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Biomedical subjects

F O Simpson

Publications and source records attributed to F O Simpson.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1989

Effect of enalapril on handling of a sodium chloride load by genetically hypertensive and normotensive rats.

1. Enalapril was given in the drinking water (300 mg/L) for 4.5 days to normotensive (N) and genetically hypertensive (GH) rats on zero sodium intake. An intraperitoneal NaCl load was given 12 h after enalapril was started. 2. Enalapril did not increase the maximum rate of sodium excretion, but caused the rats to excrete more than the load in the first 24 h and then to have a slow fall in body sodium while on a sodium-free diet. 3. In terms of the Strauss et al. (1958) concept of body sodium, enalapril appears to lower the basal level. However, in addition it causes a slow leak of sodium which becomes apparent when sodium intake is very low.

Animals↗
PubMed1988

What do middle-aged New Zealanders eat? A dietary survey in 50-54 year olds in south Canterbury and north Otago.

Information on diet was obtained from a random sample of 50-54 year olds in October 1985 when a health survey was conducted in the Timaru health district. This survey formed part of the international cardiovascular diseases and alimentary comparison (CARDIAC) study. A seven-day dietary history was obtained from 99 male and 82 female participants who were not taking any antidiabetic or antihypertensive medication. The median daily energy intake was 10.5 MJ for the men and 6.3 MJ for the women. The median daily total fat intake for men and women respectively was 103 g and 68 g. The median ratio of polyunsaturated to saturated fatty acids was low, 0.19 for the men and 0.18 for the women. Total fat contributed 37.5% to energy intake of men and 38.5% to energy intake of women and alcohol contributed 5.1% for men and 2.1% for women. Mineral and vitamin intakes were generally satisfactory. A substantial proportion of the participants, particularly women, claimed to have decreased their total food, fat, salt, meat, eggs and milk intakes and to have increased their vegetable and fish consumption.

Alcohol Drinking↗
PubMed1988

Eight-year survival study of treated hypertension at the Dunedin Hypertension Clinic 1953-1977.

The 8-year follow-up data of consecutive 5-year cohorts of hypertensive patients starting treatment at the Dunedin Hypertension Clinic between 1953 and 1977 have been analysed. There were 975 men and 1348 women. Since 1953 treatment has been initiated in progressively milder forms of hypertension, and blood pressure has been controlled at progressively lower levels. The mean age at presentation for both men and women was 51 years. The mean age at death and the cause of death did not differ significantly among the cohorts, but the percentage incidence of events (including death) over the 8-year follow-up decreased significantly (P less than 0.0001) from 76% for males and 57% for females in the 1953-1957 cohort, to 33% for males and 25% for females in the 1973-1977 cohort. Survival was poorest in the earlier cohorts, especially the 1953-1957 cohort. The 8-year relative survival of treated hypertensives compared with the general population of New Zealand improved over time and was about 0.9 for the 1973-1977 cohort, a little less for males and a little more for females.

Female↗
PubMed1988

Effect of verapamil and sodium nitroprusside on hindlimb vascular resistance in New Zealand genetically hypertensive and Japanese spontaneously hypertensive rats.

Verapamil, a calcium-entry blocker, and sodium nitroprusside, a non-specific vasodilator, were infused into the blood-perfused hindlimbs of New Zealand genetically hypertensive rats (NZGH) and spontaneously hypertensive rats (SHR), two genetic models of hypertension, and their normotensive controls, New Zealand normotensive rats and Wistar-Kyoto rats (WKY). Vasodilator responses, measured as the falls in perfusion pressure from the initial values, were similar and increased in NZGH and SHR. The responses were strongly dependent on the initial level of perfusion pressure in each strain of rat. It is concluded that increased vascular resistance, rather than a qualitative difference in vasodilator mechanisms, accounts for the enhanced responses to verapamil and sodium nitroprusside in NZGH and SHR hindlimbs.

Animals↗
PubMed1987

Handling of a sodium load by rats on a low sodium intake and frusemide.

1. Groups of rats (n = 9-10 per group) were given a medium sodium (Na) diet or a low Na diet or a low Na diet plus low or high dose frusemide in order to have their body Na in a state of surplus or deficit or neither. 2. Body Na was measured by a 22Na whole body counting method involving Na-free chow and the drinking fluid as the only source of Na (22Na-labelled NaCl). Intraperitoneal NaCl (same specific activity) loads were given and their excretion was measured by repeated measurements of body Na over the next 48 h. 3. Rats in surplus excreted more than the load; those in neither surplus nor deficit excreted more or less exactly the load (allowing for growth); those with a small deficit retained enough Na to make up most of the deficit; those with a deficit that was larger than the load retained approximately the whole load. 4. The results support the Strauss-Hollenberg concept that there is a basal body Na above which Na is excreted and below which any available Na is retained.

Animals↗
PubMed1986

Body sodium in rats: response to DOCA, adrenalectomy, changes in salt intake, and a salt load.

