bluuebunny/crossref_metadata_2025 huggingface dataset:
THE EFFECTS OF LOW‐VOLTAGE ELECTRIC SHOCK ON RESPIRATION IN THE ANAESTHETIZED CAT
Authors: Bradford A. , O'Regan R. G.
Published: December 2014

Airflow (v), expired ventilation (VE), oxygen usage (VO2), carbon dioxide production (VCO2), blood pressure (B.P.) and the electrocardiogram (e.c.g.) were measured before and after applying low‐voltage electric shocks (15–110 V a.c., 8–45 mA, 50 Hz) from the forelimb to the opposite hind limb of cats anaesthetized with pentobarbitone. Periods of shock application were either short (0·5–1·5 s) or more prolonged (10–30 s). Respiratory arrest from tetanic contractions of the respiratory muscles was always present throughout the period of shock application. Following the shocks, even those of the shortest duration, marked increases in v, respiratory rate, VE, VO2 and VCO2 were recorded. Some of these measurements were still elevated relative to pre‐shock levels 60 min in to the post‐shock period. During shocks lasting 10–30 s B.P. usually increased markedly in association with elevated pulse pressure but hypotension with absent pulses was also recorded. Following shocks of these durations both hypertensive and hypotensive phases were distinguished sometimes lasting for up to 30 min. Occasionally, the e.c.g. showed ventricular arrhythmias or cardiac standstill in the immediate post‐shock period but it was usual for these abnormalities to revert rapidly to normal sinus rhythm. Hypotension invariably followed short‐duration shocks. This study indicates that low‐voltage shocks, even those applied for short periods, can induce marked respiratory, circulatory and metabolic reactions. Possible mechanisms to account for these reactions are discussed.
INFLUENCE OF INTRADUODENAL GLUCOSE ON MEAL SIZE AND ITS MODIFICATION BY 2‐DEOXY‐D‐GLUCOSE OR VAGOTOMY IN HUNGRY PIGS
Authors: Stephens D. B.
Published: December 2014

Young growing pigs which had been trained to press a panel in order to obtain small deliveries of food and adapted to eating all their food in one meal per day were surgically fitted with an exteriorized cannula connected to the duodenum. An infusion of 250 ml 150% (w/v) glucose solution 10 min before the meal did not influence meal size, whereas a similar infusion shortly after beginning a meal significantly reduced meal size. When the membrane transport and metabolism of glucose was reduced by infusing the antimetabolite, 2‐deoxy‐D‐glucose, before the glucose infusion, the suppression of appetite was attenuated. Intrathoracic truncal vagotomy abolished the effects of intraduodenal glucose. The possibility that a receptor sensitive to transport and metabolism of glucose exists in the duodenum is discussed.
MEMBRANE POTENTIAL MEASUREMENTS IN ISLETS OF LANGERHANS FROM ob/ob OBESE MICE SUGGEST AN ALTERATION IN [Ca2+]i‐ACTIVATED K+ PERMEABILITY
Authors: Rosario Luis M. , Atwater Illani , Rojas Eduardo
Published: December 2014

High‐resistance micro‐electrodes were used to measure membrane potentials in β‐cells from islets of Langerhans of ob/ob obese mice (Norwich colony). In the presence of glucose the burst pattern of electrical activity recorded in ob/ob β‐cells, although similar to the burst pattern recorded from normal β‐cells, presents important differences. The membrane potential of the ob/ob β‐cells in the presence of 11 mM glucose in the modified Krebs solution oscillates between a silent‐phase level at ‐48 mV and an active‐phase level at ‐36 mV, similarly to normal mouse islet β‐cells. However, the average active‐phase duration is 20 s in ob/ob β‐cells compared with 5 s in normal β‐cells. The average burst frequency is 1·8 bursts/min in ob/ob β‐cells compared with 3 bursts/min in normal β‐cells. While normal β‐cells show continuous spike activity above 16 mM glucose, ob/ob β‐cells often exhibit a burst pattern of electrical activity at glucose concentrations as high as 33 mM. Compared with normal β‐cells, the relationship between spike frequency and glucose concentration is shifted towards lower concentrations in ob/ob β‐cells. Thus, the concentration for half‐maximal spike frequency is 6·9 mM for the ob/ob β‐cells and 10·2 mM for the normal β‐cells. In ob/ob β‐cells, the mitochondrial inhibitor carbonyl‐cyanide m‐chlorophenylhydrazone induces hyperpolarization of the membrane, consistent with its effect of stimulating K+ permeability in normal islets. However, quinine and the sulphonylurea glibenclamide did not block the silent phase between the bursts of electrical activity. Both drugs block the [Ca2+]i‐activated K+ permeability thought to control the membrane potential at the silent phase in normal β‐cells. The modified pattern of response to glucose and decreased sensitivity to quinine and glibenclamide suggest that the β‐cell membrane of the ob/ob islet of Langerhans has a modified [Ca2+]i‐activated K+ permeability.
MECHANICAL PROPERTIES OF THE RAT COLON: THE EFFECT OF AGE, SEX AND DIFFERENT CONDITIONS OF STORAGE
Authors: Watters D. A. K. , Smith A. N. , Eastwood M. A. , Anderson K. C. , Elton R. A.
Published: December 2014

