The purpose of this paper is to present data which have accumulated in our laboratory over several years tending to show that the relative abundance of the naturally radioactive isotope of potassium K 4° in the human body is probably about 2 per cent less than in commercial or "shelf" potassium as supplied in the market. The work was begun on account of the statement of Ernst (1934) based on an...

The practice of immunoassay has experienced a widespread transition from radioisotopic labeling to nonisotopic labeling over the last two decades. Radioisotope labels have drawbacks that hamper their applications: (i) perceived radiation hazards of reagents, (ii) regulatory requirements and disposal problems of working with radioactive materials, and (iii) short shelf-life of the labeled reagen...

Prior to 1935, studies on the absorption of phosphorus were carried out either by the use of intestinal fistulas, or by the addition of an inactive unabsorbed marker to the food, such as iron oxide in the method of Bergeim (1). Recently the excretion of calcium and phosphorus into the large intestine of the rabbit has been studied by Cowell (2) by means of the differential analysis of fecal pel...

stable isotopes of carbon, hydrogen, and nitrogen offer a number of advantages in clinical work: problems of preparation, storage, and disposal are negligible, health monitoring requirements are eliminated, and most significantly, the absence of radiochemical hazard to the patient permits their use in obstetric and pediatric measurements. It is our belief that the potential of stable isotope an...

Prior to 1935, studies on the absorption of phosphorus were carried out either by the use of intestinal fistulas, or by the addition of an inactive unabsorbed marker to the food, such as iron oxide in the method of Bergeim (1). Recently the excretion of calcium and phosphorus into the large intestine of the rabbit has been studied by Cowell (2) by means of the differential analysis of fecal pel...

The double isotope technique of Arias, Doyle, and Schimke ((1969) J. Biol. Chem. 244, 3303) with radioactive leucine as precursor has been modified to yield accurate values for rate constants of protein degradation. The advantages of the method are that it is both rapid and reproducible in that the protein whose half-life is being measured is isolated only once from one experimental organism an...

ANY observers have reported an increase in variability following exposure of pollen or seeds to the effect of ionizing radiation. In several respects the tomato is favorable material for such studies. I t is self-pollinating, and recessive mutants can therefore be uncovered promptly. It is a perennial and can be propagated by cuttings, so that plants of a previous generation can be retained, an...

Tritium is the heaviest and the only radioactive isotope of hydrogen. It decays to the stable isotope 3He by emitting low energy electrons. The short range and low energy of β‐ rays gives rise to almost complete absorption of the radiation energy within the biological matter. While some beta particles can penetrate human skin, tritium's beta particles do not have enough energy to do so. Tritium...

Sentinel lymph node biopsy (SLNB) is a simple technique that uses subdermal or peri-tumoral injection of vital blue dye and/or radioactive isotope to identify the first lymph node(s) draining the primary tumor. It has been shown to accurately predict axillary node status in patients with clinically node negative breast cancer. The SLNB is emerging as a new standard of care in patients with earl...

Although isotopic labeling has been of great use in studies of drug metabolism, the necessarily small amounts of material used in such experiments often preclude the identification of unknown metabolites by conventional chemical means. Such difficulties are commonly circumvented by adding a known non-labeled compound, suspected to be a metabolite, to the unknown mixture and reisolating the subs...