bluuebunny/crossref_metadata_2025_split huggingface dataset:
A ‘HYPERTENSINOGENIC’ CLASS OF STEROID HORMONE ACTIVITY IN MAN?
Authors: Whitworth Judith A. , Scoggins Bruce A. 
Published: June 2007

SUMMARY1. Studies in sheep have led to the concept of a ‘hypertensinogenic’ (HT) steroid hormone activity, whereby the blood pressure (BP) raising effects of adrenocortical steroids can be separated from their in vivo glucocorticoid (GC) or mineralocorticoid (MC) activities.2. The three main lines of evidence are as follows: (i) BP raising effects of ACTH cannot be reproduced by appropriate rates of infusion of steroids with GC and MC activities; (ii) certain steroids e.g. 9α‐fluorocortisol can increase BP at rates of infusion below threshold for in vivo GC or MC actions and for many steroids there is no correlation between GC, MC and HT effects; (iii) demonstration of differential antagonism of HT, MC and GC effects.3. Studies in man show that the BP effects of ACTH are due to cortisol (F) at levels which have both MC and GC activity. However, BP effects of ACTH cannot be blocked by MC and GC antagonists.4. Although complete separation of in vivo GC, MC and HT activities has not been possible in man, our own studies show a degree of dissociation. Taken together, these data suggest that steroids may raise BP by a HT mechanism distinct from classical in vivo MC or GC activities in man as well as sheep.
HAEMODYNAMIC EFFECTS OF LONG‐TERM ENDOTHELIN INFUSION IN CONSCIOUS SHEEP
Authors: Reid Amanda F. , Parkes David G. , Coghlan John P. , Scoggins Bruce A. , Whitworth Judith A. 
Published: June 2007

SUMMARY1. Synthetic human endothelin‐1 was infused intravenously at 15 μg/h for 24 h to examine its cardiovascular actions in five conscious sheep.2. Endothelin produced a maximum increase in mean arterial pressure (MAP) of + 8 mmHg at 8 h, with an increase in calculated total peripheral resistance (CTPR) of +2.6 mmHg/L per min, whilst cardiac output (CO) was unchanged. At 24 h MAP was not significantly elevated, however CTPR had increased by +2.8 mmHg/L per min and CO had decreased by 0.9 L/min.3. This study shows that long‐term administration of endothelin produces sustained arterial vasoconstriction in sheep.
CONTROLLED COMPARISON OF EFFECTS OF EXERCISE AND ALCOHOL ON BLOOD PRESSURE AND SERUM HIGH DENSITY LIPOPROTEIN CHOLESTEROL IN SEDENTARY MALES
Authors: Cox K. L. , Puddey I. B. , Morton A.R. , Masarei J. R. L. , Vandongen R. , Beilin L. J. 
Published: June 2007

SUMMARY1. Seventy‐two sedentary male drinkers, aged 20–45 years, and with mean blood pressure (BP) at entry of 132±1.2/73±0.9 mmHg, completed a 4 week study during which they were assigned randomly to either drink a low alcohol beer (effectively reducing their weekly alcohol intake from 481±47 mL to 52±5 mL) or to continue their normal drinking habits.2. Within these two groups subjects were further assigned to either a moderate exercise programme of three 30 min sessions per week of stationary cycling at 60–70% maximum workload or to a control light exercise programme where they pedalled against zero or minimal resistance.3. Both alcohol restriction and moderate exercise were associated with mean falls in bodyweight of 0.5 kg. After adjustment for bodyweight a significant main effect of alcohol restriction on systolic BP (‐4.1±1.7 mmHg, P<0.05) and diastolic BP (‐1.6±0.8 mmHg, P= 0.05) was demonstrated. There was no significant main effect of moderate exercise on systolic or diastolic blood pressure despite a significant improvement in physical fitness (maximal oxygen uptake increasing from 33.2±0.08 mL/kg per min to 35.5±0.1 mL/kg per min).4. Significant falls in high density lipoprotein cholesterol (HDLC) and triglyceride levels seen with alcohol restriction were unaffected by the increase in fitness, the magnitude of the fall being similar in both the moderate and light exercise groups.5. We conclude that in male drinkers 4 weeks of moderate exercise has no influence on serum HDLC levels and when combined with alcohol restriction does not lead to a greater fall in BP than that seen with a reduction of alcohol intake alone.
MECHANISMS INVOLVED IN THE STIMULATION OF ALDOSTERONE PRODUCTION BY ANGIOTENSIN II, VASOPRESSIN AND ENDOTHELIN
Authors: Woodcock Elizabeth A. , Tanner Jennifer K. , Caroccia Lucy M. , Little Peter J. 
Published: June 2007

