bluuebunny/crossref_metadata_2025 huggingface dataset:
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

1. 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

1. 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.
PRELIMINARY STUDIES ON INCREASED NALOXONE POTENCY AND ITS RELATIONSHIP TO MORPHINE TOLERANCE AND DEPENDENCE IN MICE
Authors: Wong Chak‐Lam , Wai Man‐Keung , Roberts Michael B.
Published: June 2007

1. Morphine pretreatment (8 0 mg/kg s.c.) induced no overt tolerance to its antinociceptive effect in mice 4 h later, but enhanced the antagonistic potency of naloxone.

2. A molecular sieve morphine pellet implanted for 24 h induced measurable tolerance, but the relative potency of naloxone was not significantly different from that observed after single‐dose morphine pretreatment. The development of tolerance and increased naloxone potency do not, therefore, run parallel.

3. Naloxone‐precipitated withdrawal symptoms were observed after single‐dose morphine and after pellet implantation. However, molecular sieve morphine pellet implantation induced a higher degree of dependence as compared with single dose morphine pretreatment.

4. These results indicate that the rate of development of increased naloxone potency and of morphine tolerance and dependence do not run parallel. This implies that caution must be exercised in regarding increased naloxone potency as a sensitive indicator of the initiation and development of tolerance and dependence to morphine.
ROLE OF THE AUTONOMIC NERVOUS SYSTEM IN THE ACUTE RESPONSES TO RENAL ARTERY PRESSURE REDUCTION IN CONSCIOUS DOGS
Authors: Anderson W. P. , Casley D. J.
Published: June 2007

1. Plasma renin and arterial pressure responses to acute renal artery pressure reduction were compared in intact dogs and ‘autonomically‐blocked’ dogs subjected to adrenalectomy, chronic guanethidine treatment and acute vagal block (methscopolamine).

2. Following reduction of renal artery pressure plasma renin activity and concentration rose more in the autonomically blocked dogs than in the intact dogs. When renal artery pressure was held at 30 mmHg for 1 h, plasma renin activity rose by 19‐1 ng/ml per h (range 11‐6‐28‐7) in autonomically blocked dogs and 3‐65 ng/ml per h (range 1‐54‐5‐89) in intact dogs. When renal artery pressure was held at 60 mmHg plasma renin activity rose 3‐28 ng/ml per h (range 2‐4‐4‐7) and 1‐90 ng/ml per h (range 1‐30‐3‐56), respectively.

3. Arterial blood pressure also rose more in autonomically blocked dogs in accord with the greater rise in plasma renin activity. The relationships between the increases in arterial pressure and plasma renin were closely similar in the two groups.

4. We conclude that the relase of renin and increase in arterial blood pressure in response to renal artery stenosis is normally inhibited by arterial baroreflexes.
TISSUE DISTRIBUTION OF ORALLY ADMINISTERED BISMUTH IN THE RAT
Authors: Lee S. P. , Lim T. H. , Pybus J. , Clarke A. C.
Published: June 2007

1. A colloidal bismuth preparation, tripotassium dicitrato‐bismuthate, was given (172 mg/kg body weight, 6/7 days) to 10 laboratory rats for 14 months. Bismuth was measured by atomic absorption spectrometry in various tissues and the pattern of distribution studied.

2. Bismuth was present in kidney, lung, spleen, liver, brain, heart and skeletal muscles, in descending order of abundance. Haematological data, renal and liver function tests were normal in the bismuth‐treated group.

3. The data suggested that chronic ingestion of bismuth in large doses in rats results in absorption and binding to tissues. Absorbed bismuth probably crosses the blood‐brain barrier.
DETERMINATION OF CATHETER WALL HEAT TRANSFER IN CARDIAC OUTPUT MEASUREMENT BY THERMODILUTION*
Authors: Kim M. E. , Lin Y. C.
Published: June 2007

1. A model system of the thermal dilution technique was used to determine in vitro the loss of thermal indicator across different sizes of polyethylene catheters.

2. Thermal indicator loss (caloric gain by the indicator fluid or caloric loss by the catheter) per unit length of catheters (H/L) increased as a function of the outer radius (OR) of the catheters. Linear regression analysis gave the following equation: H/L=0‐337OR+0‐073 (r=0‐88, P<0‐05).

3. Thermal indicator loss per unit surface area (H/SA) decreased almost linearly with the following regression equation: H/SA =–1‐860 OR+0‐364 (r=0‐97, P<001).

4. Thermal indicator loss per unit volume contained in the catheter (H/vol) decreased exponentially according to the following equation: H/vol = 89‐le−25.4(OR) (r=0‐97, P<001).

5. This study indicates that there is a measurable loss of thermal indicator during injection corresponding to a loss of between 9 and 16% (for a 11.5 cm length of PE 50 and PE 240) of the required calories for warming the injectate to 37°C. Data is provided for correction of heat loss across the wall of a given length and diameter of polyethylene tubing.
RENIN SECRETION AND RENAL VASCULAR RESISTANCE FOLLOWING PROLONGED ADMINISTRATION OF DESOXYCORTICOSTERONE (DOC) IN RATS DRINKING NORMAL SALINE
Authors: Vandongen R. , Tunney Anne
Published: June 2007

1. The effect of long‐term administration of desoxycorticosterone (DOC)‐saline on arterial blood pressure, renal vascular resistance and renin secretion rate was studied in the rat.

2. Renin secretion rate and peripheral plasma renin activity was markedly reduced in the DOC‐saline treated rats. Renal vascular resistance was comparable to that found in a corresponding control group. Responsiveness to isoprenaline suggested that the β‐adrenoceptor mediating renin release was grossly intact.

