Immunoelectron microscopic localization of laminin in rat ovarian follicles

We studied the immunohistochemical and ultrastructural distribution of laminin in ovaries of immature and mature rats. When sections from 1-8-week-old rat ovaries were labeled directly with conjugates of affinity purified anti-laminin IgG-horseradish peroxidase (HRP), the antibodies bound to all ovarian basement membranes including those surrounding follicles in different stages of maturation. In addition, intracellular labeling was seen in granulosa and theca cells of follicles undergoing rapid development (preantral and antral stages) and in basement membrane-like structures of the Call-Exner bodies. Intracellular laminin was generally not detected, however, in any cells of primordial or atretic follicles. Tissue processed for immunoelectron microscopy 1 hour after the intravenous injection of anti-laminin IgG-HRP showed binding of antibody in linear patterns along endothelial and follicular epithelial basement membranes. Discontinuous strands of laminin-positive, extracellular matrices were also seen between theca cells of all follicles. In addition, injected anti-laminin IgG labeled perisinusoidal basement membranes located within corpora luteae and patches of basement membrane material between granulosa lutein cells. When ovaries were examined 5 d after the intravenous injections of anti-laminin IgG-HRP, uneven or segmented labeling was found in subepithelial basement membranes surrounding developing follicles. Our results therefore indicate that granulosa and theca cells participate directly in basement membrane laminin biosynthesis and suggest that this new laminin is spliced into existing basement membranes during follicular growth.

Development of Dengue type-2 virus replicons expressing GFP reporter gene in study of viral RNA replication

Insertion of green fluorescent protein (GFP) encoding-gene into virus genes has provided a valuable tool for flavivirus research. This study aimed to develop dengue virus (DENV) replicons expressing GFP reporter that would provide a fast in vitro system to analyze functional roles of specific DENV sequences in viral replication. Two classes of recombinant replicon constructs were generated; one was a RNA-launched replicon with a GFP gene directly inserted into a full-length DENV genome (FL-DENV/GFP), and the other consisted of 4 types of DNA-launched DENV subgenomic replicons with GFP replacement at various structural genes (Δ-DENV/GFP). The FL-DENV/GFP resulted in GFP expression in transfected cells with no viable DENV being recovered from the transfection. The Δ-DENV/GFP constructs with partial structural gene deletion (ΔC-, ΔCprM/M-, ΔprM/M-, or ΔE-) expressed bright and long lasting GFP. The GFP expression intensity in living cells correlated well with the level of RNA replication. Various mutations in the 5'noncoding region of DENV-2 previously shown to be important genetic determinants for virus replication and mouse virulence were incorporated into the 5 different replicon constructs. Characterizations of 29 mutants demonstrated that these replicons can provide a useful platform for a quick and powerful in vitro system to analyze genetic determinants of DENV replication. These constructs can also be useful for development of vectors expressing foreign genes for various researches.

Establishment of a stable cell line coexpressing dengue virus-2 and green fluorescent protein for screening of antiviral compounds

This study aimed to generate a stable cell line harboring subgenomic dengue virus replicon and a green fluorescent gene (DENV/GFP) for a cell-based model to screen anti-DENV compounds. The gene-encoding envelope protein of DENV-2 was deleted and then replaced with fragments of the GFP gene and a foot-and-mouth-disease virus 2A-derived cleavage site. The human cytomegalovirus immediate early and antisense hepatitis delta virus ribozyme sequences were added at the 5'- and 3'-ends. An internal ribosome entry site and neomycin resistance genes were placed upstream and next to the NS1 gene. The recombinant plasmids were propagated in a mammalian cell line. A stable cell line with the brightest green fluorescent protein and the highest viral protein and RNA expression was selected from six clones. The clone was then examined for effectiveness in an antiviral drug screening assay with compounds isolated from the local plants using two known antiviral agents as controls. Two novel flavones, PMF and TMF, were discovered having DENV-inhibitory properties. The data were validated by a conventional plaque titration assay. The results indicate that this newly developed cell line is efficient for use as a cell-based model for primary screening of anti-DENV compounds.