SUMMAY1. Endothelin (ET), vasopressin (VP) and angiotensin II (AII) all stimulate aldosterone production in adrenal glomerulosa cells but the response to AII is greater than that to either ET or VP.2. Total inositol phosphate responses to AII and ET were similar but the response to VP was lower.3. Cytosolic free Ca2+ responses to AII were higher than to either of the other peptides.4. Metabolism of 145IP3 was different under stimulation by the three different peptides.5. Adrenal glomerulosa cells can distinguish between three different agonists which stimulate phosphatidylinositol turnover and produce a selective response to each peptide.
ENDOTHELIN STIMULATES INOSITOL PHOSPHATE ACCUMULATION IN RAT RIGHT AND LEFT ATRIA: A COMPARISON WITH NORADRENALINE
Authors: Kuraja Ivana J. , Woodcock Elizabeth A. 
Published: June 2007

SUMMARY1. The effect of endothelin on phosphatidylinositol turnover in rat atria was investigated by measuring the generation of inositol phosphates following [3H]‐inositol labelling.2. In the presence of 10 mmol/L LiCl, endothelin caused dose‐dependent increases in the accumulation of inositol mono, bis and trisphosphates which were maximal at 10‐6 mol/L endothelin. The dose–response relationship was similar in right and left atria, but right atria showed a higher maximal inositol phosphate response.3. Endothelin produced a rapid and transient stimulation of inositol tris‐phosphate accumulation, which peaked at 15 s followed by a slower increase which continued linearly past 20 min.4. The time course of inositol trisphosphate release under noradrenaline stimulation showed a similar profile but the maximum stimulation was smaller than endothelin.5. As with endothelin, responses to noradrenaline also were higher in right atria compared with left atria.6. These data demonstrate that endothelin receptors in rat atria are coupled to the stimulation of the phosphatidylinositol turnover pathway in an essentially similar manner to α1‐adrenoceptors. The phosphatidylinositol pathway may be important in mediating the reported cardiac actions of endothelin.
INCREASED CARDIAC ANGIOTENSIN‐CONVERTING ENZYME IN RATS WITH CHRONIC HEART FAILURE
Authors: Fabris B. , Jackson B. , Kohzuki M. , Perich R. , Johnston C. I. 
Published: June 2007

XUMMARY1. Chronic heart failure was induced in rats by ligation of the left coronary artery to produce a left ventricular myocardial infarct.2. Cardiac angiotensin‐converting enzyme (ACE) was estimated by radioligand binding in myocardial homogenates and by autoradiography studies of radioligand binding to ACE in heart sections.3. Radioligand binding studies demonstrated an increase in binding sites in animals with myocardial infarction, compared with sham operated animals. Mean increases were 457% in right atrium, 295% in left atrium, 326% in right ventricle, 187% in left ventricle and 530% in the region of the left ventricular infarct, compared with the sham left ventricle.4. Autoradiography studies confirmed tissue homogenate binding studies, demonstrating (i) a marked increase in ligand binding in the infarct area and (ii) an increase in binding density in the hypertrophied myocardium of right and left atrium, and right and left ventricle.5. The induction of cardiac ACE in the myocardium of rats with chronic heart failure may participate in the pathophysiology of cardiac hypertrophy.
DOPAMINE INFUSION IN HEALTHY SUBJECTS AND CRITICALLY ILL PATIENTS
Authors: Ratge D. , Steegmüller U. , Mikus G. , Kohse K. P. , Wisser H. 
Published: June 2007