3. A significant rise in blood pressure occurred in only 50% of the treated animals: However, no differences in weight gain, renal vascular resistance or renin levels were apparent when compared with animals which remained normotensive.

4. These findings indicate that suppression of renin secretion during prolonged DOC‐saline administration cannot be directly attributed to changes in arterial pressure, renal vascular resistance or β‐adrenoceptor sensitivity.
HAEMODYNAMICS OF HYPERTENSION IN PREGNANCY ASSESSED BY M‐MODE ECHOCARDIOGRAPHY
Authors: Larkin Hugh , Gallery Eileen D. M. , Hunyor Stephen N. , Gyory Akos Z. , Boyce E. Stewart
Published: June 2007

1. Echocardiographic haemodynamic and left ventricular parameters were determined in twenty‐one normotensives and thirty‐six hypertensives during the last trimester of pregnancy.

2. Equivalent blood pressure control was obtained in hypertensives with bed rest only, oxprenolol or methyldopa, but remained above normotensive levels.

3. Cardiac output was elevated in the last trimester of pregnancy in normotensives and hypertensives.

4. Left ventricular mass was increased in normal pregnancy, but displayed an exaggerated increase in hypertensives.

5. Total peripheral resistance was inappropriately elevated in hypertensive pregnancy, but was normalized in the oxprenolol‐treated group.

6. There was no reduction in heart rate or cardiac output in the β‐adrenoreceptor blocker‐treated group. This feature, in combination with lowered peripheral resistance, may contribute to the improvement in foetal outcome observed in maternal hypertension of pregnancy treated with oxprenolol.
ACTH HYPERTENSION MODIFIES THE HAEMODYNAMIC EFFECTS OF PROSTACYCLIN INFUSIONS IN SHEEP
Authors: Mason R. T. , Allen K. J. F. , Coghlan J. P. , Denton D. A. , Fei D. T. , Graham W. F. , Scoggins B. A. , Stewart K. W.
Published: June 2007

1. The haemodynamic effects of short‐term prostacyclin infusions (0.05‐0 50 /μg/kg per min) were investigated in conscious adult sheep.

2. Haemodynamic dose‐response curves to prostacyclin were performed before, during and after production of ACTH‐induced hypertension.

3. Prior to ACTH administration prostacyclin produced dose‐dependent reductions in mean arterial pressure, total peripheral resistance and stroke volume and these were accompanied by increases in heart rate and cardiac output.

4. After 5 days of ACTH‐induced hypertension prostacyclin produced similar effects on mean arterial pressure to those seen prior to ACTH but the effects on heart rate, cardiac output, stroke volume and total peripheral resistance were markedly increased.

5. These studies demonstrate that the responsiveness of the circulation to prostacyclin is altered in ACTH‐induced hypertension.
INHIBITION BY HYDRALAZINE OF THE CONVERSION OF DOPAMINE TO NORADRENALINE IN RAT ATRIA IN VITRO AND IN VIVO
Authors: Songkittiguna P. , Majewski H. , Rand M. J.
Published: June 2007

1. Hydralazine (10 to 2000 μnol/1) produced a concentration‐dependent inhibition of the conversion of (3H)‐dopamine to (3H)‐noradrenaline in rat isolated atria.

2. In rats treated with hydralazine (2 mg/kg, i.p.), there was an inhibition of the conversion of (3H)‐dopamine to (3H)‐noradrenaline in the intact atria in vivo.

3. Hydralazine treatment may result in the appearance of dopamine as a significant co‐transmitter in noradrenergic nerves, and this may contribute to the antihypertensive effect of hydralazine.
EFFECT OF ACTH ADMINISTRATION ON THE HAEMODYNAMIC RESPONSE TO ARGININE‐VASOPRESSIN IN SHEEP
Authors: Coghlan John P. , Denton Derek A. , Graham William F. , Humphrey Timothy J. , Mason Rex T. , Schnieder Edward G. , Scoggins Bruce A. , Whitworth Judith A.
Published: June 2007

1. Blood pressure, heart rate and cardiac output were studied in intact conscious sheep during AVP infusion at 0.1, 0.25, 0.5 and 10 μg/min for 30 minutes to determine whether pressor responsiveness to AVP was altered in ACTH‐induced hypertension.

2. Prior to ACTH treatment, AVP produced rises in blood pressure associated with a fall in heart rate and cardiac output.

3. During ACTH treatment, pressor responsiveness to AVP and decrease in cardiac output were unchanged, but reflex bradycardia was reduced.

4. ACTH‐induced hypertension in sheep is not associated with enhanced pressor responsiveness to AVP.
ACTIVATION OF PLASMA PREKALLIKREIN AND INACTIVE RENIN BY PUFF ADDER VENOM
Authors: Morris Brian J. , Lawrence Christopher H. , Catanzaro Daniel F.
Published: June 2007

The activation of inactive renin during incubation of human plasma with puff adder venom at pH 7 4 was found to be a complex process. Gel nitration on Sephacryl S‐200 indicated that the venom contains a major peak of caseinolytic and renin‐activating activity of low molecular weight. This enzyme was a metalloproteinase. During incubation with plasma the metalloproteinase formed a complex with α2‐macroglobulin and retained caseinolytic and renin‐activating activity. Venom metalloproteinase activated prekallikrein, but not plasmin, and plasma kallikrein may account for at least part of the activation of inactive renin observed.
HAEMODYNAMIC CHANGES IN ACTH‐INDUCED HYPERTENSION IN SHEEP
Authors: Graham W. F. , Allen K. J. F. , Coghlan J. P. , Denton D. A. , Humphery T. J. , Scoggins B. A. , Whitworth J. A.
Published: June 2007

1. ACTH (20 μg/kg per day) produced an elevation in blood pressure associated with an increase in cardiac output in conscious sheep, due in the first 72 h to a rise in heart rate. Stroke volume did not rise until the fourth day of ACTH treatment.

