there was a marked correlation between anaesthetic potency, as measured by the abolition of the righting response, and hypothermic potency.
The effects of removing external sodium upon the control of potassium (86Rb+) permeability in the isolated human sweat gland
Authors: Wilson SM , Bovell DL , Elder HY , Jenkinson DM , Pediani JD
Published: December 2014

The changes in cytoplasmic free calcium ([Ca2+]i) which occur in isolated human sweat glands during cholinergic stimulation have been studied indirectly by monitoring potassium permeability. The acetylcholine‐evoked permeability increase normally consists of transient and sustained phases which are attributed to the mobilization of intracellular calcium stores and to calcium influx respectively. Such consistent responses to acetylcholine could not be obtained during superfusion with bicarbonate‐free, HEPES‐buffered solutions. The human sweat gland in vitro therefore appears to have a strict requirement for bicarbonate. The sustained component of the response was not affected by total removal of external sodium, suggesting that calcium influx does not occur via a sodium‐dependent system. The transient component, however, was abolished when external sodium was replaced by N‐methyl‐D‐glucammonium (NMDG+). It therefore appears that secretagogue‐evoked mobilization of cytoplasmic calcium is dependent, in some way, upon external sodium. This dependence is not, however, absolute as the response was essentially normal when sodium was replaced by lithium.
Coronary myogenic responses to abrupt changes in aortic blood pressure in anaesthetized dogs
Authors: Dambrosio M , Gattullo D , Linden RJ , Losano G , Pagliaro P , Vono P
Published: December 2014

A transient increase in coronary transmural pressure was produced in anaesthetized dogs by occlusion of the descending thoracic aorta. Aortic blood pressure (ABP), left ventricular pressure and coronary flow were measured; coronary vascular resistance (CVR) was calculated. Results were similar in innervated and denervated hearts. Occlusion for 10 and 20 s resulted in no change in CVR for 15 s, followed by a metabolic dilatation attributable to enhanced oxygen demand; after release the fall in ABP resulted in an immediate increase in CVR, caused by vascular elastic recoil, followed by hyperaemia.
Nutrient and pharmacological stimulation of insulin‐secreting cells: marked differences in the onset of electrical activity
Authors: Dunne MJ
Published: December 2014

Whole‐cell current clamp experiments with the patch‐clamp technique have been used to investigate the electrical activity of insulin‐secreting (RINm5F) cells. When challenged with either glucose (10 mM), glyceraldehyde (10 mM), L‐alanine (5 mM) or tolbutamide (100 microM) the cells depolarized and this led to the generation of spike potentials. Marked differences in the lag times between stimulation and the onset of electrical activity were observed. Both tolbutamide and L‐alanine evoked spike potentials within on average 7 s of stimulation, whilst the effects of glucose and glyceraldehyde were only observed over a much longer delay. These variations may be explained by differences in the routes through which closure of ATP‐sensitive K+ channels is brought about.
Subcellular elemental composition in isolated cardiac myocytes from rabbit following chronic potassium depletion and acute repletion, studied by X‐ray microanalysis
Authors: Ward JP , Warley A
Published: December 2014

X‐ray microanalysis was used to estimate K, Na, Cl, Mg, P and S within the mitochondria and the myofibrillar regions of cardiac myocytes from rabbits, following dietary potassium depletion. K depletion caused no changes in mitochondrial K, but myofibrillar K was reduced. There were no changes in Na, Mg or Cl. Both areas showed increases in P but decreases in S. Acute K repletion resulted in a significant overshoot of K in both areas, coupled with a profound decrease in Cl. P was reduced in the mitochondria alone. These results may be partly explained by adaptive changes in Na+ pump activity.
Actions of halothane on single‐channel currents evoked by acetylcholine in rat myoballs
Authors: Hendry BM
Published: December 2014

The actions of halothane on single‐channel currents evoked by acetylcholine in myoballs cultured from neonatal rat skeletal muscle have been investigated using the patch clamp technique. Halothane at concentrations of 0.5‐4.0 mM was applied to inside‐out cell‐free membrane patches in the presence of 1.0 microM‐acetylcholine. Halothane produced concentration‐dependent decrease in the mean duration of the single‐channel current events; 3.0 mM‐halothane halved the slow time constant of channel closure. There was no effect on the amplitude of the single‐channel currents, and no increase in the number of closing events per burst was observed. The distribution of closed times was complex but halothane did not markedly alter the frequency of channel opening events. Halothane therefore decreased the time‐averaged acetylcholine‐evoked membrane current, largely through an increase in the rate of channel closure.
Similarities between some properties of the soma and sensory receptors of primary afferent neurones
Authors: Harper AA
Published: December 2014

