bluuebunny/crossref_metadata_2025 huggingface dataset:
VAGALLY INDUCED GASTRIC ANTRAL CONTRACTIONS AND GASTRIC EMPTYING OF A LIQUID TEST MEAL
Authors: Carr David H. , Brooks Frank P.
Published: December 2014

The emptying of a liquid test meal from the stomach was studied during, and in the absence of, electrical stimulation of cut ends of a thoracic branch of the vagus in anaesthetized cats. The test meal (154 mmol.l‐1 NaCl and 30 mg. l‐1 phenol red) was measured by collecting effluent from a duodenal fistula over a 30 min period. The stomach emptied about 60% of the meal under control conditions compared with over 90% during efferent stimulation of the vagus. The increased volumes emptied during efferent stimulation were not accounted for by secretion of gastric acid. Coincident with the vagally evoked antral contractions there was a gush of liquid from the duodenal cannula. Afferent vagal stimulation resulted in an initial marked delay of emptying followed by an acceleration so that the volume emptied after 30 min was similar to that in control experiments. Antral contractions, evoked by efferent vagal stimulation, accelerated the emptying of a liquid test meal from the stomach.
H1 AND H2 HISTAMINE ACTIONS ON LUNG VESSELS; THEIR RELEVANCE TO HYPOXIC VASOCONSTRICTION
Authors: Barer Gwenda R. , Emery Celia J. , Mohammed F. H. , Mungall I. P. F.
Published: December 2014

Pulmonary vasomotor actions of histamine and the possible relationship of histamine to hypoxic pulmonary vasconstriction were studied in anaesthetized cats with one lobe of lung perfused at constant flow and in isolated perfused rat and ferret lungs. In the cat histamine caused dilatation, biphasic responses and constriction with increasing doses. Histamine induced dilatation was better demonstrated during hypoxic vasoconstriction and was reduced by an H2 histamine antagonist; constriction with histamine was abolished by an H1 antagonist. Histamine also caused both vasodilatation and vasoconstriction in ferret lungs. A mast cell stabilizing agent had no effect on hypoxic pulmonary vasoconstriction in cats or rats. This response was unaffected in cats but greatly reduced in rats and ferrets by cyproheptadine, a combined histamine and 5‐ hydroxytryptamine inhibitor. It was unaffected in cats but abolished in ferrets by an H1 histamine inhibitor. It was again unaffected in cats but greatly reduced in rats and ferrets by an H2 histamine inhibitor. These species differences may reflect differences in mechanism but more probably reflect non‐specific effects of the inhibitors in certain circumstances. However, when drugs nearly abolished hypoxic vasoconstriction, ATP still caused vasoconstriction.
ENHANCED INTESTINAL LYMPH FORMATION DURING FAT ABSORPTION: THE IMPORTANCE OF TRIGLYCERIDE HYDROLYSIS
Authors: Turner S. G. , Barrowman J. A.
Published: December 2014

The effect of intraduodenal administration of fats was studied in the rat to define the mechanisms responsible for the substantial increase in intestinal lymph flow and protein transport which follows fat ingestion. Triglyceride in the intestinal lumen, protected from hydrolysis, does not appear to enhance intestinal lymph production. Giving both long‐and medium‐chain fatty acids, however, causes intestinal lymph flow and protein transport to increase in a manner similar to that found after giving triglyceride which is allowed to undergo hydrolysis. Bile by itself does not seem to be responsible for the phenomenon.
EFFECTS OF BILE SALTS ON THE MOTOR ACTIVITY OF THE GUINEA‐PIG GALL‐BLADDER IN VITRO
Authors: Rutishauser Sigrid C. B.
Published: December 2014

Intra‐luminal pressures were measured in in vitro preparations of the guinea‐pig gall‐bladder Intrinsic tone and spontaneous activity were recorded together with the response of the gall‐bladder to Pancreozymin. The effect of the presence of a variety of conjugated and unconjugated bile salts in the luminal fluid [pH 7·4] was studied. Sodium deoxycholate and sodium chenodeoxycholate had an inhibitory effect on motor activity at concentrations as low as 6·0x10−6 mol.l−1 Sodium taurocholate at a concentration of 3x10−3 mol.l−1 promoted regular spontaneous activity. The results are discussed in relation to their possible physiological, pathological and pharmacological implications.
THE BREATHING PATTERN AFTER BREATH‐HOLDING: THE INFLUENCE OF CHEST POSITION AND THE DRIVE TO BREATHE
Authors: Guy A. J. , Patrick J. M.
Published: December 2014

The pattern of breathing following the breaking‐point of sixty breath‐holds has been studied in five healthy adults and compared with the pattern during recovery from CO2‐rebreathing. The volume and direction of the first respiratory movement, and the VT, V relation for the first four complete breaths was measured. Only when breath‐holds were terminated with an inspiration was the accumulated drive to breathe reflected in an increased volume of the first respiratory movement: terminating expirations simply returned the chest to the resting respiratory level. The volume of the first inspiration was not influenced by the intervention of a terminating expiration, suggesting that expiratory movements do not dissipate the non‐chemical component of the drive to breathe. In three of the five subjects the tidal volumes for given levels of ventilation were greater following breath‐holding than following rebreathing. This altered pattern of breathing has been interpreted in terms of an insiratory‐augmenting reflex.
Water and Electrolyte Excretion During the Oestrous Cycle in Sheep
Authors: Michell Alastair R.
Published: December 2014