2. Calculated total peripheral resistance did not change.

3. Intravenous administration of acebutolol prior to and during ACTH administration did not modify the rise in blood pressure, but this was associated with a rise in total peripheral resistance.

4. These studies show that while ACTH‐induced hypertension is usually associated with increased cardiac output, rather than total peripheral resistance it still occurs, but is associated with a rise in total peripheral resistance if the rise in cardiac output is prevented by /J‐adrenoreceptor blockade.
TESTOSTERONE‐ANTIBIOTIC EFFECTIVENESS ON STAPHYLOCOCCUS AUREUS INFECTED RATS
Authors: Atef M. , Sokkar S. M.
Published: June 2007

(1) Male castrated rats (testosterone‐free) inoculated intraperitoneally with Staph, aureus showed severe damage in their internal organs as determined by pathological examination of the killed animals.

(2) Penicillin‐G, oxytetracycline and chloramphenicol treatment 24 h after injection markedly decreased the extent of damage.

(3) Pretreatment of castrated rats with testosterone propionate for 3 successive days before infection had a protective influence on the internal organs.

(4) Testosterone‐injected rats when treated with different antibiotics, showed a clear synergistic action with penicillin‐G and oxytetracycline but not chloramphenicol.
TOBACCO SMOKING AND CORTICAL EVOKED POTENTIALS: AN OPPOSITE EFFECT ON AUDITORY AND VISUAL SYSTEMS
Authors: Friedman Jeannette , Meares Russell
Published: June 2007

1. Auditory and visual evoked potentials produced by five intensities of tones and light flashes were recorded in twelve young men who were habitual smokers.

2. The subjects attended the laboratory on four occasions. Two recordings were made on each of the last three of these visits. They were made (i) before and after smoking, (ii) without smoking, (iii) before and after smoking after 12 h abstinence from smoking.

3. Smoking was associated with increases in the amplitudes of the components V‐VI, VI‐VII in the visual system and a decrease in the amplitude of N2P2 in the auditory system. Abstinence from smoking produced effects in the opposite direction.

4. These findings are consistent with the possibility that smoking has different and perhaps opposite effects on the visual and auditory system.

5. The findings may be helpful in re‐evaluating some of the apparently conflicting reports on the effects of smoking on perceptual processes.
THE EFFECTS OF CAPTOPRIL (SQ 14,225) ON THE SYSTEMIC AND CORONARY HAEMODYNAMICS OF THE INTACT ANAESTHETIZED DOG
Authors: Maxwell G. M. , Rencis V. , Ness D.
Published: June 2007

1. The effects of Captopril (SQ14,225), an inhibitor of angiotensin‐converting enzyme, given intravenously in a dose of 0–3 mg/kg was studied in intact anaesthetized dogs.

2. The drug caused a decrease in systemic and pulmonary arterial mean pressures, an increase in cardiac output, and hence a decrease in calculated systemic and pulmonary vascular resistances. A sustained tachycardia also occurred.

3. A minor, transient increase in coronary sinus flow was recorded, with a sustained decrease in calculated coronary vascular resistance.

4. No change was found in cardiac oxygen metabolism nor in calculated cardiac efficiency.

5. The plasma renin values increased in the control animals and those given the drug.
EFFECT OF ADRENOCORTICAL STEROIDS AND THEIR STRUCTURAL ANALOGUES ON BLOOD PRESSURE IN SHEEP
Authors: Whitworth Judith A. , Allen Kingsley J. F. , Coghlan John P. , Denton Derek A. , Fan James S. K. , Humphery Timothy J. , McDougall John G. , Scoggins Bruce A.
Published: June 2007

1. A model of adrenocortical steroid‐induced hypertension based on the effects of ACTH administration has been developed in sheep. The present studies examine the effects of a number of different steroid hormones on blood pressure to investigate their structure‐activity relationships.

2. Infusion of the major ovine adrenal steroid hormones (combined steroid infusion of Cortisol, corticosterone, 11‐deoxycortisol, aldosterone, deoxycorticosterone) reproduced the metabolic but not the blood pressure effects of ACTH.

3. Addition of 17α, 20α‐dihydroxyprogesterone and 17α‐hydroxyprogester‐one, at rates appropriate for conditions of ACTH stimulation, to the combined steroid infusion reproduced both the blood pressure and metabolic effects of ACTH.

4. 17α, 20β‐Dihydroxyprogesterone, 20β‐dihydroxy‐11‐deoxycortisol and 20β‐hydroxycortisol all had additional hypertensive activity when given with combined steroid infusion, but 16α‐hydroxyprogesterone, 11β, 17α‐dihydroxy‐progesterone, 20a‐hydroxyprogesterone and 20α‐hydroxyprogesterone did not.

5. These studies support the concept of a new class of steroid hormone action in blood pressure regulation.
SELECTIVE DEVELOPMENT OF TOLERANCE TO β‐ADRENOCEPTOR AGONISTS IN SKELETAL MUSCLE AS COMPARED WITH AIRWAY SMOOTH MUSCLE FROM THE GUINEA‐PIG
Authors: Holmberg E. , Jeppsson A.‐B. , Waldeck B.
Published: June 2007

1. Guinea‐pigs were fed with a diet containing terbutaline or placebo for 4–5 days. The trachea, soleus muscle and the extensor digitorum longus (EDL) from these animals were prepared for recording of isometric contractions in vitro.

2. After treatment with terbutaline in vivo, the response of the pilocarpine‐contracted trachea to terbutaline and isoprenaline was slightly suppressed with no change in maximum relaxation.