The mechanical properties of the rat colon were studied in old and young Sprague‐Dawley rats which were also grouped by sex. Different storage media were used. Rings of colonic tissue were submitted to pulls on an Instron 1026 tensiometer. Gender did not affect the properties of the young rat colon. The rat colon has a tensile strength of around 50 g/mm2 (which places it between the dog and the cat). It increased in strength from proximal to distal, though the rectum was weaker than the colon. The pre‐strain of the rat colon was 100% and it was capable of stretching to 200% of its original dimensions. The strength and ability to stretch fell with age, although it initially increased, in the first year of life. Physiological saline at 4 °C preserved the burst strength, percentage elongation, hysteresis and Young's modulus between 25 and 100 g stress for up to 1 week. Young's modulus between 125 and 200 g fell progressively with each day of storage. Stress relaxation rose in the first 24 h and thereafter remained constant. Salt appeared to be a good long‐term storage medium. Irradiation of the colons before storage did not affect the mechanical properties.
THE ANION SELECTIVITY OF GABA‐MEDIATED POST‐SYNAPTIC POTENTIALS IN MOUSE HIPPOCAMPAL CELLS
Authors: Biscoe T. J. , Duchen M. R.
Published: December 2014

Intracellular recordings were made from CA1 and dentate cells of the mouse hippocampal slice. When potassium acetate was used to fill the electrodes, spontaneous synaptic activity was rarely seen in CA1 or dentate cells. In contrast, when electrodes filled with potassium chloride were used, spontaneous depolarizing post‐synaptic potentials (p.s.p.s) were prominent. That these p.s.p.s were mediated by γ‐aminobutyric acid (GABA) was supported by the following: (i) they were blocked by electrophoretic application of bicuculline methiodide; (ii) their appearance was associated with the reversal of the evoked GABA‐mediated recurrent inhibitory post‐synaptic potential (i.p.s.p.) and (iii) their appearance was associated with the positive displacement of the reversal potential for the response to GABA applied by electrophoresis close to the cell soma. The interval distribution for the p.s.p.s could not be fitted by a Poisson distribution. The anionic selectivity of the conductance evoked by GABA was investigated by using the potassium salts of a range of anions to fill the electrodes. Depolarizing spontaneous p.s.p.s were seen in all cells impaled with electrodes containing potassium chloride, iodide, bromide, nitrate, or chlorate. In these cells, the reversal potential for the response to electrophoretically applied GABA was displaced in the depolarizing direction and the evoked recurrent i.p.s.p. was reversed. When anions with hydrated shells larger than chlorate (bicarbonate, sulphate, chromate, acetate or citrate) were used, spontaneous depolarizing p.s.p.s were not seen, and the reversal potential for the response to somatic GABA application and for the evoked recurrent i.p.s.p. lay between ‐70 and ‐75 mV.
FLUID COMPARTMENTATION AND ARTICULAR MECHANORECEPTOR DISCHARGE IN THE CAT KNEE JOINT
Authors: Wood L. , Ferrell W. R.
Published: December 2014

Experiments were performed to determine the effect of alteration of intra‐articular pressure in different areas of the cat knee joint on the discharge of slowly adapting mechanoreceptors in the posterior region of the joint. At physiological (subatmospheric) pressures the anterior and posterior regions of the knee joint are not hydraulically continuous. However, at supra‐atmospheric pressures between 2·5 and 9 cmH2O there is free communication between these areas. The discharge of receptors in the posterior region of the joint is influenced by intra‐articular pressure changes in the posterior region when these are supra‐atmospheric. However, pressure changes in the anterior region of the joint have little effect on the discharge of these receptors until free communication occurs between anterior and posterior regions. It is suggested that articular mechanoreceptors detect tension changes in collagen fibrils rather than volume changes of the joint capsule.
EFFECTS OF WATER AVAILABILITY ON PLASMA PROTEIN AND SODIUM CONCENTRATION, HAEMATOCRIT AND PLASMA OSMOLALITY IN THE PIG
Authors: Stephens D. B.
Published: December 2014

Eighteen young growing pigs of the Large White breed were housed in individual pens or metabolism stands and habituated to drinking their water from a bowl. Those housed in the metabolism stands were surgically fitted with a catheter placed in the jugular vein to allow collection of blood samples. The voluntary intake of water after periods of progressively increasing water deprivation was measured. The measurements were made by allowing the pigs to drink to satiety after either a 2, 4, 8, 12 or 18 h period of water deprivation. Voluntary water intake was a function of the duration of water withdrawal and the rate of intake increased with progressive deprivation. Changes in plasma concentration of sodium and protein, haematocrit and osmolality could be detected after 12 and 18 h of dehydration. The progressive changes in plasma sodium concentration ([Na+]), osmolality, protein concentration and haematocrit during adaptation to dehydration when water was withheld for 72 h were examined in six pigs. Using a technique of continuous blood sampling, the rapid changes in the same blood parameters during rehydration, when water was made freely available at the end of the 72 h period, were also monitored. The [Na+] and osmolality dropped precipitously following the onset of drinking. From the 15 min stage to the 4 h stage with water available ad libitum, the values of both parameters remained below their control levels. However, the plasma protein concentration and the haematocrit values remained significantly above their pre‐dehydration control levels up to the 4 h stage, even with water freely available, thus showing that drinking stopped even though the extracellular fluid phase remained dehydrated. Only with food available did the blood measures return to normal. It is concluded that the cellular fluid phase forms an integral part of the mechanisms involved in the termination of drinking in the pig.
OSMOTICALLY INDUCED DRINKING IN THE GOAT: AN OSMORECEPTOR OR A SODIUM RECEPTOR MECHANISM?
Authors: Thornton S. N. , Baldwin B. A. , Purdew T.
Published: December 2014

