Antihyperglycemic effect of iridoid glucoside, isolated from the leaves of Vitex negundo in streptozotocin-induced diabetic rats with special reference to glycoprotein components

The aim of present study was to isolate an iridoid glucoside from the leaves of Vitex negundo and evaluates its effects on dearrangement in plasma and tissues glycoprotein components in streptozotocin-induced diabetic rats. The levels of blood glucose, plasma and tissues glycoproteins such as hexose, hexosamine, fucose and sialic acid were significantly increased whereas plasma insulin levels were significantly decreased in diabetic rats. On oral administration of iridoid glucoside at a concentration of 50 mg/kg b.w. once daily to diabetic rats for the period of 30 days, reversed the above-mentioned hyperglycemia-induced biochemical changes to near normal levels. The anti-hyperglycemic effect of iridoid glucoside was comparable with glibenclamide, a known hypoglycemic drug. Based on the results obtained from the present study, it may be concluded that iridoid glucoside possesses significant productive effect on glycoprotein metabolism in addition to its antidiabetic effect.     

Extracellular leucine-rich repeat proteins are required to organize the apical extracellular matrix and maintain epithelial junction integrity in C. elegans

Epithelial cells are linked by apicolateral junctions that are essential for tissue integrity. Epithelial cells also secrete a specialized apical extracellular matrix (ECM) that serves as a protective barrier. Some components of the apical ECM, such as mucins, can influence epithelial junction remodeling and disassembly during epithelial-to-mesenchymal transition (EMT). However, the molecular composition and biological roles of the apical ECM are not well understood. We identified a set of extracellular leucine-rich repeat only (eLRRon) proteins in C. elegans (LET-4 and EGG-6) that are expressed on the apical surfaces of epidermal cells and some tubular epithelia, including the excretory duct and pore. A previously characterized paralog, SYM-1, is also expressed in epidermal cells and secreted into the apical ECM. Related mammalian eLRRon proteins, such as decorin or LRRTM1-3, influence stromal ECM or synaptic junction organization, respectively. Mutants lacking one or more of the C. elegans epithelial eLRRon proteins show multiple defects in apical ECM organization, consistent with these proteins contributing to the embryonic sheath and cuticular ECM. Furthermore, epithelial junctions initially form in the correct locations, but then rupture at the time of cuticle secretion and remodeling of cell-matrix interactions. This work identifies epithelial eLRRon proteins as important components and organizers of the pre-cuticular and cuticular apical ECM, and adds to the small but growing body of evidence linking the apical ECM to epithelial junction stability. We propose that eLRRon-dependent apical ECM organization contributes to cell-cell adhesion and may modulate epithelial junction dynamics in both normal and disease situations.     

Dry film refractive index as an important parameter for ultra-low fouling surface coatings

Here we demonstrate that the film refractive index (RI) can be an even more important parameter than film thickness for identifying nonfouling polymer films to undiluted human blood plasma and serum. The film thickness and RI are two parameters obtained from ellipsometry. Previously, film thickness has been correlated to ultra-low fouling properties. Practically, the film RI can be used to characterize polymer density but is often overlooked. By varying the water content in the surface-initiated atom transfer radical polymerization of zwitterionic carboxybetaine, a minimum of ～1.5 RI units was necessary to achieve <5 ng/cm(2) of adsorption from undiluted human serum. A model of the film structure versus water content was also developed. These results point to an important parameter and simple approach for identifying surface coatings suitable for real-world applications involving complex media. Therefore, ultra-low fouling using a thin film is possible if it is densely packed.     

Identification and characterization of rabbit small intestinal villus cell brush border membrane Na-glutamine cotransporter

Glutamine, the primary metabolic fuel for the mammalian small intestinal enterocytes, is primarily assimilated by Na-amino acid cotransporters. Although Na-solute cotransport has been shown to exist in the brush border membrane (BBM) of the absorptive villus cells, the identity of Na-glutamine cotransport in rabbit small intestinal villus cells was unknown. Na-dependent glutamine uptake is present in villus BBM vesicles. An intravesicular proton gradient did not stimulate this Na-dependent glutamine uptake, whereas Li+ did not significantly suppress this uptake. These observations in concert with amino acid substitution studies suggested that Na-glutamine cotransporter in the villus cell BBM was the newly identified cotransporter B0AT1 (SLC6A19). Quantitative real-time PCR identified the message for this cotransporter in villus cells. Thus a full-length cDNA of B0AT1 was cloned and expressed in MDA-MB-231 cells. This expressed cotransporter exhibited characteristics similar to those observed in villus cells from the rabbit small intestine. Antibody was generated for B0AT1 that demonstrated the presence of this cotransporter protein in the villus cell BBM. Kinetic studies defined the kinetic parameters of this cotransporter. Thus this study describes the identification, cloning, and characterization of the Na-amino acid cotransporter responsible for the assimilation of a critical amino acid by the absorptive villus cells in the mammalian small intestine.     