The electrical properties of the somata of neurones associated with low‐threshold, cutaneous mechanoreceptors were studied in young, anaesthetized rats. The adaptation properties of slowly and rapidly adapting afferents were compared by recording from the somata during mechanical stimulation of the skin and during the injection of depolarizing current pulses through the recording electrode. Membrane potential and action potential conformation were recorded from each cell, together with the axonal conduction velocity. Axonal conduction velocities were in the ranges 62‐18 m/s (A alpha/beta) and 7‐4 m/s (A delta). Somata with A alpha/beta‐axons which were associated with slowly adapting receptors gave sustained discharges when depolarized by injected current, whereas those associated with rapidly adapting receptors gave a brief discharge only (median response: five impulses). Somata with A delta‐axons had similar characteristics to fast‐conducting, rapidly adapting afferents. In a separate study it was shown that, for neurones which gave an adapting response to intracellular current injection, action potentials recorded from the somata were able to follow electrical stimulation of their axons at frequencies up to 100 Hz, indicating that the adaptation of responses to mechanical stimulation in the other experiments was not due to failure of impulses to invade the somata. The results suggest that the adaptation properties of a mechanoreceptor may be due to the presence of a particular type of ionic channel in the terminals of the nerve which is also present in the membrane of its soma.
Regulation of mouse mammary cell differentiation by extracellular milk proteins
Authors: Wilde CJ , Blatchford DR , Peaker M
Published: December 2014

Differentiation of mammary epithelial cells prepared from pregnant mice was stimulated by culture on floating collagen gels in the presence of lactogenic hormones. Differentiation was measured by the induction of casein synthesis and fatty acid synthase activity, both of which increased by up to 15‐fold during 12 days of culture. Addition of a 10–30 kDa fraction of goat whey proteins to culture medium from day 3 inhibited casein synthesis by greater than 20% compared with control cultures on days 4–12, and prevented further induction of fatty acid synthetase activity. Inhibition of secretory cell differentiation by this fraction, which is known to inhibit milk synthesis acutely in explant culture and lactating goats, suggests that similar autocrine mechanisms may mediate the sequential local effects on milk yield and cell differentiation elicited by manipulation of milking frequency or efficiency.
Kinetics of lactate and glucose metabolism in the pregnant ewe and conceptus
Authors: Hodgson JC , Mellor DJ , Field AC
Published: December 2014

Two monotocous and two ditocous ewes were infused at 124–130 days of gestation with a mixture of L‐[U‐14C]lactate and D‐[6‐3H]glucose via a maternal or umbilical catheter, separate days being used for each infusion. Plateaux‐specific radioactivities of plasma lactate and glucose were used to derive a four‐pool model describing the fluxes between the lactate and glucose pools of the infused conceptus and mother. The average turnover rate of lactate was 23.3 and 13.2 mg carbon min‐1 in the conceptus and 32.0 and 44.0 mg carbon min‐1 in the mother for monotocous and ditocous ewes, respectively. Glycolysis rates within both conceptus and mother in all sheep were high, accounting for about 80 and 60% of the respective rates of lactate turnover. The synthesis of glucose from lactate accounted for 13 and 31% of the glucose turnover in the mother in monotocous and ditocous ewes, respectively, but was insignificant in the conceptus. Glycolysis within the conceptus used only glucose which had entered and mixed with the conceptus glucose pool; there was no direct transfer of carbon from the maternal glucose pool to the conceptus lactate pool. This finding is an important validation for the use of tracer methods to determine glucose use within the whole conceptus rather than within fetal corporeal tissues alone.
An investigation into the influence of vasopressin on perfusion of the cortex and papilla of the rat kidney
Authors: Huang CL , Davis G , Johns EJ
Published: December 2014

