bluuebunny/crossref_metadata_2025_split huggingface dataset:
L‐TRYITOPHAN‐INDUCED DEPRESSION OF THE PRESSOR RESPONSE TO CLONIDINE IN ANAESTHETIZED RATS
Authors: Nolan P. L. , Brazenor R. M. 
Published: June 2007

SUMMARY1. The interaction of the serotonin precursor L‐tryptophan with the pressor responses of the anaesthetized rat to the intravenous injection of clonidine, adrenaline and angiotensin has been studied.2. Pretreatment of rats with L‐tryptophan (100 mg/kg) depressed the pressor response to clonidine but had no effect on the responses elicited by adrenaline or angiotensin.3. The L‐tryptophan‐induced depression of the clonidine response was prevented by pretreating rats with either Rö 44602, carbidopa, BW 172C58, methys‐ergide or by pithing.4. Intravenous infusions of serotonin depressed the pressor responses to clonidine, adrenaline and angiotensin in both intact anaesthetized and pithed rats.5. It is concluded that the depressant action of L‐tryptophan is dependent on its conversion within the periphery to serotonin. This action is also dependent on or mediated by the sympathetic nervous system.
MEASUREMENT OF 42K CONCENTRATION IN THE MUCOSAL PORTION OF THE INTESTINE WITHOUT TISSUE SAMPLES: AN APPROACH TO THE MEASUREMENT OF MUCOSAL BLOOD FLOW IN THE DOG
Authors: Eade M. N. , Arroll B. , Quinn J. P. 
Published: June 2007

SUMMARY1. The concentration of 42K within the jejunal mucosa was measured by intraluminal miniature Geiger‐Müller tubes shielded with platinum foil.2. Isotope concentration measured by tissue assay of jejunal mucosa gave similar results to that obtained by the Geiger‐Müller tubes.3. Isotope measurement by shielded Geiger‐Müller tubes obviates the need for tissue samples and permits repeat measurement in the same animal. This should find physiological application in measuring the mucosal portion of total intestinal blood flow by the indicator fractionation technique.
EFFECT OF CIMETIDEME ON THE HEALING OF RESTRAINT‐INDUCED GASTRIC EROSIONS IN THE RAT
Authors: Lee S. P. , Clarke A. C. , Tasman‐Jones C. 
Published: June 2007

SUMMARY1. Rats after a 24 h restraint developed acute gastric erosions. Cimetidine in a dose of 100 mg/kg body weight was given subcutaneously every 8 h to a group of 150 rats after restraint. A second group received saline subcutaneously (placebo group).2. Erosions in the placebo group required up to 45 days to heal (median healing time approximately 24 days). Cimetidine treatment reduced the median healing time to approximately 12 days.3. Cimetidine in this dose promotes healing of acute gastric erosions in the rat induced by restraint.
A SEQUENTIAL STUDY OF ADRENOCORTICOSTEROID LEVEL IN HUMAN PREGNANCY
Authors: Wintour E. M. , Coghlan J. P. , Oddie C. J. , Scoggins B. A. , Walteis W. A. W. 
Published: June 2007

SUMMARY1. Peripheral plasma levels of aldosterone, corticosterone, Cortisol, 11‐deoxycorticosterone (DOC) and 11‐deoxycortisol were measured sequentially throughout pregnancy in eleven women.2. Mean plasma concentrations were significantly increased above non‐pregnant values at 8 weeks for DOC, at 12 weeks for corticosterone, Cortisol and 11‐deoxycortisol, but not until 24 weeks for aldosterone.3. It is suggested that during human pregnancy, the maternal adrenal is responding differently to corticotrophin, pituitary or placental, and that other factors, for example prolactin, may be stimulating the adrenal directly or modifying the action of corticotrophin.
SELECTIVE STIMULATION OF INTRACARDIAC PREGANGLIONIC VAGAL FIBRES OF THE DOG ATRIUM
Authors: Chiba S. 
Published: June 2007