3. After treatment with terbutaline in vivo the maximum depression of the incomplete tetanic contractions of the soleus muscle brought about by terbutaline or isoprenaline was diminished by about 70%. The response of the EDL was also attenuated after previous treatment with terbutaline in vivo.

4. These data indicate a selective development of tolerance to the effects of β‐adrenoceptor agonists in skeletal muscle as compared with tracheal smooth muscle.

5. The present results provide an experimental analogue to the clinical observation that patients being treated with β‐adrenoceptor agonists become tolerant to the tremorogenic rather than to the bronchodilating effect.
BARORECEPTOR REFLEX IN THE RAT AFTER CONVERTING ENZYME INHIBITION OR ANGIOTENSIN RECEPTOR BLOCKADE
Authors: Coleman Thomas G. , Salgado Maria Cristina O. , Bengis Roy G. , Davis Milton H. , Dent Ann C.
Published: June 2007

1. One component of baroreflex responsiveness was quantitated in conscious rats using the heart rate response to a pressor injection of phenylephrine.

2. Endogenous angiotensin and its effectiveness were manipulated by sodium deprivation, converting enzyme inhibition and infusion of an angiotensin analogue. None of these manoeuvres changed the observed reflex responsiveness.

3. We conclude that endogenous angiotensin has no influence on the component of baroreceptor function that is described by the slope of the arterial pressure‐heart rate relationship.
TOLERANCE TO THE EFFECTS OF Δ1‐TETRAHYDROCANNABINOL ON THE PRESSOR RESPONSES TO NORADRENALINE IN RATS
Authors: Li D. M. F.
Published: June 2007

l. The depressor response, but not the cardiac slowing response, to the acute intravenous administration of Δ1‐THC (1 mg/kg) was significantly reduced in urethane anaesthetized rats, which had been treated with daily injections of Δ1‐THC (2 mg/kg, i.p.) for 10 days (P<0.01).

2. No significant differences in either the depressor or the negative chronotropic effects of an acute intravenous injection of Δ1‐THC (1 mg/kg) were observed in anaesthetized rats which had been treated with PVP (8 mg/kg per day, i.p.) for 10 days.

3. The depressor and cardiac slowing responses to an acute intravenous dose of Δ1‐THC (1 mg/kg) were not significantly different between Δ1‐THC‐ and PVP‐treated animals which had been pithed.

4. The potentiating effects of Δ1‐THC on the pressor responses to intravenously administered noradrenaline were significantly reduced (P<0.001) in urethane anaesthetized rats which had been treated with Δ1‐THC, but not in anaesthetized PVP‐treated animals.

5. Tolerance to the potentiating effect of Δ1‐THC on the responses to noradrenaline has also been demonstrated in anaesthetized Δ1‐THC‐treated rats, but not in pithed Δ1‐THC treated ones.

6. It is concluded that the development of tolerance to the depressor action of Δ1‐THC, and its potentiating effect on the noradrenaline pressor responses requires the presence of an intact central nervous system.
ANGIOTENSIN AND THE CARDIAC BAROREFLEX RESPONSE TO PHENYLEPHRINE
Authors: Lee W. B. , Lumbers E. R.
Published: June 2007

1. In adult conscious sheep the pressor actions of infused angiotensin II were prevented by the concomitant intravenous infusions of sodium nitroprusside. The effect of such intravenous infusions of angiotensin II on the cardiac baroreflex response to transient rises in arterial pressure caused by intravenous phenylephrine was studied.

2. Intravenous infusion of angiotensin II caused a reduction in pulse interval in the absence of any change in arterial pressure. It also caused a reduction in baroreflex sensitivity measured by determining the relation between pulse interval and systolic pressure during the rise in pressure caused by injection of phenylephrine.

3. After administration of the converting enzyme inhibitor (captopril) the mean baroreflex sensitivity of 3 of 4 pregnant ewes increased.

4. It is concluded that high levels of angiotensin II can modify the cardiac baroreceptor reflex response so that the heart rate is inappropriately high for a given systolic pressure and that it reduces the sensitivity of the cardiac baroreflex response to transient changes in arterial pressure.
CIRCULATING HYPOTENSIVE FACTOR IN PREGNANT SPONTANEOUSLY HYPERTENSIVE RATS
Authors: Kubota T. , Yamada T.
Published: June 2007

1. Blood pressure decreased significantly at a late stage of pregnancy in spontaneously hypertensive rats (SHRs) but this reduction tended to disappear shortly after delivery. Since acute and chronic administration of progesterone, prolactin and estrone failed to reduce blood pressure, these hormones were not responsible for a fall of blood pressure at a late stage of pregnancy in SHRs. Exogenous administration of prostaglandin E2 (PGE2) significantly reduced blood pressure, but endogenous prostaglandin E1 (PGE1), PGE2 and prostaglandin F2α(PGF2α) in plasma did not increase at a late stage of pregnancy.

2. Plasma from pregnant SHRs produced a significant reduction of blood pressure in male and female SHRs, but the plasma from male and non‐pregnant female SHRs failed to reduce blood pressure. Plasmas from pregnant SHRs were less effective in reducing blood pressure when tested in Wistar Kyoto rats (WKYs).

