PubMed Health⌕ Search

Biomedical subjects

F O Simpson

Publications and source records attributed to F O Simpson.

At least 19 recordsLinked to original sources
PubMed1992

Effect of enalapril on body sodium and handling of a sodium chloride load in hypertensive and normotensive rats.

1. The effect of enalapril on handling of an Na load and on body Na during 96 h of zero Na intake was measured in hypertensive rats (GH and SHR) and their normotensive controls (N and WKY) by a whole body counting method. 2. Enalapril treatment led to a greater fall in body Na in the first 24 h after the Na load (as expected from the known effect of ACE inhibition on aldosterone production) and thus to a slightly faster excretion of an amount equivalent to the load. 3. Enalapril-treated rats were unable to maintain body Na on a zero Na intake. This was also expected from the known effect on aldosterone production, though other mechanisms are not excluded. The effect was more marked in the SHR and WKY than in GH and N but there was no significant difference in this effect between the hypertensives and their respective control strains.

Animals↗
PubMed1992

Salt and hypertension: revisited.

1. There is only one known environmental factor that possibly could hold the key to much of the problem of 'essential' hypertension and this is salt. Without a high or moderately high salt intake, other environmental factors may be largely inoperative. The evidence, which still falls somewhat short of certainty, is briefly reviewed.

Humans↗
PubMed1990

A questionnaire survey of symptoms in a hypertension clinic.

OBJECTIVE: to assess symptoms of patients on antihypertensive therapy. SETTING: hospital hypertension clinic. DESIGN: self administered questionnaire (sent and returned by mail) listing 23 symptoms; four grades of response (none, mild or seldom, moderate or sometimes, severe or frequent); special scale for nocturia and appetite. PATIENTS: 302 patients completed the questionnaire (87% of those to whom it was sent); 109 of these patients completed it a second time, after an interval of four months, so that repeatability could be assessed. REPEATABILITY: scores were high, ranging from 0.92 to 0.99, for all symptoms except flushing (all grades 0.91), nausea (all grades 0.90) and sleepiness (severe, 0.82) (method of Bulpitt et al). RESULTS: overall prevalence of symptoms was high, but most were mild or infrequent. Women had significantly greater prevalence of oedema, flushing and insomnia than men and tended to assess their symptoms more often as severe or frequent. Nocturia was the only symptom more common in those above median age (62 yr) than in those below. Lack of energy was the only symptom more prevalent in the treated than in the untreated. No difference in prevalence of symptoms was detected between those taking or not taking a specific type of drug (beta blocker, diuretic, ACE inhibitor, calcium antagonist). CONCLUSION: in patients whose antihypertensive therapy has been carefully adjusted to try to avoid symptomatic side effects, the burden of such side effects appears to be very small.

Female↗
PubMed1990

Managing hypertension: drugs, life-style manipulation or benign neglect? Medical, ethical and economic considerations.

Antihypertensive drugs have been of major benefit to people with moderate or severe hypertension and have contributed enormously to fundamental physiological knowledge. Antihypertensive therapy in milder hypertension reduces the incidence of stroke by 40% or more, may reduce myocardial infarction and prevents progression to more severe hypertension or heart failure but is being criticised as not cost-effective. Much of this criticism is based on deductions from inappropriate data. Nevertheless, it is likely that money is in some cases being wasted on the treatment of people who were not truly hypertensive in the first place. It is also likely that drug dosage is often unnecessarily high. Clearly it is vital that treatment is delivered as economically as possible. A reduction in the prevalence of hypertension would be the best way to reduce costs. Obesity and a high alcohol intake are associated with a higher blood pressure at any age. A high salt intake throughout life appears to be associated with a rise in blood pressure in the second half of life and may well be the main factor in hypertension. A radical rethinking of the method of pricing of medical care should be considered, so as to provide incentives to people to adopt life-style measures that lead to avoidance of hypertension (and other cardiovascular risk factors) or, in established hypertension, to a reduction in the need for medication.

Antihypertensive Agents↗
PubMed1990

Surfeit and deficit of sodium: evidence from studies of body sodium in rats.

