Phytotoxicity and cytotoxicity of the fumonisin C and P series of mycotoxins from Fusarium spp. fungi

Fumonisin C (FC) and P (FP) are two recently identified series of sphingosine-analog mycotoxins, for which biological activities have not previously been reported. FC1, FC2 and OH-FC1 (1 microM) exhibited strong phytotoxicity comparable to the standard FB1 in duckweed (Lemna pausicotata L.) cultures, whereas FC3 and FC4 were moderately phytotoxic. Conversely, FP1 exhibited weak phytotoxicity only at higher concentrations (> or =10 microM). These mycotoxins exhibited a similar pattern of cytotoxicity with FB1-sensitive cultured mammalian cell lines, H4TG and MDCK.     

Subunit composition and oligomer stability of oat beta-glucosidase isozymes

Oat beta-glucosidase (EC 3.2.1.21) has two isomeric forms, type I and type II, which are composed of 60 kDa peptides. To study the subunit composition and the stability of multimeric structure, the type I and II were purified from the primary leaves and coleoptiles of the etiolated oat seedlings where the isozymes are expressed organ-specifically. The monomers of the isozymes were isolated by urea-denatured gel electrophoresis followed by electroblotting. N-Terminal amino acid sequencing of the monomers indicated that the type I consisted of a peptide of ALESAKQVKPWQVPKRDWFP (As-Glu 1), and the type II having a peptide of ALESGKLKPWQIPKRDWFP (As-Glu 2) and As-Glu 1 in 1:1 ratio. The C-terminal amino acid of the As-Glu 1 was alanine and that of the As-Glu 2 was lysine. The As-Glu 2 was more negatively charged than the As-Glu 1. The type I isozyme is thus homomultimer of As-Glu 1 monomer and the type II heteromultimer of As-Glu 1 and As-Glu 2 monomers in 1:1 ratio. Partial denaturation of the multimers with urea and CaCl2 broke down the higher multimers to the lower multimers, which were in turn dissociated into homodimers and heterodimer. Denaturation study with urea and CaCl2 indicate that the higher multimers of the homooligomeric type I were more stable than those of the heterooligomeric type II and that hydrophobic interactions were important in the multimer formation. The homodimers were found to be more stable than the heterodimer. These results indicate that different combinations of the As-Glu 1 and As-Glu 2 monomers form the two isozymes of oat beta-glucosidase with different enzymatic properties and structural stability.     

A flammability performance comparison between synthetic and natural clays in polystyrene nanocomposites

Polymer‐clay nanocomposites are a newer class of flame retardant materials of interest due to their balance of mechanical, thermal and flammability properties. Much more work has been done with natural clays than with synthetic clays for nanocomposite flammability applications. There are advantages and disadvantages to both natural and synthetic clay use in a nanocomposite, and some of these, both fundamental and practical, will be discussed in this paper. To compare natural and synthetic clays in regards to polymer flammability, two clays were used. The natural clay was a US mined and refined montmorillonite, while the synthetic clay was a fluorinated synthetic mica. These two clays were used as inorganic clays for control experiments in polystyrene, and then converted into an organoclay by ion exchange with an alkyl ammonium salt. The organoclays were used to synthesize polystyrene nanocomposites by melt compounding. Each of the formulations was analysed by X‐ray diffraction (XRD), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). Flammability performance was measured by cone calorimeter. The data from the experiments show that the synthetic clay does slightly better at reducing the heat release rate (HRR) than the natural clay. However, all the samples, including the inorganic clay polystyrene microcomposites, showed a decreased time to ignition, with the actual nanocomposites showing the most marked decrease. The reason for this is postulated to be related to the thermal instability of the organoclay (via the quaternary alkyl ammonium). An additional experiment using a more thermally stable organoclay showed a time to ignition identical to that of the base polymer. Finally, it was shown that while polymer‐clay nanocomposites (either synthetic or natural clay based) greatly reduce the HRR of a material, making it more fire safe, they do not provide ignition resistance by themselves, at least, at practical loadings. Specifically, the cone calorimeter HRR curve data appear to support that these nanocomposites continue to burn once ignited, rather than self‐extinguish. Copyright © 2004 John Wiley & Sons, Ltd.     

