Nitrogen availability and leaching during the terrestrial phase in a várzea forest of the Central Amazon floodplain

Availability and leaching of dissolved inorganic N (DIN = NH₄⁺ + NO₃^-) in soil were measured in a periodically flooded forest of the Central Amazon floodplain (várzea) during one terrestrial phase. Special emphasis was on the effects of a legume and a non-legume tree species. NH₄⁺-N accounted for more than 85% of DIN even at the end of the terrestrial phase although it decreased throughout the experimental period. While extractable NO₃^–-N was always low in the soil (less than 15% of DIN), the amount of leached NO₃^–-N was in the same range as NH₄⁺-N. Under the legume trees mean DIN contents of the topsoil were higher than under the non-legume trees. DIN leaching from the topsoil (0–20 cm) was significantly higher under the legume trees than at the other sites, also indicating a higher N availability. Therefore, despite considerable leaching legume trees may be an important source of N supporting a high biomass production of the várzea forest.     

Characterization of metabolites of hydroxycinnamates in the in vitro model of human small intestinal epithelium caco-2 cells

Hydroxycinnamic acids are antioxidant phenolic compounds which are widespread in plant foods, contribute significantly to total polyphenol intakes, and are absorbed by humans. The extent of their putative health benefit in vivo depends largely on their bioavailability. However, the mechanisms of absorption and metabolism of these phenolic compounds have not been described. In this study, we used the in vitro Caco-2 model of human small intestinal epithelium to investigate the metabolism of the major dietary hydroxycinnamates (ferulate, sinapate, p-coumarate, and caffeate) and of diferulates. The appearance of metabolites in the medium versus time was monitored, and the various conjugates and derivatives produced were identified by HPLC-DAD, LC/MS, and enzyme treatment with beta-glucuronidase or sulfatase. Enterocyte-like differentiated Caco-2 cells have extra- and intracellular esterases able to de-esterify hydroxycinnamate and diferulate esters. In addition, intracellular UDP-glucuronosyltransferases and sulfotransferases existing in Caco-2 cells are able to form the sulfate and the glucuronide conjugates of methyl ferulate, methyl sinapate, methyl caffeate, and methyl p-coumarate. However, only the sulfate conjugates of the free acids, ferulic acid, sinapic acid, and p-coumaric acid, were detected after 24 h. The O-methylated derivatives, ferulic and isoferulic acid, were the only metabolites detected following incubation of Caco-2 cells with caffeic acid. These results show that the in vitro model system differentiated Caco-2 cells have the capacity to metabolize dietary hydroxycinnamates, including various phase I (de-esterification) and phase II (glucuronidation, sulfation, and O-methylation) reactions, and suggests that the human small intestinal epithelium plays a role in the metabolism and bioavailability of these phenolic compounds.     

Immunomodulation therapy for feline leukemia virus infection.

Clinically ill feline leukemia virus (FeLV)-infected cats, treated with Staphylococcus protein A (SPA) or oral interferon alpha (IFN), or both, were compared with cats treated with saline (SAL). Nine cats received SPA/SAL, nine received SPA/IFN, 10 received SAL/IFN, and eight received SAL/SAL. Twelve cats survived and completed the 100-week therapy. Significantly more owners of cats treated with SPA/SAL thought their cat's health improved during treatment compared to owners of cats treated with SAL/SAL (P=0.05, pair-wise comparison) or SPA/IFN (P=0.05, pair-wise comparison). No significant differences in body weight, temperature, hematocrit, red blood cell counts, mean corpuscular hemoglobin concentration, reticulocyte counts, white blood cell or neutrophil numbers, lymphocyte concentrations, bone-marrow cytopathology, FeLV status, survival time, activity, or appetite scores were observed. No significant differences in the owners' subjective assessment of their cat's health following treatment with SAL/IFN, SPA/IFN, or SAL/SAL were seen. Therapy with SPA as a single agent results in the owners' subjective impression of improved health of their FeLV-infected cats.     

Identification of a chromosome 18q gene that is altered in colorectal cancers

Allelic deletions involving chromosome 18q occur in more than 70 percent of colorectal cancers. Such deletions are thought to signal the existence of a tumor suppressor gene in the affected region, but until now a candidate suppressor gene on this chromosomal arm had not been identified. A contiguous stretch of DNA comprising 370 kilobase pairs (kb) has now been cloned from a region of chromosome 18q suspected to reside near this gene. Potential exons in the 370-kb region were defined by human-rodent sequence identities, and the expression of potential exons was assessed by an "exon-connection" strategy based on the polymerase chain reaction. Expressed exons were used as probes for cDNA screening to obtain clones that encoded a portion of a gene termed DCC; this cDNA was encoded by at least eight exons within the 370-kb genomic region. The predicted amino acid sequence of the cDNA specified a protein with sequence similarity to neural cell adhesion molecules and other related cell surface glycoproteins. While the DCC gene was expressed in most normal tissues, including colonic mucosa, its expression was greatly reduced or absent in most colorectal carcinomas tested. Somatic mutations within the DCC gene observed in colorectal cancers included a homozygous deletion of the 5' end of the gene, a point mutation within one of the introns, and ten examples of DNA insertions within a 0.17-kb fragment immediately downstream of one of the exons. The DCC gene may play a role in the pathogenesis of human colorectal neoplasia, perhaps through alteration of the normal cell-cell interactions controlling growth.