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Despite the importance of peroxisomal oxidation in branched-chain lipid (phytol, cholesterol) detoxification, little is known regarding the factors regulating the peroxisomal uptake, targeting, and metabolism of these lipids. Although in vitro data suggest that sterol carrier protein (SCP)-x plays an important role in branched-chain lipid oxidation, the full physiological significance of this peroxisomal enzyme is not completely clear. To begin to resolve this issue, SCP-x-null mice were generated by gene ablation of SCP-x from the SCP-x/SCP-2 gene and fed a phytol-enriched diet to characterize the effects of lipid overload in a system with minimal 2/3-oxoacyl-CoA thiolytic activity. It was shown that SCP-x gene ablation 1) did not result in reduced expression of SCP-2 (previously thought to be derived in considerable part by posttranslational cleavage of SCP-x); 2) increased expression levels of key enzymes involved in [alpha]- and [beta]-oxidation; and 3) altered lipid distributions, leading to decreased hepatic fatty acid and triglyceride levels. In response to dietary phytol, lack of SCP-x resulted in 1) accumulation of phytol metabolites despite substantial upregulation of hepatic peroxisomal and mitochondrial enzymes; 2) reduced body weight gain and fat tissue mass; and 3) hepatic enlargement, increased mottling, and necrosis. In summary, the present work with SCP-x gene-ablated mice demonstrates, for the first time, a direct physiological relationship between lack of SCP-x and decreased ability to metabolize branched-chain lipids. sterol carrier protein x; gene targeting; sterol carrier protein 2; liver fatty acid binding protein; phytanic acid

The possibility that sterol carrier protein-2 (SCP-2) might interact with caveolin-1 and caveolae was studied since SCP-2 binds both cholesterol and phosphatidylinositol. It was shown for the first time that SCP-2 selectively interacted with caveolin-1, both within the cytoplasm and at the plasma membrane and thus the study contribute to the understanding of the role SCP-2 in cholesterol and phosphatidylinositol targeted from intracellular sites of synthesis in the endoplasmic reticulum to caveolae/lipid rafts at the cell surface plasma membrane.

Research has been conducted on the N-terminal membrane binding domain of sterol carrier protein-2. Results indicate that though this domain is inactive in mediating intermembrane sterol transfer it can enhance this transfer.

Interaction of the rotavirus enterotoxin NSP4 with membrane reveals that it undergoes secondary structural changes influenced by the lipid composition of the memebrane vesicles. Data show that NSP4 preferentially binds to highly curved, small unilamellar membrane vesicles composed of negatively charged phospholipids.

SYNOPSIS Objectives. The Minnesota Department of Health surveyed registered mammography facilities to assess their accreditation status prior to full implementation of the Federal Mammography Quality Standards Act (MQSA), which mandated […]

Abstract Background Rotavirus NSP4 localizes to multiple intracellular sites and is multifunctional, contributing to RV morphogenesis, replication and pathogenesis. One function of NSP4 is the induction of early secretory diarrhea by binding surface receptors to initiate signaling events. The aims of this study were to determine the transport kinetics of NSP4 to the exofacial plasma membrane (PM), the subsequent release from intact infected cells, and rebinding to naïve and/or neighboring cells in two cell types. Methods Transport kinetics was evaluated using surface-specific biotinylation/streptavidin pull-downs and exofacial exposure of NSP4 was confirmed by antibody binding to intact cells, and fluorescent resonant energy transfer. Transfected cells similarly were monitored to discern NSP4 movement in the absence of infection or other viral proteins. Endoglycosidase H digestions, preparation of CY3- or CY5- labeled F(ab)2 fragments, confocal imaging, and determination of preferential polarized transport employed standard laboratory techniques. Mock-infected, mock-biotinylated and non-specific antibodies served as controls. Results Only full-length (FL), endoglycosidase-sensitive NSP4 was detected on the exofacial surface of two cell types, whereas the corresponding cell lysates showed multiple glycosylated forms. The C-terminus of FL NSP4 was detected on exofacial-membrane surfaces at different times in different cell types prior to its release into culture media. Transport to the PM was rapid and distinct yet FL NSP4 was secreted from both cell types at a time similar to the release of virus. NSP4-containing, clarified media from both cells bound surface molecules of naïve cells, and imaging showed secreted NSP4 from one or more infected cells bound neighboring cell membranes in culture. Preferential sorting to apical or basolateral membranes also was distinct in different polarized cells. Conclusions The intracellular transport of NSP4 to the PM, translocation across the PM, exposure of the C-terminus on the cell surface and subsequent secretion occurs via an unusual, complex and likely cell-dependent process. The exofacial exposure of the C-terminus poses several questions and suggests an atypical mechanism by which NSP4 traverses the PM and interacts with membrane lipids. Mechanistic details of the unconventional trafficking of NSP4, interactions with host-cell specific molecules and subsequent release require additional study.