SUMMARY1. Direct electrical stimulation (0.05 ms, 5.0 V and 30 Hz) caused negative chronotropic and inotropic effects on the blood‐perfused, isolated dog atrium.2. These negative effects of electrical stimulation were significantly blocked not only by treatment with atropine or tetrodotoxin, but also by hexamethonium, although hexamethonium did not modify the effects of injected acetylcholine.3. These results suggest that direct electrical stimulation on the isolated, blood‐perfused dog atrium readily causes a release of acetylcholine by excitation of parasympathetic pre‐ganglionic fibres.
EFFECTS OF VARIOUS DRUGS ON THE OSMOTIC LYSIS OF RAT MAST CELLS
Authors: Day R. O. , Wade D. N. 
Published: June 2007

SUMMARY1. Rat mast cells were exposed to low osmotic pressures to produce a ‘nonspecific’ disruption of the mast cell, with release of histamine along with other intracellular contents.2. The effect of non‐steroidal anti‐inflammatory drugs and various other drugs upon osmotically induced histamine release was examined.3. Representative non‐steroidal anti‐inflammatory drugs indomethacin, phenylbutazone and flufenamic acid, the acidic compounds ethacrynic acid, iopanoic acid and probenecid, and the local anaesthetic lignocaine, all caused a dose‐dependent facilitation of osmotically induced histamine release compared to controls. All drugs were active at 0.1 mmol/1.4. The previously observed inhibition of compound 48/80 and the antigen‐induced histamine release from rat mast cells by similar concentrations of the drugs used in the present study are unlikely to be due to mast cell plasma membrane stabilization.
THE NATURE OF THE PRESSOR RESPONSE TO CAROTID ARTERY OCCLUSION IN THE HEXAMETHONIUM‐TREATED RAT
Authors: Chahl Loris A. , Cross R. B. 
Published: June 2007

SUMMARY1. The blood pressure monitored from the cannulated right carotid artery and heart rate responses to occlusion of the intact left carotid artery were investigated in rats.2. Hexamethonium abolished the response to ganglion stimulants but not that to carotid occlusion, although the time course and nature of the response were altered.3. The pressor response to carotid occlusion in the presence of hexamethonium was not abolished by carotid sinus denervation, vagal section, tubocurarine, atropine, ethyl alcohol or an angiotensin II antagonist, but it was abolished by high doses of phenoxybenzamine. In six out of eight experiments the response was not abolished by cervical cord section.4. It was concluded that the pressor response to carotid occlusion in the presence of hexamethonium in the rat involves an adrenergic mechanism which is at least in part independent of the autonomic ganglia, and which is mediated by an agent liberated from the brain, possibly under conditions of cerebral ischaemia.
INTRARENAL ACTION OF ANGIOTENSIN II IN RESTORING RENAL ARTERY PRESSURE AFTER ACUTE RENAL ARTERY STENOSIS
Authors: Anderson W. P. , Korner P. I. , Johnston C. I. , Angus J. A. , Casley D. J. 
Published: June 2007

SUMMARY1. The renal artery of conscious dogs was acutely narrowed over 30 s to reduce renal artery pressure distal to the stenosis to 40 mmHg and the stenosis was maintained for 1 h. The distal renal artery pressure was rapidly restored to a plateau slightly below pre‐stenosis values within 10–15 min. Rises in systemic blood pressure and plasma renin activity were small and transient.2. This restoration was an active process, mediated by the intrarenal effects of angiotensin II (AH), since it was greatly diminished or abolished when the renal artery was narrowed in the presence of angiotensin I‐converting enzyme inhibitor or angiotensin receptor antagonist (l‐Sar‐8‐Ue All). However, it was not diminished by ‘total’ autonomic effector blockade.3. This angiotensin II‐mediated restoration of renal artery pressure may be of homeostatic significance for the maintenance of glomerular filtration rate.
DECREASED CARDIAC β‐ADRENOCEPTORS IN HYPERTENSIVE RATS
Authors: Woodcock E. A. , Funder J. W. , Johnston C. I. 
Published: June 2007