Electrolyte excretion was observed during 24 oestrous cycles in housed sheep, together with mixed salivary Na/K ratio during 10 additional cycles. 1. The sharp fall in food and fluid intake at oestrus accompanied a peak of sodium excretion which changed to peak retention 3 days later, both in faeces and urine. 2. Potassium excretion declined with food intake at oestrus but subsequently failed to recover to pre‐oestrous levels dispite full recovery of dietary intake. 3. Curiously, water intake also recovered completely whereas urinary and faecal water retention continued; faecal loss actually exceeded renal excretion on these liberal water intakes. 4. Changes in salivary, urinary and faecal Na/K indicated an aldosterone peak neither during the luteal phase nor at oestrus but three days later. The data raise questions concerning the regulation of water and electrolyte balance within the normal cycle. They also provide a baseline for the investigation of renal effects of gonadal steroids. Possible roles for aldosterone, ADH and progesterone in maintaining fluid and electrolyte balance are discussed, emphasising problems confronting species which have evolved with heavy obligatory potassium excretion but undependable supplies of sodium and water.
Parotid Salivary Flow and Composition During Infusion of Acetylcholine and Atropine into the Carotid Artery of Conscious Sodium‐Replete Sheep
Authors: Beal A. M.
Published: December 2014

The rate of salivary flow and the concentrations of the major electrolytes in parotid saliva and arterial plasma of conscious sodium‐replete sheep were measured during resting salivary secretion and when salivary flow was either increased by intracarotid infusion of acetylcholine at 10–30 nmol. min‐1 for 20 min or reduced by intracarotid infusion of atropine at 14 nmol. min‐1 for 50 min. During both treatments salivary phosphate concentration was always negatively correlated with salivary flow and salivary bicarbonate concentration was always positively correlated with flow. The chloride concentration of the saliva during the acetylcholine infusion experiments was positively correlated with salivary flow whereas when atropine was infused the chloride concentration was negatively correlated with flow. Acetylcholine infusion caused the potassium concentration of the saliva to increase significantly resulting in a marked increase in the total rate of loss of potassium in the saliva. The salivary potassium concentration fell significantly at the onset of atropine infusion and then rose progressively so that the potassium concentration was elevated by the end of the infusion. In both treatments the concentrations of sodium and hydrion were negatively correlated with salivary flow rate. The maximum sodium concentration which occurred in the low‐flow saliva of the atropine infusion was substantially higher than the concentration that would be achieved by equilibrium with the aqueous phase of arterial plasma. It was concluded that the negative correlation between salivary flow and sodium concentration occurred because the reabsorption of sodium from the saliva by the excurrent duct system was minimal in sodium‐replete sheep which would have low levels of mineralocorticoids in the circulation. The inconsistency between this study and previous reports presumably reflects differences in the criteria used to define the sodium status of the animals.
Sympathetic and β‐Adrenergic Stimulation of Parotid Salivary Secretion in Sheep
Authors: Patterson J. , Titchen D. A.
Published: December 2014

The effects of sympathetic and β‐adrenergic stimulation (with isoprenaline) on the secretion of parotid saliva were examined in anaesthetized and totally pithed preparations of sheep. This was studied against a background of spontaneous secretion or of secretion augmented by pilocarpine. In addition to the previously established α‐ adrenergic sympathetic motor effect causing mechanical expulsion of saliva, a β‐ adrenergic secretory response has now been identified. Characteristically, the secretory effect was obtained from electrical stimulation of the cervical sympathetic nerve trunk when lower frequencies or shorter pulse durations were used. This secretory effect and similar responses to isoprenaline were blocked by propranolol.

Two phenomena confirmed that the β‐adrenergic responses to sympathetic stimulation were secretory: namely there were nett increases in the amount of fluid formed (by as much as 128% or as great as 93·9 mg saliva.gm gland‐1.min‐1), and they were accompanied by increases in the protein content of the parotid saliva (up to 8–9 fold). The amounts of protein rose from resting levels of 10–170 µg.ml‐1 (expressed as equivalents of bovine serum albumin) to as high as 840µg.ml‐1 in response to single i.v. injections of 2 µg.kg‐1 of isoprenaline, and to 1240µg.ml‐1 with cervical sympathetic nerve stimulation.

It is concluded that there is a sympathetic secretory innervation in parotid salivary glands of sheep that is mediated by β‐adrenergic mechanisms.
Maintenance of Normal Serum Calcium Level in the Hyperprolactinaemic Rat
Authors: Tan C. M. , Tan G. J. S.
Published: December 2014

The effect of experimentally induced chronic hyperprolactinaemia in male rats on the serum levels of calcium has been examined. Chronic elevation of circulating prolactin levels had no significant effect on the serum calcium levels and normal blood calcium homeostasis was still maintained.
Segmental and Intersegmental Organization of Neurones in the Substantia Gelatinosa Rolandi of the Cat's Spinal Cord
Authors: Cervero F. , Iggo A. , Molony V.
Published: December 2014

Single unit electrical activity has been recorded from neurones in the Substantia Gelatinosa Rolandi (SG) of the lumbar spinal cord of chloralose anaesthetized and gallamine paralysed cats. SG neurones were identified on the basis of five previously defined criteria [Cervero, Iggo and Molony, 1979b]. The surface of the spinal cord containing Lissauer's tract was stimulated electrically in order to excite axons running through Lissauer's tract. In about half of the animals studied Lissauer's tract was in addition surgically isolated by sectioning the adjacent dorsal column and dorso‐lateral funiculus. The responses of 32 intracellularly recorded and 78 extracellularly recorded SG neurones to stimulation of Lissauer's tract and surrounding structures have been analysed. Ten SG neurones had axons in Lissauer's tract that projected for distances between 15 and 41 mm (two and three segments rostral to their origin). The majority of the SG neurones studied did not project beyond their segments of origin. The mean conduction velocity of the long projecting SG neurones was 10·3 m.s‐l (range 4·6–18·3 m.s−1), corresponding to conduction in small myelinated fibres. All 110SG neurones studied were excited post‐synaptically by stimulation of Lissauer's tract and evidence is given to support the view that it was monosynaptically mediated. The latencies and threshold of the post‐synaptic activation indicated that it was mediated by a group of Aδ fibres within Lissauer's tract. All SG neurones studied showed a long period of inhibition (200–500ms) following the initial excitation. This inhibition was mediated by large myelinated fibres since it appeared at stimulus intensities that were threshold for excitation of the largest dorsal column or dorso‐lateral funiculus fibres. When axons in Lissauer's tract were recruited by electrical stimulation the period of inhibition lasted as long as 1s. The segmental somatotopic organization of the SG neurones was found to be similar to the larger dorsal horn neurones of the same spinal cord segments.
Endometrial Blood Flow in Anaesthetized Sheep as Measured with Krypton‐85 Clearance and Microsphere Techniques
Authors: Fraser I. S. , Brown B. W. , Mattner P. E.
Published: December 2014

