The availability of artificial isotopes of physiologically important elements has made possible measurement of the amount of these constituents in the living human body by application of the principle of isotope dilution. A known amount of isotope is administered and allowed to exchange with its naturally occurring brothers while its excretion is measured. When equilibrium is attained, the quantity of element in which the isotope is "diluted" is inversely proportional to the concentration of artificial isotope in natural isotopes (specific activity) of any body sample. This quantity of element we refer to as the body content of "exchangeable" element, which in the case of complete exchange is the total amount of element in the body. Development tracer was carried out (2), and, independently, normal values of the exchangeable sodium in man were determined with Na24 in another laboratory (3).The primary purposes of this study were to develop a method for the measurement of the amount of exchangeable potassium in the living human and to determine such values in healthy adult men. It became evident early that complete exchange was not attained during the period of observation afforded by safe tracer doses of K42 and that choice of a representative sample for analysis was a major problem. It was also evident that the significance of "normal" measurements would be enhanced by examination of the correlations that might exist with other body indices and that might permit extension of our data to studies of other healthy persons and pathologic states.The body content of potassium is an anthropometric value comparable to body weight, surface area or height and correlations with such measurements were investigated for possible clinical applications. Potassium on a weight basis is an extremely small fraction of the body, approximately 0.2 %, which assumes importance because it is the predominant cation of intracellular fluid. We should expect, then, to derive the greatest significance from studies of potassium in relation to intracellular water but present methods for measuring this phase of body water are indirect and difficult. Despite reservations cell water was estimated in this study as the difference between total body water and thiocyanate space. The almost exclusively intracellular position of potassium renders it probable that the body content of potassium is a good index of cellular mass. This possibility was explored by studying the correlations with total body water, basal oxygen con-1280
THE LARGE NUMBER of children who are accidentally injured or killed each year makes it urgent to develop effective means to re¬ duce the frequency and severity of childhood injuries. As a step toward reducing accidents, the California State Department of Public Health in 1955 undertook a series of investiga¬ tions {1-4) culminating in a large-scale study of childhood accidents. This paper, on the first phase of this study, describes in detail the distribution of injury rates for the study popu¬ lation as a whole and for subgroups determined by age, sex, race, and sibling order. It includes Mr. Manheimer is director of the Family Research
It is well known that specific agents active in the early months of pregnancy may cause certain congenital malformations. German measles was reoognized in the 1940's as one cause; more recently thalidomide taken by mothers early in pregnancy was found to be responsible for deformities in thousands of babies. These and similar discoveries have spurred the search for other agents operating early in pregnancy.On pursuing such research, however, one may find no routine medical records of factors of possible relevance. Hence, existing sources of data concerning events early in pregnancy need to be supplemented (1). The time of collection of the data from the mother is crucial. Gathering information at the end of pregnancy may introduce serious biases. For example, the mother of a malformed child, seeking a reason for the child's defect, is more likely to recall and report unusual events during pregnancy than is the mother of a nornal child (2).Obtaining the desired information at the time of the woman's first prenatal visit to the physician should reduce these biases, but difficulties in recall would still remain. Even among women obtaining prenatal care in the first trimester, only a small proportion start such care
This study is another indication of the need for careful reporting, backed up by epidemiological investigation, as a basis for analyses of accidents that will lead to logical design of control measures. It also suggests the value of further work that will more accurately relate accident experience to exposure and risk.
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