SUMMARY1. β‐Adrenoceptors have been investigated in cardiac and renal cell membranes from hypertensive and normal rats.2. The 125I‐labelled β‐adrenoceptor antagonist l‐(4‐iodophenoxy)‐3‐isopropyl‐aminopropan‐2‐ol was used to measure directly the number and affinity of receptors.3. Cardiac membranes from hypertensive rats had a lower concentration of β‐adrenoceptors than membranes from control normotensive animals, but the affinities of the receptors remained unchanged. Receptor concentration decreased by half and was similar in each of the three models of experimental hypertension investigated.4. In contrast, kidney membranes from hypertensive animals had the same β‐adrenoceptor concentration and affinity as membranes from normotensive rats.5. The decrease in cardiac β‐adrenoceptor concentration may reflect an increase in cardiac sympathetic drive in these experimental hypertensive models.
THE MEASUREMENT OF GLOMERULAR BLOOD FLOW IN THE RAT KIDNEY: INFLUENCE OF MICROSPHERE SIZE
Authors: Sabto J. , Bankir L. , Grünfeld J. P. 
Published: June 2007

SUMMARY1. Radioactively labelled microspheres were used to determine glomerular blood flow in glomerular populations with distinct vascular characteristics. Two batches of microspheres (15 ± 5.0 μm diameter and 7.0–10 μm diameter) were utilized.2. The results show that the larger microspheres overestimate the superficial glomerular blood flow (414 ± 61 nl/min, mean ± s.e.m.) and underestimate the deep glomerular blood flow (98 ± 10 nl/min), when compared with the data obtained with 7.0–10 μm diameter microspheres (317 ± 30 nl/min and 209 ± 23 nl/min, respectively).3. The rheological artefact associated with the use of larger microspheres is confirmed by finding an uneven size distribution of microspheres lodged in the glomeruli. In each of three experiments, the mean diameter of 200 microspheres lodged in the superficial glomeruli (16.43 ± 0.27 μm, 15.87 ± 0.23/mi and 16.58 ± 0.27 Jim) was significantly greater than that found in the deep glomeruli (15.36 ± 0.15μm, 15.25 ± 0.21 μm and 15.73 ± 0.24μm; P<0.01, <0.05 and < 0.01, respectively). No such difference was detected when the 7.0–10 μm spheres were used.4. Glomerular blood flow can be measured at all depths of the rat's cortex and the demonstrated rheological artefact associated with use of the larger spheres is circumvented with the use of 7.0–10 μm microspheres.
HAEMODYNAMIC EFFECTS OF ISOMETRIC HANDGRIP EXERCISE IN PATIENTS CONVALESCENT FROM MYOCARDIAL INFARCTION
Authors: Baccelli G. , Valentini R. , Gregorini L. , Cellina G. , Mancia G. , Ludbrook J. , Zanchetti A. 
Published: June 2007

SUMMARY1. Cardiac performance in response to 30% maximal isometric handgrip exercise was studied in fourteen patients convalescing uneventfully from a first myocardial infarction. In each patient, heart rate, mean arterial blood pressure and cardiac index were measured, and total peripheral resistance was calculated. The covariance of changes in the mean arterial blood pressure and cardiac index in these patients was matched against tolerance limits calculated from published data for normal subjects.2. All patients had normal haemodynamic values at rest, and showed the usual rise of heart rate and mean arterial pressure during handgrip exercise. However, in six patients (group 1) the rise in mean arterial pressure was, as in normal subjects, accounted for mainly by a rise in cardiac index, with no consistent change in peripheral resistance. In eight patients (group 2), the mean arterial pressure rose to the same level as in group 1, but with a consistent increase in peripheral resistance and a smaller rise in the cardiac index.3. It is suggested that in a substantial proportion of patients who are making a seemingly uncomplicated recovery from myocardial infarction, it may be possible to unmask an impairment of left ventricular function by means of isometric handgrip exercise.
CARDIAC EFFECTS OF SALBUTAMOL‐INDUCED HYPOKALAEMIA IN THE CONSCIOUS DOG
Authors: Wahlqvist M. L. , Shanahan E. A. , Dennis P. M. , Pullan P. T. , Wilmshurst E. G. 
Published: June 2007