Uterine blood flow rates were obtained with a Krypton (85Kr) clearance technique and with radio‐active microspheres in six anaesthetized, non‐pregnant ewes (a total of ten comparisons). 85Kr was administered, via a catheter, into the abdominal aorta and β‐emissions were detected with a catheter‐type semi‐conductor detector probe situated in the lumen of a uterine horn.

In seven instances, the 85Kr clearance curve had only one component while in the remaining three instances the curves could be resolved into two components. The flow rates derived from the single component curves and the mean flow rates calculated from the curves with two components were of the same order as, and highly correlated with, estimates of capillary blood flow obtained with microspheres for either the caruncles, the inter‐caruncular endometrium or the total endometrium (r=0·832, r=0·822 and r=0·841, respectively, P<0·005). There was no correlation between the flow rates obtained with the 85Kr technique and estimates of myometrial capillary blood flow obtained with microspheres.
Breath Hydrogen (H2) and Methane (CH4) Excretion Patterns in Normal Man and in Clinical Practice
Authors: Tadesse K. , Smith Dorothy , Eastwod M. A.
Published: December 2014

Breath H2 and CH4 daily excretion patterns were studied in 20 healthy individuals whilst on their regular diets and fasting. The average H2 excretion level was found to be 85 ml day‐1 on habitual meals and less than 35 ml day‐1 whilst fasting. The mean excretion in breath at any one time was less than 0·5 µmol.l–1 and individual breath sample excretion rarely exceeded 0·90 µmol.l–1. H2 excretion followed a regular pattern, being high in the morning, falling until about mid‐day and rising during the early afternoon. The pattern of excretion remained essentially similar from day to day. Fasting decreased the overall excretion level and abolished the afternoon rise. CH4 excretion did not follow any regular pattern over the day and was individual with a third of the participants excreting above 0·1 , µmol.l–1 and the rest nothing or below 0·10 µmol.l–1. In 15 of the subjects mouth‐to‐caecum transit time was measured employing the breath H2 test and using three different oligosaccharides of different molecular weight and varying osmolalities. The mouth‐to‐caecum transit time (MCTT) for lactulose was found to be 90±7 min, for raffnose 168±35 min, and for stachyose 290±0 min. Fasting and different osmolalities of the same oligosaccharides did not alter the MCTT. Administering the three oligosaccharides to a patient with colostomy did not show a difference in the H2 evolution time. Using the breath H2 test as a method of detection of lactose intolerance showed that the test is relatively more reliable, non‐invasive and simple when compared to blood glucose measurement of mucosal lactase activity.
DO THE BLOOD VESSELS OF THE ANTLER VELVET OF THE RED DEER HAVE AN ADRENERGIC INNERVATION?
Authors: Rayner V. , Ewen S. W. B.
Published: December 2014

Samples of antler velvet and pedicle skin of Red deer were snap‐frozen, freeze‐dried and treated with hot formaldehyde vapour. Sections (4 µm thick) were epi‐illuminated with ultra‐violet light. No blue‐green fluorescence characteristic of adrenergic nerves was seen in sections from the antler velvet except in one castrate, although the blood vessels of the pedicle skin were well innervated. Yellow fluorescence characteristic of 5‐hydroxytryptamine was present in mast cells in the velvet. The lack of a discrete adrenergic vasomotor innervation of the antler blood vessels makes it unlikely that antlers in velvet control heat loss by functioning as heat radiators.
INTRACELLULAR MARKING OF IDENTIFIED NEURONES IN THE SUPERFICIAL DORSAL HORN OF THE CAT SPINAL CORD
Authors: Molony V. , Steedman Wilma M. , Iggo A. , Cervero F.
Published: December 2014

Intracellular iontophoresis of horseradish peroxidase has been used to mark identified neurones in the superficial dorsal horn of cats. The cats were anaesthetized with α‐chloralose and paralysed with gallamine triethodide. Four specific nocireceptive neurones in the marginal zone and seven neurones in the substantia gelatinosa were recovered. One of the former and four of the latter are described in detail and are illustrated as reconstructions from serial sections. The results confirm previous conclusions that the substantia gelatinosa contains neurones classified as ‘inverse’ and that the nocireceptive neurones of lamina I are Waldeyer cells.
TOLERANCE OF HIGH ALTITUDE ACCLIMATIZED RATS TO BLOOD LOSS AT SEA LEVEL
Authors: Cherdrungsi Pipat
Published: December 2014

