66 research outputs found
The influence of manure phytic acid on phosphorus solubility in calcareous soils
Manure characteristics can influence the potential for P transfer in
runoff following land application of manures. This research assessed
the influence of manure characteristics on P solubility in calcareous
soils using manures from poultry (Gallus Domisticus) fed a variety
of grain-based diets with the manures containing a range of total P
(5.6-16.4 g P kg-1), water-extractable P (WEP, 0.9-4.7 g P kg -1),
phytic acid P (0.1-7.6), total N/P ratios (2.6-5.1), and total C/P ratios
(19.5-75.7). In addition, mono-ammonium phosphate fertilizer and
reagent grade inositol hexaphosphate (phytic acid [PA]), were included,
as well as a control treatment with no P additions. Treatments
were incorporated into two soils (Portneuf [Coarse-silty, mixed,
superactive, mesic Durinodic Xeric Haplocalcids] and Millville
[Coarse-silty, carbonatic, mesic Typic Haploxerolls]) at three rates
(10, 20, and 40 mg P kg -1) and incubated for a total of 18 wk with
subsamples taken at 2, 5, 9, and 18 wk. Soil samples were analyzed for
inorganic and organic NaHCO3 (Olsen) extractable P and select soils
were analyzed at 0 and 12 wk by 31P nuclear magnetic resonance
spectroscopy (NMR) for soil P characterization. The percentage of
WEP and PA (of total P) in the manures were linearly related (r 2 =
0.94). Increases in Olsen P over time were positively related to the
percentage of monoester P in the treatments. At 2 wk, there was a
strong negative correlation between the amount of PA added in the
treatments and increases in Olsen P. However, by 18 wk, Olsen P was
more closely related to the amount of C or N added with the treatments.
Changes in PA content of manures due to dietary modification may
influence P sorption on calcareous soils in the short-term while other
characteristics such as C/P ratio may exert a stronger influence over
changes in soil test P over longer time periods
Association of transcription-coupled repair but not global genome repair with ultraviolet-B-induced Langerhans cell depletion and local immunosuppression.
Exposure to ultraviolet-B radiation impairs cellular immune responses. This immunosuppression seems to be associated with Langerhans cell migration. DNA damage appears to play a key role because enhanced nucleotide excision repair, a pathway essential for elimination of ultraviolet-B-induced DNA lesions, strongly counteracts immunosuppression. To determine the effect of DNA repair on ultraviolet-B-induced local immunosuppression and Langerhans cell disappearance, three mouse strains carrying different defects in nucleotide excision repair were compared. XPC mice, which were defective in global genome repair, were as sensitive to ultraviolet-B-induced local suppression of contact hypersensitivity to picryl chloride as their wild-type littermates. CSB mice, defective in transcription-coupled repair, were far more sensitive for immunosuppression as were XPA mice, defective in both transcription-coupled repair and global genome repair. Only a moderate depletion of Langerhans cells was observed in XPC mice and wild-type littermates. Ultraviolet-B-induced Langerhans cell depletion was enhanced in CSB and XPA mice. Hence, the major conclusion is that local immunosuppression is only affected when transcription-coupled DNA repair is impaired. Furthermore, a defect in transcription-coupled repair was linked to enhanced ultraviolet-B-induced Langerhans cell depletion. In combination with earlier experiments, it can be concluded that Langerhans cell disappearance is related to ultraviolet-B-induced local but not to systemic immunosuppression
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