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Biomedical subjects

F O Simpson

Publications and source records attributed to F O Simpson.

At least 55 records · Page 3Linked to original sources

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↗

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↗

Effects of DOCA and salt intake on body sodium, fluid intake, blood pressure and excretion of a sodium load in rats.

Body sodium was measured repeatedly by a whole-body counting method (22Na) in control and deoxycorticosterone acetate (DOCA)-treated Wistar rats taking a sodium-free pelleted diet and drinking a choice of H2O and either 0.5% NaCl or 0.1% NaCl (n = 11 per group, four groups). Body sodium was higher in DOCA-treated than in control rats and higher in rats on 0.5% NaCl than in those on 0.1% NaCl. These differences persisted even when all sodium intake was stopped. An intraperitoneal NaCl load was excreted at least as rapidly by the DOCA-treated as by the control rats. Commencement of excretion was slower in the rats on 0.1% NaCl than in those on 0.5% NaCl. It is concluded that DOCA raises the basal level of body sodium but does not slow down the excretion of sodium in the body in excess of the basal level.

Animals↗

Iodide excretion in a salt-restriction trial.

Twenty-four hour urinary iodide excretion was measured twice, with a four month interval, in 133 individuals who were in a 12-month salt-restriction study in an area where iodine-deficiency goitre was once common and where most household salt is iodised. Half the subjects were salt restricted; their mean 24 h sodium excretion after eight months was 89 mmol for men and 73 mmol for women. Iodide excretion correlated with sodium excretion in the whole group on each occasion. After eight months mean 24 h iodide excretion in the salt-restricted group (men 1.3 SD 0.6 mumol, women 1.1 SD 0.4 mumol) was lower (p less than 0.01) than that in the control group (men 1.8 SD 0.8 mumol, women 1.7 SD 0.8 mumol), but was reasonable in terms of recommended dietary allowances (1.2 mumol, 150 mg). Mean iodide content of local milk was 1.3 mumol/l. Any salt that is used in the home should continue to be iodised. However, it has become unnecessary in this population to use salt (ie, iodised salt) simply in order to avoid iodine deficiency, so long as other foodstuffs continue to contain iodine as at present. As the other sources of iodine may be subject to change, the adequacy of intake of iodine from these sources should be monitored from time to time in samples of the population.

Adolescent↗

Handling of a salt load by hypertensive and normotensive rats on normal and low intakes of sodium.

The handling of an intraperitoneal salt (NaCl) load (about 10% of body Na) was studied by means of a whole-body counting method using 22Na in four strains of rat: spontaneously hypertensive rats (SHR), normotensive Wistar-Kyoto rats (WKY), New Zealand genetically hypertensive rats (GH), and outbred normotensive rats (N). The rats had previously been equilibrated so that their body Na was of the same specific activity as the injected NaCl. The load was given first at 10 weeks of age, while the rats had a choice of water and 0.5% NaCl to drink, and again at 13 weeks when the rats had a choice of water and 0.04% NaCl. All the strains excreted the load more slowly when on the low Na intake. The SHR excreted the load most quickly and the WKY most slowly. There was no difference between the GH and N rats in this respect. The SHR differed from the other strains in having an increased appetite for salt and an increased total body sodium relative to body weight.

Animals↗

Body sodium level in hypertensive and normotensive rats: effects of dietary sodium levels and sodium loads.

Rats of the genetically hypertensive (GH) strain do not have an increased body sodium content or increased natriuresis of hypertension. Spontaneously hypertensive rats (SHR), on the other hand, have an increased body sodium content and an increased rate of excretion of a sodium load. They also have an increased appetite for salt. In a study on three groups of normotensive rats with high normal, low normal, and very low sodium intakes, respectively, body sodium content was highest with the highest intake and lowest with the lowest intake. At the age of 22 weeks, after being on these intakes for 6 weeks, all three groups were put on a low sodium intake. Body sodium content of the two groups with the previous higher intakes failed to fall to the level of the group with the previous lowest intake. Thus there may be a prolonged carryover effect of salt intake in rats. The results are discussed in terms of the set point theory for sodium homeostasis.

Animals↗

Salt and hypertension: current data, attitudes, and policies.

Evidence linking salt and hypertension is on the whole growing stronger, but the situation is still not clear-cut. The relationship between sodium intake and prevalence of hypertension is complicated; it is suggested that in the middle range of sodium intake another factor, possibly linked to the renal handling of sodium, contributes to the prevalence of hypertension. Attitudes among investigators and the medical profession are probably moving toward favouring salt restriction, at least for people with hypertension. The general public is also probably becoming more favourably disposed toward reducing salt consumption. Policies regarding salt in various countries appear to be hesitant, probably reflecting scientific uncertainty. Sodium content should be included on food package labels. SI units should now be universally used for the sodium content of foods on diet sheets and on package labels.

Attitude of Health Personnel↗

Evidence against a circulating ouabain-like transport inhibitor as a cause of increased red cell sodium in essential hypertension.

