Selecting analytical target pesticides in monitoring: Sensitivity analysis and scoring.

Measuring river water concentrations of all pesticides applied in a catchment area is a daunting task. This study aims to develop new score tables for selecting analytical target pesticides. Sensitivity analyses were conducted using a diffuse pollution hydrologic model to quantitatively evaluate the influence of pesticide properties (e.g., log K(OC), degradability [half-life]) on concentrations of rice-farming pesticides in river water. Using the results of the analyses, score tables were systematically designed for the pesticide properties such that the sum of the scores for a particular pesticide, designated as the contamination index, was proportional to the expected/predicted concentration of that pesticide in river water. The contamination indexes for pesticides applied in three river basins were calculated and compared with the corresponding observed pesticide concentrations. Correlations between contamination indexes and observed concentrations were fairly good. Pesticides were ranked according to the quotients obtained by dividing the pesticide concentrations predicted from the contamination indexes by the corresponding drinking-water quality guideline values, and pesticide candidates to be monitored were successfully selected on the basis of a threshold quotient.

Sensitivity analysis using a diffuse pollution hydrologic model to assess factors affecting pesticide concentrations in river water.

We quantitatively evaluated the factors that affect the concentrations of rice-farming pesticides (an herbicide and a fungicide) in river water by a sensitivity analysis using a diffuse pollution hydrologic model. Pesticide degradation and adsorption in paddy soil affected concentrations of the herbicide pretilachlor but did not affect concentrations of the fungicide isoprothiolane. We attributed this difference to the timing of pesticide application in relation to irrigation and drainage of the rice paddy fields. The herbicide was applied more than a month before water drainage of the fields and runoff was gradual over a long period of time, whereas the fungicide was applied shortly before drainage and runoff was rapid. However, the effects of degradability-in-water on the herbicide and fungicide concentrations were similar, with concentrations decreasing only when the rate constant of degradation in water was large. We also evaluated the effects of intermittent irrigation methods (irrigation/artificial drainage or irrigation/percolation) on pesticide concentrations in river water. The runoff of the fungicide, which is applied near or in the period of intermittent irrigation, notably decreased when the method of irrigation/artificial drainage was changed to irrigation/percolation. In a sensitivity analysis evaluating the synergy effect of degradation and adsorbability in soil, the degradation rate constant in soil greatly affected pesticide concentration when the adsorption coefficient was small but did not affect pesticide concentration when the adsorption coefficient was large. The pesticide concentration in the river water substantially decreased when either or both the degradation rate constant in soil and adsorption coefficient was large.

Management of calcium and bone abnormalities in hemodialysis patients.

In chronic renal failure, hyperphosphatemia, hypocalcemia, hyperparathyroidism, reduced activation of vitamin D, decreased level of calcium-sensing receptor, osteitis fibrosa, and osteomalacia are features related to calcium abnormalities. Hyperparathyroidism is a risk factor for survival of hemodialysis patients as well as hypoparathyroidism, which is another feature in hemodialysis patients. Treatment of these abnormalities includes control of parathyroid hormone (PTH) secretion, counteracting hyperphosphatemia, correction of hypocalcemia, and others. Various kinds of vitamin D analogs have been introduced recently in addition to calcitriol and alfacalcidol, which have a rather long history (eg, maxacalcitol and falecalcitriol). Sevelamer is a newly developed phosphate binder to treat soft-tissue calcification.

Direct observations of freeze-etching processes of ice-embedded biomembranes by atomic force microscopy.

We have fabricated a cryogenic atomic force microscope that is designed for structural investigation of freeze-fractured biological specimens. The apparatus is operated in liquid nitrogen gas at atmospheric pressure. Freeze-fracturing, freeze-etching and subsequent imaging are carried out in the same chamber, so that the surface topography of a fractured plane is easily visualized without ice contamination. A controlled superficial sublimation of volatile molecules allows us to obtain three-dimensional views of ultrastructures of biological membranes.