After acclimatization to high altitude, the sea level haemorrhagic tolerance of rats was measured by determining the bleeding volume which resulted in death under anaesthesia following cannulation. For each animal this was recorded as a bleeding volume index (BVI), the total volume of blood lost per 100 g of body weight. The mean BVI of altitude acclimatized rats was greater than that for non‐acclimatized rats (P 〈 0·001), showing that chronic exposure to altitude enabled the animals to tolerate more severe blood loss. Evidence is presented which suggests that the increased haemorrhagic tolerance resulted, in part, from an increased initial blood volume and an increased ability for arterial blood pressure regulation during haemorrhage.
CARDIOVASCULAR CHANGES ELICITED BY VAGAL GASTRIC AFFERENTS IN THE RAT
Authors: Grundy D. , Davison J. S.
Published: December 2014

Cardiovascular changes elicited by gastric distension in the urethane anaesthetized rat are described. Heart rate changes were mediated via a vago‐vagal pathway with ‘in‐series’ tension receptors in the stomach wall providing the afferent input and cholinergic cardio‐inhibitory fibres forming the efferent pathway. Blood pressure changes occurred independently of the heart rate changes; the main afferent pathway was again vagal but the efferent outflow was non‐cholinergic and probably sympathetic.
THE EFFECT OF COOLING ON TRANSMISSION OF IMPULSES IN VAGAL NERVE FIBRES ATTACHED TO ATRIAL RECEPTORS IN THE DOG
Authors: Linden R. J. , Mary D. A. S. G. , Weatherill D.
Published: December 2014

In anaesthetized dogs, the effect of graded cooling on the transmission of the maximum frequency of impulses, evoked by supramaximal stimulation, was studied in myelinated and non‐myelinated vagal fibres attached to receptors in the atria. In these fibres, it is shown that first, there is a continuous relation between the maximum frequency of transmission of impulses and vagal temperatures ranging between 37°C and the temperature at complete blockade (no conduction at 0·5 impulses.s‐1) for these fibres; second, there is a direct relationship between the maximum frequency of transmission of impulses and the conduction velocity. It is concluded that the maximum frequency of transmission of impulses in vagal fibres attached to atrial receptors in the dog is related to temperature and conduction velocity. This relationship between maximum frequency of transmission and temperatures provides a quantitative explanation for the previously observed effects of cooling the vagi on the responses to stimulation of atrial receptors which were used to show that the reflex increases in heart rate and reflex reduction in activity in renal nerves involved only atrial receptors attached to myelinated vagal fibres.
ROLE OF ANGIOTENSIN II AND BRADYKININ IN THE DIURESIS CAUSED BY STIMULATION OF ATRIAL RECEPTORS
Authors: Knapp M. F. , Linden R. J. , Mary D. A. S. G. , Pearson M. J.
Published: December 2014

The diuretic response to stimulation of left atrial receptors, by distending balloons located either at the pulmonary vein‐left atrial junctions or in the body of the left atrium, was studied during blockade of the generation of angiotensin II using a continuous infusion of angiotensin converting enzyme inhibitor, SQ 14,225, in anaesthetized dogs. Despite blockade of angiotensin conversion, known also to potentiate the activity of bradykinin, a diuretic response was obtained in each dog; the response was similar to that observed in dogs without blockade of angiotensin conversion. Angiotensin II and bradykinin did not significantly influence the rate of secretion of Malpighian tubules of Rhodnius prolixus, which have been shown capable of detecting the blood‐borne agent known to mediate the diuretic response. It is concluded that neither angiotensin II nor bradykinin is likely to be the blood‐borne agent released by stimulation of atrial receptors.
INTERNALIZATION OF OUABAIN AND REPLACEMENT OF SODIUM PUMPS IN THE PLASMA MEMBRANES OF HeLa CELLS FOLLOWING BLOCK WITH CARDIAC GLYCOSIDES
Authors: Lamb J. F. , Ogden Pat
Published: December 2014

The cardiac glycosides, ouabain or digoxin, when applied to HeLa cells at a concentration of 1 µM, block all Na/K pumping. The recovery of the cells from such a block involves a process of internalization of the glycoside, with its subsequent excretion and the appearance of a working Na pump at the plasma membrane. The rate of recovery of pump function probably does not depend on the direct dissociation of the glycoside from the sodium pumps on the plasma membrane. Low temperature and vinblastine slow the rate of glycoside loss from the cells (the t½ is normally about 20 h). No other agent examined altered the excretion rate. The recovery of pump function (t½ of 6 h) was reduced by all factors examined, i.e. low temperature, vinblastine, low serum concentration, cycloheximide and chloropromazine. We think this means that glycoside excretion and pump recovery are not directly related, though recovery may ultimately depend on glycoside excretion. The recovery in pump function which does occur in the absence of protein synthesis is thought to be due to a store of preformed sodium pumps held in the cell. Fresh HeLa cells ‘turnover’ their sodium pumps at a slow rate, i.e. they internalize their pumps and replace them with new ones at a rate of about 1% per hour. When pumps on the plasma membrane are blocked with cardiac glycosides, the rate of replacement can be increased by a factor of at least 4. This, therefore, constitutes a repair process. It is shown that HeLa cells provide a good model for the detoxification mechanism present in the human heart treated with therapeutic concentrations of glycosides.
THE NATURE OF THE ATRIAL RECEPTORS RESPONSIBLE FOR A REFLEX INCREASE IN ACTIVITY IN EFFERENT CARDIAC SYMPATHETIC NERVES
Authors: Linden R. J. , Mary D. A. S. G. , Weatherill D.
Published: December 2014