Changes in sodium concentration and osmolality in lateral ventricle cerebrospinal fluid (c.s.f.) caused by intracarotid infusion of hypertonic solutions were measured in conscious goats. Intracarotid infusion (1·5 ml.min−1) of 1·0 or 2·0 mol.kg−1 or urea 4·0 mol.kg−1 produced significant increases in osmolality and increases in sodium concentration of the c.s.f. 5 and 10 min after the beginning of the infusion. No significant effect was seen following intracarotid infusion of 0·15 M‐NaCl. Only intracarotid NaCl 1·0 or 2·0 mol.kg−1 caused significant drinking. Blood osmolality was significantly increased by the two hypertonic NaCl solutions as well as by hypertonic urea. In conclusion, drinking in goats following peripheral administration of hypertonic solutions is probably due to an osmoreceptor mechanism. A c.s.f. sodium receptor mechanism is unlikely because hypertonic NaCl or urea both increased the sodium concentration in c.s.f. but only the osmotically effective NaCl solution produced significant drinking.
OUABAIN‐EVOKED [3H]NORADRENALINE RELEASE FROM THE RABBIT PULMONARY ARTERY IN CALCIUM‐FREE SOLUTION
Authors: Török Tamás L. , Magyar Kálmán
Published: December 2014

[3H]noradrenaline ([3H]NA) release from the isolated main pulmonary artery of the rabbit has been measured in the presence of neuronal (cocaine, 3 x 10−5 M) and extraneuronal (corticosterone, 5 x 10−5 M) uptake blockers. 10−4 M ouabain significantly increased the [3H]NA release in normal external ionic environments after an initial delay (20–30 min). Excess K (23·6 mM) failed to affect the resting [3H]NA outflow, significantly inhibited the ouabain‐stimulated [3H]NA release and shortened the initial delay by about 10‐20 min. Higher concentration of K (47·2 mM) enhanced the outflow of [3H]NA. In the absence of external Ca and in the presence of 1 mM EGTA, 23·6 mM‐K failed to exert an inhibitory action on ouabain evoked transmitter release. Higher concentrations of K, however, significantly inhibited the [3H]NA‐releasing effect of ouabain without changing the resting outflow of labelled neurotransmitter. The initial delay of ouabain‐evoked [3H]NA release was shortened by increasing the concentration of K. Total substitution of external Na by K (143·3 mM) increased the [3H]NA release in the absence of external Ca. After the Na gradient was re‐established in Ca‐free solution the release of [3H]NA was terminated. Under these conditions the NA‐releasing action of ouabain was dependent on the preceding perfusing period in Na‐free solution, being smaller if longer exposure time was used. When external Na was substituted by Li (137·4 mM) in Ca‐free solution the [3H]NA release was dramatically increased. After Na readmission ouabain was ineffective in producing transmitter release. It is suggested that in the main pulmonary artery of the rabbit, when the electrochemical gradient of Ca is reversed, ouabain is effective in producing transmitter release if the internally stored Ca has not been completely lost. Since in Ca‐free solution the ouabain‐evoked [3H]NA release can be inhibited by external K it seems that the transmitter release observed is due to a Na‐dependent release of intracellular Ca rather than the penetration of ouabain into the cell followed by direct inhibition of the active transport of internal store membranes.
ELECTROPHYSIOLOGICAL STUDIES ON ISOLATED HUMAN ECCRINE SWEAT GLANDS
Authors: Jones Christopher J. , Hyde David , Lee Catherine M. , Kealey Terence
Published: December 2014

Human eccrine sweat glands were isolated by shearing and the potential differences across the basolateral membranes determined using bevelled micro‐electrodes filled with 4 M potassium acetate. Stable resting potentials of up to ‐81 mV were recorded. Alterations in external potassium concentration from 1·2 to 100 mM caused the membrane potential to change over a 70 mV range in cells of high resting potential, indicating that the basolateral membrane is largely potassium permeable. Input impedance was determined by constant current injection and found to be in the range 4‐80 MΩ. On giving a bolus injection of acetylcholine to produce a final concentration of 10−6‐10−7 M, four types of response were observed: (i) depolarization, in a proportion of cells with resting potentials of ‐66 to ‐80 mV (n = 19), (ii) hyperpolarization, in a group of cells with resting potentials of ‐47 to ‐70 mV (n = 22), (iii) no change, in some cells of ‐40 to ‐81 mV resting potential (n = 22) and (iv) micro‐electrode dislodgement (n = 8). In cells depolarizing to acetylcholine, the depolarization was short‐lived and in thirteen cases was followed by a ‘rebound’ hyperpolarization. Input impedance decreased during depolarization in one‐third (n = 5) of the cells in which satisfactory measurement could be made and increased during the final phase of depolarization or during rebound hyperpolarization. In cells hyperpolarizing to acetylcholine, the hyperpolarization was usually accompanied by an increase in input impedance. In ten of the twenty‐two cells which showed no change to a first dose of acetylcholine, the agonist was administered at least two more times. In two cells (resting potentials ‐62 mV, ‐64 mV) a hyperpolarization was observed whereas in three others (resting potentials ‐66 mV, ‐70 mV, ‐81 mV) depolarization occurred. The effects of acetylcholine, whether depolarizing or hyperpolarizing, were reversibly inhibited by atropine and irreversibly reduced by ouabain. Experiments performed on glands maintained for up to 30 h in supplemented RPMI 1640 tissue culture medium yielded essentially similar results to those performed on freshly isolated glands.
DOES STIMULATION OF THE LEFT ATRIAL RECEPTORS AFFECT THE ACTIVITY IN EFFERENT VAGAL NERVES TO THE HEART IN DECEREBRATE DOGS?
Authors: Walters G. E. , Mary D. A. S. G. , Linden R. J.
Published: December 2014

