Sterols as bio-markers for waste impact and source characterization in stream sediment.

Sterols are involved in life processes in organisms and are therefore potential biomarkers for assessment of environmental ecosystems. Current data indicate that sterols are persistent in stream sediments, since sterols are not sufficiently soluble in water to be readily detected in water samples. Stream sediment therefore can act as an integrating exposure index of pollution for animal or human waste in streams. The study reported here was conducted in two phases. Phase 1 involved development and validation of a simplified method for the determination of sterols, and Phase 2 involved application of that method to evaluate actual environmental samples. Stream sediment samples from agricultural settings, wastewater-treatment-facility outfalls, and recreational state parks in Iowa and Pennsylvania were analyzed for sterol compounds. Sterol profiles differ considerably among animals, and the study distinguished sterol profiles within stream sediments. Feces from different animal species were also analyzed to provide reference sterol profiles. Individual-sterol and total-sterol concentrations were determined. Sterols were observed in 73.4 percent of environmental sediment samples tested (n = 124) and at 100 percent of the sites (n = 18). Coprostanol, a key indicator of fecal pollution, was observed in 38.7 percent of the environmental sediment samples tested and at 72.2 percent of the sites. Samples were collected from multiple points at selected sites, and duplicate samples were analyzed at a frequency of 16.1 percent. One to five months later, additional samples were collected from the duplicate locations and were analyzed. Data generated by the study provide a basis for stream sediment monitoring that enables the chronological recording of waste impact; this method may be coupled with other measurements to determine the extent and possible source of stream contaminants.

Method validation for the simultaneous determination of fecal sterols in surface waters by gas chromatography-mass spectrometry.

Besides microbiological methods, fecal pollution of surface waters is estimated by gas chromatographic (GC) determination of sterols present in human and animal sewage effluents. The most frequently used biomarkers for the evaluation of contamination levels include coprostanol, cholesterol, dihydrocholesterol, stigmasterol, beta-sitosterol, and stigmastanol. Although several GC techniques are used to measure these compounds in aquatic systems, the analytical performance of GC-mass spectrometric (MS) determination of these sterols has not been systematically characterized. Therefore, the aim of this work is to validate a simple and rapid GC-MS method for the simultaneous analysis of six sterols, considering all parameters and requirements defined by Good Laboratory Practice. Following liquid-liquid extraction of spiked surface water samples, the extracts are silylated and analyzed by GC-MS. The method is evaluated for linearity and limits of detection and quantitation, as well as for precision, extraction efficiency, and stability. The assay is linear up to 160 ng; the limits of detection and quantitation are 5-10 ng and 20 ng, respectively. The within- and between-day precision ranged from 1% to 9% and 1% to 16%, respectively. The extraction efficiency was 65-80%. The stability studies indicate that the sterols in surface water samples begin to degrade after 24 h of refrigerated storage. However, three freeze/thaw cycles could be performed without their decomposition. The method is applied to the analysis of surface water and wastewater samples. The technical advantages make this GC-MS analysis suitable for routine environmental monitoring of fecal pollution in aquatic systems.

Postpartum blindness: two cases.

We present 2 cases, one eclamptic patient and one noneclamptic patient, of headache, cortical blindness, and seizures. Both patients demonstrated findings consistent with posterior leukoencephalopathy syndrome. Posterior leukoencephalopathy syndrome is a rapidly evolving neurologic condition that is characterized by headache, nausea and vomiting, seizures, visual disturbances, altered sensorium, and occasionally focal neurologic deficits. Posterior leukoencephalopathy syndrome can be triggered by numerous conditions, including preeclampsia-eclampsia, and can be seen in the postpartum period. It is characterized predominately by white matter vasogenic edema of the occipital and posterior parietal lobes. This condition can be difficult to differentiate clinically from cerebral ischemia, and magnetic resonance imaging with diffusion-weighted imaging and apparent diffusion coefficient are needed to do so. In most cases of posterior leukoencephalopathy syndrome, the prognosis is excellent, with full resolution of symptoms.