In dogs anaesthetized with chloralose, distension of small balloons in the right upper and middle pulmonary vein‐atrial junctions, to stimulate left atrial receptors, caused an increase in heart rate and an increase in activity in efferent sympathetic nerve fibres in cardiac branches of the right stellate ganglion. Cooling of the cervical vagi in steps reduced the magnitude of the responses in these sympathetic nerve fibres. In four dogs, the response in six preparations of sympathetic nerves was slightly reduced with the vagi at 18 °C and markedly reduced or abolished at 12 °C. In these nerves there was no significant response to distension of the balloons when the cervical vagi were cooled to 9 °C. The effect of cooling the vagi was the same as the previously shown effect of cooling on the increase in activity in myelinated afferent vagal fibres and the increase in heart rate during stimulation of atrial receptors. It is concluded that the increase in activity in efferent sympathetic cardiac nerve fibres during distension of small balloons in the pulmonary vein‐atrial junctions involves receptors discharging into myelinated vagal nerve fibres; receptors which discharge into non‐myelinated vagal nerves or afferent sympathetic nerve fibres are not involved in this response. Thus, the efferent sympathetic nerve fibres studied are likely to represent the efferent pathway of the response of an increase in heart rate to distension of the small balloons.
THE RESPONSE IN EFFERENT CARDIAC SYMPATHETIC NERVES TO STIMULATION OF ATRIAL RECEPTORS, CAROTID SINUS BARORECEPTORS AND CAROTID CHEMORECEPTORS
Authors: Linden R. J. , Mary D. A. S. G. , Weatherill D.
Published: December 2014

The reflex increase in activity in efferent cardiac sympathetic nerve fibres in response to distension of small balloons in the pulmonary vein‐atrial junctions was studied in dogs anaesthetized with chloralose; the carotid sinuses were isolated and perfused with blood. In the efferent cardiac nerves which responded to distension of the balloons there was no significant change in the control activity, or in the magnitude of the response during changes in carotid sinus pressure from 8 to 30 kPa, during changes in the blood perfusing the sinuses from arterial to venous or during stimulation of the cutaneous branch of the left radial nerve. In contrast, in efferent cardiac nerves which did not respond to the distension of the balloons, consistent and significant changes in activity resulted from stimulating arterial baroreceptors, chemoreceptors or a cutaneous branch of the radial nerve. It is concluded that efferent cardiac sympathetic nerve fibres which respond by an increase in activity to stimulation of the atrial receptors, constitute a group of nerve fibres which are separate from those responding to stimulation of receptors in the carotid region or to stimulation of peripheral somatic nerves.
PHYSIOLOGICAL ROLE OF A SLOW, VOLTAGE‐SENSITIVE, SYNAPTIC RESPONSE MEDIATED BY AN IDENTIFIED SEROTONIN‐CONTAINING NEURONE
Authors: Cottrell G. A.
Published: December 2014

In Helix, activation of an identified serotonin‐containing neurone produces a slow, markedly voltage‐sensitive, depolarizing synaptic potential in another identified neurone, the A neurone. Accommodation of impulse activity in the A neurone observed with repetitive applied constant‐amplitude pulses is markedly reduced by activating the serotonin neurone. Activation of the serotonin neurone also prolongs the duration of the A neurone action potential.
β‐ADRENERGIC EFFECTS ON COMPOSITION OF PAROTID SALIVARY SECRETION OF SHEEP ON FEEDING
Authors: Patterson J. , Brightling P. , Titchen D. A.
Published: December 2014

Observations were made in sheep, before and after fresh food was given during teasing with food and after rumination, on the flow of parotid saliva and its protein, Mg2+, K+, Na+ and Cl‐ concentrations. The animals studied had either a cannulated or fistulated parotid salivary duct. Parotid salivary flow, protein, Mg2+, K+ and Cl‐ increased markedly following feeding. The increases in protein and Mg2+, but not in flow, were largely blocked by the I.V. administration of propranolol (1 mg.kg‐1). Whereas the actual ingestion of food was associated with large increases in protein (up to 42·5 times, to as high as 1760 µg.ml‐1 of saliva), teasing with food caused relatively minor increases in parotid saliva. There were slight, if any, changes in protein concentration during the increased parotid salivary flows of rumination, whether chewing was on the same side or contralateral to the cannulated parotid salivary duct. It is concluded that a β‐adrenergic mechanism previously demonstrated in acute experiments contributes to increases in the secretion of protein of the parotid saliva when sheep eat. There was a close correlation between the concentrations of protein and of Mg2+ but not of the other electrolytes studied.
EFFECT OF VISCOSITY OF TEST MEALS ON GASTRIC EMPTYING IN DOGS
Authors: Ehrlein Hans‐Jörg , Pröve J.
Published: December 2014

In five dogs gastric emptying of low, medium and high viscosity meals was measured via a duodenal cannula. The rate of emptying depended on the viscosity of the test meals: the time for half emptying was 4·5 ± 2·2 min with the low viscosity liquid meal (1 centipoise), 28·9 ± 9·5 min with the test meal of medium viscosity (105 centipoise), and 43 ± 11·8 min with the test meal of high viscosity (106 centipoise). The emptying curves of the medium and high viscosity meals were sigmoid, whereas the curve representing the emptying of the low viscosity liquid meal followed an exponential pattern. Results indicate that the viscosity of the meal is an important factor for the rate of gastric emptying.
AMINO NITROGEN METABOLISM FOLLOWING ADMINISTRATION OF INDIVIDUAL AMINO ACIDS OR MEAT IN CONSCIOUS DOGS
Authors: Lee Karen E. , Summerill R. A.
Published: December 2014