Binding of intravenously injected antibodies against laminin to developing and mature endocrine glands

To determine whether circulating antibodies against laminin can bind in vivo to basement membranes within endocrine glands, affinity-purified sheep or rabbit anti-laminin IgG was intravenously injected into rats. One to five hours after injection, anti-laminin IgG was bound to all basement membranes of adrenal and anterior pituitary glands of mature as well as 2-day-old newborn rats as shown by immunofluorescence microscopy. After the injection of anti-laminin conjugated directly to horseradish peroxidase (HRP), HRP reaction product was also present throughout adrenal and pituitary basement membranes in mature and immature glands 1-5 h post-injection. Ultrathin Lowicryl sections from rats that received unconjugated rabbit anti-laminin IgG 1 h prior to fixation with paraformaldehyde were labeled directly with anti-rabbit IgG-colloidal gold. In these cases, gold also bound specifically over the lamina densa and lamina rara. When adrenal or pituitary glands from mature rats were examined by immunofluorescence 1 week after the injection of sheep anti-laminin IgG, the patterns and amounts of bound sheep IgG were indistinguishable from those observed 1 h after injection. In contrast, significantly less fluorescence was present in glands from 7-day-old rat pups that had received anti-laminin IgG 5 days earlier. In addition, when anti-laminin IgG-HRP was injected into newborns and glands were fixed 5 days later, lengths of labeled endothelial and epithelial basement membranes were often interspersed with unlabeled lengths in zones of cellular proliferation in the outer adrenal cortex and throughout the pituitary gland. These results indicated that unlabeled basement membranes in these regions were probably assembled after the injection of anti-laminin IgG, which would also explain diminished labeling of basement membranes in these animals. Despite the continued presence of heterologous anti-laminin IgG within endocrine basement membranes, however, rat IgG, rat C3, inflammatory cells, or histologic abnormalities were observed in neither newborn nor adult glands under the conditions examined here. Sections from rats injected with control IgG or control IgG-HRP were entirely negative by immunofluorescence, immunoperoxidase, and immunogold techniques. We therefore conclude that (1) apparently large amounts of circulating anti-laminin IgG can bind to adrenal and pituitary basement membranes, and (2) at least some of these basement membranes are assembled during development by progressive splicing of newly synthesized matrix into that already present.

Characterization of recombinant dengue-2 virus derived from a single nucleotide substitution in the 5' noncoding region

Variants of wild-type dengue serotype 2 (DEN-2) virus containing nucleotide substitutions at positions 14, 15, or 57 in the 5' NCR were constructed by PCR-mediated site-directed mutagenesis. All three viruses containing a single point substitution demonstrated attenuation phenotype as evidenced by decreases replication and plaque size in cell culture assay. All three variants were less neurovirulent in newborn mice compared to the wild type. The mutants were immunogenic in adult mice immunogenicity and maintained stable replication characteristics following passage in mice. The variant viruses were competent for replication in Aedes aegypi mosquito vector, albeit at lower levels of infection and dissemination in the mosquito than the wild-type Den-2 16681 virus. Although all of the viruses, including the wild type, were found transmissible in mosquito life cycles, they were found subsequentially decreased in efficiency of infection, transmission, and dissemination rates along the mosquito generations and all of them remained genetically stable.

Gonadectomy induces laminin biosynthesis and basement membrane assembly in anterior pituitary glands of adult rats

Laminin biosynthesis and basement membrane assembly in anterior pituitary glands of gonadectomized rats were studied by immuno-electron microscopy and radioimmunoassay. Three weeks after gonadectomy, rats received intravenous injections of sheep anti-laminin IgG conjugated to horseradish peroxidase, and glands were fixed and processed for microscopy 1 h later. Peroxidase reaction product uniformly labeled all perivascular and glandular epithelial basement membranes. In addition, reaction product was also found in abnormally multi-layered basement membranes seen especially beneath gonadotrophs, and unusual basement membrane-like structures projecting between gonadotrophs were also labeled. Pituitary sections from gonadectomized rats labeled with pre-embedding immunoperoxidase and post-embedding immunogold techniques also localized intracellular laminin within biosynthetic organelles and "light body" vesicles of gonadotrophs. Neither abnormal basement membrane structures nor intracellular laminin were detected in pituitaries of nongonadectomized, control rats. Radioimmunoassays of pituitary homogenates showed nearly twice as much soluble laminin (approximately 15 ng/gland) in gonadectomized rats than in controls (approximately 8 ng/gland), which paralleled gland growth, but serum laminin concentrations did not differ (approximately 10 ng/ml in both groups). When anterior pituitary glands of gonadectomized rats that received injections of anti-laminin IgG-HRP were fixed 5 days after injection, lengths of unlabeled basement membrane were distributed between labeled lengths. This indicated that new basement membrane was "spliced" into old by a process similar to that seen in normal development. Supplementation of gonadectomized rats with testosterone, however, arrested laminin biosynthesis and basement membrane assembly and reversed glandular hypertrophy. These results indicate that, in an absence of sex hormone feedback, renewed synthesis of basement membrane components occurs in the anterior pituitary and is probably necessary to support the additional growth and differentiation of gonadotrophs and other pituitary cells.