An investigation was undertaken to examine the effects of vasopressin on blood pressure and perfusion of the cortical and papillary regions of the kidney, and to determine the receptor subtype involved. Pentobarbitone‐anaesthetized rats were used and laser‐Doppler flowmetry applied to measure regional renal haemodynamics. Infusion of vasopressin at 10, 20 and 40 mU kg‐1 min‐1 caused dose‐related increases in blood pressure and reductions in cortical and papillary perfusion of approximately 21, 35 and 41%, respectively at the highest dose. Administration of the V1‐receptor antagonist, [1‐(beta‐mercapto‐beta,beta‐cyclopentamethylene propionic acid), 2‐(o‐methyl)tyrosine]‐Arg8‐vasopressin, at 1 microgram kg‐1 plus 5 micrograms kg‐1 h‐1 or four times this dose had no effect on the basal levels of any variable. Vasopressin administration during the low dose of antagonist increased blood pressure and reduced papillary perfusion, the magnitudes of which were only slightly less than those obtained in the absence of the drug, whereas there was a significant attenuation of the response in cortical perfusion. During infusion of the V1 antagonist at 4 micrograms kg‐1 plus 20 micrograms kg‐1 h‐1, vasopressin had no effect on either blood pressure or renal haemodynamics. Infusion of the V2 antagonist, [d(CH2)5, D‐Phe2, Ile4, Arg8, Ala9‐NH2]‐vasopressin at 1 microgram kg‐1 plus 5 micrograms kg‐1 h‐1, and twice this dose had no effect on the basal value of any variable and had no effect on the ability of vasopressin to induce an increase in blood pressure or cause reductions in renal cortical and papillary perfusions. However, the administration of the V2 antagonist at 4 micrograms kg‐1 plus 20 micrograms kg‐1 h‐1 significantly attenuated blood pressure, cortical and papillary perfusion responses to the vasopressin. These studies have shown that vasopressin, given at doses which increased blood pressure, caused dose‐related decreases in perfusion of renal cortex as well as the papilla. The data further show that these systemic and renal actions were mediated primarily by V1‐receptors and that the contribution of V2‐receptors at these vascular beds was very small.
Contacts between group Ia muscle spindle afferent axons and GABA‐immunoreactive perikarya in lamina VI of cat spinal cord
Authors: Dawe GS , Maxwell DJ
Published: December 2014

Three group Ia muscle spindle afferent axons were labelled with horseradish peroxidase and terminations in lamina VI examined. Eleven perikarya were contacted by the three fibres; these were examined using a post‐embedding immunostaining technique for GABA. Three neurons were found to be positively labelled for GABA. It is likely that these cells are involved in inhibition of primary afferent fibres and non‐reciprocal inhibition of motoneurons.
A study of the action of angiotensin II on perfusion through the cortex and papilla of the rat kidney
Authors: Huang CL , Davis G , Johns EJ
Published: December 2014

The effect of angiotensin II on blood pressure and perfusion of blood through the cortex and papilla regions of the kidney was determined in pentobarbitone‐anaesthetized rats which were subjected to laser‐Doppler flowmetry to estimate regional renal haemodynamics. Angiotensin II was infused at 10, 45 and 150 ng (kg body weight‐1 min‐1) which caused dose‐related increases in blood pressure of 3, 12 and 24%, respectively, and decreases in cortical perfusion of 9, 15 and 24%, respectively. Papillary perfusion did not change at any dose of angiotensin II. This pattern and magnitude of responses to angiotensin II in blood pressure, cortical and papillary perfusions was essentially unaffected (a) following blockade of cyclo‐oxygenase activity with indomethacin (1.3 mg kg‐1 plus 2 mg kg‐1 h‐1), (b) during infusion of a bradykinin antagonist, at 1.3 micrograms min‐1, (c) when renal perfusion pressure was regulated at control levels and (d) following Methylene Blue administration to inhibit potential endothelial‐derived relaxing factor production. By contrast, infusion of phenylephrine at 5, 10 and 20 micrograms kg‐1 min‐1 caused dose‐related increases in blood pressure and decreases in both cortical and papillary perfusions reaching some 28, 7 and 17% respectively at the highest dose of phenylephrine used. These results showed that both cortex and papilla were sensitive to vasoconstrictor agents. They are compatible with the suggestion that angiotensin II regulates cortical but not papillary perfusion in the kidney, and that these responses do not depend on prostaglandin, bradykinin, renal perfusion pressure or endothelium‐derived relaxing factor.