Normal conscious dogs were given a meal of meat or doses of individual amino acids by stomach tube. The concentration of amino nitrogen in systemic arterial plasma and the rate of urea production both increased; the magnitude and time course of these increases varied with the individual amino acid administered. There was a relationship between the plasma amino nitrogen concentration and urea production following L‐serine, L‐alanine, L‐proline, dicarboxylic acids and L‐cystine similar to that obtained after meat ingestion. It is suggested that these amino acids were transaminated as rapidly as they were absorbed to produce an increase in a general pool of amino acids. Following L‐threonine, L‐valine, D‐serine and immediately after glycine, a small increase in urea production was accompanied by a large increase in plasma amino nitrogen concentration. It is suggested that these amino acids ‘escaped' transamination in the gut wall and liver and that the increase in plasma amino nitrogen was due to a high concentration of the individual amino acid administered.
GLOMERULAR FILTRATION RATE FOLLOWING ADMINISTRATION OF INDIVIDUAL AMINO ACIDS IN CONSCIOUS DOGS
Authors: Lee Karen E. , Summerill R. A.
Published: December 2014

Normal conscious dogs were given 100 mmol glycine, L‐serine, L‐alanine, L‐threonine, L‐proline, L‐glutamic acid (50 mmol), L‐aspartic acid and L‐valine by stomach tube. All these amino acids increased glomerular filtration rate (G.F.R.). There was no increase in G.F.R. following L‐cystine or D‐serine. The intravenous infusion of L‐proline, but not glycine, caused increase in G.F.R. The results suggest that the increase in G.F.R. was not due to a high plasma concentration of the individual amino acids but was related to the metabolism of amino acids with production of urea. It is postulated that after meat and during the metabolism of amino acids a factor is released which reaches and acts on the kidney to cause the increase in G.F.R.
CONTRACTILE PROPERTIES AND FIBRE COMPOSITION OF RAT SKELETAL MUSCLE: EFFECT OF MILD HYPERTHYROIDISM
Authors: Nicol Colin J. M. , Maybee Sarah H.
Published: December 2014

The effect of a chronic mild elevation of plasma triiodothyronine levels upon the contractile properties and fibre distribution of skeletal muscle was studied. The isometric twitch characteristics and passive tension‐length relationship were studied in the soleus and extensor digitorum longus muscles of anaesthetized rats injected for increasing periods with triiodothyronine. This treatment results in a progressive speeding in the rates of isometric contraction and relaxation of the soleus and in a concomitant decrease in the elasticity of the muscle. There was also a conversion of slow to fast fibre types in the soleus, demonstrated histochemically. It is concluded, in view of differences in the magnitudes and time courses of the various changes, that triiodothyronine increases the rates of contraction and relaxation of existing slow fibres and contraction in the soleus muscle as a whole before any change occurs which is attributable to slow‐fast fibre interconversion. The possible mechanisms of the early thyroid hormone effects on muscle are discussed.
NUMBERS AND SIZES OF NERVE FIBRES IN MOUSE SPINAL ROOTS
Authors: Biscoe T. J. , Nickels S. M. , Stirling C. A.
Published: December 2014

The numbers of myelinated and non‐myelinated nerve fibres in the spinal roots of one strain of mouse have been counted from electron micrographs and the accuracy of counting procedures assessed. Non‐myelinated nerve fibres are present in the ventral roots at all levels though the largest number are found in the thoracic and L1, L5, L6 and S1 ventral roots. The number is very small in L2, L3 and L4 ventral roots which are those supplying the hind limb. Fibre diameter histograms were obtained from measurements of cross sectional area for myelinated and non‐myelinated fibres in L1 and L4 ventral roots. The relationship of myelin thickness to axon diameter shows that to a near approximation the myelin thickness is ⅕ to ¼ the axon diameter. A measure of circularity was calculated, the ratio of the measured cross‐sectional area to the area calculated from the measured perimeter assuming the fibre to be circular, and plotted against the axon perimeter for L1 and L4 ventral root myelinated fibres. This showed a tendency for larger fibres to be less circular than smaller fibres.
THE EFFECTS OF BLACK WIDOW SPIDER VENOM ON THE INNERVATION OF MUSCLES PARALYSED BY BOTULINUM TOXIN
Authors: Gomez S. , Queiroz L. S.
Published: December 2014

Botulinum toxin (BoTx) was injected into the muscles of one leg in mice causing local paralysis. Black widow spider venom (b.w.s.v.) was then injected into the paralysed muscles 3 or 15 d later. In both groups b.w.s.v. destroyed the nerve terminals poisoned by BoTx. In the 15 d group axonal sprouts, which had formed due to the block of neuromuscular transmission by BoTx, were also destroyed. Within a few days the motor nerve terminals regenerated and the muscles recovered from paralysis at a faster rate than after BoTx alone. Recovery seemed to begin earlier in muscles where axonal sprouting was already advanced when b.w.s.v. was injected. The normal pattern of innervation was re‐established in both groups, which was in marked contrast with muscles after BoTx alone where numerous sprouts and many ectopic end‐plates had formed.
THE EFFECTS OF STIMULATION OF THE LEFT ATRIAL RECEPTORS IN THE CAT
Authors: Scott Evelyn M. , Roberts A. P. , Tierney N. M.
Published: December 2014

In the cat, distension of the left atrial appendages by means of small balloons resulted in variable changes in the heart rate. Distension of the junctions between the upper two left pulmonary veins and the left atrium resulted in a small but statistically significant increase in the heart rate. Distension did not result in any significant changes in the blood pressure. The increases in heart rate are far less than observed in the dog and it is suggested that the atrial receptors might play a less important role in cardiovascular control in the cat than they do in the dog.
THE MODE OF ACTION OF INTRAVENOUS PENTAGASTRIN INJECTIONS ON FORESTOMACH MOTILITY OF SHEEP
Authors: Nicholson T.
Published: December 2014