The concept of a basal level of body sodium (Strauss' state 'between surfeit and deficit') was studied by means of body sodium measurements in rats on different sodium intakes, in some cases after diuretic pretreatment. At a certain level of body sodium, when sodium intake was just enough to allow for body growth, a sodium chloride load (followed by a zero sodium intake) was excreted more or less quantitatively in 24-48 h. In rats pretreated with an ample sodium intake, the load was excreted more quickly and some additional sodium was also excreted. In rats pretreated with diuretic and a zero sodium diet, body sodium was very low and a sodium chloride load was retained to an extent that was more or less appropriate to the deficit. In a subsidiary part of the study, rats pretreated with a low sodium intake and frusemide and continuing on frusemide during and after the load, excreted a sodium chloride load at much the same rate as rats given a load following pretreatment with a very low sodium diet alone (i.e. not given a diuretic); after excreting the load they were able to maintain a stable (though reduced) level of body sodium in spite of cessation of sodium intake. Rats pretreated with hydrochlorothiazide, and continuing on this drug during and after the load, had a continued loss of sodium after cessation of sodium intake. The results are discussed in the light of the Strauss concept and appear to confirm it. Basal body sodium is, by inference, identified as the level at which delivery of sodium to the distal tubule exactly equals distal sodium reabsorption.

Animals↗
PubMed1990

Changes in clinical characteristics and drug treatment of hypertension over 40 years at the Dunedin Hypertension Clinic.

The clinical characteristics of the 4,170 hypertensive patients referred to the Dunedin Clinic from 1950 to 1989 have been compared for eight successive 5-year periods. A gradual decrease in the severity of referred hypertension and an increase in the proportion of patients already on treatment at the time of referral (currently 50%) were noted. For male patients, mean +/- SD initial lying blood pressure was 179 +/- 27/116 +/- 19 mm Hg in 1950-1954 and 158 +/- 25/91 +/- 14 mm Hg in 1985-1989. Corresponding prevalence data for target organ damage among male patients were retinal grade 3 or 4, 49% and 3%; cardiomegaly on chest radiograph, 60% and 26%; electrocardiogram left ventricle strain pattern, 28% and 3%; and serum urea levels greater than 10 mmol/L, 16% and 5%, respectively. For women there was a similar trend. The number of patients on drugs in each of nine categories and the percent use of each drug category for each year during 1950-1989 was recovered from computerized data files. The percentage peak usage of ganglion blockers was in 1950-1958, adrenergic neuron blockers in 1963-1970, centrally acting drugs in 1965-1968, diuretics in 1960-1982, beta-blockers in 1974-1987, alpha-blockers in 1980-1987, and angiotensin converting enzyme inhibitors and calcium antagonists in 1989. The diuretics have been the most enduring drugs, followed by the beta-blockers.

Ambulatory Care Facilities↗
PubMed1990

The control of body sodium in relation to hypertension: exploring the Strauss concept.

The overall control of body sodium relies on mechanisms that have close links to blood pressure control and hypertension. The Strauss concept of a basal level of body sodium, below which any available sodium is retained and above which any extra sodium is excreted (at a rate exponentially related to the amount present in the body), has been confirmed in rat studies. Total body sodium, on an average sodium intake, thus consists of basal plus extra: the proportions of these can vary and this makes interpretation of total body sodium difficult. Basal body sodium is, in theory, the level at which delivery of sodium to the distal nephron equals distal reabsorption of sodium. The latter is largely determined by aldosterone and, indeed, basal body sodium is high in primary aldosteronism and low in Addison's disease. The half-life of extra sodium is short in primary aldosteronism and long in Addison's disease: it is also short in some hypertensive subjects but in general lengthens with age. The exact mechanisms involved are still uncertain. Most of this work is based on step reductions in sodium intake. Step increases in sodium intake appear to lead to more complicated adjustment processes, with a delay in commencing excretion followed by some under-damping of the system before a new higher level of body sodium and a new equilibrium of intake and excretion is reached.

Animals↗
PubMed1990

Salt appetite, body sodium, handling of a NaCl load, renin, and aldosterone in genetically and spontaneously hypertensive rats.

Salt appetite, body sodium, handling of a NaCl load, plasma renin activity (PRA), and plasma aldosterone concentration (PAC) were compared in New Zealand genetically hypertensive (GH) and Japanese spontaneously hypertensive rats (SHRs) and their respective normotensive controls [normal Wistar (N) and Wistar-Kyoto (WKY) rats]. Salt appetite was increased in SHRs compared with GH, N, and WKY rats when rats were on salt-free chow and given a choice of distilled water and NaCl solution. Body sodium, measured by whole body counting, was higher in SHRs than in the other strains but did not differ among GH, N, and WKY rats. The rate of excretion of a NaCl load was not increased in GH rats and was slightly increased in SHRs only when on a very low NaCl intake. PRA and PAC (radioimmunoassay) were lower in SHRs than in GH, N, and WKY rats. PAC had a significant negative correlation with body sodium across the four strains. There is no evidence of any abnormality in sodium regulation in GH rats. However, the SHRs have an increased salt appetite and an increased body sodium even when sodium intake is limited; PRA and PAC appear to have responded appropriately to the increased body sodium.