Body Na was studied by an isotope method in rats on Na-free diet plus a choice of H2O and 0.5% or 0.1% NaCl. Two groups (1 on 0.5%, 1 on 0.1% NaCl) had Silastic deoxycorticosterone acetate (DOCA) implants, two similar groups were sham operated, and a fifth group (on 0.5% NaCl) underwent adrenalectomy (ADX). Saline consumption increased in DOCA-treated and ADX rats. Body Na was increased by DOCA and by drinking 0.5% NaCl compared with 0.1% NaCl. Body Na after intraperitoneal NaCl loading (which raised body Na 8-10%) and withdrawal of NaCl drinking fluids was analyzed by use of the model y = Ae-a(t-d) + Be-bt, where y is body Na at time t and d is delay before fast rate constant a is established; d was greater on the lower Na intake. Rate constant a was not reduced by chronic DOCA treatment. Coefficient B of the slow exponential, representing the basal level to which body Na falls on zero Na intake, and equivalent to Hollenberg's "set-point," was higher in DOCA-treated rats. This analysis makes use of Hollenberg's set-point concept, but the findings suggest that the set-point is related to mineralocorticoid activity and is thus presumably variable.

Adrenalectomy↗
PubMed1986

Comparison of various genetic hypertensive rat strains.

Comparative studies on nine genetic hypertensive rat strains [two stroke-prone spontaneously hypertensive rats (SHRSP) and Dahl salt-sensitive (DS) strains, and one strain each of spontaneously hypertensive rats (SHR), Lyon hypertensive rats (LH), Milan hypertensive strain (MHS), genetically hypertensive rats (GH) and Sabra hypertensive rats (SBH)] and their respective controls [two Dahl salt-resistent (DR) strains and one strain each of Wistar-Kyoto rats (WKY), Lyon normotensive rats (LN); Lyon low blood pressure rats (LL), Milan normotensive strain (MNS), genetically normotensive rats (GN) and Sabra normotensive rats (SBN) and their original strain, Sabra rats (SB)], in groups consisting of 6-10 males from each strain, were carried out at 10-12 weeks of age under the same experimental conditions. After checking the developmental course of blood pressure and changes in body weight, they were killed at 12 weeks of age for blood analysis and organ-weight examinations. The SHRSP and SHR showed markedly higher blood pressure levels and earlier blood pressure rises in comparison with other hypertensive strains, although they had higher blood pressure than their respective controls. Among various organ weights examined, all hypertensive strains commonly showed increases in left ventricular weight in proportion to blood pressure rises. Kidney weights were significantly decreased only in MHS compared with MNS, while they were either unchanged or significantly greater in other hypertensive strains. Weights of adrenal glands were greater in the two strains of DS and in LH than in their respective control strains. These comparative data indicate possible differences in the pathogenic mechanism involved in these genetic hypertensive rat strains.

Animals↗
PubMed1986

Electrolytes and spontaneous genetic hypertension in rats.

Electrolytes are involved to a greater or lesser extent in the hypertension of probably all the inbred strains but it is difficult to sort out whether the involvement is primary or secondary and the detected abnormalities differ in the various strains. The fundamental faults are still elusive, except perhaps in the Dahl salt-sensitive rats, which appear to have a form of mineralocorticoid hypertension. Sodium and calcium appear to be the electrolytes most closely implicated in the pathogenesis of hypertension but potassium, magnesium and chloride should not be neglected. More data are needed. Knowledge gained from rat studies is useful in the context of both basic physiology and human hypertension.

Animals↗
PubMed1985

Alcohol consumption and blood pressure in a New Zealand community study.

The relationship between stated alcohol consumption and blood pressure was investigated in 901 adults who participated in a multiphasic health survey in Milton in May 1981. Subjects taking oral contraceptives or drugs which could lower blood pressure were excluded. Eighty-five percent of men and 52% of women reported taking some alcohol at least once a month. The percentage using alcohol was highest (96%) in men aged 20-29 years. The reported mean weekly intake by users was 171 g for men and 56 g for women. After adjustment for age and body mass index, there was a positive association between alcohol intake and blood pressure for men. The mean systolic and diastolic pressures of male heavy alcohol users (300 g or more alcohol per week) were, respectively, 9.8 and 8.9 mmHg higher than those of male non-drinkers. No relationship between alcohol intake and blood pressure was found in the women.

Adult↗
PubMed1985

Monovalent and divalent cations in hypertension.

The relationship of four cations (sodium, potassium, calcium, magnesium) to hypertension is reviewed. It seems reasonable to advise some reduction in sodium intake, and an initial goal of a mean intake of 120 mmole per day for men and 90-100 mmole per day for women is suggested. Some increase in potassium intake may well be justifiable but is better achieved through potassium-containing foods than by any artificial supplements. The data for calcium and magnesium are not sufficiently strong to warrant any recommendation for a change in intake at present.

Calcium↗