SUMMARY1. Little is known about the metabolism and the pharmacokinetics of dopamine (DA) in critically ill patients. To study the influence of the total administered DA dose on the disposition of free (i.e. unconjugated) and sulfoconjugated DA, plasma levels of free and sulfoconjugated DA were measured following infusion of 5 μg DA/kg per min for 0.5 and 3 h in six healthy volunteers and in eight critically ill patients receiving DA at the same infusion rate for 6.5 to 329 h.2. In patients and volunteers steady state concentrations of free DA showing fairly large inter‐individual variations (12.4–73.4 μg/L) were reached within 10 min of the beginning of the infusion.3. DA sulfate was generated immediately. In volunteers peak values of the sulfoconjugate were observed 15–60 min after the termination of the DA infusion. In patients steady state concentrations of conjugated DA (63–80 μg/L) were reached within 5–10 h of DA infusion.4. The initial half‐life (t1/2α), the terminal elimination half life (t1/2) and the distribution volume of free DA in the volunteers were significantly higher after 3 h of the DA infusion as compared to the shorter infusion. These parameters as well as the total plasma clearance of free DA were independent of the length of the DA infusion period in patients. The large distribution volumes of 19.8–75 L/kg indicate that DA has been taken up by peripheral tissues.5. Substantial inter‐individual variations in the patients' clearance of free DA (3.9–16.5 L/kg per h) may partly explain the variability in haemodynamic responses to DA infusion reported in clinical studies. No effects of DA on the systolic and diastolic blood pressures or the plasma concentrations of norepinephrine were found in the healthy subjects. The physiological significance of sulfated DA as a potential reserve pool for free DA has to be further clarified.
EFFECT OF DIMETHYLSULPHOXIDE ON CYSTEAMINE‐INDUCED DUODENAL ULCERATION IN RATS
Authors: Ali B. H. 
Published: June 2007

ABSTRACT1. Rats were pretreated with dimethylsulphoxide (DMSO) at concentrations of 2, 4 and 6% v/v in the drinking water for 7 days, then injected with a single subcutaneous dose of cysteamine (28 mg/100 g bodyweight) to induce duodenal ulceration.2. DMSO reduced, in a dose‐dependent manner, the incidence and extent of the ulceration.3. Mucus duodenal content was not significantly affected by either DMSO or cysteamine treatments.
A LACK OF POTENCY FOR THE δ‐OPIOID ANTAGONIST NALTRINDOLE AFTER MICROINJECTION INTO THE ROSTRAL VENTROLATERAL MEDULLA OF RABBITS
Authors: Morilak David , Drolet Guy , Chalmers John 
Published: June 2007

SUMMARY1. Naltrindole is a novel δ‐opioid antagonist which is highly potent in vitro. We examined the effects on arterial pressure of naltrindole (0.3–300 pmol) after microinjection into the pressor area of the rostral ventrolateral medulla of chloralose‐anaesthetized rabbits.2. Naltrindole itself had no significant effects on arterial pressure, and only slightly attenuated the hypotensive effect of an exogenous agonist ([d‐Ala2, d‐Leu5]‐enkephalin). This is in contrast to previous demonstration of a marked pressor effect following another δ‐antagonist, ICI 174,864.3. Thus, naltrindole, tested in vivo against endogenous opioid effects, does not appear to be as potent as it is in vitro, and in this case was virtually ineffective.
INFLUENCE OF CARDIAC AFFERENTS ON TIME‐DEPENDENT CHANGES IN THE RENAL SYMPATHETIC BAROREFLEX OF CONSCIOUS RABBITS
Authors: Bell Leonard B. , Dorward Patricia K. , Rudd Carl D. 
Published: June 2007