3. It is concluded that a hypotensive factor is circulating at a late stage of pregnancy in SHRs.
THE EFFECT OF RENAL DENERVATION ON ACTH‐INDUCED HYPERTENSION IN SHEEP
Authors: Whitworth Judith A. , Denton D. A. , Graham W. F. , Humphery T. J. , Scoggins B. A. , Coghlan J. P.
Published: June 2007

1. The effect of renal denervation on ACTH‐induced hypertension in sheep has been examined.

2. Both intact and renally denervated sheep showed similar rises in blood pressure following ACTH treatment.

3. Following renal denervation, the initial urinary sodium retention and ACTH‐withdrawal natriuresis typical of ACTH administration in intact sheep were absent, and the fall in blood pressure was delayed.
LACK OF PROLONGED EFFECT OF ANTIDIURETIC HORMONE ON THE RENIN‐ALDOSTERONE SYSTEM IN THE DOG
Authors: Young David B. , McCaa Robert E.
Published: June 2007

1. The effects of maximally antidiuretic, subpressor antidiuretic hormone (ADH) administration on the renin‐aldosterone system were studied in dogs during 4 days of continuous intravenous infusion of ADH at a rate of 0.067 mU/kg per min. Water intake was limited to 700 ml/day to avoid changes in fluid volume status.

2. At the conclusion of the four‐day study, plasma sodium concentration had fallen from 140.3 ± 0.8 to 137.2 ± 2.0 mmol/l, plasma potassium concentration, 22Na space, and mean arterial pressure remained within the control ranges.

3. Neither plasma renin activity nor plasma aldosterone concentration showed any tendency to change in response to the ADH infusion.

4. The results indicate that physiologic levels of ADH have no prolonged, direct effect on the renin‐aldosterone system.
FAILURE OF ASPIRIN TO MODIFY THE HYPOTENSIVE ACTION OF CAPTOPRIL IN SPONTANEOUSLY HYPERTENSIVE RATS
Authors: DiNicolantonio R. , Dusting G. J. , Hutchinson J. S. , Mendelsohn F. A. O.
Published: June 2007

1. Oral administration of the angiotensin converting enzyme inhibitor, captopril (30 mg/kg per day) to spontaneously hypertensive rats of the Okamoto strain progressively reduced arterial blood pressure by 60 mmHg over 4–5 days.

2. Oral treatment of spontaneously hypertensive rats with aspirin (200 mg/kg per day) for one week did not alter blood pressure, but it greatly reduced the vasodepressor effects of intravenous injections of arachidonic acid (3 mg/kg).

3. The fall in blood pressure of spontaneously hypertensive rats treated concurrently with both aspirin (200 mg/kg per day) and captopril (30 mg/kg per day) was not different to the fall observed in rats treated with captopril alone.

4. The hypotensive action of captopril in spontaneously hypertensive rats does not appear to be due to stimulation of vasodilator prostanoid biosynthesis.
ALCOHOL AND BLOOD PRESSURE IN A WORKING POPULATION
Authors: Arkwright P. D. , Beilin L. J. , Rouse I. , Armstrong B. , Vandongen R.
Published: June 2007

1. The association between alcohol consumption and blood pressure was studied in 491 Government employees. The men, aged 21–45 years, volunteered to complete a health questionnaire and submitted to standardized measurements of blood pressure, heart rate and body size.

2. Average weekly alcohol consumption correlated with systolic pressure (R = 0.18, P<0.001) but not with diastolic pressure. Systolic pressure increased progressively with increasing alcohol consumption with no obvious threshold effect. An effect of alcohol was seen independent of age, obesity (Quetelet's index) or cigarette smoking.

3. Results indicate that alcohol ranks close to obesity as a preventable cause of essential hypertension in the community.
HYPERTENSION THROUGH ADRENALINE ACTIVATION OF PREJUNCTIONAL β‐ADRENOCEPTORS
Authors: Majewski H. , Tung L.‐H. , Rand M. J.
Published: June 2007

1. Adrenaline can enhance the stimulation‐induced release of transmitter noradrenaline in sympathetically innervated tissues by activating prejunctional β‐adrenoceptors.

2. Adrenaline incorporated into sympathetic transmitter stores by neuronal uptake can be subsequently released as a co‐transmitter and can then activate prejunctional β‐adrenoceptors, thus completing a facilitatory feedback loop.

3. Rats chronically treated with adrenaline develop elevated blood pressures compared to control rats, β‐adrenoceptor blockade prevents the rise in blood pressure.

4. Activation by adrenaline of facilitatory prejunctional β‐adrenoceptors of sympathetic nerves innervating cardiovascular effector tissues may explain adrenaline‐induced rises in blood pressure.
PSYCHOSOCIAL STRESS INDUCES TUBULOINTERSTITIAL NEPHRITIS UNRELATED TO HYPERTENSION IN CBA MICE
Authors: Henry James P. , Stephens Patricia M.
Published: June 2007

1. Groups of mice interacting socially in complex population cages become hypertensive. Some also develop fatal chronic tubulointerstitial nephritis.

2. Long‐term administration of the cardioselective β‐blocker metoprolol controls stress‐induced elevation of plasma renin and adrenal tyrosine hydroxylase. It also normalizes blood pressure. Despite the effectiveness of this sympathetic blockade, the incidence of nephritis was not diminished.

3. The fact that stress‐induced increases of adrenal weight and plasma cortico‐sterone persist during metoprolol treatment points to the independence of the pituitary‐adrenal cortical system and its possible role in the aetiology of renal disease.
DUAL EFFECTS OF CLONIDINE ON RAT PREJUNCTIONAL α‐ADRENOCEPTORS
Authors: Medgett I. C. , Rand M. J.
Published: June 2007

1. The effects of clonidine (1.0 μmol/l) and phentolamine (3.0 μmol/l) on the stimulation‐induced efflux of radioactivity were assessed in rat isolated atria and tail arteries in which transmitter stores had been labelled with (3H)‐noradrenaline.

2. In atria, clonidine did not affect transmitter release when stimulation was for 10 s periods at frequencies of 1, 2 or 5 Hz, whereas at 10 Hz there was a significant 1.2‐fold enhancement of release. Phentolamine enhanced release with stimulation at 5 Hz and 10 Hz by 1.5‐ and 2.5‐fold respectively.

