Darrell Van Campen

Partitioning of cadmium, copper, lead and zinc amongst above-ground parts of seed and grain crops grown in selected locations in the USA

The distribution of Cd, Cu, Pb and Zn in above-ground parts of corn, small grains and pulse crops was investigated. Sampled parts included grain or seed, leaves, stems, silk and husks of corn-ears, rachilla and chaff of small grains and pods of bean plants. The distribution of these elements was variable and reflected, primarily, their relative mobility between plant parts including transfer into the grain. Generally, Zn and Cu were preferentially transferred into the seed or grain, while Cd and Pb were selectively excluded from these organs. For example, the distribution pattern in ears of corn was: for Cd, husks > silk > grain; for Zn, silk > grain > husks. The selective transfer of Zn and Cu into seed or grain, in contrast to the restricted movement of Cd and Pb into these organs, may be the result of selective absorption of Zn and Cu over Cd and Pb by vascular transfer cells within the plants reproductive tissues. The effect of soil type on Cd, Cu, Pb and Zn levels in cereal grain or pulse seed was small compared to the differences found in the concentrations of these elements between different plant organs. Thus, grain and seed crops serve as natural barriers to the movement of the potentially toxic heavy metals, Cd and Pb, into the animal/human food chain, minimising their transfer from soils while conserving Zn and Cu levels in edible portions of these crops.

Soil-Related Nutritional Problem Areas for Grazing Animals

Research to correct trace element deficiencies and toxicities in plants has resulted in increased production of many food and forage plants in the United States and in other parts of the world. The increases in forage crop production have contributed to overall increases in animal production. However, increased animal production has not always paralleled increased production of forage crops. Such disparities arise when meeting the nutritional requirements and mineral tolerances of the plant fails to satisfy the nutritional needs of the animals that are eating the plants. In Australia, use of trace elements has transformed land destined as “trace element deserts” into productive grazing land (Anderson and Underwood, 1959). However, some of these improved pastures were less productive than others when productivity was assessed in terms of animal production. Recognizing the trace element requirements of grazing animals is essential when forage plants are grown primarily for animal feed.

Aflatoxin B1 reduces Na+-Pi co-transport in proximal renal epithelium: studies in opossum kidney (OK) cells

In vivo studies indicate that aflatoxin B1 (AFB1) may affect the renal regulation of inorganic phosphate (P(i)), possibly by altering the renal response to parathyroid hormone (PTH). Therefore, the present study utilized opossum kidney (OK) cells, a mammalian renal epithelial cell line, to determine whether AFB1 exposure alters sodium-phosphate (Na(+)-P(i)) co-transport and the hormonal modulation thereof. OK cells are an established renal cell line with many properties analogous to the proximal renal epithelium, including receptors for PTH, insulin, and high levels of Na(+)-P(i) co-transport. PTH and insulin have been shown to decrease and increase Na(+)-P(i) co-transport, respectively, in OK cells. In the present study, AFB1-treated cells responded to PTH; however, AFB1 exposure decreased Na(+)-P(i) uptake such that additional decreases in Na(+)-P(i) uptake in response to PTH were minimal. In the presence of insulin, AFB1-treated cells were only able to increase Na(+)-P(i) uptake to levels 30% below that of control cells. The net result was that the range of the proximal renal epithelium to adjust Na(+)-P(i) co-transport in response to hormonal modulation was reduced by AFB1 exposure. Sodium-dependent L-alanine uptake was measured and was found not to be affected by the highest concentration of AFB1; thus, indicating that AFB1 exposure may have specific effects on Na(+)-P(i) uptake and does not generally inhibit Na(+)-dependent transport. These observations are evidence that AFB1 exposure may alter key elements of renal function. Such effects raise concern that AFB1 exposure may have broad physiological impact in addition to its known carcinogenic properties.

Zinc Accumulation by Hepatocytes Isolated from Male Rats of Different Zinc Nutritional Status

Some characteristics of Zn uptake and effects of various multivalent cations, metabolic inhibitors, hormones, and sulfhydryl-blocking agents on Zn accumulation by rat hepatocytes in monolayer culturel or in suspensions2 have been reported. Hepatocytes used in these studies were isolated from rats fed Zn-adequate (ZA) diets. The study reported here was conducted to evaluate the effect of rat Zn status on Zn uptake by isolated hepatocytes.