Effect of reducing groundwater on the retardation of redox-sensitive radionuclides.

Laboratory batch sorption experiments were used to investigate variations in the retardation behavior of redox-sensitive radionuclides. Water-rock compositions were designed to simulate subsurface conditions at the Nevada Test Site (NTS), where a suite of radionuclides were deposited as a result of underground nuclear testing. Experimental redox conditions were controlled by varying the oxygen content inside an enclosed glove box and by adding reductants into the testing solutions. Under atmospheric (oxidizing) conditions, radionuclide distribution coefficients varied with the mineralogic composition of the sorbent and the water chemistry. Under reducing conditions, distribution coefficients showed marked increases for 99Tc (from 1.22 at oxidizing to 378 mL/g at mildly reducing conditions) and 237Np (an increase from 4.6 to 930 mL/g) in devitrified tuff, but much smaller variations in alluvium, carbonate rock, and zeolitic tuff. This effect was particularly important for 99Tc, which tends to be mobile under oxidizing conditions. A review of the literature suggests that iodine sorption should decrease under reducing conditions when I- is the predominant species; this was not consistently observed in batch tests. Overall, sorption of U to alluvium, devitrified tuff, and zeolitic tuff under atmospheric conditions was less than in the glove-box tests. However, the mildly reducing conditions achieved here were not likely to result in substantial U(VI) reduction to U(IV). Sorption of Pu was not affected by the decreasing Eh conditions achieved in this study, as the predominant sorbed Pu species in all conditions was expected to be the low-solubility and strongly sorbing Pu(OH)4. Depending on the aquifer lithology, the occurrence of reducing conditions along a groundwater flowpath could potentially contribute to the retardation of redox-sensitive radionuclides 99Tc and 237Np, which are commonly identified as long-term dose contributors in the risk assessment in various radionuclide environmental contamination scenarios. The implications for increased sorption of 99Tc and 237Np to devitrified tuff under reducing conditions are significant as the fractured devitrified tuff serves as important water flow path at the NTS and the horizon for a proposed repository to store high-level nuclear waste at Yucca Mountain.

Assessing field-scale migration of radionuclides at the Nevada Test Site: "mobile" species.

Many long-lived radionuclides are present in groundwater at the Nevada Test Site (NTS) as a result of 828 underground nuclear weapons tests conducted between 1951 and 1992. In conjunction with a comprehensive geochemical review of radionuclides (3H, 14C, 36Cl, 99Tc and 129I) that are presumably mobile in the subsurface, we synthesized a body of radionuclide activity data measured from groundwater samples collected at 18 monitoring wells, to qualitatively assess their migration at the NTS over distances of hundreds of meters and over timescales of decades. Tritium and 36Cl showed little evidence of retardation, while the transport of 14C may have been retarded by its isotopic exchange with carbonate minerals in the aquifer. Observed local reducing conditions (either natural or test-induced) will impact the mobility of certain redox-sensitive radionuclides (especially 99Tc) that were otherwise soluble and readily transported under oxidizing conditions. Conversely, strongly oxidizing conditions may impact the mobility of 129I which is mobile under reducing conditions. The effect of iodine speciation on its transport deserves further attention. Indication of delayed transport of some "mobile" radionuclides (especially 99Tc) in the groundwater at the NTS suggested the importance of redox conditions of the natural system in controlling the fate and transport of radionuclides, which has implications in the enhanced performance of the potential Yucca Mountain repository, located adjacent to the NTS, to store high-level nuclear wastes as well as management of radionuclide contamination in legacy nuclear operations facilities.

The role of orthodontics in implant dentistry.

Orthodontic treatment of partially edentulous patients is difficult, especially if a significant number of teeth are missing. With loss of teeth, adjacent or opposing teeth usually tip, drift or over-erupt leaving spaces that are not optimal for replacement of missing teeth. Orthodontic correction of these spatial relationships will aid prosthetic replacement of the missing teeth, function, hygiene and aesthetics. Orthodontists rely on teeth to provide the anchorage to correct malocclusions. With patients with an intact dentition dental anchorage is usually adequate to facilitate tooth movement. In some partially edentulous patients however, insufficient anchorage may present to correct the malocclusion. In these patients implants can provide additional anchorage. At times, osseointegrated implants can also be used to support restorations after completion of orthodontic therapy if treatment planning is precise. The use of implants for orthodontic anchorage requires an interdisciplinary approach and precise planning to achieve optimal results.

Spontaneous enophthalmos associated with asymptomatic maxillary sinus disease (silent sinus syndrome): case report.

BACKGROUND: Cases of spontaneous enophthalmos (in otherwise asymptomatic patients) that are unrelated to trauma, surgery, or systemic disease have been reported infrequently in the literature. CASE REPORT: We present a 41-year-old patient who demonstrated this recently reported constellation of findings referred to as silent sinus syndrome. CONCLUSION: Consideration should be given to the causes of spontaneous and acquired enophthalmos and the possibility of silent sinus syndrome. Other causes of enophthalmos based on the clinical features should also be considered.

Targeted HIV screening at a Los Angeles prenatal/family planning health center.