SUMMARY1. Infusion of salbutamol (3.0 μg/min after a bolus injection of 100 μg) produced hypokalemia in conscious dogs.2. Measurement of arterial and coronary sinus potassium differences revealed no significant potassium loss from the heart with established hypokalaemia.3. Shortly after the initial salbutamol bolus and before steady‐state hypokalaemia had been achieved during salbutamol infusion, a prolongation of QTC occurred; this corresponded to a significant myocardial potassium loss of ‐0.12 mmol/1 plasma.4. Urinary electrolyte excretions indicated that the hypokalaemia was not due to urinary potassium loss.5. It was deduced that potassium had moved intracellularly. No change in hydrogen ion status occurred to account for this. Pronounced rises in plasma insulin immunoreactivities during salbutamol infusions suggested this as one mechanism for potassium shifts.
A NOVEL ACTIVITY CAGE FOR RATS: CHARACTERIZATION OF SOME PHENYLETHYLAMINE DERIVATIVES WITH CENTRAL STIMULANT AND DEPRESSANT EFFECTS
Authors: Dunn R. I. , Ghosh P. , Bolt A. G. , Mrongovius R. I. 
Published: June 2007

SUMMARY1. A novel activity cage for rats is described. Eight light beams are aimed at a light‐conducting perspex rod at the centre of a cylindrical cage. The photoresistor at the end of the rod detects the changes in light intensity produced by interruption of the light beams.2. The apparatus is simple to operate and was capable of detecting small differences in the motor activity of groups of rats.3. Dose‐dependent increases in motor activity were produced by dexampheta‐mine (1.36 to 27.3 μmol/kg, i.p.). The depressant effects produced by 20 μmol/kg doses of norfenfluramine were greater than those of fenfluramine. Large doses (100 μmol/kg) of tranylcypromine stimulated motor activity whereas its m‐isomer, m‐2‐phenylcyclopropylamine, depressed motor activity.
THE EFFECTS OF THYROID STATUS ON DIGOXIN DISTRIBUTION IN THE RAT
Authors: Veroni M. , Shenfield G. M. 
Published: June 2007

SUMMARY1. Tritiated digoxin was injected intravenously into euthyroid, hyperthyroid and hypothyroid rats. The rats were killed at intervals up to 24 h and tritium in serum and tissues counted.2. Serum concentrations of tritium in the hyperthyroid animals were less than in the control group, whereas the concentrations in the hypothyroid group were similar to those in the control group.3. Cardiac tissue concentrations of tritium were higher in the hyperthyroid group than in the control group, but in the hypothyroid group were similar to the control group.4. The decreased serum levels in the hyperthyroid rats were probably due to an increased volume of distribution.5. Pharmacological resistance to digoxin in hyperthyroidism must be due to some alteration in cardiac function and it is suggested that this is an increase in Na/K ATPase receptors.
DIFFERENT POTENCIES OF [ASP1, ILE5]‐ AND [ASN1 VAL5]‐ANGIOTENSIN II IN STIMULATING ALDOSTERONE PRODUCTION FROM RAT ADRENAL ZONA GLOMERULOSA CELLS IN VITRO
Authors: Mendelsohn F. A. O. 
Published: June 2007

SUMMARY1. Rat adrenal zona glomerulosa cells were incubated in Krebs Ringer bicarbonate medium containing bovine serum albumin. Aldosterone production was measured by radioimmunoassay.2. Both [Asp1, Ile5]‐angiotensin II ('free acid') and (Asn1, Val5]‐angiotensin II ('amide'), (10−5 mol/1), stimulated aldosterone output but the free acid compound produced a larger increase in steroid output than the amide.3. This difference in steroidogenic activity could not be explained by differences in purity or initial concentration or by stimulation of the contaminating fasciculata cells.4. However, serial bioassays of the media revealed that the amide form of angiotensin was degraded more rapidly than the free acid form.5. The different potency of these two forms of angiotensin II could explain some of the reported discrepancies of the action of angiotensin II on rat adrenal tissue or cells in vitro.
MECHANISMS UNDERLYING THE CARDIOVASCULAR ACTION OF A NEW DIHYDROPYRIDINE VASODILATOR, YC‐93
Authors: Satoh K. , Yanagisawa T. , Taira N. 
Published: June 2007