Red cell sodium and potassium concentrations, and total ouabain-sensitive and ouabain-insensitive first order red constants for sodium efflux, were measured in 15 patients (11 female, 4 male) with essential hypertension (162 +/- 14/99 +/- 7 (s.d. mmHg) and 15 normotensive control subjects (117 +/- 17/64 +/- 10 mmHg) individually matched for age (45.8 +/- 10 versus 45.7 +/- 10 years, respectively, sex, weight (68.6 +/- 16.1 versus 64.7 +/- 11.2 kg) and blood group. To test for possible plasma inhibitors of sodium transport in hypertension, total efflux rate constants were measured in red cells incubated in two plasma samples, from either the same or the complementary (paired) subjects, respectively. Intracellular sodium was significantly increased in patients (11.8 +/- 3.45 versus 8.75 +/- 2.48 mmols/l of red cell water; P = 0.023). Intracellular potassium and total and ouabain-sensitive sodium efflux rate constants, were similar in both groups. Sodium efflux was similar when cells were incubated in the homologous and complementary plasma samples. Ouabain-insensitive rate constants were decreased in the patients (0.16 +/- 0.08 versus 0.20 +/- 0.05 h-1) but the difference was of borderline significance (P = 0.059). These results confirm the presence of abnormal intracellular sodium concentrations and membrane transport in essential hypertension but are not consistent with the suggestion that the abnormalities are due to a circulating sodium transport inhibitor.

Adult↗

Selenium and risk factors for cardiovascular disease in New Zealand.

Blood selenium (Se) concentrations and glutathione peroxidase (GSHPX) activities were measured in 118 men (39 +/- SD 15 yr) and 112 women (42 +/- 16 yr) randomly selected from the total respondents (1192) to health survey in Milton, a low soil-selenium area in Otago. GSHPx activities were marginally lower for men (11.9 +/- 3.2 units/g Hb) than for women (12.9 +/- 3.8 units/g Hb). Blood, erythrocyte and plasma selenium concentrations were about the same for both sexes and means for all subjects (61 +/- 15; 73 +/- 19; 49 +/- 12 ng Se/ml) were almost identical with a control group of Otago blood donors. No differences in blood levels could be associated with smoking, use of oral contraceptives, arthritis and/or rheumatism, or anti-hypertensive drugs. No relationship was found for the men or women between any of the parameters of selenium status and any of the parameters of risk factors for cardiovascular disease measured in the health survey: age, Quetelet's index, total skinfolds, systolic and diastolic pressure, pulse rate, plasma lipids and lipoprotein lipid concentrations. Moreover no relationship was found for the subgroups (36% group) of men and of women with plasma selenium below 45 ng Se/ml. This study indicates that if selenium is important it does not operate through the risk factors of cardiovascular disease as presently understood.

Adolescent↗

24-h exchangeable sodium in genetically hypertensive and normotensive rats.

Total exchangeable sodium (Nae) was measured in NZ genetically hypertensive (GH) rats, random bred normotensives (N), Japanese spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats WKY. SHR rats were found to have significantly higher Nae than any of the other 3 strains. This confirms results previously obtained using a different method for Nae measurements.

Animals↗

Evaluation of xenon-133 renal blood flow measurement in the intact rat.

The xenon-133 method for measuring renal blood flow in the intact rat was evaluated by direct measurement using a nonhemolyzing pump to perfuse kidneys in situ with the rat's own blood. Flows were calculated from the xenon data by means of four commonly used types of analysis: compartmental analysis using the weighted arithmetic mean (WAM), compartmental analysis using the weighted harmonic mean (WHM), stochastic analysis (SA), and initial slope analysis (ISA). WHM and SA estimate actual blood flows, whereas WAM and ISA provide only an index of mean renal flow. All results correlated well with the pumped flows (r values ranged from 0.79 to 0.98). However, the various types of analysis gave a wide range of calculated flows. This may explain some of the variation found in mean renal flow values reported in the literature. The method of choice was WHM, using only the first two compartments; the regression line between this (y) and direct measurement (x) was y = 0.98x + 0.17, r = 0.96.

Animals↗

A pilot study to test the feasibility of salt restriction in a community.

Index subjects were selected from the population of Milton studied in the May 1981 survey. Index subjects aged 64 or less with a systolic blood pressure 138-179 mmHg (18.35/23.8 kPa), including those on antihypertensive treatment, were invited to participate with their families. Index subjects were divided into two matched groups. One group was randomly assigned to be the control group and the other to be the salt-restriction group. Age, weight, height and 24-hour urinary excretion of sodium, potassium and creatinine at the start of the study in August 1981 were similar for the control and salt-restriction groups. When tested in November 1981, the salt-restriction group had achieved a reduction in 24-hour sodium excretion to a mean of 84 mmol for men and 70 mmol for women; corresponding values for the control groups were 150 and 120 mmol. A further test in March 1982 showed little further change. Potassium output changed very little. Attitudes to the low-salt diet varied, but 87 percent found it tolerable or actually preferable. There is no doubt that major reductions in sodium intake are feasible. However, if these are to be achieved on a large scale, food, manufacturers will need to offer a variety of low-sodium foods.

Adolescent↗

Licorice consumption among high school students.

A survey was carried out of licorice intake among 603 4th and 5th form pupils of two Dunedin high schools. Licorice was eaten on a regular (weekly) basis by 29 percent of the girls and 17 percent of the boys. At least 200 g (of black licorice confectionery) was eaten weekly by 5.9 percent of the girls and 4.9 percent of the boys; at least 500 g was eaten weekly by 1.8 percent of the girls and I percent of the boys. The intake reported by two pupils exceeded 1000 g per week.

Adolescent↗