The investigation involved the recording of pressure changes in the reticulum and rumen of sheep. Rapid, intravenous injection of pentagastrin (0·2–1·0 µg/kg body wt.) inhibited motility during eating and rumination as well as in sheep at rest. In anaesthetized sheep, after bilateral cervical vagotomy, contractions of the reticulum and rumen produced by stimulation of the vagus nerve were not prevented by pentagastrin injections (0·2–l·0 µg/kg body wt.). In anaesthetized sheep with the left vagus nerve intact, stimulation of the central end of the right vagus nerve failed to elicit reflex contractions of the reticulum for 210–390 s after the intravenous injection of pentagastrin (0·6–0·7 µg/kg body wt.).
STUDIES ON THE MOVEMENT OF GLUCOSE, PYRUVATE AND LACTATE INTO THE AMPULLA AND ISTHMUS OF THE RABBIT OVIDUCT
Authors: Leese H. J.
Published: December 2014

The appearance of glucose, pyruvate and lactate in fluid recirculated through the lumen of the ampulla and isthmus of the rabbit oviduct has been followed for 2 h in vivo. Each nutrient appeared in the lumen of the ampulla at approximately 1·8 times its rate in the lumen of the isthmus. The circumference of the mucosa lining the two regions was measured together with the distribution of ciliated and secretory cells. The surface area of the mucosa lining the ampulla was 343 mm2, and that lining the isthmus, 191 mm2. It is tentatively suggested that the capacity of the ampulla and isthmus to transport small molecules is a function of their respective mucosal surface areas.
UPTAKE OF CHLOROTETRACYCLINE INTO MOUSE EGGS
Authors: House C. R. , Bland K. P.
Published: December 2014

The fluorescent compound chlorotetracycline (CTC) enters the mouse egg by a mechanism. controlled by the oolemma. The intracellular distribution of CTC is non‐uniform and during the early stages of uptake fluorescent patches are observed at the egg's surface probably close to the oolemma. Lanthanum blocks the entry of CTC into the egg's cytoplasm and in this condition the CTC remains at the surface of the egg; the labelled site is not the zona pellucida and is likely to be the outer surface of the oolemma. The results of this study of CTC uptake support the idea that this compound labels divalent ( or trivalent) cations in the neighbourhood of cell membranes.
DIURESIS FROM STIMULATION OF LEFT ATRIAL RECEPTORS IN DOGS: FURTHER PURIFICATION OF THE CAUSATIVE AGENT FROM PLASMA
Authors: Pither J. M. , Knapp M. F. , Pearson M. J. , Linden R. J.
Published: December 2014

Stimulation of atrial receptors by distension of a balloon in the left atrium of anaesthetized dogs results in a reflex diuresis mediated by an unknown humoral agent. This paper reports the further purification from plasma of acetone extracts of the humoral agent which may mediate the diuretic response. Activity of the humoral agent was detected using the Malpighian tubules of Rhodnius prolixus. Gel filtration of the acetone extracts on Sephadex G‐25 and G‐100, followed by dialysis of the fraction from Sephadex G‐100 that contained the humoral agent, showed that the activity of the agent was associated with a high molecular weight fraction (〉 30000). Acetone extracts of the humoral agent were also shown to be stable to treatment with HCl for 1 h at 25°C. After this acid treatment, gel filtration on Sephadex gels and Bio‐Gel P‐2 showed that the agent was of low molecular weight (〈 1800). It is concluded that the activity of the humoral agent, as detected by the Malpighian tubule preparation, is associated with a molecule of low molecular weight which may be bound to a larger molecule from which it can be dissociated by acid treatment.
ABOLITION OF ATRIAL RECEPTOR DIURESIS AND OF RELEASE OF HUMORAL AGENT BY COOLING THE VAGAL NERVES
Authors: Knapp M. F. , Pearson M. J. , Pither J. M. , Linden R. J.
Published: December 2014

Stimulation of atrial receptors in anaesthetized dogs results in a reflex increase in urine flow mediated by vagal myelinated fibres and, in part, by a humoral agent of unknown identity. The humoral agent has been detected by an in vitro preparation of the Malpighian tubules of Rhodnius prolixus. The purpose of this investigation was to determine whether the present extract of plasma purporting to contain the humoral agent is also related to the reflex diuresis. In nine chloralose anaesthetized dogs atrial receptors were stimulated by distension of a balloon in the left atrium. Plasma samples collected before and during distension of the balloon, respectively, were precipitated with acetone, acid‐treated and fractionated on Bio‐Gel P‐2. The purified samples were tested for the activity of the humoral agent on the Malpighian tubule preparation. In each dog, distensions of the balloon were performed with the cervical vagal nerves at 9 and 37°C. Cooling the vagal nerves to 9°C abolished the reflex diuresis and abolished the activity of the humoral agent recovered from a Bio‐Gel P‐2 fraction (molecular weight range 100–1800) which elutes between the void volume and the salt fraction. It was concluded that the substance recovered from Bio‐Gel P‐2 is associated with the diuresis in response to stimulation of atrial receptors; it is suggested that its presence is dependent on the integrity of the afferent limb of the atrial receptor reflex.
ARTERIAL PLASMA COMPOSITION DURING COMPENSATORY INCREASE IN MILK SECRETION IN THE GOAT: RELATION TO RATE LIMITATION
Authors: Henderson A. J. , Peaker M.
Published: December 2014

Colchicine was injected into one mammary gland of goats at peak lactation. Milk secretion in the treated gland decreased to 40% of the previous level while that in the other gland increased to reach 126% of its previous level. The concentrations of tyrosine and glucose in arterial plasma increased while those of lysine, arginine asparagine, glycine, alanine and ornithine decreased; the concentrations of other amino acids and of acetate did not change significantly. The results are discussed in relation to factors which normally limit the rate of milk secretion and to the mechanism by which compensatory increases occur in one gland during the inhibition of secretion in the other. These and previous results are not compatible with the view that arterial plasma concentrations of essential amino acids are rate‐limiting for milk secretion.
β CELL MEMBRANE POTENTIAL AND INSULIN RELEASE; ROLE OF CALCIUM AND CALCIUM: MAGNESIUM RATIO
Authors: Atwater Illani , Frankel Barbara J. , Rojas Eduardo , Grodsky Gerold M.
Published: December 2014