SUMMARY1.The mechanisms underlying the cardiovascular action of YC‐93, a new dihydropyridine vasodilator with cyclic AMP phosphodiesterase inhibitory activity, was investigated by comparing its effects wth those of papaverine in various isolated, blood‐perfused heart preparations of the dog.2. In all preparations YC‐93 injected into the nutrient arteries produced a dose‐dependent increase in blood flow, and in this respect YC‐93 was about twenty times more potent than papaverine on a weight basis.3. In sinoatrial node preparations YC‐93 injected into the sinus node artery decreased sinus rate in a dose‐dependent manner, and in large doses produced atrial standstill.4. In atrioventricular (a.v.) node preparations YC‐93 injected into the a.v. node artery increased a.v. conduction time in a dose‐dependent manner, and in large doses produced a second or third degree block of a.v. conduction. However YC‐93 injected into the anterior septal artery scarcely affected a.v. conduction.5. In spontaneously contracting papillary muscle preparations YC‐93 injected into the anterior septal artery failed to affect ventricular automaticity in doses which markedly decreased developed tension of papillary muscles.6. In papillary muscle preparations driven at a fixed rate YC‐93 injected into the anterior septal artery produced a dose‐dependent decrease in developed tension of papillary muscles.7. Unlike YC‐93, papaverine decreased a.v. conduction time in a.v. node preparations and increased developed tension of papillary muscle preparations.8. The cardiac effects of YC‐93 elucidated in the present experiments are characteristic of calcium‐antagonistic vasodilators. The action of YC‐93 as an inhibitor of cyclic AMP phosphodiesterase does not appear to play a role in its cardiac action.
ANGIOTENSIN, HYPOXIA, VERAPAMIL AND PULMONARY VESSELS
Authors: Suggett A. J. , Mohammed F. H. , Barer Gwenda R. 
Published: June 2007

SUMMARY1. The action of angiotensin II on lung vessels was compared in dogs, cats, ferrets and rats using isolated perfused lungs and lobes of lungs perfused in vivo, both at constant flow, so that increases in inflow pressure at constant outflow pressure indicated increases in resistance.2. Angiotensin II caused some increases in resistance in dogs, cats and rats but not ferrets. The increases were small compared with changes in the systemic circulation. Larger increases could be obtained in isolated lungs where there was no interference from rises in left atrial pressure.3. All four species showed pulmonary vasoconstriction during hypoxia and ferret lungs were especially responsive. Thus angiotensin II cannot be the mediator of hypoxic vasoconstriction in all these species.4. Angiotensin II significantly increased the response to hypoxia in isolated cat and rat lungs while also increasing baseline inflow pressure; the response to hypoxia was not altered in ferrets. Angiotensin II may therefore enhance reactivity of pulmonary vessels.5. Verapamil, an inhibitor of calcium transport across cell membranes, reduced the response to hypoxia in rats and ferrets more than it reduced the response to angiotensin II in rats or prostaglandin F2α in ferrets. Thus hypoxic pulmonary vasoconstriction probably involves transport of calcium.
THE INFLUENCE OF DIBUTYRYL ADENOSINE CYCLIC MONOPHOSPHATE ON CELL PROLIFERATION IN THE EPITHELIUM OF THE JEJUNAL CRYPTS, THE COLONIC CRYPTS AND IN COLONIC CARCINOMATA OF RAT
Authors: Tutton P. J. M. , Barkla D. H. 
Published: June 2007