Antiproliferative potential of gallic acid against diethylnitrosamine-induced rat hepatocellular carcinoma

One of the focuses in current cancer chemoprevention studies is the search for nontoxic chemopreventive agents that inhibit the initiation of malignant transformation. Cancer biomarkers are quantifiable molecules involved in the physiologic or pathologic events occurring between exposure to carcinogens and the development, progression of cancer. Biomarkers may be the consequence of a continuous process, such as increased cell mass, or a discrete event, such as genetic mutation. Analysis of tumor markers can be used as an indicator of tumor response to therapy. Gallic acid is a naturally available polyphenol, possess strong antioxidant activity with a capacity to inhibit the formation of tumors in several cancer models. In the present study, we investigated the antiproliferative effect of gallic acid during diethylnitrosamine (DEN)-induced hepatocellular carcinoma (HCC) in male wistar albino rats. DEN treatment resulted in increased levels of aspartate transaminase, alanine transaminase, alkaline phosphatase, acid phosphatase, lactate dehydrogenase, gamma-glutamyltransferase, 5'-nucleotidase, bilirubin, alpha-fetoprotein, carcinoembryonic antigen, argyophillic nucleolar organizing regions, and proliferating cell nuclear antigen. Gallic acid treatment significantly attenuated these alterations and decreased the levels of AgNORs and PCNA. These finding suggests that gallic acid is a potent antiproliferative agent against DEN-induced HCC.     

Structural and immunogenicity analysis of chimeric B-cell epitope constructs derived from the gp46 and gp21 subunits of the envelope glycoproteins of HTLV-1.

B-cell epitopes were selected from the gp21 and gp46 subunits of the envelope glycoprotein of human T-cell lymphotropic virus type 1 (HTLV-1) by computer-aided analyses of protein antigenicity. Molecular modeling was used to design and synthesize the epitopes as chimeric constructs with promiscuous T-helper epitopes derived either from the tetanus toxoid (amino acids 947-967) or measles virus fusion protein (amino acids 288-302). Circular dichroism measurements revealed that the peptides had a secondary structure that correlated well with the crystal structure data or predicted structure. The chimeric peptides were then evaluated for their immunogenicity in rabbits or mice. Antibodies against one of the epitopes derived from the gp21 subunit were found to be neutralizing in its ability to inhibit the formation of virus-induced syncytia. These studies underscore the importance of the gp21 transmembrane region for the development of vaccine candidates. The applicability of a chimeric approach is discussed in the context of recent findings regarding the role of gp21 transmembrane region in the viral fusion process.     

Hydrophobic substitutions in the first residue of the CRAC segment of the gp41 protein of HIV

We investigated the peptides N-acetyl-AWYIK-amide and N-acetyl-VWYIK-amide corresponding to single amino acid substitutions in LWYIK, a segment found in the gp41 protein of HIV and believed to play a role in sequestering this protein to a cholesterol-rich domain in the membrane. The effects of these peptides on the thermotropic phase transitions of 1-stearoyl-2-oleoylphosphatidylcholine (SOPC) and mixtures of SOPC and cholesterol were intermediate between that having the wild-type sequence (LWYIK) and another (IWYIK), the least active peptide previously studied. This correlated with results from studies of single mutations in the gp41 protein of HIV-1, in which L679 of the LWYIK segment is replaced with either A or V, measuring the capability of TZM-BL HeLa-based HIV-1 indicator cells to form syncytia. The peptides were also comparatively analyzed in silico. All together, the results suggest that the mode of interaction of this region of gp41 with the polar heads of membrane lipids contributes to its cholesterol selectivity and that this is somehow related to the biological activity of the viral glycoprotein.