In anaesthetized dogs with an intact neuraxis, distension of small balloons at the pulmonary vein‐atrial junctions to stimulate atrial receptors with myelinated vagal afferent nerves causes an increase in heart rate but does not influence the activity in efferent vagal cardiac nerves. However, it has been suggested from experiments performed in decerebrate dogs that stimulation of atrial receptors causes a tachycardia partly mediated by a decrease in activity in efferent vagal nerves. In the present study in chloralose‐anaesthetized dogs, following total decerebration (four dogs) or partial decerebration (four dogs) at the level of the mid‐brain, distension of the small balloons caused an increase in heart rate but did not affect the activity in efferent vagal nerve fibres which responded by an increase in activity to stimulation of carotid baroreceptors and chemoreceptors. These results show that stimulation of the left atrial receptors in totally or partially decerebrate dogs causes an increase in heart rate but does not influence the activity in efferent vagal cardiac nerves.
POTASSIUM AND RUBIDIUM PERMEABILITY AND POTASSIUM CONDUCTANCE OF THE β‐CELL MEMBRANE IN MOUSE ISLETS OF LANGERHANS
Authors: Dawson Christine M. , Croghan P. C. , Scott Angela M. , Bangham J. A.
Published: December 2014

The efflux of 42K+ and 86Rb+ has been studied in collagenase‐isolated normal mouse islets of Langerhans. In double‐labelled experiments, the ratio of efflux rate constants of Rb+ and K+ (kRb/kK) was 0·80 in 5 mM‐K+ and 0 glucose. The ratio was unaffected by glucose concentrations up to 22·2 mM. In the presence of 50 mM‐K+, 0 glucose, the ratio increased to 0·91 and in 50 mM‐Rb+, 0 glucose and 0 K+, the ratio was 1·06. With these limitations, the results indicate that 86Rb+ is an acceptable isotope for K+. Using the Goldman model, K+ and Rb+ permeability coefficients and K+ slope and chord conductances were computed. The permeabilities decreased in glucose and in high K+ or high Rb+. In the case of high external K+, the K+ conductances increased. Also there may be more than one type of K+ channel with differing selectivities to K+ and Rb+. The addition of glucose in the presence of 50 mM‐K+ had no further effect on Rb+ permeability. It is suggested that there are about ten small K+ channels open in the resting β‐cell and that progressive closure of these channels is involved in the depolarization of the cell membrane that initiates spike activity.
FLUID BALANCE DURING FOOD DEPRIVATION AND AFTER INTRARUMINAL LOADS OF WATER OR ISOTONIC SALINE IN LACTATING AND ANOESTRAL GOATS
Authors: Dahlborn K. , Karlberg B. E.
Published: December 2014

A study was made of water and salt balance during a 28 h period of starvation in lactating and anoestral goats. Food deprivation caused diminished water intake in all but one animal, and the secretion of urine and milk gradually decreased. The plasma volume and the glomerular filtration rate were reduced, the plasma Na concentration lowered, and the plasma renin activity and plasma aldosterone concentration raised during starvation, After 28 h without food the goats were given a load of water or saline into the rumen. The fall in the plasma protein concentration that occurred indicates that the plasma volume increased in all animals within 4 h of receiving saline, but was unchanged after the water load. The plasma Na concentration decreased further after the water load, but increased in all animals after the saline load. The plasma renin activity and plasma aldosterone concentration remained elevated after the intraruminal water load, but fell towards basic values after the saline load. The renal Na excretion decreased during food deprivation, and showed no increase within 4 h of saline loading. It appears that only the load of saline restored the salt and water homoeostasis of the animal. Lactating and anoestral goats do not apparently differ in their response to starvation. The effects of starvation on fluid balance seem to become as severe in goats as in monogastric species despite food reservoirs in the reticulo‐rumen and omasum at the onset of food deprivation.
THE EFFECT OF DAY LENGTH ON THE DURATION OF PREGNANCY AND THE ONSET OF PARTURITION IN THE RAT
Authors: Flint A. P. F. , Heap R. B. , Ingram D. L. , Walters D. E.
Published: December 2014

Rats mated under normal lighting conditions of a 24 h day were transferred to a sound‐proof room with period lengths (T) of 24 h (12 h light and 12 h dark, 12L:12D), or 22 h (11L:11D). During the first 15 d of pregnancy the rats were kept together in a large enclosure and the locomotor activity of the group was recorded. From day 15 they were kept separately, in cages, and from day 21 the number of litters born was noted every 3 h.

On 12L:12D, rats displayed well defined periods of activity which were closely related to photoperiod. Mean activity was greatest in the dark, and overall activity declined after day 13 of gestation. On 11L:11D, coupling of locomotor activity to the dark phase was retained initially, but was not sustained throughout the period of study. Activity in the light was comparable to that in the dark at the time when the light:dark cycles of 11L:11D became reversed relative to those of 12L:12D.

Rats on a 24 h day had a peak time of delivery at 519 h after mating (21·6 cycles of 12L:12D) and those on a 22 h day at 527 h (24·0 cycles of 11L:11D; difference, P 〈 0·002). The 11L:11D cycle therefore increased rather than decreased the duration of pregnancy, implying that elapsed time rather than the number of light:dark cycles experienced has the greater influence on the length of gestation. Of the animals on a 24 h day 76% had their litters in the light phase of the cycle, whereas only 36% of those on a 22 h day gave birth in the light (P 〈 0·02).
HYPOPHOSPHATAEMIA AND VITAMIN D METABOLISM IN SHEEP
Authors: Maunder E. M. W. , Pillay A. V. , Care A. D.
Published: December 2014

The effect of dietary induced hypophosphataemia on vitamin D metabolism was studied in four conscious sheep. No change in the plasma concentrations of 25‐hydroxyvitamin D3 and 1,25‐dihydroxyvitamin D3 (1,25(OH)2D3) were found during hypophosphataemia when compared with normophosphataemia. In addition both the metabolic clearance rate and the production rate of plasma 1,25(OH)2D3 were unaltered during hypophosphataemia. This suggests that changes in circulating levels of 1,25(OH)2D3 were not necessary for the increased efficiency of intestinal phosphorus absorption seen in phosphorus‐depleted hypophosphataemic sheep, and may explain why there is no increase in efficiency of intestinal calcium absorption in phosphorus depleted sheep. Increases in phosphataemia induced acutely by intravenous phosphate infusion for 3 h also had no effect on plasma 1,25(OH)2D3 concentration. It is concluded that in the sheep, unlike non‐ruminant animals, chronic hypophosphataemia does not increase plasma 1,25(OH)2D3 concentrations and plays no physiological role in regulating its production or metabolism.
INTERNAL POTASSIUM ACTIVITY IN FERRET VENTRICULAR MUSCLE
Authors: Reverdin E. C. , Illanes A. , McGuigan John A. S.
Published: December 2014