Glucose‐induced insulin release from perfused rat pancreas was compared with glucose‐induced changes in membrane potential of β cells from mouse islets. Extracellular concentrations of Ca and Mg were varied as steps, simultaneously or separately, from 10% to 200% of normal in the presence of 11·1 mM glucose. A change in Ca induced a transient change in electrical activity paralleled by a transient change in insulin release. If the Ca/Mg ratio was maintained, steady‐state insulin release remained constant between 10% and 200% Ca, while electrical activity showed alterations. Analysis of burst parameters indicated that increased or decreased Ca entry was balanced by decreased or increased excitability. It is postulated that the β cell contains a compensator mechanism for the regulation of Ca influx.
THE QUEST FOR THE INHIBITORY NEUROTRANSMITTER IN BOVINE TRACHEAL SMOOTH MUSCLE
Authors: Cameron A. R. , Johnston C. F. , Kirkpatrick C. T. , Kirkpatrick Melanie C. A.
Published: December 2014

The effect of inhibitory nerve stimulation on the mechanical, membrane potential and membrane conductance responses of isolated bovine tracheal smooth muscle has been studied. Membrane responses were measured in a sucrose‐gap apparatus. In order to record inhibitory responses, it was necessary to increase tone in the preparation by applying a drug such as histamine. When tone was raised, repetitive field stimulation of intrinsic nerves caused depolarization and contraction, followed by relaxation and a suppression of histamine‐induced slow waves. Hyperpolarization of the membrane was only seen following prolonged nerve stimulation, and there was no change in membrane conductance. The inhibitory effect of nerve stimulation was abolished by tetrodotoxin, but was not abolished by atropine, indomethacin, propranolol, naloxone or the purinergic blockers quinidine and theophylline. It was not satisfactorily mimicked by catecholamines, by γ‐amino‐n‐butyric acid (GABA) or by purines.

Nerves with catecholamine fluorescence could not be found in the tracheal muscle layer. Neither adrenergic nor purinergic types of nerve terminal could be found in the tracheal muscle layer during ultrastructural examination of over one thousand nerve profiles. Vasoactive intestinal peptide (VIP) caused relaxation of the histamine‐contracted tracheal muscle, suppressed the slow wave and caused slight hyperpolarization at higher concentrations, without affecting the membrane conductance. VIP was found in samples of tracheal muscle at a mean concentration of 1·95 ng/g. When the effluent solution flowing past isolated tracheal muscle strips was assayed for VIP, samples collected during inhibitory nerve stimulation had much higher concentrations of the peptide than samples collected before stimulation, after stimulation, or during stimulation in the presence of tetrodotoxin (10–6 mol/l). The VIP content of the effluent during control periods was 73·8 pg/ml, and during stimulation was 167·5 pg/ml. It is suggested that VIP might be the non‐adrenergic inhibitory neurotransmitter in bovine tracheal smooth muscle.
BRAIN TISSUE GRAFTS IN THE CENTRAL NERVOUS SYSTEM: REVERSAL OF HYPOGONADISM
Authors: Gibson M. J. , Krieger D. T. , Perlow M. J. , Davies T. F. , Zimmerman E. A. , Ferin M. , Charlton H. M.
Published: December 2014

Transplantation of brain tissue from normal donors into the central nervous system of animals with specific central neurochemical deficiencies has been used to remedy such defects. The present studies demonstrate that the hypogonadism present in the adult male hypogonadal (hpg) mouse that is secondary to hypothalamic gonadotropin releasing hormone (GnRH) deficiency can be corrected by grafts into the anterior third ventricle of fetal preoptic area (p.o.a.) tissue. The p.o.a. is a primary site of localization of GnRH neurones in rodents. As compared with untreated hpg males, or with hpg males that had received control cortical tissue implants, the hpg animals with p.o.a. grafts showed measurable levels of GnRH within the hypothalamus. Immunocytochemical studies revealed GnRH within the transplants. Increased pituitary and plasma LH and FSH, and testicular growth with full spermatogenesis, were also evident in the hpg males that had received p.o.a. implants.
HYPOTHALAMIC NEURONE ACTIVITY: HORMONE RELEASE AND BEHAVIOUR IN FREELY MOVING RATS
Authors: Summerlee A. J. S.
Published: December 2014

A technique for taking long‐term recordings from single hypothalamic neurones in freely moving rats is described. The neurones were classed as magnocellular on the basis of antidromic activation from a chronically implanted neurohypophyseal stimulating electrode. Activity of magnocellular neurones in suckling revealed that 73% of the spontaneously discharging cells (n = 8) showed bursts of high‐frequency excitation time‐locked to reflex milk ejection. These cells were classed as putative oxytocinergic neurones. Non‐responsive magnocellular neurones (n = 3) were tentatively identified as vasopressinergic. In many ways, these periods of activation were similar to those described in anaesthetized animals. The differences between these experimental situations are discussed. The discharge patterns of nine magnocellular neurones was studied in natural labour and correlated to the observed events of parturition. The activity of these cells was then followed in the post‐partum suckling period and differentiated into activity recorded from putative oxytocinergic and vasopressinergic cells on the basis of their response before reflex milk ejection. All magnocellular neurone showed bursts of increased discharge after forceful abdominal straining movements but only the putative oxytocinergic neurones (n = 4) showed activation before delivery.