3. In tail arteries, clonidine reduced release when stimulation was for 30 s periods at a frequency of 1 Hz, but did not affect release at 2 Hz or 5 Hz. Phentolamine in each case produced an approximately 1.5‐fold enhancement of release.

4. In the pithed rat, spinal stimulation of cardioaccelerator fibres produced a tachycardia, the magnitude of which depended on the frequency and duration of stimulation. Clonidine (10jug/kg, i.v.) caused either a reduction or an enhancement of the response depending on the frequency and duration of stimulation; in the presence of phentolamine (2 mg/kg, i.v.), clonidine had no effect.

5. The results are consistent with partial agonistic actions of clonidine at prejunctional a‐adrenoceptors in the rat cardiovascular system; such effects may be of relevance to the mechanism of the clonidine withdrawal syndrome.
REGULATION OF UTERINE SMOOTH MUSCLE BRADYKININ RECEPTORS BY BRADYKININ LEVELS AND ANGIOTENSIN CONVERTING ENZYME INHIBITOR IN THE RAT
Authors: Yasujima M. , Matthews P. G. , Johnston C. I.
Published: June 2007

1. Bradykinin infusion (0.1 μg/min i.v.) decreased the number of uterine bradykinin receptors by 20% at Day 2. Bradykinin receptors returned to control levels at Day 7.

2. Captopril infusion (1.7μg/min i.v.) induced prolonged decreases in the number of uterine bradykinin receptors of 15% at Day 2 and of 13% at Day 7, respectively.

3. The number of uterine bradykinin receptors was increased in two‐kidney, one clip hypertensive rats by 19%.

4. These results suggest that endogenous bradykinin participates in the regulation of uterine bradykinin receptors.

5. Decreased uterine bradykinin receptors induced by captopril might reflect increased endogenous bradykinin.
IMPORTANCE OF ANTIDIURETIC PROPERTIES OF VASOPRESSIN IN EXPERIMENTAL RENAL HYPERTENSION
Authors: Woods R. L. , Johnston C. I.
Published: June 2007

1. Homozygous Brattleboro rats with hereditary hypothalamic diabetes insipidus (DI) developed one‐kidney, one‐clip (1K–1C) and two‐kidney, one‐clip (2K–1C) Goldblatt renal hypertension.

2. However, the systolic blood pressure (SBP) in 1K–1C Brattleboro rats was significantly lower than in non‐DI hypertensive 1K–1C Long‐Evans (LE) rats.

3. Treatment with the synthetic antidiuretic analogue of vasopressin, DDAVP (l‐desamino‐8‐D‐arginine vasopressin), increased the SBP in the DI rats to the same level as in 1K–1C Long‐Evans. This elevation of SBP was associated with increased extracellular fluid volume in the DI rats after DDAVP.

4. The results suggest that vasopressin is not essential for the development of renal hypertension but the absolute levels of blood pressure achieved in 1K–1C hypertension are volume‐dependent and thus influenced by the water‐retaining properties of vasopressin.
OPIATES INHIBIT THE DOPAMINERGIC ENHANCEMENT OF THE RENAL RESPONSE TO ALDOSTERONE IN THE RAT
Authors: Adam William R. , Danks Janine A. , Goland Gary
Published: June 2007

1. Both naloxone, an opiate antagonist, and levorphanol, an opiate agonist, inhibit the enhanced renal response to aldosterone produced by both ℓ‐dopa pretreatment and a high K+ diet.

2. This supports the evidence for a common mechanism of action for the enhancement of the renal response to aldosterone produced by ℓ‐dopa and a high K+ diet. Whether this mechanism is dopaminergic or opiate is uncertain.

3. The inhibition of the enhanced response, produced by ℓ‐dopa, by opiates is consistent with previous findings of displacement of 3H‐dopamine from renal homo‐genates by opiates and supports the hypothesis that the binding sites relate to the renal response to aldosterone.
HAEMODYNAMIC RESPONSE TO ACTH ADMINISTRATION IN ESSENTIAL HYPERTENSION
Authors: Whitworth Judith A. , Saines D. , Andrews J. , Sloman J. G. , Scoggins B. A.
Published: June 2007

1.The haemodynamic and volume response to ACTH administration was investigated in six patients with mild, untreated essential hypertension and two patients with Addison's disease on maintenance steroids. Blood pressure, heart rate and weight were recorded daily. Plasma volume (125I‐HSA) and cardiac output (thermo‐dilution) were measured during the control period and on the 5th day of ACTH treatment.

2. In the hypertensive subjects, mean arterial pressure rose from 94.3 ± 2.2 to 105.7 ± 2.8 mmHg on the 5th day of ACTH administration (P<0.02). Plasma volume rose from 29.8 ± 2.2 to 34 ± 2.2 ml/kg. Cardiac index increased from 2.85 ± 0.21 to 3.32 ± 0.14 l/min per m2 (P<0.05). Cardiac output rose from 5.81 ± 0.69 to 6.72 ± 0.59 l/min. Calculated total peripheral resistance, heart rate and body weight were unchanged. No such changes were seen in patients with Addison's disease.

3. The haemodynamic characteristics of ACTH in patients with mild untreated essential hypertension are similar to those in the experimental model of ACTH induced hypertension in sheep.
EFFECTS OF NEONATAL SYMPATHECTOMY BY 6‐HYDROXYDOPAMINE ON BLOOD PRESSURE AND INTRAVASCULAR VOLUME IN YOUNG STROKE‐PRONE SPONTANEOUSLY HYPERTENSIVE RATS
Authors: Rascher Wolfgang , Dietz Rainer , Schömig Albert , Voss Ute , Gross Franz
Published: June 2007

1. Stroke‐prone spontaneously hypertensive rats (SHRSP) and normotensive Wistar Kyoto rats (WKY) were ‘chemically sympathectomized’ immediately after birth with 6‐hydroxydopamine (6‐OHDA, 100 mg/kg s.c. daily) for the first 10 days of life.