Measurements of the K activity (aiK) in ferret ventricle were made using either single‐ or double‐barrelled K‐sensitive micro‐electrodes. aiK was also estimated from the Nernst equation by measuring the membrane potential when changing the external K concentration. Microelectrodes filled with the Corning K sensor gave unreliable results most probably due to interference from some substance(s) in the heart cells. Reproduceable measurements were obtained using a valinomycin cocktail as the K sensor. The mean value ± S.D. for aiK from four experiments which met strict criteria for calibration, electrode penetration and drift was 104 mmol/l ± 9 mmol/l. If all nine experiments were taken the value was 101 mmol/l ± 8 mmol/l. Estimation from the Nernst equation gave values of aiK that were on average 20 mmol/l higher than the measured values with the valinomycin cocktail. It is recommended that a valinomycin cocktail be used to measure aiK.
VASCULAR AND LIPOLYTIC RESPONSES OF THE INGUINAL FAT PAD OF THE SHEEP TO ADRENERGIC STIMULATION, AND THE EFFECTS OF DENERVATION AND AUTOTRANSPLANTATION
Authors: Thompson G. E.
Published: December 2014

Electrical stimulation of sympathetic nerves supplying an inguinal fat pad, in the anaesthetized sheep, produced effects on blood flow through the fat pad which differed when the nerves were intact or sectioned. Lipolysis was stimulated and the output of individual fatty acids into venous plasma was compared with their composition in the adipose tissue triglycerides. Close‐arterial infusion of noradrenaline also produced lipolysis but, again, effects on the circulation differed when the fat pad was in situ or chronically autotransplanted to the neck. Close‐arterial infusion of dopamine produced a similar response to noradrenaline. It is concluded that sympathetic nerves and noradrenaline may have a predominantly vasodilatory effect on adipose tissue in the sheep, but the response after acute or chronic denervation is predominantly vasoconstriction. Noradrenaline and dopamine stimulate fat mobilization independently, but the fatty acids mobilized may not be entirely representative of those stored in the adipose tissue triglyceride.
MORPHOLOGICAL, BIOCHEMICAL AND SECRETORY STUDIES ON RAT PANCREATIC DUCTS MAINTAINED IN TISSUE CULTURE
Authors: Argent B. E. , Arkle S. , Cullen M. J. , Green R.
Published: December 2014

Interlobular ducts were isolated from the pancreas of copper‐deficient rats and maintained in culture on polycarbonate filter rafts. Within 8 h the ends of the ducts had sealed. This was followed by a marked dilatation of the lumen, a flattening of the epithelium against the surrounding connective tissue layer and an over‐all swelling of the duct. Apart from a reduction in their height, a fall in the number of intracellular fat droplets and a widening of intercellular spaces, epithelial cells within the cultured ducts retained all the ultrastructural characteristics of those in freshly isolated preparations. The basal concentration of adenosine 3',5'‐phosphate (cyclic AMP) in the cultured ducts was 43·3 ± 6·8 µmol.l−1 duct epithelium (n = 5) and was increased to 188·9 ± 55·2 µmol.l−1 duct epithelium (n = 5) in the presence of 10−8 M secretin. The basal rate of fluid secretion, measured using micropuncture techniques, was 0·16 ± 0·03 nl.h−1.nl−1 duct epithelium (n = 12). This was increased 14‐fold by 10−8 M secretin while the dose of the hormone required for half‐maximal secretion was about 2 x 10−11 mol.l−1. The concentration of chloride ions in secreted fluid and perifusion buffer were similar. Variation in culture time up to 52 h had no effect on fluid secretion, and the response to secretin was dependent on the presence of bicarbonate ions in the perifusion fluid. N6,O2‐dibutyryl adenosine 3',5'‐phosphate (dibutyryl cyclic AMP) also increased fluid secretion but caerulein had no effect. We suggest that isolated ducts secrete fluid at comparable rates to ducts in situ within the pancreas of copper‐replete rats.
EFFECT OF DISTENSION OF THE URINARY BLADDER ON EFFERENT CARDIAC SYMPATHETIC NERVE FIBRES WHICH RESPOND TO STIMULATION OF ATRIAL RECEPTORS
Authors: Hassan A. A. M. , Hicks M. N. , Walters G. E. , Mary D. A. S. G.
Published: December 2014

The effect of distension of the urinary bladder on the activity in the efferent cardiac sympathetic nerves which responded to stimulation of atrial receptors or those which responded to stimulation of carotid baroreceptors or chemoreceptors, was studied in dogs anaesthetized with chloralose; the urinary bladder was distended with warm saline, small balloons were positioned at the right pulmonary vein‐atrial junctions and distended with 1 cm3 saline, and the carotid sinuses were vascularly isolated and perfused with blood at constant flow. The efferent cardiac sympathetic nerve fibres which responded to stimulation of carotid baroreceptors and chemoreceptors by a decrease in activity always responded with an increase in activity in response to distension of the urinary bladder. In contrast, in those efferent cardiac sympathetic nerve fibres which did not respond to an increase in carotid sinus pressure, but responded to stimulation of atrial receptors by an increase in activity, distension of the urinary bladder neither caused a significant change in activity nor produced a reproducible pattern of response. It is concluded that the efferent cardiac sympathetic nerve fibres which respond to stimulation of atrial receptors are separate from those which respond to distension of the urinary bladder.
THE EFFECT OF A METABOLIC INHIBITOR UPON THE PROPERTIES OF THE CEREBRAL VASCULATURE DURING A WHOLE‐HEAD SALINE PERFUSION OF THE RAT
Authors: Luthert P. J. , Greenwood J. , Pratt O. E. , Lantos P. L.
Published: December 2014

