Arsenic is widely distributed in the environment by natural and human means. The potential for adverse health effects from inorganic arsenic depends on the level and route of exposure. To estimate potential health risks of inorganic arsenic, the apportionment of exposure among sources of inorganic arsenic is critical. In this study, daily inorganic arsenic intake of U.S. adults from food, water, and soil ingestion and from airborne particle inhalation was estimated. To account for variations in exposure across the U.S., a Monte Carlo approach was taken using simulations for 100,000 individuals representing the age, gender, and county of residence of the U.S. population based on census data. Our analysis found that food is the greatest source of inorganic arsenic intake and that drinking water is the next highest contributor. Inhalation of airborne arsenic-containing particles and ingestion of arsenic-containing soils were negligible contributors. The exposure is best represented by the ranges of inorganic arsenic intake (at the 10 th and 90 th percentiles), which were 1.8 to 11.4 µg/day for males and 1.3 to 9.4 µg/day for females. Regional differences in inorganic arsenic exposure were due mostly to consumption of drinking water containing differing inorganic arsenic content rather than to food preferences.
A chromatographic system using DEAE-Sephadex A-50 with 0.04 m pyrophosphate buffer, pH 7.5, and a linear KC1 gradient to 0.50 m KC1 separates monomeric myosin from aggregated myosin, other unidentified proteins, and ribonucleic acid (RNA).The procedure has been applied to myosin preparations from skeletal muscle of rabbit, chicken, and K-zeveral investigators have employed column chromatography for the purification of myosin. Brahms (1959) and Perry (1960) used DEAE-cellulose with 0.2 m KC1 buffered with Tris to pH 7.4, and obtained some degree of fractionation, but the bulk of the material passed directly through the column without retention. Perry (1960) also employed a buffer system (0.16 m KC1-0.02 m Tris, pH 8.2) with a KC1 gradient that resulted in a separation of myosin from ribonucleoprotein and other proteins that passed through unretarded. However, the adenosine triphosphatase (ATPase)* 1 **activity varied considerably across the myosin peak, and dimers not present in the starting material were seen in the myosin purified by this procedure. Based on the work of Brahms and Brezner (1961), who showed that myosin was soluble in polyphosphates at low ionic strength, Asai (1963) used DEAE-cellulose columns, ATP in the solvent, and a KC1 gradient to obtain chromatograms that were similar to those obtained with the pH 8.2 system of
SUMMARY
Malonaldehyde and/or substances closely resembling it occur in foods as decomposition products of oxidizing polyunsaturated fatty acids. The reaction of malonaldehyde with various food constituents was studied. In the presence of water, malonaldehyde exists mainly as its nonvolatile enolate anion. As such, it can react with amino acids, proteins, glycogen, and other food constituents to form products in which the malonaldehyde exists in bound form. Aqueous malonaldehyde can be converted to its volatile isomer by acidification only but acid and heat are necessary to release malonaldehyde from its bound state in proteins. These combined observations throw light on problems connected with the quantitative recovery of 2‐thiobarbituric‐acid‐reactive substances (TBRS) in moist foods. Proteins prepared from frozen tuna fish contained appreciable amount of bound TBRS.
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