2. Body weight gain was diminished in both groups as compared with sham‐treated controls. Blood pressure was reduced in ‘sympathectomized’ SHRSP, and also WKY rats had a slightly lower blood pressure than control rats.

3. Plasma concentration of angotensin II and renin content of the kidney were not influenced by 6‐OHDA.

4. ‘Sympathectomized’ SHRSP retained similar amounts of sodium than sham‐treated SHRSP when sodium retention is expressed per body weight gained. Plasma and blood volumes were increased in both SHRSP and WKY rats, whereas packed cell volume was significantly decreased.

5. These results demonstrate the significance of an intact sympathetic nervous system for the development of hypertension in SHRSP. The expanded plasma and blood volume in ‘sympathectomized’ rats indicate an important role of the sympathetic nervous system and/or the arterial blood pressure for the regulation of intravascular volume.
A COMPARISON OF THE ACTIVITY OF THE ANGIOTENSIN CONVERTING ENZYME INHIBITORS SQ 14 225, SA 446, AND MK 421
Authors: Takata Y. , Nicolantonio R. Di , Mendelsohn F. A. O. , Hutchinson J. S. , Doyle A. E.
Published: June 2007

This study was designed to compare the activity of three structurally different drugs (SQ 14 225, SA 446, and MK 421) as inhibitors of angiotensin converting enzyme in vivo and to compare their effects in two experimental models of hypertension.

2 MK 421 was less effective than SA 446 or SQ 14 225 in suppressing the pressor responses to intravenous angiotensin I 3 min after the administration of low doses of the converting enzyme inhibitors (CEIs) but more effective than SA 446 or SQ 14 225 30 min or longer after doses of CEIs ranging from 25 to 2500 nmol/kg i.v.

3 The CEIs administered at 8 μmol/kg intravenously blocked the pressor response to angiotensin I (AI) to a similar maximal effect but the time for recovery was much slower for MK 421 than for SQ 14 225 or SA 446. After oral administration (15 mg/kg) prolonged blockade was observed with each of the three drugs although some recovery occurred with SA 446 after 5 h. The effect of a small dose of MK 421 intravenously (0.4 μmol/kg) was more prolonged in anaesthetized than in conscious spontaneously hypertensive rats (SHR).

4 Anaesthetized adult SHR showed slow progressive falls of blood pressure after 8 /unol/kg of each drug intravenously although the effect of SA 446 was less than for SQ 14 225 or MK 421 which were equipotent. After acute oral administration of each CEI at 80 μmol/kg, conscious SHR showed significant falls in blood pressure but the effect of SA 446 was less than the other two inhibitors which appeared equipotent.

6 After chronic oral administration of the drugs to conscious SHR, SA 446 (80 μmol/kg per day) did not alter blood pressure although SQ 14 225 was effective at this dose. At a higher dose of 160 /μmol/kg per day SA 446 significantly lowered blood pressure of SHR in a manner similar to the same dose of SQ 14 225 or MK 421.

7. We conclude that the three drugs are potent, orally effective converting enzyme inhibitors. The duration of action was in the order MK 421 >SQ 14 225 >SA 446. MK 421 appears the most potent due to both a higher affinity for converting enzyme in vitro and a longer persistence of action in vivo. In renal hypertension, the drugs appeared equipotent but in the SHR at low doses, SA 446 was ineffective.
EFFECT OF INDOMETHACIN ON RESPONSES OF SHEEP ISOLATED CORONARY ARTERY TO ARACHIDONIC ACID
Authors: Cornish E. J. , Goldie R. G. , Krstew E. V. , Miller R. C.
Published: June 2007

Indomethacin (2.8 μmol/1) did not consistently affect basal tone of sheep coronary artery strips, while a ten‐fold higher concentration increased tension in 50% of the preparations tested. When acetylcholine was used as a spasmogen, oscillations in induced tone and relaxations produced by arachidonic acid (6.6 μmol/1) were abolished by indomethacin, 2.8 μmol/1 and 7 μmol/1, respectively.

Prostacyclin (PGI2) and prostaglandin E1 decreased and PGE2 increased arterial tension while PGF2α was inactive. Responses to PGI2 were reduced by indomethacin (28 μmol/1) but not by indomethacin (2.8 μmol/1).

It is suggested that sheep isolated coronary arteries synthesize and release prostacyclin in the presence of acetylcholine and arachidonic acid and that such synthesis can be inhibited by indomethacin.
REVERSAL OF RENOVASCULAR HYPERTENSION
Authors: Swales J. D. , Bing R. F. , Russell G. I. , Thurston H.
Published: June 2007

1. The fall in blood pressure observed in both early and chronic phase Goldblatt 2‐kidney 1‐clip hypertension produced by removing or unclipping the ischaemic kidney is due to a profound fall in peripheral resistance.

2. The two procedures have an equal effect upon peripheral resistance and the lesser efficacy of nephrectomy in lowering blood pressure is due to a greater rise in stroke volume perhaps associated with a greater degree of sodium retention.

3. Neither changes in sodium balance, in the renin‐angiotensin system nor in vascular reactivity explain the fall in blood pressure.