Aldosterone↗
PubMed1990

Risk predictors in treated hypertension.

The data for patients referred to the Dunedin Hypertension Clinic (975 men, 1,348 women) between 1953 and 1977 have been examined by the Cox proportional hazards method for significant age-corrected predictors of 8-year cardiovascular and total mortality. For men, some significant predictors were systolic and diastolic blood pressure (BP), indices of target organ damage (heart and eyes) and smoking at presentation, and achieved BP and serum cholesterol at follow-up. For women, serum cholesterol, diabetes, target organ damage (heart and eyes) and smoking at presentation, and achieved BP level at follow-up were predictors. Relative risk for total or cardiovascular mortality was increased in both sexes most by smoking and by increased levels of achieved BP.

Blood Pressure↗
PubMed1990

Flow cytometric analysis of cell cycle of cultured aortic smooth muscle cells from two strains of genetically hypertensive rats.

The growth curves of aortic smooth muscle cells (SMCs) from spontaneously hypertensive rats (SHRs) and their normotensive controls, Wistar-Kyoto (WKY) rats, and genetically hypertensive (GH) rats and their normotensive outbred controls (N) were compared. The proportion of cells in the various phases of the cell cycle was measured by flow cytometry. SHR cells showed significantly shorter doubling time than WKY rat cells, but doubling times for GH and N rats did not differ and were nearly the same as for SHRs. SHRs showed significantly greater proportion of S-phase (DNA-synthesizing) cells compared to WKY rat cells in the exponential growth phase. No significant difference was observed between GH and N rats in the proportion of cells in other phases of the cell cycle. GH and N rat cells stopped dividing in fetal calf serum (FCS)-free Dulbecco's Modified Eagle Medium (DMEM), whereas SHR and WKY rat cells continued to progress through the cell cycle in serum-free DMEM. The responses of FCS-deprived-arrested cells to the addition of FCS were similar in GH and N rats. SHRs showed a prolonged increase in S-phase cells in response to FCS compared to WKY rat cells, but maximum effects were similar. Enhanced cell proliferation in SHRs is not present in the other hypertensive strain of rats and is not explained by a simple hyperresponse to FCS.

Animals↗
PubMed1990

Fallacies in the interpretation of the large-scale trials of treatment of mild to moderate hypertension.

Data from large-scale trials of treatment of mild to moderate hypertension are being misinterpreted and unjustifiably extrapolated to general populations. The main errors include acceptance of "entry" pressures as typical in spite of evidence that true blood pressure was much lower, extrapolation of results in low-risk volunteers to the whole population, neglect of treatment given to the most endangered control subjects, and the assumption that the burden of side effects seen in a rigid high-dose trial is typical of that seen when the same or better drugs are used in clinical practice. The health risks of hypertension and the benefits conferred by antihypertensive therapy are being played down unjustifiably on the basis of inappropriate data.

Clinical Trials as Topic↗
PubMed1985

Clinical studies with ketanserin in hypertension.

To assess efficacy and side effects during chronic oral therapy, we studied the effect of ketanserin (Kn) in 17 hypertensive patients for a period up to 1 year. Ketanserin controlled blood pressure satisfactorily in 25%, in part in 50% and had little or no effect in 25%. Reduction in diastolic pressure equalled that in systolic pressure at rest and after exercise and during handgrip. Pulse rate was slowed. Dosage in excess of 60 mg of Kn per day caused troublesome central nervous system symptoms or headache in some patients. A nonsteroidal antiinflammatory drug appeared to antagonize the antihypertensive effect of Kn in one patient. Red cell rigidity and platelet aggregation to ADP and collagen were significantly decreased. Serum potassium and uric acid were significantly decreased; serum creatinine increased during Kn treatment. The antihypertensive and pulse slowing effects of Kn were confirmed during the year's study, in a randomized placebo-controlled crossover study.

Aged↗
PubMed1979

Age, adiposity, blood pressure and blood lipids in a rural New Zealand population.

Multiple regression analysis of data on age, blood pressure, adiposity and blood lipids from a rural New Zealand population of over 1200 adults has been undertaken. The results show that rises in blood lipids over time in the population are independent of age and correlate significantly with adiposity. Thus plasma cholesterol and triglycerides correlate with adiposity (expressed as Quetelet's index or skinfold thickness) in men whereas significant correlation in women was only between adiposity and plasma triglycerides. Systolic and diastolic blood pressure in men was strongly correlated with their plasma triglycerides, but not cholesterol, when the effect of age and adiposity was removed. In women however only a weak correlation was observed between plasma triglycerides and systolic blood pressure. The significance of the findings is discussed.

Adult↗