In 1988, the Los Angeles County Health Department conducted a blinded human immunodeficiency virus (HIV) seroprevalence study at a public prenatal (PN) and family planning (FP) center serving mostly Hispanic women in order to determine seroprevalence and to evaluate the center's targeted HIV screening program. Four women (0.13 percent) tested positive (3/1801 PN and 1/1167 FP). Three reported no risk factors; one reported a history of syphilis since 1978. Voluntary HIV testing was selectively offered to women who reported risk factors for HIV infection. Only 14 percent (96/685) of clients offered testing chose to do it: 28 percent (14/50) of clients classified as being at highest risk of infection, and 27 percent (16/59) of women who judged themselves to have some chance of being exposed to HIV. None of the four women who tested positive by blinded testing chose testing. While few women at this center were infected with HIV, higher risk women were not persuaded to be tested through a targeted screening program. Blinded HIV seroprevalence studies provide a tool for both tracking infection in a population and evaluating screening programs.

Distant metastases in epithelial ovarian carcinoma.

A review of 255 patients with epithelial ovarian carcinoma revealed that metastases consistent with Stage IV disease developed in 97 patients (38.0%) at some time during the natural history of their disease. Malignant pleural effusions developed in 63 patients (24.7%), and their median survival (from the time of diagnosis of the effusion) was 6 months. Parenchymal liver metastases developed in 24 patients (9.4%; median survival, 5 months); parenchymal lung metastases in 18 patients (7.1%; median survival, 8 months); distant lymph node metastases in 18 patients (7.1%; median survival, 9 months); subcutaneous nodules in nine patients (3.5%; median survival, 12 months); a malignant pericardial effusion in six patients (2.4%; median survival, 2.3 months); central nervous system metastases in five patients (2%; median survival, 1.3 months); and bone metastases in four patients (1.6%; median survival, 4 months). Patients with Stage IV disease at the time of diagnosis had a median survival of 9.1 months, while patients with a delayed occurrence of distant metastases had a median survival of only 4 months from the time of diagnosis of the distant metastases. Significant risk factors for distant metastases were malignant ascites, peritoneal carcinomatosis, large metastatic disease within the abdomen, and retroperitoneal lymph node involvement at the time of the initial surgery. The significance of positive retroperitoneal nodes and bulky upper abdominal disease has important therapeutic implications.

Cytoreductive surgery in ovarian carcinoma: feasibility and morbidity.

Between 1974 and 1984, 70 patients underwent primary cytoreductive surgery for ovarian carcinoma at the University of California at Los Angeles. During the period of January 1974 to December 1978, optimal cytoreduction was achieved in 56.4% of the patients. With increased experience, this figure improved to 87.1% in the period of January 1979 to December 1983. The most common morbidity associated with the procedure was fever and prolonged ileus. Bowel resection was required in 20% of the patients and was not associated with increased morbidity. More liberal use of the end-to-end anastomosis stapling device facilitated low colon reanastomosis without colostomy, which contributed to the improved patient acceptance.

Synergistic effects of combination sequential immunotherapies in a murine ovarian cancer model.

The antitumor effects of Corynebacterium parvum in a murine ovarian teratocarcinoma model depend upon a sequential activation of neutrophils and macrophages within the peritoneal cavity. We studied the sequential administration of biological response modifiers that independently activate each phase of the response. Tumor-challenged mice treated by i.p. injection of a pyridine-extracted fraction of cell-free Propionibacterium acnes (PA-PE, 1400 micrograms) demonstrated prolonged survival in less than 20% of the cases. An i.p. injection of a detoxified Salmonella endotoxin (DSE) preparation (150 micrograms) had no effect on tumor outgrowth. However, i.p. treatment with PA-PE (1400 micrograms), followed by 150 micrograms of DSE 1 day later, resulted in long-term survival (greater than 100 days) in 40 to 60% of mice. This antitumor effect was only evident when PA-PE was administered first (before DSE) and optimal when DSE was administered 24 h after PA-PE. The synergistic antitumor effect could be duplicated when tumor-challenged mice were first treated i.p. with peritoneal polymorphonuclear leukocytes, elicited by injection of PA-PE, and then treated with DSE 18 h later. These data indicate that appropriately timed injection of biological response modifiers with complementary effects can result in a synergistic prevention of tumor growth.

Some factors influencing the effect of cholesterol on streptolysin O activity.

Inhibition of streptolysin O activity by cholesterol depends on the latter being in free form. The normal esterified and protein-bound cholesterol fractions in serum do not influence streptolysin O activity. However, high cholesterol levels in rabbits fed cholesterol with cholic acid were associated with an increased antistreptolysin O effect. It is suggested that this occurs when all available protein sites are saturated and where a true ;free' cholesterol fraction is present. Splitting the esterified cholesterol fraction of human sera with raised cholesterol levels, by means of pancreatin, produced an increased antistreptolysin O effect, again presumably because of saturation of protein-binding sites. Similarly, removal of non-esterified cholesterol from sera of cholesterolfed rabbits, by means of digitonin, reduced antistreptolysin O activity of the sera. Evidence is presented that combination of bovine serum albumin and streptolysin O has a steric hindrance effect on attachment of cholesterol to streptolysin O. The method described for the estimation of free cholesterol is extremely sensitive, being capable of detecting concentrations of less than 1.0 mug/ml.