Mechanisms of anti-atherosclerotic functions of soy-based diets

Soy-based diets have been reported to protect against the development of atherosclerosis. However, the underlying mechanism(s) for this protection remains unknown. Although atherosclerosis was traditionally considered a disease associated with impaired lipid metabolism, in recent years the inflammatory components of atherosclerosis have been explored. Recent studies have convincingly delineated that uncontrolled chronic inflammation is the principal contributing factor for the initiation and progression of atherosclerosis. Interaction between activated monocytes and vascular endothelial cells is an early event in atherogenesis. The adhesion of leukocytes, including monocytes, to the inflamed-vascular endothelium and their transmigration into intima initiate the inflammatory processes. Following transmigration, monocytes in the intima are transformed to macrophages, which take up oxidized-LDL (oxLDL) to generate lipid-laden macrophages, also known as foam cells. Hence, in this review article the inflammatory processes associated with atherosclerosis and possible anti-inflammatory functions of soy-based diets contributing to the prevention of atherosclerosis are presented.     

Production of insulin-like growth factor-II (MSA) by endoderm-like cells derived from embryonal carcinoma cells: possible mediator of embryonic cell growth

The present study was carried out to determine if an insulin-like growth factor (IGF) type activity might be produced by embryonal carcinoma-derived cells. The cell line used to condition growth medium for the isolation of secreted growth factors was a newly established Dif 5 cell type. Dif 5 cells are a differentiated endoderm-like cell type derived from F9 embryonal carcinoma cells (which possess properties similar to mouse embryonic stem cells) following extensive exposure to retinoic acid. When growth medium conditioned by Dif 5 cells is chromatographed on Sephadex G-75 in 1 M acetic acid two peaks of activity are observed which compete for specific [125I]iodo multiplication stimulating activity (MSA) binding to PYS cells. MSA is the rat homologue of human IGF-II. The high molecular weight fraction (Mr approximately 60K) apparently corresponds to IGF-binding protein as determined by its ability to bind [125I]iodo-MSA. The low molecular weight fraction (Mr approximately 8K) is biologically active as this fraction stimulates [3H]thymidine incorporation into serum-starved chick embryo fibroblasts. Radioimmunoassay data indicate that the IGF-like activity produced by Dif 5 cells is more closely related to IGF-II than to IGF-I. Undifferentiated embryonal carcinoma stem cell lines (F9, Nulli, and PCC4) produced little of this MSA-like activity, while PYS-2 (parietal endoderm-like) cells produced about 16 ng MSA/10(6) cells/24 hr as determined by radioimmunoassay. Dif 5 and PSA-5E (visceral endoderm-like) cells, are found to secrete significant amounts of MSA into the growth medium (30-50 ng MSA/10(6) cells/24 hr). These findings offer further support to a proposal that MSA (IGF-II) produced by endoderm cells, particularly visceral endoderm, may serve as an early embryonic growth factor.     

Waterbirds and substrate quality of the Pichavaram wetlands,southern India

The water and mud characteristics of the six types of wetlands in Pichavaram were compared in order to determine whether the habitat of waterbird species was characterized by them. Waterbird species richness was most influenced by mud phosphorus levels. Variation in water pH was the principal factor that determined waterbird diversity. The water level mainly determined the density of waterbirds. Levels of pH and nitrites in the water also appeared to influence significant variations in waterbird diversity and density, respectively. Bottom substrate variables, viz. pH and phosphorus levels, were also significantly correlated with the density and richness of waterbirds, respectively. Water quality factors, viz. pH and nitrite and mud pH and phosphorus, were correlated with the abundance, while water depth was correlated with the accessibility of prey to the birds.     

Chloramphenicol acetyltransferase, a cytoplasmic protein is incompatible for export from Bacillus subtilis.

Bacillus subtilis cells expressing a hybrid protein (Lvsss-Cat) consisting of the B. amyloliquefaciens levansucrase signal peptide fused to B. pumilus chloramphenicol acetyltransferase (Cat) are unable to export Cat protein into the growth medium. A series of tripartite protein fusions was constructed by inserting various lengths of the Cat sequences between the levansucrase signal peptide and staphylococcal protein A or Escherichia coli alkaline phosphatase. Biochemical characterization of the various Cat protein fusions revealed that multiple regions in the Cat protein were causing the export defect.     