The effect of the metabolic inhibitor 2,4‐dinitrophenol (DNP) has been assessed during a simple in situ Ringer solution perfusion of the rat brain. The preparation was perfused, with or without the addition of DNP, for periods ranging up to 30 min. Following this pre‐test perfusion, both the vascular permeability and cerebral perfusate flow were assessed. In the absence of DNP significant barrier disruption had taken place by 10 min and the flow rates showed greater fluctuations with time. In the presence of DNP, however, perfusate flow remained constant and the blood‐brain barrier remained intact to [14C] mannitol for at least 10 min, but subsequently the flow rate dropped and the barrier began to show evidence of disruption. The unbound visual marker, Evans Blue, was apparently excluded from all regions other than those that are known to lack a blood‐brain barrier. The water content of the brain showed no significant increase until 20 min. Patency of the capillaries was demonstrated by direct visualization of the cerebral vasculature with an Indian ink‐gelatin mixture and in some animals there was evidence of incomplete filling following 30 min of perfusion. It is concluded that the use of DNP in the perfusate provides a useful preparation for the short‐term study of passive properties of the blood‐brain barrier, such as carrier‐facilitated diffusion, as well as mechanisms of barrier opening.
STUDIES ON THE MATURATION OF THE SMALL INTESTINE OF THE FETAL SHEEP. I. THE EFFECTS OF BILATERAL ADRENALECTOMY
Authors: Trahair J. F. , Perry R. A. , Robinson P. M. , Silver M.
Published: December 2014

The effect of bilateral adrenalectomy at 120 d gestation on subsequent maturation of proximal and distal small intestine was investigated in chronically catheterized fetal sheep. Ten adrenalectomized and fourteen controls were examined at 136 d; some following infusion of [3H]thymidine at 3‐6 d or 4 h before termination of pregnancy. Mean plasma cortisol levels were 5·3 ± 0·7 ng/ml in the adrenalectomized group; control values ranged from 14 to 39 ng/ml level during the 2‐week experimental period. Fetal body growth was significantly increased following adrenalectomy. In the small intestine, growth of mucosal structures was reduced, especially in distal regions. Villus height was significantly reduced in both regions. External muscle thickness was significantly increased in both regions. Despite these changes there was no alteration in villus enterocyte morphology, nor were there any significant changes in villus or crypt densities. The proportion of crypt cells labelled with [3H]thymidine was unaffected by adrenalectomy. In proximal regions, migration rate of labelled enterocytes declined from 12·0 to 5·83% villus height/d (P 〈 0·025) after adrenalectomy; there was no change in migration rate in distal regions. The estimated renewal time was greater in both proximal and distal regions in adrenalectomized compared with control fetuses.
STUDIES ON THE MATURATION OF THE SMALL INTESTINE IN THE FETAL SHEEP. II. THE EFFECTS OF EXOGENOUS CORTISOL
Authors: Trahair J. F. , Perry R. A. , Robinson P. M. , Silver M.
Published: December 2014

The effect of cortisol on small intestinal maturation was investigated in catheterized fetal sheep by infusing 2 mg cortisol/d between 105 and 115 d gestation (term ca. 147 d). This treatment resulted in a fivefold increase in plasma cortisol compared with catheterized control fetuses of the same age. There were no detectable changes in enterocyte morphology after the cortisol infusion; the size and density of most intestinal components were largely unaffected by the treatment. By contrast, the kinetics of the enterocyte population were significantly altered by the raised cortisol levels. The proportion of crypt cells labelled was significantly increased from 0·20 ± 0·04 to 0·33 ± 0·03 in the proximal region (P 〈 0·01) and from 0·22 ± 0·03 to 0·31 ± 0·02 in the distal region (P 〈 0·01). The migration of enterocytes in both regions was significantly increased to nearly twice the control values (P 〈 0·05). Correspondingly, renewal time was almost halved in both regions, while cell density was unchanged in distal and decreased in proximal regions. Hence cell loss appeared to have increased as a result of the cortisol infusion. The kinetic parameters for the villus enterocyte population of the fetuses receiving cortisol before 115 d were of similar magnitude to those previously seen in the normal near‐term fetus. To this extent exogenous cortisol treatment given before a pre‐partum surge mimicked the action of the endogenous hormone in late gestation.
PARTITIONING OF POLAR FATTY ACIDS INTO LYMPH AND PORTAL VEIN AFTER INTESTINAL ABSORPTION IN THE RAT
Authors: McDonald George B. , Weidman Margaret
Published: December 2014

We tested the hypothesis that fatty acids destined for the portal vein after intestinal absorption would be diverted into lymph when infused along with a saturated long‐chain fatty acid. Thoracic fistula rats were infused intraduodenally with either linolenic (l8:3), lauric (12:0), or decanoic (10:0) acid, or with each fatty acid in combination with 5 mM palmitic acid (16:0), in micellar solutions of taurocholate (10 mM) and 2‐mono‐oleoylglycerol. Lymphatic transport of linolenic acid was enhanced by co‐absorption with palmitic acid: when 0·1 mM linolenic acid was infused alone, 32 ± 8% of that absorbed and transported beyond the mesentery was carried in lymph. The addition of palmitic acid to the infusate increased the percentage transported in lymph to 56 ± 10% (P 〈 0·005). The increment was due to enhanced intracellular re‐esterification of linolenate into triacylglycerol. When 5 mM linolenic acid was infused, the comparable figures for lymphatic transport were 55 ± 2% for linolenate infused alone and 66 ± 6% for linolenate infused with palmitate (P 〈 0·005). In contrast, the predominantly portal venous transport of lauric and decanoic acids was unaffected by co‐absorption with palmitate. We conclude that the partitioning of long‐chain fatty acids between portal blood and lymph is dependent on the luminal milieu, in addition to polarity of the fatty acid and the rate of absorption. Unsaturated long‐chain fatty acids have a substantial portal transport under conditions which simulate normal food ingestion.
INERTIA, RESONANT FREQUENCY, STIFFNESS AND KINETIC ENERGY OF THE HUMAN FOREARM
Authors: Walsh E. G. , Wright G. W.
Published: December 2014