4. A reduction in renal sympathetic afferent activity and a medullary based vasoactive humoral system may play a role although the nature and extent of that role remain to be defined.
INHIBITION OF GUINEA‐PIG RENAL [Na + K]‐ATPase BY NORMOTENSIVE HUMAN PLASMA: EFFECTS OF A HIGH SODIUM DIET
Authors: Wellard R. M. , Myers J. B. , Danks J. A. , Morgan T. O. , Adam W. R.
Published: June 2007

1. The effect of plasma taken from normotensive humans, while on a low and high sodium diet, on [Na + K]‐ATPase and 3H‐ouabain binding was measured in tubules from guinea‐pig kidneys.

2. Plasma from the high sodium, compared to the low sodium, diet period: (a) inhibited [Na + K]‐ATPase activity; (b) decreased 3H‐ouabain affinity for binding sites; (c) increased the number of available 3H‐ouabain binding sites; (d) decreased [Na + K]‐ATPase turnover (activity/3H‐ouabain binding sites).

3. The inhibition of [Na plus; K]‐ATPase suggests an increase in a (possible) natriuretic factor. The decreased affinity of 3H‐ouabain binding suggests an endogenous ouabainoid, which may be the natriuretic factor.
ELEVATION OF BLOOD PRESSURE IN HYPERTENSIVE RATS AFTER LESIONING SEROTONIN NERVES IN THE DORSOMEDIAL MEDULLA OBLONGATA
Authors: Howe P. R. C. , Rogers P. F. , King R. A. , Smith R. M.
Published: June 2007

1. The possibility that serotonin (5HT) nerve endings in the dorsomedial medulla oblongata participate in the control of blood pressure was investigated in stroke‐prone hypertensive rats and in normotensive rats.

2. 5HT nerves were destroyed by injecting 5,7‐dihydroxytryptamine bilaterally into the solitary tract nucleus. Immunohistochemical and biochemical examination revealed a selective loss of 5HT nerves throughout the dorsomedial medulla with little damage in adjacent regions.

3. Arterial blood pressure and heart rate, measured at daily intervals, were similar in lesioned and sham‐operated normotensive rats. However, in the hypertensive rats, blood pressure was substantially elevated at 6‐9 days after the lesions compared with sham operations. There were no accompanying changes in heart rate.
THE DISTRIBUTION OF ARTERIOLOSCLEROSIS ALONG THE ARTERIOLES IN DOCA HYPERTENSIVE RATS
Authors: Walker M. B. , Boyd G. W.
Published: June 2007

1. The development of structural changes along the length of small arterioles (mean internal diameter 20‐30 m̈m) was studied in uninephrectomized DOCA/salt hypertensive rats over a period of 10 weeks, by casting the arteriolar branchings in the ileum with Microfil (coloured silicone rubber).

2. Along with a reduction in mean arteriolar diameter, irregular structural changes, manifested as focal narrowings along the arteriolar lengths, developed in the hypertensive animals, becoming most marked after 8‐10 weeks.

3. The severity of the changes appeared to be related to both the level and duration of the hypertension.

4. The irregular nature of the changes is difficult to account for on the basis of any direct local pressure effect.
THE EFFECT OF KETANSERIN IN ESSENTIAL HYPERTENSION
Authors: Anderson A. , Morgan T. , Dumpys R.
Published: June 2007

1. Ketanserin, a 5HT2‐receptor blocking drug was given to 17 patients with essential hypertension.

2. Satisfactory control was achieved in 13 patients.

3. Control was not as satisfactory when given once daily.

4. There was no rebound effect when the drug was ceased.

5. Side‐effects were few.

6. Ketanserin was a satisfactory drug to reduce blood pressure in patients with moderate hypertension.
PREVENTION OF STRUCTURAL ARTERIOLAR CHANGES IN DOCA HYPERTENSION WITH HYDRALLAZINE
Authors: Vial J. H. , Yong A. C. , Boyd G. W.
Published: June 2007

1. Structural changes in resistance vessels were studied by (a) hindquarter perfusion; and (b) planimetry of cross‐sections of renal arterioles in uninephrectomized rats treated for 10 weeks with saline and either DOCA (deoxycorticosterone acetate), DOCA plus hydralazine, vehicle plus hydralazine or vehicle only.

2. DOCA‐treated rats developed hypertension and structural change. Addition of hydralazine prevented both hypertension and the development of structural change.

3. Structural arteriolar change in DOCA/salt hypertension is related to the high blood pressure or a closely associated factor rather than some other effect of DOCA.
CAPILLARY PERMEABILITY IN NORMAL AND HYPERTENSIVE HUMAN PREGNANCY
Authors: Hunyor S. N. , McEniery P. T. , Roberts K. A. , Bellamy G. R. , Roffe D. J. , Gallery E. D. M. , Gyory A. Z. , Boyce E. S.
Published: June 2007

1. Capillary permeability (CP) is elevated in late normal pregnancy, when compared to postpartum values.

2. In women with pregnancy associated hypertension (PAH), pregnancy CP levels are not different from postpartum and are less than in normal pregnancy.

3. These changes in capillary permeability are not explained by alterations in serum albumin.
VASOACTIVITY GENERATED FROM PLATELETS BY IMMUNE COMPLEXES IN PRE‐ECLAMPSIA
Authors: Medcalf R. L. , Kuhn R. J. P. , Iwanov V. , Mathews J. D. , Moulds R. F. W.
Published: June 2007

1. Circulating immune complexes in excess of the equivalent of 20 m̈g/ml heat‐aggregated IgG were found in fourteen out of twenty patients diagnosed as having preeclampsia.

2. Only six of the nineteen controls tested had similar levels of immune complexes. Recent studies have established that concentrations of heat aggregated IgG in excess of 20 m̈g/ml activate human platelets to release sufficient concentrations of vasoactive agents to constrict a human blood vessel in vitro.

3. It is therefore suggested that in vivo platelet activation by circulating immune complexes may release sufficient concentrations of vasoactive agents to contribute to the hypertension in pre‐eclampsia.