Four experiments were performed in which two subjects on two occasions drank approximately 1 pc radon plus daughters in 100 ml of water. Measurements on radon loss in expired air, whole body Radium C content, and radon in the blood permit the calculation of an (MPC), of 2.0 x lo-* pc/ml for occupational exposure. This is based on the stomach as the critical organ, but doses to the lung, kidney, and liver are estimated.
The influence of phenytoin on theophylline elimination was studied in six healthy, nonsmoking subjects who were not taking any other drugs. Subjects were given an intravenous infusion of theophylline (aminophylline), 5 mg/kg, and several blood specimens were drawn over the following 24 hr for theophylline concentration determination. Subjects then began a 2-wk course on oral phenytoin, 300 mg/day, and on day 15 were again challenged with theophylline. For each subject theophylline clearance (ClT) was greater when taking phenytoin (range 31% to 65%). Mean ClT of the six subjects was 45% greater when taking phenytoin than when not taking phenytoin. In one subject, 24-hr urine collections were obtained in the untreated and treated state for analysis of theophylline metabolites. These results showed a general increase in excretion for each of the three major theophylline metabolites in the phenytoin pretreated state compared to the control state. Results indicate that phenytoin increases theophylline elimination. Patients taking phenytoin may require larger theophylline doses than recommended to achieve therapeutic blood theophylline concentrations.
The theory of a5Kr solubility in the body is discussed and a weight partition coefficient, equal to the Ostwald coefficient divided by absorber density, is defined to facilitate study of solubility in intact tissue and dose calculations.In vivo weight partition coefficients were determined in guinea pigs for blood and 22 other organs and tissues using a dual-isotope technique that permits simultaneous determinations for whole and bloodless tissue. The highest coefficients found for bloodless tissue were: omental fat (0.42 1) ; subcutaneous fat (0.405) ; thymus (0.259) ; lymph nodes (0.138) ; bone marrow (0.134); and adrenals (0.102). In general, the in vivo coefficients agreed well with predictions based on in vitro solubility determinations and the fat-protein-water composition of the tissue as reported in the literature.Ostwald coefficients were determined in vitvo for 85Kr into guinea pig blood, guinea pig brain homogenate, dog blood, cat blood, Chinese hamster blood, 0.9% NaCl solution and 10% EDTA solution.
Guinea pigs were exposed via the respiratory tract for 12 hr to E5Kr concentrations ranging from 54 to 520 ,uCi/cms and observed for 60 days or until death, whichever occurred first. The 30-day median lethal exposure was 4450 (pCi/cm3) hr which corresponds to estimated doses of 316 rads to the bone marrow, 340 rads to the whole body, and 7876 rads to the lungs. The marrow and whole-body doses, times of death and the gross clinical and necropsy observations were consistent with death by the "hematopoietic syndrome" but lung injury was dominant in animals that survived for more than 30 days. The whole-body and marrow doses delivered at the median lethal exposure and the observed times of death are similar to those reported in X-or gamma-radiation lethality studies.
When rats were exposed to 2 mg l-1 (approximately 640 ppm) of carbon disulfide (CS2) for 4 h, the concentration of free CS2 in the red blood cells (RBCs) approached a plateau within 2 h. Free CS2 in plasma reached a steady state concentration within 15 min of exposure. More than 90% of the free CS2 in blood was found in the RBCs regardless of the length of exposure. In vitro studies showed that about 90% of the free CS2 partitioned into the RBCs regardless of whether the CS2 was added first to the plasma or directly to the RBCs. Hence, it appears that the RBC is the major carrier of CS2 in blood. It was found that 98% of the free CS2 in red blood cell lysates was associated with hemoglobin. Free CS2 in RBCs was readily partitioned into olive oil (RBCs/oil = 1/6), less readily into the plasma (RBCs/plasma = 12/1), and only to a small extent into phosphate buffer (RBCs/buffer = 39/1). The extraction of free CS2-loaded RBCs into albumin solution increased with increasing albumin concentrations. CS2 can be extracted with buffer, protein solution, and oil, indicating that CS2 in RBCs can be transferred to the medium in which the RBCs contact. It is proposed that RBCs may also play an important role in the transport of CS2 from lung to tissues and vice versa. The possible role of RBCs in the transport of other organic solvents in the blood is also discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.