Targeted disruption of the ubiquitous CNC-bZIP transcription factor, Nrf-1, results in anemia and embryonic lethality in mice

The CNC-basic leucine zipper (CNC-bZIP) family is a subfamily of bZIP proteins identified from independent searches for factors that bind the AP-1-like cis-elements in the beta-globin locus control region. Three members, p45-Nf-e2, Nrf-1 and Nrf-2 have been identified in mammals. Expression of p45-Nf-e2 is largely restricted to hematopoietic cells while Nrf-1 and Nrf-2 are expressed in a wide range of tissues. To determine the function of Nrf-1, targeted disruption of the Nrf-1 gene was carried out. Homozygous Nrf-1 mutant mice are anemic due to a non-cell autonomous defect in definitive erythropoiesis and die in utero.     

Expression of killer cell inhibitory receptors on human uterine natural killer cells

The establishment of the human placenta in early pregnancy is characterized by the presence of large numbers of natural killer (NK) cells within the maternal decidua in close proximity to the fetally-derived invading extravillous trophoblast which expresses at least two HLA class I molecules, HLA-G and HLA-C. These NK cells have an unusual phenotype, CD56(bright) CD16, distinguishing them from adult peripheral blood NK cells. They may control key events in trophoblast migration and therefore placentation. Human NK cells in peripheral blood express receptors for polymorphic HLA class I molecules. This family of receptors, known as killer cell inhibitory receptors (KIR), are expressed on overlapping subsets of NK cells to give an NK cell repertoire which differs between individuals. Using a panel of monoclonal antibodies to several members of the KIR family and analysis by flow cytometry, we have found that KIR are expressed by decidual NK cells. There is variation in both the percentage of cells expressing a particular receptor and the density of receptor expression between decidual NK cells from different individuals. Comparison of NK cells from decidua and peripheral blood of the same individual showed that NK cells from these two different locations express different repertoires of KIR. Receptors are present in individuals who do not possess the relevant class I ligand, raising the possibility that these NK receptors may be involved in recognition of the allogeneic fetus by the mother at the implantation site.     

How sexually permissive are Singaporeans?

This paper presents data on two surveys done in 1989 and 1992 that indicated the attitudes of Singaporeans to sexuality. Both surveys revealed that Singaporeans have sexually conservative attitudes and those who have a lower education, are single, above the age of 40, are Malays/Muslims hold more conservative views.     

Characterization of heterologously expressed recombinant retinoic acid receptors with natural or synthetic retinoids

The first step in retinoid action is binding to their nuclear receptors. Therefore, characterization of binding characteristics of retinoids is of major importance. Human retinoic acid receptors alpha (hRAR alpha), hRAR beta, and mouse RAR gamma (mRAR gamma) were expressed heterologously in Escherichia coli as a recombinant glutathione S-transferase (GST) fusion protein. The expressed fusion proteins were functional and bound specifically to the all-trans-retinoic acid (RA). The dissociation constants (Kd) for RA were 1.4 nM for GST-hRAR alpha, 1.4 nM for GST-hRAR beta, and 3.3 nM for GST-mRAR gamma, respectively. The fusion proteins were further used for competitive displacement assays to determine the displacement constant (DC50) for other selected retinoids. All-trans-RA and 4-oxo-all-trans-RA have high affinity with all three receptors (DC50 = 0.8-55 nM). The 13-cis RA binds to hRAR alpha with low affinity, but not to other RARs evaluated here. All-trans-N-ethylretinamide, all-trans-retinylacetate, and an ethyl ester of tetrahydronaphthalene derivative had no affinity to any RARs. The hRAR alpha and mRAR gamma receptors did not bind a naphthalene carboxylic acid derivative of RA, but hRAR beta binds this chemical with high affinity. Results indicated that the three recombinant proteins were functional in binding various RA congeners. The affinity and binding data of these retinoids were compared to their observed teratogenic activity.     

An application of hierarchical linear models to meta-analysis in nursing research

OBJECTIVES: To compare the effect of using regions of interest (ROIs) of different size and shape on the fractal index of alveolar bone. STUDY DESIGN: Two sets of clinical posterior bitewing radiographs were used to calculate the fractal index (S). Two comparisons were made. First, S was calculated from large interdental ROIs that included small amounts of root structure and compared with S from small ROIs that included no root structures. Then S was calculated from large interdental ROIs (similar to those used for the first set) and compared with S calculated from ROIs that included nearly all of the mandibular alveolar bone (and adjacent root) present on the bitewing. RESULTS: For the first comparison, paired t-tests showed that fractal indices calculated with the large ROIs were significantly different from the respective indices calculated from the small ROIs (P < 0.001). For the second comparison, the fractal indices calculated from the large quadrant ROIs were not significantly different from those calculated from the large ROIs (P = 0.120). CONCLUSION: ROI size and shape may affect the results of fractal analysis of alveolar bone.