Contraindications to the repositioning of fractured or dislocated limbs in the fields

Supracondylar fractures of the femor or humerus and fractures of the radius, ulna, tibia or fibula, plus crush injuries of the limbs, most likely should not be manipulated in the field because of the potential for traumatizing adjacent nerves, veins and arteries. An emergency splinting system that allows immobilization without repositioning has been developed. Furthermore, fractures in or about the elbow, wrist, knee, or ankle should not be subjected to reduction in the field, unless there are compelling reasons to justify the risk of producing significant additional trauma. Conservative immobilization without repositioning may yield a more positive prognosis for the patient.     

Hypermutability of mouse chromosome 2 during the development of x-ray-induced murine myeloid leukemia

In an effort to identify the precise role of a deletion at regions D-E of mouse chromosome 2 [del2(D-E)] during the development of radiation-induced myeloid leukemia, we conducted a serial sacrifice study in which metaphase chromosomes were examined by the G-banding technique. Such metaphase cells were collected from x-irradiated mice during the period of transformation of some of the normal hematopoietic cells to the fully developed leukemic phenotype. A group of 250 CBA/Ca male mice (10-12 weeks old) were exposed to a single dose of 2 Gy of 250-kilovolt-peak x-rays; 42 age-matched male mice served as controls. Groups of randomly selected mice were sacrificed at 20 hr, 1 week, and then at intervals of 3 months up to 24 months after x-irradiation. Slides for cytogenetic, hematological, and histological examination were prepared for each animal at each sacrifice time. An expansion of cells with lesions on one copy of chromosome 2 was evident in 20-25% of treated mice at each sacrifice time. The majority of such lesions were translocations at 2F or 2H, strongly suggesting hypermutability of these sites on mouse chromosome 2. No lesions were found in control mice. The finding leads to the possibility that genomic lesions close to 2D and 2E are aberrants associated with radiation leukemogenesis, whereas a single clone of cells with a del2(D-E) may lead directly to overt leukemia. The data also indicate that leukemic transformation arises from the cumulative effects of multiple genetic events on chromosome 2, reinforcing the thesis that multiple steps of mutation occur in the pathogenesis of cancer.     

Molecular dynamics simulations of the docking of substituted N5- deazapterins to dihydrofolate reductase

Orientations of the deazapterin ring and the conformational preferences of groups appended to the deazapterin ring in a set of 8-substituted deazapterin cations docked into the dihydrofolate reductase (DHFR) binding site have been investigated using a methodology based on the simulated annealing technique within molecular dynamics (MD) simulations. Of five possible binding pockets for the 8-substituents, identified from a preliminary manual docking study, one has been definitively eliminated after an analysis of MD trajectories, while another remains uncertain. Using a new method based on standard thermodynamic cycles and a linear approximation of polar and non-polar free energy contributions from MD averages, binding affinities of the different ligands in each binding site have been correlated with experimental dissociation constants. The study has provided insights into structure-activity relationships for use in the design of modified inhibitors of DHFR.      

Aging behavior of metal oxide aerogels

Aerogels of titania, zirconia, niobia, and silica were prepared by CO₂ supercritical drying of the corresponding alcogels. Their porous texture could be modified by further aging of the alcogels. This kind of textural modification was found to be different according to the nature of the metal precursor and sol-gel conditions. This paper was presented at the 8th APCChE (Asia Pacific Confederation of Chemical Engineering) Congress held at Seoul between August 16 and 19, 1999.     

Thermochemistry and Aqueous Durability of Ternary Glass Forming Ba-Titanosilicates: Fresnoite (Ba2TiSi2O8) and Ba-Titanite (BaTiSiO5)

Barium titanosilicates are possible oxide forms for the immobilization of short-lived fission products in radioactive waste. Ba₂TiSi₂O₈ (fresnoite) and BaTiSiO₅ (Ba-titanite) samples were prepared by a solid-state synthesis. The enthalpies of formation of Ba₂TiSi₂O₈ crystal and glass at 25°C and of BaTiSiO₅ glass were obtained from drop solution calorimetry in a molten lead borate (2PbO–B₂O₃) solvent at 701°C. The enthalpy of formation for fresnoite composition samples from constituent oxides was exothermic and became more exothermic with increasing crystallinity. Differential scanning calorimetry revealed that the crystallization rate of the fresnoite glasses increased with increasing devitrification. A modified Product Consistency Test-Procedure B (PCT-B) was used to collect solubility data on the fresnoite and titanate phases. The tests suggest that both glassy and crystalline fresnoite exhibit favorable aqueous stability and should be explored further as radioactive waste forms for long-term storage.