油菜甾醇内酯类化合物结构与活性的相关性

比较了19种油菜甾醇内酯类似物和有关甾体化合物在水稻叶片倾斜及萝卜幼苗生长试验中的生物活性。表油菜甾醇内酯(24—Epi—BR)在两个系统中都具有很强的生物活性。C_2位失去羟基(香蒲甾醇)仅在水稻试验中有高活性,改变C_22位侧链结构(2α,3α双羟基—6—酮—23,24—双失碳—β—高-5α—胆烷酸甲酯)在萝卜试验中仍有活性。     

The role of transforming growth factor (TGF)-β in modulating the immune response and fibrogenesis in the gut

Transforming growth factor (TGF)-β, a pleiotropic cytokine released by both immune and non-immune cells in the gut, exerts an important tolerogenic action by promoting regulatory T cell differentiation. TGF-β also enhances enterocyte migration and regulates extracellular matrix turnover, thereby playing a crucial role in tissue remodeling in the gut. In this review we describe the mechanisms by which abnormal TGF-β signaling impairs intestinal immune tolerance and tissue repair, thus predisposing to the onset of immune-mediated bowel disorders, such as inflammatory bowel disease and celiac disease. Additionally, we will discuss potential therapeutic strategies aiming at restoring physiologic TGF-β signaling in chronic intestinal diseases.     

Pentagalloylglucose down-regulates mast cell surface FcεRI expression in vitro and in vivo

Mast cell activation by immunoglobulin E (IgE)-mediated stimuli is a central event in the pathogenesis of allergic disorders. The present report shows that treatment with pentagalloylglucose (PGG) resulted in a down-regulation of FcεRI surface expression on mucosal-type murine bone marrow-derived mast cells (mBMMCs), which correlated with a reduction in IgE-mediated activation of mBMMCs. Furthermore, PGG prevented development of allergic diarrhea in a food-allergy mouse model and suppressed the up-regulated FcεRI surface expression on mast cells derived from the food-allergy mouse colon. These findings on PGG suggest its therapeutic potential for allergic diseases through suppressing the FcεRI surface expression.     

Concentration-dependent Effects of Nuclear Lamins on Nuclear Size in Xenopus and Mammalian Cells

A fundamental question in cell biology concerns the regulation of organelle size. While nuclear size is exquisitely controlled in different cell types, inappropriate nuclear enlargement is used to diagnose and stage cancer. Clarifying the functional significance of nuclear size necessitates an understanding of the mechanisms and proteins that control nuclear size. One structural component implicated in the regulation of nuclear morphology is the nuclear lamina, a meshwork of intermediate lamin filaments that lines the inner nuclear membrane. However, there has not been a systematic investigation of how the level and type of lamin expression influences nuclear size, in part due to difficulties in precisely controlling lamin expression levels in vivo. In this study, we circumvent this limitation by studying nuclei in Xenopus laevis egg and embryo extracts, open biochemical systems that allow for precise manipulation of lamin levels by the addition of recombinant proteins. We find that nuclear growth and size are sensitive to the levels of nuclear lamins, with low and high concentrations increasing and decreasing nuclear size, respectively. Interestingly, each type of lamin that we tested (lamins B1, B2, B3, and A) similarly affected nuclear size whether added alone or in combination, suggesting that total lamin concentration, and not lamin type, is more critical to determining nuclear size. Furthermore, we show that altering lamin levels in vivo, both in Xenopus embryos and mammalian tissue culture cells, also impacts nuclear size. These results have implications for normal development and carcinogenesis where both nuclear size and lamin expression levels change.     

Maintenance of highly contractile tissue-cultured avian skeletal myotubes in collagen gel

Summary Highly contractile skeletal myotubes differentiated in tissue culture are normally difficult to maintain on collagen-coated tissue culture dishes for extended periods because of their propensity to detach as a sheet of cells from their substratum. This detachment results in the release of mechanical tension in the growing cell “sheet” and, consequently, loss of cellular protein. We developed a simple method of culturing high density contractile primary avian myotubes embedded in a collagen gel matrix (collagel) attached to either a stainless steel mesh or nylon support structure. With this system the cells are maintained in a highly contractile state for extended periods in vitro under tension. Structural integrity of the myotubes can be maintained for up to 10 d in basal medium without serum or embryo extract. Total cellular protein and myosin heavy chain accumulation in the cells can be maintained for weeks at levels which are two to three times those found in timematched controls that are under little tension. Morphologically, the myotubes are well differentiated with structural characteristics of neonatal myofibers. This new collagel culture system should prove useful in the analysis of in vitro gene expression during myotube to myofiber differentiation and its regulation by various environmental factors such as medium growth factors, innervation, and mechanical activity. This work was supported by grant AM 36266 from the National Institutes of Health, Bethesda, MD, and grant NAG2-414 from the National Aeronautics and Space Administration, Washington, D.C. Parts of this work have appeared in abstract form, In Vitro 23:24a; 1987.     