SUMMARY1. The stability of the renal sympathetic baroreflex and nasopharyngeal reflex, and the role of cardiac sensory receptors, was studied in conscious rabbits over a 5 h experimental period.2. Renal sympathetic nerve activity (SNA) was recorded during (i) slow ramp changes in mean arterial pressure (MAP) of 1–2 mmHg/s induced by inflating perivascular balloon cuffs, and (ii) the inhalation of cigarette smoke. Experiments were repeated in other rabbits after blocking cardiac afferents with 5% intrapericardial procaine.3. Baroreflex responses to the first two caval cuff inflations of the day were significantly greater than subsequent responses. After this, triplicate sets of reflex curves were relatively stable during a 2 h period in the morning. When the experiment was repeated in the afternoon, there was a significant attenuation of baroreflex range and a small fall in resting renal SNA which were abolished by pericardial procaine.4. Changes in baroreflex properties were minimal when the reflex was assessed only twice, at the beginning and end of a 5 h period. No change was seen in the nasopharyngeal reflex whether the rabbits had been subjected to few or to many cuff inflations.5. We conclude that time dependent changes can occur in the renal sympathetic baroreflex of conscious rabbits which must be allowed for by appropriate protocol design. These include increasing inhibitory influences from cardiac sensory receptors in experimental situations requiring multiple reflex estimations.
EVIDENCE FOR THE INHIBITORY EFFECT OF 5‐HYDROXYTRYPTAMINE AT CENTRAL AND PERIPHERAL SITES ON OVULATION IN RABBITS
Authors: Mishra N. , Tangri K. K. , Bhargava K. P. , Gupta M. L. 
Published: June 2007

SUMMARY1. The effect of 5‐hydroxytryptamine (5‐HT) has been investigated on ovulation per se as well as on induced ovulation in rabbits.2. 5‐HT administered intracerebroventricularly (i.c.v.) did not induce ovulation per se.3. The ovulation was induced by coitus, subcutaneous administration of progesterone and intravenous administration of cupric acetate.4. Postcoital and progesterone induced ovulation was found to be blocked by i.c.v. administered 5‐HT.5. Cupric acetate induced ovulation was, however, not found to be blocked by i.c.v. administered 5‐HT.6. Intraperitoneal administration of 5‐HT was found to block cupric acetate induced ovulation.7. It is concluded that 5‐HT exerts an inhibitory control over ovulation by acting at central as well as at peripheral sites in rabbits.
CHARACTERISTICS OF CARDIOVASCULAR REFLEXES ORIGINATING FROM 5‐HT3 RECEPTORS IN THE HEART AND LUNGS OF UNANAESTHETIZED RABBITS
Authors: Evans Roger G. , Ludbrook John , Michalicek Jan 
Published: June 2007

SUMMARY1. When phenylbiguanide (1‐PBG) (6.25–400 μg) was injected into the left atrium, right atrium or pulmonary artery of unanaesthetized rabbits it caused dose‐dependent falls of heart rate and arterial pressure, and short‐lived hypopnoea or apnoea. The threshold dose was 50–100 μg. Maximal falls of heart rate (86–108 beats/min) and arterial pressure (33–35 mmHg) occurred at a dose of 200 μg. The latency between injection and onset of the bradycardia was 2.2–2.6 s and did not depend on the route. Cardiac output fell transiently with heart rate, but at the time of the maximal fall of arterial pressure it had returned to normal. All effects were abolished by intrapericardial procaine. The haemodynamic effects were exaggerated by sino‐aortic barodenervation. Intrapericardial 1‐PBG (200–400 μg) was without effect. Injection of 1‐PBG (>50–100 μg) into the aortic arch caused a variable increase in heart rate and arterial pressure.2. When both cervical vagus nerves were crushed the depressor effects of atrial 1‐PBG were reduced by only 76–84%.3. The dose–response curves for left atrial and pulmonary artery injection of 1‐PBG were shifted successively to the right by intravenous infusion of the 5‐HT3 antagonist MDL72222 (0.1 and 1.0 mg/kg).4. We conclude that in unanaesthetized rabbits left atrial 1‐PBG selectively excites myocardial afferents, whereas right atrial or pulmonary artery 1‐PBG excites afferents that originate close to the pulmonary vasculature. In each case 1‐PBG acts through pharmacologically specific 5‐HT3 receptors. The afferents run mainly, but not exclusively, in the vagus nerves. The reflex fall of arterial pressure is accounted for almost entirely by a decrease in peripheral resistance.
HYPERTENSION AND COMPONENTS OF VASCULAR RESISTANCE
Authors: West Malcolm J. 
Published: June 2007