Urease catalysis and structure: X. Alternate bonding-site isozymes of jackbean urease

Three previously uncharacterized, nongenetic urease isozymes have been analyzed by sucrose density gradient sedimentation, gel electrophoresis, and chemical reactivity. The full complement of isozymes could be reliably generated by choosing appropriate levels of NaCl, pH, and ethylene glycol, and was stable for several days in dilute solution. The three forms of interest were found to be quaternary isomers of other isozymes, but differed from them qualitatively in their bonding sites, with disulfide bonds being substituted for noncovalent bonds. The separation of these isomer-pairs during sedimentation and electrophoresis cannot be readily explained by differences in size or charge, but must rather arise from a difference in shape. A simple two-dimensional model can provide the appropriate molecular architecture to satisfy these requirements: Only one of the two half-units in each α-urease molecule undergoes disulfide bonding during polymerization, and it does so with two adjacent molecules, thus producing asymmetric polymers from symmetric starting components.     

The açaí flavonoid velutin is a potent anti-inflammatory agent: blockade of LPS-mediated TNF-α and IL-6 production through inhibiting NF-κB activation and MAPK pathway

Recent studies have shown that some flavonoids are modulators of proinflammatory cytokine production. In this study, velutin, a unique flavone isolated from the pulp of açaí fruit (Euterpe oleracea Mart.), was examined for its effects in reducing lipopolysaccharide-induced proinflammatory cytokine tumor necrosis factor (TNF)-α and interleukin (IL)-6 production in RAW 264.7 peripheral macrophages and mice peritoneal macrophages. Three other structurally similar and well-studied flavones, luteolin, apigenin and chrysoeriol, were included as controls and for comparative purposes. Velutin exhibited the greatest potency among all flavones in reducing TNF-α and IL-6 production. Velutin also showed the strongest inhibitory effect in nuclear factor (NF)-κB activation (as assessed by secreted alkaline phosphatase reporter assay) and exhibited the greatest effects in blocking the degradation of inhibitor of NF-κB as well as in inhibiting mitogen-activated protein kinase p38 and JNK phosphorylation; all of these are important signaling pathways involved in production of TNF-α and IL-6. The present study led to the discovery of a strong anti-inflammatory flavone, velutin. This compound effectively inhibited the expression of proinflammatory cytokines TNF-α and IL-6 in low micromole levels by inhibiting NF-κB activation and p38 and JNK phosphorylation.     

Utilization of a receptor reserve for effective amplification of mitogenic signaling by an epidermal growth factor mutant deficient in receptor activation

The idea of a receptor reserve in mediating cellular function is well known but direct biochemical evidence has not been easy to obtain. This study stems from our results showing that L15 of epidermal growth factor (EGF) is important in both EGF receptor (EGFR) binding and activation, and the L15A analog of human EGF (hEGF) partially uncouples EGFR binding from EGFR activation (Nandagopal et al., [1996] Protein Engng 9:781-788). We address the cellular mechanism of mitogenic signal amplification by EGFR tyrosine kinase in response to L15A hEGF. L15A is partially impaired in receptor dimerization, shown by chemical cross-linking and allosteric activation of EGFR in a substrate phosphorylation assay. Immunoprecipitation experiments reveal, however, that L15A can induce EGFR autophosphorylation in intact murine keratinocytes by utilizing spare receptors, the ratio of total phosphotyrosine content per receptor being significantly lower than that elicited by wild-type. This direct biochemical evidence, based on function, of utilization of a receptor reserve for kinase stimulation suggests that an EGF variant can activate varying receptor numbers to generate the same effective response. L15A-activated receptors can stimulate mitogen-activated protein kinase (MAPK) that is important for mitogenesis. The lack of linear correlation between levels of receptor dimerization, autophosphorylation, and MAPK activation suggests that signal amplification is mediated by cooperative effects. Flow cytometric analyses show that the percentages of cells which proliferate in response to 1 nM L15A and their rate of entry into S-phase are both decreased relative to 1 nM wild-type, indicating that MAPK activation alone is insufficient for maximal stimulation of mitogenesis. Higher concentrations of L15A reverse this effect, indicating that L15A and wild-type differ in the number of receptors each activates to induce the threshold response, which may be attained by cooperative activation of receptor dimers/oligomers by van der Waal's weak forces of attraction. The maintenance of a receptor reserve underscores an effective strategy in cell survival.