Purpose: To evaluate the suitability of a novel epoxy-based resin, Filtek Silorane, for orthodontic bracket bonding on unprepared enamel. Materials and Methods: Shear forces to bovine enamel were measured for Filtek Silorane and Transbond XT in combination with steel, ceramic, and polymer brackets. For Filtek Silorane, etching was performed with the Silorane self-etching primer alone or an additional previous application of phosphoric acid. Transbond XT (conventional methacrylate) was used for the control group and the enamel was previously etched with 35% phosphoric acid. All samples were thermocycled (1000X, 5°to 55° C). Shear bond testing was done with an Instron 3344 at a crosshead speed of 1 mm/min. In addition, adhesive remnant index (ARI) scores were evaluated. Results: The shear forces showed a weak adhesion of Filtek Silorane to unprepared enamel both with the selfetching primer and conventional etching (0.87 to 4.28 MPa). The shear forces of the control group were significantly higher (7.6 to 16.5 MPa). The ARI scores showed a clear failure at the enamel/adhesive interface for all Filtek Silorane samples. For the combination of Transbond XT and different brackets, the failure was found at the adhesive/bracket interface. Conclusion: The novel epoxy-based resin Filtek Silorane is not appropriate for bonding of brackets to unprepared enamel. [ABSTRACT FROM AUTHOR]

Several studies are conducted to explain the structure, as well as the function of the sterol carrier protein-2 (SCP-2) and the 20-amino acid N-terminal presequence. The presequence is shown to be extremely significant in regulating the structure of the protein.

The various factors that contribute to regulation of cholesterol dynamics between plasma membrane lipid rafts/caveolae and serum lipoproteins/apoproteins are discussed.

The interaction between caveolin-1 and sterol carrier protein-2 (SCP-2) is examined by yeast two-hybrid, in vitro binding and fluorescence resonance energy transfer (FRET) analyses. The results have helped in understanding SCP-2's role in the enhancement of cholesterol retention within the cell as well as regulation of distribution of signaling lipids at plasma membrane caveolae.

MDCK cells are used to isolate four types of lipid domain fraction that include detergent-resistant membranes (DRM) obtained with Triton X-100, nondetergent caveolae/rafts (NDCR), nondetergent affinity-purified caveolae/rafts (ACR), and noncaveolae/nonrafts (NR). ACR exhibited the least cross contamination with other plasma membrane domains or intracellular membranes, in marked contrast to DRM that contained the highest level of cross contaminants.

Research demonstrates that the liver cytoplasmic sterol carrier protein-2 mediates phosphatidylinositol transfer, distribution, and intracellular signaling. Data indicate that recombinat sterol carrier protein-2 stimulates by 13-fold the transfer of phosphatidylinositol from microsomal membranes to caveolae acceptor membranes.

The Teaching Gap: Best Ideas from the World's Teachers for Improving Education in the Classroom, James W Stigler and James Hiebert, 1999. xiv + 210 pp., $23 cloth. ISBN 0-684-85274-8. [...]

Each set contains 8 different student books, 1 answer case, and 1 teacher's resource guide, $54.95 each. Level 1, ISBN 1-57162-337-X. Level 2, ISBN 1-57162-338-8. Level 3, ISBN 1-57162-339-6. Level [...]