SUMMARY1. In renal wrap hypertension in the rabbit and in essential hypertension in humans, non‐autonomic components of resistance are the major factors contributing to elevated blood pressure.2. The central nervous system plays an important role in moment to moment blood pressure control but is not responsible for maintenance of elevated pressure in essential hypertension.3. Specific regions of the brain‐stem maintain vascular tone through the effects of bulbospinal neurones which are organized both topographically and by chemical content.4. Structural wall thickening in resistance vessels in hypertension is a manifestation of an abnormality of a growth controlling process.5. Although several structural muscle growth factors have been identified, it is likely that only a few regulatory processes are critical.6. Future studies in hypertension should examine associations between genetic markers of medial thickening and environmental influences.
ACUTE EFFECTS OF EXERCISE ON PLASMA LIPIDS, NORADRENALINE LEVELS AND PLASMA VOLUME
Authors: Krum H. , Conway E. L. , Howes L. G. 
Published: June 2007

SUMMARY1. Total plasma cholesterol, high‐density lipoprotein cholesterol (HDL‐C), low density lipoprotein cholesterol (LDL‐C), noradrenaline, haematocrit, haemoglobin and heart rate were measured in blood sampled from an antecubital vein in nine volunteers after 1 min standing and at intervals up to 1 h following 5 min of vigorous bicycle exercise.2. Heart rates and plasma noradrenaline levels rose substantially immediately following exercise and gradually returned toward baseline levels 60 min post‐exercise.3. Total plasma cholesterol levels rose by 24% immediately post‐exercise and slowly returned to baseline levels 60 min post‐exercise. Similar changes were observed for LDL‐C (20.2%) and HDL‐C (27.7%). As a result, LDL:HDL ratios did not alter.4. These changes in total plasma cholesterol, HDL‐C and LDL‐C were explained by changes in plasma volume that occurred as a consequence of vigorous exercise.5. Changes in plasma volume may be a mechanism by which some environmental factors such as stress are associated with elevated plasma cholesterol levels.
EFFECTS OF CLONIDINE ON BLOOD PRESSURE AND HEART RATE RESPONSES TO AN EMOTIONAL STRESS IN THE RAT: A SPECTRAL STUDY
Authors: Blanc Jocelyne , Grichois Marie‐Laure , Elghozi Jean‐Luc 
Published: June 2007

SUMMARY1. The fluctuations that underlie the spontaneous variability of blood pressure (BP) and heart rate (HR) were investigated in conscious normotensive rats using power spectral analysis.2. Air jet stimulation determined a significant BP rise associated with a tachycardia. This environmental mild stressor amplified the 195–605 mHz oscillations of HR which are under autonomic control. No habituation to this stressor was observed since a second stimulation determined similar responses.3. Clonidine (10 μg/kg, i.v.) prevented the BP rise normally associated with air jet stimulation. In addition, clonidine dramatically reduced the amplitude of BP and HR oscillations in the frequency region of 195–605 mHz.4. It is concluded that a mild emotional stressor elicits in normotensive rats a rise in BP and HR associated with modified spectral profiles reflecting sympathetic hyperactivity. Clonidine minored the effects of stress on BP and HR variability and also prevented BP elevation.
DIFFERENTIAL ACTIONS OF THE MEDIAL REGION OF CAUDAL MEDULLA ON AUTONOMIC NERVE ACTIVITIES
Authors: Yen C. T. , Hwang J. C. , Su C. K. , Lin Y. F. , Yang J. M. , Chai C. Y. 
Published: June 2007