The biodynamics of the forearm of a number of relaxed human subjects have been investigated using a printed motor as a torque generator. Oscillation in the horizontal plane at the resonant frequency has been maintained by feed‐back of a modified velocity signal. By means of negative position feed‐back the stiffness could be artificially increased and the resonant frequency accordingly elevated. From these changes it has been possible to calculate limb inertia and muscle stiffness, treating the limb as a torsion pendulum. The correlation of inertia with the fifth power of limb length has been studied, this relationship being predicted on theoretical grounds. A significant correlation was found between resonant frequency and the square root of the reciprocal of inertia, a relationship also predicted on theoretical grounds. As the limb was kept on resonance the motion was limited solely by the damping. When the rate of oscillation was increased by the use of added stiffness the peak velocity increased, indicating that the damping was reduced. The mean inertia and mean stiffness values for the men were higher than those for the women. The kinetic energy of rapid voluntary movements was greater in men than in women.
PERIPHERAL VASCULAR RESPONSES TO CHANGES IN LEFT VENTRICULAR PRESSURE IN ANAESTHETIZED DOGS
Authors: Challenger S. , McGregor K. H. , Hainsworth R.
Published: December 2014

In dogs anaesthetized with chloralose, cardiac receptors were stimulated by increases in left ventricular systolic pressure effected by changes in aortic root pressure. Left atrial and carotid sinus pressures were controlled. A large step increase in ventricular pressure resulted in transient decreases in heart rate, systemic arterial perfusion pressure and perfusion pressure to a vascularly isolated hind limb. The magnitudes of these responses were about three‐quarters of those to either a large change in carotid sinus pressure or aortic root injection of 20 µg veratridine. Steady‐state responses were smaller. There was no significant change in perfusion pressure to a perfused cutaneous vein. Graded changes in ventricular systolic pressure showed that the most sensitive pressure range was between 20 and 24 kPa. These results indicate that changes in left ventricular pressure result in significant vasodilation in the hind limb and in other regions and that responses are obtained when the pressure is moderately elevated.
RELATIONSHIPS BETWEEN PLASMA HORMONE CONCENTRATIONS, UDDER DEVELOPMENT AND THE PRODUCTION OF EARLY MAMMARY SECRETIONS IN TWIN‐BEARING EWES ON DIFFERENT PLANES OF NUTRITION
Authors: Mellor D. J. , Flint D. J. , Vernon R. G. , Forsyth I. A.
Published: December 2014

Ewes carrying twin fetuses were maintained during late pregnancy on a uniformly high plane (well fed), a uniformly low plane (underfed) or a low plane rising to a high plane (refed) of nutrition. The maternal plasma concentrations of hormones concerned with udder development, colostrum production and milk secretion were measured in samples obtained during the last 32 d before and the first 18 h after birth. Udder weights were derived from their linear dimensions, the yields of mammary secretions by hand milking during the first 18 h after birth and the transition from colostrum to milk was indicated by changes in the concentrations of lactose, lipid and immunoglobulin G. Underfeeding reduced prenatal udder development and colostrum accumulation and delayed the post‐natal transition to milk secretion. Refeeding previously underfed ewes to a high plane during the last 5 d before birth had no effect on udder growth, but it did return the secretory functions of udder tissue to the levels observed in well‐fed ewes. Nutritional effects on the plasma concentrations of insulin, placental lactogen, prolactin, cortisol and oestradiol‐17β were small or absent. The relative changes in the plasma concentrations of growth hormone and insulin were such that the growth hormone: insulin ratio increased markedly during the last 11 d before birth in the underfed and refed ewes but not in the well‐fed ewes. These differences in the growth hormone: insulin ratio were associated with greater increases in udder growth rate in the underfed and refed ewes than in the well‐fed ewes. The plasma concentrations of progesterone decreased before birth in all ewes, but the decrease was delayed by underfeeding and refeeding rapidly overcame this effect. The slower progesterone withdrawal in the underfed ewes was associated with a delay in lactogenesis. It is concluded that the nutritionally induced changes in the growth hormone: insulin ratio and in the progesterone concentrations were the most likely endocrine determinants of the observed differences in the rates of mammogenesis and lactogenesis, respectively, but possible independent effects of substrate supply to the udder remain to be clarified.
THE EFFECT OF DIET, INTRARUMINAL pH AND OSMOLARITY ON SODIUM, CHLORIDE AND MAGNESIUM ABSORPTION FROM THE TEMPORARILY ISOLATED AND WASHED RETICULO‐RUMEN OF SHEEP
Authors: Gaebel G. , Martens H. , Suendermann Margret , Galfi P.
Published: December 2014

