Effects of dose and dose protraction on embryotoxicity of 14.1 MeV neutron irradiation in rats.

The embryotoxic effects of neutron radiation on rodent embryos are documented, but there is disagreement about the dose-response relationship and the impact of protracting the dose. Pregnant rats were exposed to total absorbed doses of 0.15 to 1.50 Gy 14.1 MeV neutrons on day 9.5 after conception, coincident with the most sensitive stage of embryonic development for the induction of major congenital malformations. In general terms, the incidence of embryotoxic effects increased with increasing total absorbed dose. However, the dose-response relationship differed depending on the parameter of embryotoxicity chosen, namely, intrauterine death, malformations or very low body weight. In a second study, embryos were exposed to a single embryotoxic absorbed dose (0.75 Gy) administered at a range of dose rates, from 0.10 to 0.50 Gy/h. The results offer no evidence that protraction of this selected dose significantly increased or decreased the incidence or pattern of embryotoxicity of the neutron exposure used in this study. The results do not support the hypothesis of a linear dose-response relationship for the effects of prenatal neutron irradiation that contribute to embryotoxicity for total absorbed doses of 0.15 to 1.50 Gy.

Comparative effects of neutron irradiation and X irradiation on the embryonic development of the rat.

Our aim was to compare the dose-response relationship for the embryotoxic effects of 0.43 MeV neutrons with those of 240 kVp X rays after in utero exposures during early organogenesis in the rat. At 9.5 days after conception, pregnant rats were exposed to 0.025 to 0.35 Gy 0.43 MeV neutrons at a dose rate of 0.04 to 0.07 Gy/h. Comparable biological effects were produced using 0.50 to 2.05 Gy 240 kVp X rays. Neutron irradiation produced a greater proportion of offspring with very low body weight than with malformations when compared to X rays. There were no embryotoxic effects observed at neutron exposures of 0.025, 0.049, 0.079, 0.10, 0.15 and 0.20 Gy or X-ray exposures of 0.50 and 0.96 Gy. Taken together, the results suggest that the mechanisms by which neutron irradiation affects embryonic development may, in part, be both quantitatively and qualitatively different from those by which X irradiation affects development. These results support the generalization that the embryo exhibits a nonlinear response to increasing doses of ionizing radiations during the period of early organogenesis.

The application of diagnostic specific cost profiles to cost and reimbursement control in hospitals.

A system has been developed to generate hospital budgets based on the types of patients served. Several hundred classes of patients are defined according to clinical attributes such as diagnoses and surgical procedures, and for each class a profile of resources consumed is determined. The class definitions are based both on homogeneity of patient care processes as well as resource consumption. These profiles are expressed as revenues generated by charging departments and as costs both direct and indirect for all services. A methodology has been developed to associate all indirect costs with their source for each service included in the profile. From a forecast of patient load by class, budgets can be computed from the cost profiles and revenues determined from the charging profiles. Further analysis thus can include the effect of changes in case mix as well as changes in patient care processes. The effect on revenues of different reimbursement mechanisms can also be projected as a function of the case mix. The system is currently being implemented for demonstration and evaluation of the Yale-New Haven Hospital.

Comparison of X-ray and gamma-ray dose-response curves for pink somatic mutations in Tradescantia clone 02.

Microdosimetric data indicate that the mean specific energy, eta, produced by individual charged particles from X-rays and gamma rays is different for the two radiation qualities by nearly a factor of two. In order to test whether this influences the initial, linear component in the dose-effect relations, a comparison was made between dose-response curves for pink somatic mutations in Tradescantia clone 02 stamen hairs following X and gamma irradiations. Absorbed doses ranged from 2.66 to 300 rad.The results are in agreement with predictions made on the basis of microdosimetric data. At low doses gamma rays are substantially less effective than X-rays. The RBE of gamma rays vs. X-rays at low doses was approximately 0.6, a value lower than those usually reported in other experimental systems.

A system for cost and reimbursement control in hospitals.

This paper approaches the design of a regional or statewide hospital rate-setting system as the underpinning of a larger system which permits a regulatory agency to satisfy the requirements of various public laws now on the books or in process. It aims to generate valid interinstitutional monitoring on the three parameters of cost, utilization, and quality review. Such an approach requires the extension of the usual departmental cost and budgeting system to include consideration of the mix of patients treated and the utilization of various resources, including patient days, in the treatment of these patients. A sampling framework for the application of process-based quality studies and the generation of selected performance measurements is also included.

An elusive factor affecting mutation frequency in Tradescantia stamen hairs: its influence on r.b.e.

A comparison of data from several experiments designed to determine either relative biological effectiveness (r.b.e.) or oxygen-enhancement ratios (o.e.r.) as a function of neutron energy revealed a puzzling variability in mutational response for pink mutations in Tradescantia stamen hairs. For some reason that we cannot determine, when the exposure fixtures and accompanying experimental procedures were changed as necessitated by the two studies, the expected mutation frequencies changed for X-rays and for four neutron energies. The other four neutron energies gave the expected results. As a consequence of these changes in mutation frequencies, the magnitude of r.b.e. values changed as well as the relationship of r.b.e. to neutron energy. Consequently, when r.b.e. values were determined using a closed but aerated exposure fixture instead of exposures made in free air, the resulting r.b.e. versus neutron-energy curve more closely paralleled that found by others for the inhibiton of root growth in Vicia faba.