Soil phosphorus dynamics following land application of unsaturated and partially saturated red mud and water treatment residuals.

The secondary use of P-sorbing industrial by-products as a fertilizer or soil conditioner is gaining increased attention, particularly in light of diminishing reserves of rock phosphate traditionally used to manufacture P fertilizer. This study examined applications of red mud (RM) and water treatment residuals (WTR) at two levels of P saturation (i.e. 'as received' and partially saturated) in a soil incubation and runoff plot study. When incubated with soils ranging in texture and initial P concentration, P-sorbing residuals that were less enriched with P decreased water-extractable soil P (WEP) concentration to a greater extent than more P saturated residuals. In contrast to WTR treatments, not all of the RM applications decreased soil WEP concentrations below those of the control soils. The runoff study investigated soil P dynamics when partially P-saturated RM and WTR's were surface applied to grass plots at 2 t ha-1 on Day 0, followed by three rainfall simulations (7 cm h-1 for 30 min, Days 2, 7 and 28) and at 3 t ha-1 on Day 70 followed by two more rainfall simulations (Days 77 and 96). Application of residuals at these rates did not significantly increase dissolved reactive P (DRP) in runoff compared with unamended controls during the study. Forage cuttings taken 90 days after the first rainfall simulation indicated that nutrient uptake was not compromised by the application of the residuals. Overall results indicate that WTRs may be a more suitable soil amendment than RM residuals given their greater ability to reduce soil WEP across a range of soils without simultaneously increasing Mehlich-3 extractable soil P concentrations above the upper threshold limit (150 mg P kg-1), and their minimal impact on plant nutrient uptake.

Decision tree analysis as a supplementary tool to enhance histomorphological differentiation when distinguishing human from non-human cranial bone in both burnt and unburnt states: A feasibility study.

This feasibility study was undertaken to describe and record the histological characteristics of burnt and unburnt cranial bone fragments from human and non-human bones. Reference series of fully mineralized, transverse sections of cranial bone, from all variables and specimen states, were prepared by manual cutting and semi-automated grinding and polishing methods. A photomicrograph catalogue reflecting differences in burnt and unburnt bone from human and non-humans was recorded and qualitative analysis was performed using an established classification system based on primary bone characteristics. The histomorphology associated with human and non-human samples was, for the main part, preserved following burning at high temperature. Clearly, fibro-lamellar complex tissue subtypes, such as plexiform or laminar primary bone, were only present in non-human bones. A decision tree analysis based on histological features provided a definitive identification key for distinguishing human from non-human bone, with an accuracy of 100%. The decision tree for samples where burning was unknown was 96% accurate, and multi-step classification to taxon was possible with 100% accuracy. The results of this feasibility study strongly suggest that histology remains a viable alternative technique if fragments of cranial bone require forensic examination in both burnt and unburnt states. The decision tree analysis may provide an additional but vital tool to enhance data interpretation. Further studies are needed to assess variation in histomorphology taking into account other cranial bones, ontogeny, species and burning conditions.

Selenium modulates peroxidation in the absence of glutathione peroxidase in Musca domestica.

Adult houseflies fed a low-selenium diet showed a 73% decrease in total Se compared to those given 1.0 ppm Se in their drinking water. This decrease was associated with a 84.4% increase in thiobarbituric acid reactants and a 16.3% increase in conjugated dienes. These increases were unrelated to activities of glutathione S-transferases, superoxide dismutases and catalase and to levels of reduced and oxidized glutathione, all of which were unaltered by Se deficiency. Since houseflies lack glutathione peroxidase, Se apparently modulates peroxidation in these animals independent of the antioxidant enzymes and glutathione.

Relative importance of intracellular glutathione peroxidase and catalase in vivo for prevention of peroxidation to the heart.

The relative importance in vivo of catalase and the selenoenzyme glutathione peroxidase for protection against peroxidation was assessed in the rat heart. Each of these enzymes was modulated by feeding animals a low selenium diet either unsupplemented or supplemented with 0.5 parts per million of selenium, with or without the catalase inhibitor, 3-amino-1,2,4-triazole, in their drinking water. After 8 weeks, selenium deficient rats had 88% reductions in cytosolic and mitochondrial glutathione peroxidase activities. These reductions were accompanied by increased peroxidation in heart homogenates and mitochondrial suspensions. Since increased mitochondrial peroxidation only occurred when both the cytosolic and mitochondrial glutathione peroxidase activities were compromised, these selenoenzymes appear to work in tandem and reductions in both are a prerequisite for increased peroxidation in this organ. Peroxidation did not occur in aminotriazole treated animals even though cytosolic catalase activity was inhibited by 65-80%. Moreover, inhibition of catalase activity did not exacerbate the level of peroxidation in selenium deficient animals depleted of glutathione peroxidase activity. Because increased peroxidation was only associated with reductions in glutathione peroxidase activity irrespective of catalase activity, the selenoenzyme appears to be more important for detoxification of hydrogen peroxide in the heart.

Selenium-independent glutathione peroxidase activity associated with glutathione S-transferase from the housefly, Musca domestica.

1. A glutathione S-transferase having Se-independent glutathione peroxidase activity was isolated from 100,000 g supernatant from housefly homogenate. 2. The specific activity of the partially purified Se-independent glutathione peroxidase was 1776 nmol NADPH oxidized/min/mg protein, representing an 87-fold purification. 3. The Mr of this enzyme was estimated to be 37,000 and 26,000 by gel filtration chromatography and gel electrophoresis, respectively. 4. Selenium-dependent glutathione peroxidase activity could not be detected in this same supernatant. 5. Se-independent glutathione peroxidase activity should be considered in future studies of the insect antioxidant defense system.

Significance of alterations in hepatic antioxidant enzymes. Primacy of glutathione peroxidase.

The relative contributions of catalase and the selenoenzyme glutathione peroxidase (GSH-Px) were elucidated in the rat liver by selectively modulating the activities of these enzymes using dietary selenium (Se) and the catalase inhibitor 3-amino-1,2,4-triazole (3-AT). Increased peroxidation occurred only in Se-deficient rats with markedly reduced cytosolic and mitochondrial GSH-Px activities. Although 3-AT treatment resulted in a 75% reduction of hepatic catalase activity and also a 20% reduction of both cytosolic and mitochondrial superoxide dismutase (SOD) activity, no incremental increase in peroxidation was observed over that associated with Se deficiency. In Se-deficient animals, treatment with 3-AT resulted in a doubling of cytosolic GSH-Px. This was associated with a 49% elevation in hepatic Se suggesting that increased Se may have contributed to the enhanced GSH-Px activity. These results suggest that GSH-Px plays the pivotal role in preventing hepatic peroxidation. Furthermore, the effects of 3-AT in vivo are not restricted to inhibition of catalase activity insofar as it also affects cytosolic GSH-Px activity and cytosolic and mitochondrial SOD activities.

The effect of selenium deficiency on peroxidative injury in the house fly, Musca domestica. A role for glutathione peroxidase.

Selenium-dependent glutathione peroxidase activity is documented for the first time in insects. Reduction in glutathione peroxidase activity in the cytosol of adult house flies by lowering selenium in the diet results in significant increases in peroxidative injury. Catalase activity, while higher in low-selenium flies than in selenium-supplemented flies, does not prevent lipid peroxidation. The discovery of glutathione peroxidase activity in insects eliminates an anomaly which partially limited the usefulness of these animals as models for the study of the antioxidant defense system.