SUMMARY1. The inhibitory effects produced by activation of the medial region of caudal medulla on activities of the left and right cardiac sympathetic, vagus and greater splanchnic nerves were studied in chloralose‐urethane anaesthetized cats.2. Electrical stimulation of the medial region produced an 80–92% inhibition of the sympathetic nerve activities, and a 45% and 58% inhibition of the left and right cardiac vagal nerve activities, respectively. There were no significant differences between effects elicited in the left and right autonomic nerves. Similar but smaller inhibitory effects were produced by micro‐injection of sodium glutamate (0.5 mol/L) or DL‐homocysteic acid (50 mmol/L) to the same medullary sites.3. These data suggest that neurons residing in the medial medullary region exert strong inhibitory effects on autonomic nerve activities. Since the vasculature is principally innervated by sympathetic nerves, inhibition of sympathetic nerve activities might be the principal factor responsible for the depressor effects caused by activation of the medial region of caudal medulla. The heart is innervated both by sympathetic and parasympathetic nerves. Thus, their simultaneous inhibition during activation of the medial region elicits only a weak and variable inhibition of the heart.
ALTERED RESPONSES OF AORTIC SMOOTH MUSCLE FROM SPRAGUE‐DAWLEY RATS WITH SALT‐INDUCED HYPERTENSION
Authors: Obiefuna Peter C. M. , Ebeigbe Anthony B. , Sofola Olusoga A. , Aloamaka C. Peter 
Published: June 2007

SUMMARY1. The contractile responses of aortic ring preparations from Sprague‐Dawley rats made hypertensive by 6‐week dietary salt loading were studied. The test and control diet contained 8.0 and 0.3% NaCl, respectively. Aortic rings from salt‐loaded rats showed enhanced sensitivity to nor‐adrenaline (NA) but not to serotonin. Contractile responses to CaCl2 in Ca‐free NA‐containing medium was significantly enhanced in salt‐loaded rats, but was unchanged in K+‐depolarised medium. K+induced relaxation (a functional indicator of Na‐K adenosine triphosphatase activity) was sensitive to 10 μmol/L ouabain and was significantly attenuated in aortic rings from salt‐loaded rats. The results suggest that hypertension induced by salt‐loading is associated with enhanced sensitivity to NA, increased Ca2+ entry through receptor‐operated channels, and impairment of Na‐K ATPase enzyme activity.
ROLE OF NON‐ESTERIFIED FATTY ACIDS IN REGULATING PLASMA CHOLESTEROL TRANSPORT
Authors: Barter Philip J. 
Published: June 2007

SUMMARY1. The cholesteryl ester transfer protein (CETP) promotes an equimolar exchange of cholesteryl esters between the high density lipoproteins (HDL) and low density lipoproteins (LDL) in human plasma.2. Sodium oleate converts this CETP‐mediated process of exchange into one of net mass transfer of cholesteryl esters from HDL to LDL.3. Thus, conditions which increase the concentration of non‐esterified fatty acids in plasma may favour the redistribution of cholesterol from the non‐atherogenic HDL to the atherogenic LDL fraction.
ANGIOTENSIN II RECEPTOR SUBTYPES IN RAT BRAIN
Authors: Song Keifu , Allen Andrew M. , Paxinos George , Mendelsohn Frederick A. O. 
Published: June 2007

SUMMARY1. Angiotensin II (AII) receptor binding was localized in the rat brain by in vitro autoradiography using the antagonist analogue, 125I‐[Sar1, Ile8] AII. AII receptor binding was then differentiated into type I and type II subtypes by displacement with unlabelled non‐peptide antagonists specific for AII subtypes.2. Type I binding was determined as that inhibited by Dup753 (10 μmol/L) and type II binding as that inhibited by XD329‐1 (10 μmol/L). The reducing agent dithiothreitol (DTT) decreased the binding to type I receptors and enhanced the binding to type II receptors.3. Structures such as the vascular organ of the lamina terminalis, subfornical organ, median preoptic nucleus, area postrema, nucleus of the solitary tract, which are known to be related to some central actions of AII, contain exclusively type I AII receptors.4. In contrast, the locus coeruleus, ventral and dorsal parts of lateral septum, superior colliculus, subthalamic nucleus, some nuclei of the thalamus, and the nuclei of the inferior olive contain predominantly type II AII receptors.5. These results reveal important pharmacological heterogeneity of brain AII receptors which suggest different regional functions and are relevant to the central actions of emerging classes of new non‐peptide AII receptor antagonists.