The Calibration of a High-Sensitivity Large Area Whole-Body Counter

Barnaby, C F; Jasani, B M

doi:10.1088/0031-9155/13/4/306

Cited by 12 publications

(12 citation statements)

References 5 publications

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“…Whole-body potassium was measured with a sensitive liquid scintillation whole body counter, the details of which are given by Barnaby & Jasani (1968). Lean body mass was calculated on the assumption that 1 kg of lean body mass contained 68-1 mmol of potassium (Forbes, Gallup & Hush, 1961).…”

Section: Clinical Science and Molecular Medicinementioning

confidence: 99%

Studies of Amino Acid and Protein Metabolism in Normal Man with l-[U-14C]Tyrosine

et al. 1976

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1. Six men were infused intravenously for 10 h with a tracer amount of L-[U-14C]tyrosine while on a standardized food intake. 2. Measurements of plasma L-[14C]-tyrosine specific radioactivity and the excretion rate of 14CO2 were made at frequent intervals and showed plateau labelling of plasma and expired carbon dioxide within 6-8 h. The tyrosine flux was calculated from the specific radioactivity in plasma at plateau value. 3. The excretion rate of 14CO2, corrected for retention of label within the bicarbonate pool, showed that oxidation accounted for 20% of the tyrosine flux. Urinary excretion of label was negligible. 4. Rates of protein synthesis were calculated from the flux of tyrosine after subtracting the proportion oxidized. Although the mean rate of synthesis was consistent with other measurements of protein turnover, the individual values ranged from 284 to 387 g/day. The variation was not reduced by relating turnover to body weight, lean body mass or energy expenditure. 5. Estimating the rates of protein breakdown from the tyrosine flux involved some assumptions about pathways of phenylalanine metabolism. The use of a labelled essential amino acid would therefore give more accurate values for short-term measurements of whole body protein turnover.

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Section: Clinical Science and Molecular Medicinementioning

confidence: 99%

Studies of Amino Acid and Protein Metabolism in Normal Man with l-[U-14C]Tyrosine

et al. 1976

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“…Total body potassium was measured by determing the 4OK content of each patient using a liquid scintillation whole-body counter as described. 14 15 The errors of the method result in a coefficient of variation of 4 20o for measurement of a person with a total body potassium of 3500 mmol (3500 mEq). For each patient an expected value for total body potassium was obtained based on age, sex, height, and weight using relations determined in a study of a normal population.…”

Section: Methodsmentioning

confidence: 99%

Spironolactone in essential hypertension: evidence against its effect through mineralocorticoid antagonism.

Hoffbrand¹,

Edmonds²,

Smith³

1976

BMJ

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term basis to medical inpatients. Since there is no pharmacological evidence to support the current practice of using two different benzodiazepines together, and a potential reduction in cost to the Health Service of changing the practice, we undertook a randomised double-blind patient-preference study to test the hypothesis that one of the three commonly used benzodiazepines (flurazepam, nitrazepam, and diazepam) was better than the others as a short-term hypnotic in medical inpatients.This study design was chosen because of simplicity, economy in staff time, minimum patient interference, use of each patient as his own control, and the benefits of a sequential analysis design. Such trial methods have been shown to be reproducible and reliable in assessing symptomatic drug treatment qualitatively provided only that the basic symptoms under treatment do not vary on a daily basis.' Variability of symptoms in patientpreference studies are of considerable significance and may invalidate the use of this technique. Nevertheless, this did not constitute a significant problem in our study, and Zelvelder,8 in an extensive review of the techniques of evaluating hypnotics, recommended this approach as the most efficient one available for evaluating short-term hypnotic efficacy. Our studies confirmed that the benzodiazepines are effective hypnotics9 and failed to show a clinically significant difference in efficacy between them when used in this setting. Despite the relatively small numbers of patients, the incidence of undesired effects (usually excessive sedation) seemed to be higher with nitrazepam than with diazepam or flurazepam. Our data also show that older patients admitted to medical wards have a significant preference for a benzodiazepine as a hypnotic rather than an antihistamine.

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“…The potassium-40 content of each individual was measured with a highly sensitive liquid-scintillation whole-body counter (Barnaby & Jasani, 1968;Jasani & Edmonds, 1971). Individuals removed outer clothing, shoes and watches before entering the counter and an 800 s count was made.…”

Section: Measurement Of Total Body Potassiummentioning

confidence: 99%

“…A potassium standard source (3 kg of potassium chloride in a polythene container) was counted for radioactivity before and after each measurement and a number of 800 s background measurements were also recorded with the counter containing a waterfilled phantom. Complete details of the methods used for calibration and assessment of the errors involved have been previously described (Barnaby & Jasani, 1968). Together these errors meant that the coefficient of variation for measurement of an individual .…”

Section: Measurement Of Total Body Potassiummentioning

confidence: 99%

“…having a total body potassium of 3500 mmol was 4'2%. The counter was calibrated with phantoms containing a solution of potassium chloride in distilled water, and by giving a small dose of potassium-42 (about 1 j.lCi) to some normal, obese and wasted individuals (Barnaby & Jasani, 1968). The expressions K B W and K FFM used subsequently refer to the total body potassium divided by the body weight or by the fat-free mass respectively.…”

Section: Measurement Of Total Body Potassiummentioning

confidence: 99%

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Total Body Potassium and Body Fat Estimation in Relationship to Height, Sex, Age, Malnutrition and Obesity

1975

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1. Total body potassium was estimated by 40-K measurement with a high-sensitivity whole body counter in normal individuals over a wide age range and in patients who were obese or were grossly wasted as a result of various conditions which restricted food intake. 2. Potassal males and females, but when individuals of different age groups were matched for height, a significant fall in total body potassium with increasing age was observed only in males. Total body potassium of females was about 75% that of males of similar height when young, the sex difference decreasing with ageing. In the normal population, total body potassium was significantly correlated with height and with weight; regression equations for various relationships are given. 3. Fat-free mass was estimated from total body potassium, values of 65 and 56 mmol of potassium/kg fat-free mass being used for males and females respectively. Body fat estimated by this method correlated well with skinfold measurements over a wide range of body weight but in malnourished individuals having inadequate food intake there was considerable fat-free mass from total body potassium appear unsatisfactory in malnutrition. Considerable differences between expected and observed values of total body potassium were found in muscular individuals and in normal individuals who were thin but whose body weight was relatively constant. 4. The patients with malnutrition were low both in body fat as estimated by skinfold thcikness and in total body potassium estimated on the basis of height. Plasma potassium was, however, normal and potassium supplements did not increase the total body potassium. 5. Total body potassium of obese individuals was not significantly different from that of normal weight individuals on the basis of height. Total body potassium fell on weight reduction with a very low energy diet of 1260 kJ (300 kcal.) daily but changed little with a 3300 kJ (800 KCAY POTASSIUM WAS BEST PREDICTED FROM THE INDIVIDUAL'S HEIGHT. For those whose body weight was less than expected, the use of weight gave the best prediction but the error was considerable when the weight deviation was large.

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The Calibration of a High-Sensitivity Large Area Whole-Body Counter

Cited by 12 publications

References 5 publications

Studies of Amino Acid and Protein Metabolism in Normal Man with l-[U-14C]Tyrosine

Studies of Amino Acid and Protein Metabolism in Normal Man with l-[U-14C]Tyrosine

Spironolactone in essential hypertension: evidence against its effect through mineralocorticoid antagonism.

Total Body Potassium and Body Fat Estimation in Relationship to Height, Sex, Age, Malnutrition and Obesity

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