Pharmacological activity of Kaempferia parviflora extract against human bile duct cancer cell lines

A crude ethanol extract of Kaemperia parviflora Wall. Ex Baker and a purified compound, 5,7,4-trimethoxyflavone (KP.8.10), were evaluated for pharmacological effects on human cholangiocarcinoma cell lines (HuCCA-1 and RMCCA-1). The cells were incubated with various concentrations of extract for various time periods and metabolic activity (MTT assay) was assessed for cell viability. The results showed a dose-dependent effect of both crude ethanol extract and the pure compound. CC50s for the crude extract on HuCCA-1 and RMCCA-1 cells were 46.1 microg/ml and 62.0 microg/ml, respectively. Values for the pure compound could not be determined because of solubility problems. Interestingly, K. parviflora ethanol extract and KP.8.10 at low concentrations (10-20 microg/ml and 2.5-5 microg/ml, respectively) markedly reduced rhHGF-induced invasion by HuCCA-1 and RMCCA-1 cells across matrix-coated transwell plates. Higher concentrations of K. parviflora ethanol extract (60 and 80 microg/ml) and KP.8.10 (20 microg /ml) dramatically changed the cellular morphology and caused death in both cell types. KP.8.10 further exhibited progressive action via caspase-3 mitochondrial enzyme activation, enhancing cellular toxicity in a time-dose dependent fashion. Therefore, 5,7,4-trimethoxyflavone appeared to be a bioactive component of K. parviflora extract capable of exerting anti-cancer action. The results suggested a benefit of this edible plant in prevention and treatment of cholangiocarcinoma.

Loss and rearrangement of glomerular basement membrane laminin during acute nephrotoxic nephritis in the rat

Many earlier studies have shown that the intravenous injection into rats of sheep antibodies against rat glomerular basement membrane (GBM) induces a rapid influx of neutrophils and proteinuria (nephrotoxic nephritis or NTN). The GBM antigens recognized by nephrotoxic antibodies (NTAbs) have not been identified conclusively. Our experiments presented here, however, showed that NTAbs did not significantly reduce binding of anti-laminin IgGs to laminin-coated enzyme-linked immunosorbent assay (ELISA) plates or to the GBM in vivo, indicating little cross-reactivity between the NTAbs and laminin. To evaluate possible changes in GBM architecture during acute stages of NTN, the ultrastructural distribution of laminin was determined by postfixation, postembedding immunogold labeling, and compared between normal and nephritic rats. The density of immunoreactive GBM laminin was significantly reduced in rats with acute NTN. In addition, conjugates of anti-laminin IgG and horseradish peroxidase were intravenously injected into rats that then received injections of NTAbs. Anti-laminin peroxidase conjugates were also injected after administering NTAbs. In both cases, an overall decrease in anti-laminin peroxidase reaction product was observed as compared to normal controls. The densest labeling was seen in the lamina rara interna, especially in areas of endothelial cell detachment. Some immunoperoxidase reaction product was also bound to basal surfaces of detaching endothelial cells, demonstrating the removal of at least some laminin from the GBM. A decrease in GBM binding of intravenously injected anti-laminin IgG, both before and after injection of rats with NTAbs, was also confirmed by postembedding immunogold labeling. Furthermore, morphometry showed that the GBM was significantly wider in nephritic rats than in controls, indicating a redistribution of laminin over a greatly increased area. These immunoultrastructural findings show, therefore, that GBM architecture is altered in the early phase of NTN.