Six mature sheep fitted with rumen fistulae underwent four consecutive feeding periods, of 15 weeks each, i.e. (1) hay only; (2) 36% hay, 64% concentrate; (3) 10% hay, 90% concentrate; and (4) hay only again. The net absorption of sodium, chloride and magnesium from the washed rumen filled with artificial rumen fluids was tested during each feeding period. The artificial rumen fluids varied either in osmolarity (315 and 422 mosmol l−1) or in pH (6·78 and 4·79). Further, the surface area of rumen papillae was determined. The feeding of increasing proportions of concentrate resulted in an increase of the surface area of rumen papillae and in an elevated net absorption of sodium, chloride and magnesium. Hypertonicity (422 mosmol l−1) of the artificial rumen fluid caused net influx of water into the rumen but did not influence net absorption of the electrolytes irrespective of the feeding regimen. When the pH was lowered this led to a decrease in net absorption of sodium, chloride and magnesium and in transmural potential difference. The extent of the pH‐induced decrease in net ion transport and potential difference was less in sheep receiving high‐concentrate diets. When only hay was fed after the period of feeding 90% concentrate diets the surface area of the papillae, the absorptive capacity of the rumen epithelium and the resistance against low pH returned to control levels. The findings show a reversible adaptive response of rumen epithelial functions to different diets.
THE INFLUENCE OF GASTROINTESTINAL INFUSIONS OF GLUCOSE ON REGULATION OF FOOD INTAKE IN PIGS
Authors: Gregory P. C. , McFadyen M. , Rayner D. V.
Published: December 2014

The influence of gastrointestinal infusions of glucose on short‐term and 24 h control of food intake was studied in sixteen pigs fed twice per day and nine fed three times per day. The pigs were fitted with up to four catheters each, placed in the stomach, the duodenum and at 2 and 8 m from the ligament of Treitz (l.t.). Infusions were given into the catheters, beginning 30 min before the first meal (two feeds) or second meal (three feeds) of the day, and continuing until the pigs stopped eating. The effects of the infusions on both short‐term and 24 h intakes were the same whether the pigs were given two or three feeds per day. Infusions of glucose (400 g/l) into the stomach or small intestine altered short‐term (meal) intake, but had no effect on intake at the following meal. With glucose infusion at rates above a threshold level (4 ml/min) to the stomach, duodenum or ileum (8 m from l.t.) food intake at that meal was suppressed such as to compensate for the amount of energy infused. Glucose infusions to the jejunum (2 m from l.t.) caused greater inhibition of short‐term intake than infusions elsewhere, and 6 ml/min glucose inhibited intake by more than the amount of energy infused. Duodenal injection of the local anaesthetic lignocaine markedly suppressed the inhibition of intake caused by gastric infusion of glucose. The reductions in intake with glucose infusions at various rates into the stomach or duodenum were nearly identical to those with the same rates of infusion of NaCl at the same high osmolarity. It is concluded that glucose activation of receptors over a large part of the small intestine participates in the short‐term control of energy intake in the pig, and that the receptors are activated equally by glucose in terms of an osmotic or caloric stimulus. It is suggested that activation of these receptors is involved in the caloric regulation of gastric emptying leading to gastric distension and inhibition of further intake.
DIABETES MELLITUS IN THE RAT: DIMINUTION IN THE NUMBER OF CELLS IN THE THYMUS AND OF LYMPHOCYTES IN THE BLOOD
Authors: Warley Alice , Daniel P. M. , Guthrie D. L.
Published: December 2014

In diabetic rats there is a rapid fall in the weight of the thymus with a great loss in the numbers of thymocytes. In this paper we show that there is also a marked diminution in the number of lymphocytes in the peripheral blood, although the numbers of neutrophils and monocytes are not affected. Since the thymus is thought to be the site in which T‐lymphocytes develop, it is suggested that the paucity of lymphocytes in the peripheral circulation reflects the loss of cells from the thymus. The diminution in the number of circulating lymphocytes in diabetes may account for the liability of diabetics to suffer severely from infections.
CATECHOLAMINES AND DOPAMINE‐β‐HYDROXYLASE SECRETION FROM PERFUSED GOAT ADRENAL GLANDS
Authors: Yamada Yutaka , Nakazato Yoshikazu , Ito Shigeo , Teraoka Hiroki , Ohga Akira
Published: December 2014

Splanchnic nerve stimulation caused a frequency‐dependent increase in catecholamine (CA) secretion which attained a maximum at 10 Hz in perfused goat adrenal glands. Acetylcholine (ACh) and nicotine also caused a dose‐dependent increase in CA secretion. The percentage of three catecholamines released (adrenaline, 51‐56%; noradrenaline, 42‐47; dopamine, 1·3‐2%) were not significantly different among three different stimuli. These values were almost the same as those found in the extract of adrenal gland and in purified chromaffin granules. The response to ACh was completely abolished by hexamethonium alone. Pilocarpine was ineffective in increasing CA secretion. Dopamine‐β‐hydroxylase (DBH) activity increased with the increase in CA secretion in response to splanchnic nerve stimulation and ACh, though the declining phase of DBH was much slower than that of CA. The ratios of CA to DBH activity released for 25 min during and after splanchnic nerve stimulation and ACh infusion were 0·40 ± 0·07 and 0·50 ± 0·07, respectively. The ratio was 0·41 ± 0·06 in chromaffin granules. The results indicate that only nicotinic receptors are involved in CA secretion and that DBH may be useful as an index of exocytosis in goat perfused adrenal glands.
THIXOTROPY: THE EFFECT OF STRETCH SIZE IN RELAXED FROG MUSCLE
Authors: Lakie M. , Robson Lesley G.
Published: December 2014

Small forces were applied to isolated frog muscle; the resulting displacements were used to calculate muscle stiffness (elastic modulus, E). Stiffness is much greater for small forces within the range of the Short Range Elastic Component (SREC; Hill, 1968). ‘Stirring’ the muscle greatly reduces the stiffness, but only when the applied force is small. Stiffness subsequently returns to its original level. This strongly suggests that muscle thixotropy (Lakie, Walsh & Wright, 1984) is a property of the SREC.