Effects of sulfate on the acute toxicity of selenate to freshwater organisms.

This study evaluated the relationship between ambient sulfate concentrations and acute selenate toxicity to freshwater aquatic life. Previous studies indicated that increasing sulfate concentrations reduced selenate bioconcentration and toxicity. However, these studies generally were not conducted in a manner that was conducive to their use in deriving a water quality criterion. We compiled results from previous studies and generated additional data to help define a selenate-sulfate relationship for acute toxicity. Selenate toxicity was determined in standardized test waters with varying sulfate concentrations using Ceriodaphnia dubia, Gammarus pseudolimnaeus, Hyalella azteca, and Pimephales promelas as the test organisms. Analysis of test results indicated that a significant relationship does exist between acute selenate toxicity and ambient sulfate concentrations. Data from these tests and previous studies were combined to develop a statistical relationship sufficiently robust to derive a sulfate-dependent water quality criterion for selenate. The relationship is similar to those commonly derived between divalent metals and hardness to adjust water quality criteria.

Acute toxicity of sodium selenate to two daphnids and three amphipods.

This study evaluated the acute toxicity of sodium selenate to two daphnid and three gammarid amphipod species. The daphnids, Ceriodaphnia dubia and Daphnia pulex, were evaluated in 48-hour static tests and the amphipods, Gammarus pseudolimnaeus, Gammarus lacustris, and Hyalella azteca, were evaluated in 96-hour static and flow-through tests. Tests resulted in mean LC50's of 1.92, 9.12, 1.82, 3.05, and 1.95 mg/L selenium for C. dubia, D. pulex, G. pseudolimnaeus, G. lacustris, and H. azteca, respectively. The LC50's for the G. pseudolimnaeus tests are more than 30-fold higher than previously reported LC50's for the same or similar species. The explanation for these differing results appears to be partially, but not entirely, explained by differences in ambient pH between the new studies and previous ones. Depending on how the new data are included in U.S. EPA's selenium freshwater quality criterion data set, the selenate acute water quality criterion (i.e., Criterion Maximum Concentration) increases from 12.8 to as high as 583 microg/L selenium.

Effect of cyclical therapy with phosphorus and etidronate on axial bone mineral density in postmenopausal osteoporotic women.

Forty seven women with postmenopausal osteoporosis and at least one but no more than four vertebral compression fractures received sequential and cyclical therapy with phosphorus and etidronate (p/etid). During the same 2-year period of observation, three other groups of patients received either sodium fluoride (n = 12), estrogen replacement therapy (n = 12), or vitamin D and calcium (Ca++) alone (n = 15). Axial bone mineral density (BMD) was measured by means of dual-photon absorptiometry. Lateral thoracic and lumbar spine radiographs were taken to assess fractures. Bone mineral density increased from baseline during p/etid therapy: Mean 15.7 +/- 1.6% (SD) (P less than 0.001). During the same time, the patients in the sodium fluoride group showed a comparable increase in their BMD from baseline: mean 15.7 +/- 1.1% (P less than 0.001). During the first year of therapy, patients in the estrogen replacement group had an increase in their BMD from baseline: mean: 4.6% +/- 1.1% (P less than 0.05). No change in BMD was seen in the control group that received vitamin D and Ca++ alone. No patient who received p/etid, sodium fluoride, or estrogen replacement therapy had any new vertebral compression fractures or height loss, whereas in the control group that received vitamin D and Ca++ alone 6 out of 15 had height loss and at least one new vertebral fracture (P less than 0.01). p/etid therapy increases BMD in women with postmenopausal osteoporosis comparable to sodium fluoride but without side effects or toxicity and stabilizes vertebral compression fractures.

The dental health of 12-year-old children in Dominica: a report of a survey using WHO methods.

As part of the process of assisting in the planning of a primary dental health care system in the Commonwealth of Dominica, we conducted a survey of mostly 12-year-old children. The purpose of the survey was to assess the oral health status and identify the needs for treatment and prevention. Secondary purposes included training Dominican dental auxiliaries and assistants to collect epidemiologic data and to use the findings to compare oral health status by region and previous coverage by the auxiliaries. The sample was obtained from schools throughout the country. Examinations were conducted according to standard WHO methods, using mirrors and explorers. The findings were recorded on prepared forms and the data were processed in Toronto using microcomputers. We found 31% of children to be caries-free and the mean DMFT score to be 2.5 (95% CI 2.2-2.7). Only 8% of lesions had been treated. No differences were observed by region but in areas covered by dental auxiliaries, children had fewer decayed teeth, fewer DMFT and higher F/DMFT ratios. Only 17% scored 0 on the CPITN index and 63% scored 2, meaning they had calculus. Debris was 3.6 times more likely to be found among those with gingival bleeding or calculus compared to those with periodontal health. Single surface restorations made up 82% of the estimated 2.0 caries treatment services required. The survey findings will allow planners to design specific preventive and treatment programs to meet Dominica's needs.

Hypodipsia in geriatric patients.

Hypernatremia in elderly patients is most often due to the patients mental incapacity or physical inability to obtain water despite intact thirst sensation. Hypodipsia leading to hypernatremia is not often considered in alert, elderly subjects since hypodipsia is not a recognized consequence of nonaphasia-producing cerebrovascular accidents. Described herein are six elderly patients who had such cerebrovascular accidents and who had recurrent hospitalizations for dehydration and hypernatremia. Hypernatremia in this group was due to hypodipsia and could only be prevented by prescribing daily fluid intake as a medication order. Hypodipsia should be considered as a cause of hypernatremia in elderly subjects even when they seem fully capable of requesting and obtaining water.

Polyuric prerenal failure.

Prerenal failure is traditionally accompanied by oliguria and represents the normal renal adaptation to retain salt and water and correct the prerenal state. Nonoliguria occurring in the setting of acute renal failure usually represents acute tubular necrosis (ATN) since the kidney has lost its ability to extract salt and water. We report nine cases of patients with acute renal failure occurring in the setting of impaired systemic hemodynamic states and yet who were nonoliguric without strong evidence for ATN. The common defect in these subjects with "polyuric prerenal failure" was a blunted urinary concentrating ability. Polyuria and renal failure occurring despite evidence for impaired systemic hemodynamics may not necessarily be ATN, may still be prerenal, and should be recognizable and promptly reversible if treated appropriately.

Hypomagnesemia. Suppression of secondary hyperparathyroidism in chronic renal failure.

Chronic renal failure is accompanied by secondary hyperparathyroidism. Inhibition of parathyroid hormone secretion has been reported to be induced by hypomagnesemia in conditions other than chronic renal failure, since severe hypomagnesemia is rare in chronic renal failure. In the case reported here, the patient had chronic renal failure and malabsorption-induced hypomagnesemia; she exhibited hypoparathyroidism while hypomagnesemic, and hyperparathyroidism after magnesium was replaced. Hypomagnesemia induced parathyroid hormone suppression in this patient with chronic renal failure, despite the presence of chronic hyperfunctioning parathyroid cells.