Detachment of Brain Pericytes from the Basal Lamina is Involved in Disruption of the Blood–Brain Barrier Caused by Lipopolysaccharide-Induced Sepsis in Mice

The blood–brain barrier (BBB) is highly restrictive of the transport of substances between blood and the central nervous system. Brain pericytes are one of the important cellular constituents of the BBB and are multifunctional, polymorphic cells that lie within the microvessel basal lamina. The present study aimed to evaluate the role of pericytes in the mediation of BBB disruption using a lipopolysaccharide (LPS)-induced model of septic encephalopathy in mice. ICR mice were injected intraperitoneally with LPS or saline and were sacrificed at 1, 3, 6, and 24 h after injection. Sodium fluorescein accumulated with time in the hippocampus after LPS injection; this hyperpermeability was supported by detecting the extravasation of fibrinogen. Microglia were activated and the number of microglia increased with time after LPS injection. LPS-treated mice exhibited a broken basal lamina and pericyte detachment from the basal lamina at 6–24 h after LPS injection. The disorganization in the pericyte and basal lamina unit was well correlated with increased microglial activation and increased cerebrovascular permeability in LPS-treated mice. These findings suggest that pericyte detachment and microglial activation may be involved in the mediation of BBB disruption due to inflammatory responses in the damaged brain.     

The farnesylated nuclear proteins KUGELKERN and LAMIN B promote aging-like phenotypes in Drosophila flies

The nuclear lamina consists of a meshwork of lamins and lamina-associated proteins, which provide mechanical support, control size and shape of the nucleus, and mediate the attachment of chromatin to the nuclear envelope. Abnormal nuclear shapes are observed in aging cells of humans and nematode worms. The expression of laminΔ50 , a constitutively active lamin A splicing variant in Hutchinson–Gilford progeria syndrome patients, leads to the lobulation of the nuclear envelope accompanied by DNA damage, and loss of heterochromatin. So far, it has been unclear whether these age-related changes are laminΔ50 specific or whether proteins that affect nuclear shape such as KUGELKERN or LAMIN B in general play a causative role in senescence. Here we show that in adult Drosophila flies, the size of the nuclei increases with age and the nuclei assume an aberrant shape. Moreover, induced expression of the farnesylated lamina proteins Lamin B and Kugelkern cause aberrant nuclear shapes and reduce the lifespan of adult flies. The shorter lifespan correlates with an early decline in age-dependent locomotor behaviour. Expression of kugelkern or lamin B in mammalian cells induces a nuclear lobulation phenotype in conjunction with DNA damage, and changes in histone modification similar to that found in cells expressing laminΔ50  or in cells from aged individuals. We conclude that lobulation of the nuclear membrane induced by the insertion of farnesylated lamina-proteins can lead to aging-like phenotypes.     

Müller glia endfeet,a basal lamina and the polarity of retinal layers form properly in vitro only in the presence of marginal pigmented epithelium

Summary Dissociated embryonic chicken retinal cells regenerate in rotary culture into cellular spheres that consist of subareas expressing all three nuclear layers in an inside-out sequence (rosetted vitroretinae). However, when pigmented cells from the eye margin (peripheral retinal pigment epithelium) are added to the system, the sequence of layers is identical with that of an in-situ retina (laminar vitroretinae). In order to elucidate further the lamina-stabilizing effect exerted by the retinal pigment epithelium, we have compared both systems, laying particular emphasis on the ultrastructure of the basal lamina and of Müller glia processes. Ultrastructurally, in both systems, an outer limiting membrane, inner segments of photoreceptors and the segregation of cell bodies into three cell layers develop properly. Synapses are detectable in a premature state, although only in the inner plexiform layer of laminar vitroretinae. Although present in both systems, radial processes of juvenile Müller glia cells are properly fixed at their endfeet only in laminar vitroretinae, since a basal lamina is only expressed here. Large amounts of laminin are detected immunohistochemically within the retinal pigment epithelium and along a basal stalk that reaches inside the laminar vitroretinae. We conclude that the peripheral retinal pigment epithelium is essential for the expression of a basal lamina in vitro. Moreover, the basal lamina may be responsible both for stabilizing the correct polarity of retinal layers and for the final differentiation of the Müller cells.     

Gall mite Fragariocoptes setiger (Eriophyoidea) changes leaf developmental program and regulates gene expression in the leaf tissues of Fragaria viridis (Rosaceae)

The interaction of plants with certain types of parasites leads to the formation of galls, organised structures that create the habitat of the parasite, caused by an abnormal proliferation of host plant's cells under the influence of growth regulators, secreted by the parasite, or by the plant itself under the influence of the parasite. Arthropods, mites in particular, are the largest group of gall‐inducing phytoparasites, but the mechanisms of their interaction with plants remain virtually unexplored. The interaction of the gall‐inducing eriophyoid mite Fragariocoptes setiger with Fragaria viridis plants was used as a model gall–mite system where data were obtained on the changes in the histological structure of F. viridis leaf blades under the influence of the mites as well as F. viridis gene expression during gall formation. For histological purposes, gall formation was split into four stages with each corresponding to the age of the gall as well as to specific changes that occur during that period. A dramatic change of adaxial–abaxial polarity of the lamina throughout the four stages was observed. Moreover, qRT‐PCR analysis of F. viridis gene expression in the developing gall revealed changes in the expression levels of certain meristem‐specific genes, as well as the genes that determine adaxial–abaxial polarity and signalling of phytohormones.