SUMMARY1. Cell proliferation in the jejunal crypts, the colonic crypts and in dimethyl‐hydrazine (DMH)‐induced adenocarcinomata of rat colon was measured using a stathmokinetic technique.2. Dibutryl cyclic adenosine monophosphate (dibutyryl cAMP) was found to inhibit cell proliferation in colonic crypts and in colonic adenocarcinomata.3. Dibutryl cAMP at very high doses was found to inhibit jejunal crypt cell proliferation but at lower doses was found to accelerate jejunal crypt cell proliferation.4. Neither bilateral adrenalectomy nor chemical sympathectomy was found to abolish the ability of dibutryl cAMP to stimulate jejunal crypt cell proliferation.5. The present results are difficult to interpret in terms of known hormonal influences on cell proliferation in the tissues examined and of established actions, of these hormones on cyclic nucleotide metabolism in other tissues.
COMPARISON OF METHODS FOR ELICITING THE BARORECEPTOR‐HEART RATE REFLEX IN CONSCIOUS RABBITS
Authors: Faris I. B. , Iannos J. , Jamieson G. G. , Ludbrook J. 
Published: June 2007

SUMMARY1. Two methods were used for altering blood pressure in conscious rabbits by up to ± 30 mmHg from the resting level in order to characterize the barorecep‐tor‐heart rate reflex. These were to inflate descending aortic or inferior vena caval cuffs, or to give brief intravenous infusions of phenylephrine or glycerol trinitrate. The relation of change in blood pressure to change in heart interval was examined, both during the initial ‘ramp’ changes of these variables and when they had reached a ‘steady‐state'.2. Both methods allowed the construction of'steady‐state’ sigmoid stimulus‐response curves whose parameters were reproducible within animals, and which were attended by a relatively small variance between animals. The inflatable‐cuff method gave a higher average value for maximum gain than the vasoactive drug method (10.0 v 5‐4 ms/mmHg) and a narrower pressure range between the threshold and saturation points of the response, but values for the other parameters were similar. Corresponding parameters obtained by the two methods correlated closely.3. After denervating all arterial baroreceptors except one carotid sinus, ‘steady‐state’ maximum gain by cuff‐inflation was reduced to 3.1 ms/mmHg, and to 2‐6 ms/mmHg by the vasoactive drug method. The heart interval range between upper and lower plateau levels was reduced, but the pressure range between threshold and saturation points was widened, with both methods.4. During the initial ‘ramp’ changes of blood pressure the sensitivity of the reflex was described by the slope of the linear regression of heart interval on ‘mean blood pressure. The slopes obtained by aortic cuff inflation, and by infusion of either vasoactive drug, correlated positively with ‘steady‐state’ maximum gain. However, the reproducibility of the ‘ramp’ method was inferior to that of the ‘steady‐state’ method with respect to reflex sensitivity, and other parameters of the stimulus‐response relation cannot be estimated.5. Complete baroreceptor denervation virtually eliminated heart rate changes over the range of blood pressures usually employed. However, when blood pressure was increased by more than 40 mmHg a profound reflex bradycardia and hypopnoea were then evoked.
SODIUM BALANCE AND PLASMA RENIN ACTIVITY DURING THE DEVELOPMENT OF TWO‐KIDNEY GOLDBLATT HYPERTENSION IN RATS
Authors: Doyle A. E. , Duffy S. G. 
Published: June 2007

SUMMARY1. In two experiments severe hypertension (systolic blood pressure 180 mmHg) was induced in rats by constricting one renal artery with a silver clip (two‐kidney, one clip hypertension; 2KIC). Blood pressure, plasma renin activity (PRA) and body weight were measured for 35 days after clipping. Plasma sodium concentration and carcass sodium content were measured at the conclusion of the experiment. To determine the relationship between sodium intake, PRA and the development of severe hypertension, half of the rats were given a normal diet and water to drink; the other half were given a low sodium diet and 0‐9% saline to drink.2. In both experiments, two patterns of responses were observed. Group (1) had reduced growth rate, and marked elevation of PRA. Some, but not all of these animals had histological evidence of malignant nephrosclerosis in the untouched kidney. In the other group (11), weight gain was normal and PRA was normal or only slightly elevated.3. Group 1 animals drinking saline, had raised carcass sodium levels, whereas those drinking water had no increase in carcass sodium.4. The results confirm that hypertension in the 2KIC model is not always associated with a raised PRA.5. The coexistence of a raised PRA and increased total body sodium suggests that the PRA does not rise as a result of sodium depletion in this model.