Dietary indigestible components exert different regional effects on luminal mucin secretion through their bulk-forming property and fermentability

The purpose of this study was to examine the effects of dietary indigestible components on mucin secretion in the respective parts of the gastrointestinal tract through their physico-chemical properties. Rats were fed either a control diet or diets containing 5% polystyrene foam (PSF), 5% fructooligosaccharide (FOS), 5% PSF + 5% FOS, or 10% beet fiber for 10 d. Mucins in the small intestine and feces were greater in the PSF, PSF + FOS, and beet fiber groups than in the control and FOS groups. In the cecum, greater mucins were observed in the FOS, PSF + FOS, and beet fiber groups than in the control and PSF groups. None of the dietary treatment was effective on gastric mucins. Cecal mucins were significantly correlated with the cecal pool sizes of total short-chain fatty acids. The correlation between fecal mucins and fecal numbers was also significant. The results suggest that the effect of the bulk-forming property of the dietary indigestible component on mucin secretion is limited to the duct, while fermentability is effective only in the cecum.     

Genetic structure of the protist Physarum albescens (Amoebozoa) revealed by multiple markers and genotyping by sequencing

Myxomycetes are terrestrial protists with many presumably cosmopolitan species dispersing via airborne spores. A truly cosmopolitan species would suffer from outbreeding depression hampering local adaptation, while locally adapted species with limited distribution would be at a higher risk of extinction in changing environments. Here, we investigate intraspecific genetic diversity and phylogeography of Physarum albescens over the entire Northern Hemisphere. We sequenced 324 field collections of fruit bodies for 1–3 genetic markers (SSU, EF1A, COI) and analysed 98 specimens with genotyping by sequencing. The structure of the three-gene phylogeny, SNP-based phylogeny, phylogenetic networks, and the observed recombination pattern of three independently inherited gene markers can be best explained by the presence of at least 18 reproductively isolated groups, which can be seen as cryptic species. In all intensively sampled regions and in many localities, members of several phylogroups coexisted. Some phylogroups were found to be abundant in only one region and completely absent in other well-studied regions, and thus may represent regional endemics. Our results demonstrate that the widely distributed myxomycete species Ph. albescens represents a complex of at least 18 cryptic species, and some of these seem to have a limited geographical distribution. In addition, the presence of groups of presumably clonal specimens suggests that sexual and asexual reproduction coexist in natural populations of myxomycetes.     

Indispensable function of the germ nucleus for postconjugational stomatogenesis in Paramecium caudatum: Evidence against its genic function shown by hypohaploid micronuclei

It is known that the germinal micronucleus at the stages of gametogenesis and/or fertilization has an indispensable function for the postconjugational development of oral apparatus (stomatogenesis) in Paramecium caudatum. To determine whether this function is due to some specific genes in the micronucleus, postconjugational stomatogenesis was examined in the conjugation of haploid and hypohaploid cells. Haploid clones were obtained by conjugation between amicronucleate cells and diploid micronucleate cells. After conjugation between these haploid clones or between the haploid clones and amicronucleate clones, we succeeded in obtaining hypohaploid clones that have various types of nullisomic micronuclei. If a few genes in the micronucleus control postconjugational stomatogenesis, some hypohaploid micronuclei should undergo stomatogenesis normally, but others should not. In the present work, however, almost all the hypohaploid micronuclei developed the oral apparatus and formed food vacuoles. We can apparently rule out the possibility that a few specific genes of the micronucleus are required for postconjugational stomatogenesis in Paramecium caudatum, unless selection operates to retain the chromosomes with the essential gene(s). Dev. Genet. 23:142–150, 1998. © 1998 Wiley-Liss, Inc.     

Ralfuranones contribute to mushroom‐type biofilm formation by Ralstonia solanacearum strain OE1‐1

After invasion into intercellular spaces of tomato plants, the soil‐borne, plant‐pathogenic Ralstonia solanacearum strain OE1‐1 forms mushroom‐shaped biofilms (mushroom‐type biofilms, mBFs) on tomato cells, leading to its virulence. The strain OE1‐1 produces aryl‐furanone secondary metabolites, ralfuranones (A, B, J, K and L), dependent on the quorum sensing (QS) system, with methyl 3‐hydroxymyristate (3‐OH MAME) synthesized by PhcB as a QS signal. Ralfuranones are associated with the feedback loop of the QS system. A ralfuranone productivity‐deficient mutant (ΔralA) exhibited significantly reduced growth in intercellular spaces compared with strain OE1‐1, losing its virulence. To analyse the function of ralfuranones in mBF formation by OE1‐1 cells, we observed cell aggregates of R. solanacearum strains statically incubated in tomato apoplast fluids on filters under a scanning electron microscope. The ΔralA strain formed significantly fewer microcolonies and mBFs than strain OE1‐1. Supplementation of ralfuranones A, B, J and K, but not L, significantly enhanced the development of mBF formation by ΔralA. Furthermore, a phcB‐ and ralA‐deleted mutant (ΔphcB/ralA) exhibited less formation of mBFs than OE1‐1, although a QS‐deficient, phcB‐deleted mutant formed mBFs similar to OE1‐1. Supplementation with 3‐OH MAME significantly reduced the formation of mBFs by ΔphcB/ralA. The application of each ralfuranone significantly increased the formation of mBFs by ΔphcB/ralA supplied with 3‐OH MAME. Together, our findings indicate that ralfuranones are implicated not only in the development of mBFs by strain OE1‐1, but also in the suppression of QS‐mediated negative regulation of mBF formation.     

Different abilities of escape mutant-specific cytotoxic T cells to suppress replication of escape mutant and wild-type human immunodeficiency virus type 1 in new hosts

There is much evidence that in human immunodeficiency virus type 1 (HIV-1)-infected individuals, strong cytotoxic T lymphocyte (CTL)-mediated immune pressure results in the selection of HIV-1 mutants that have escaped from wild-type-specific CTLs. If escape mutant-specific CTLs are not elicited in new hosts sharing donor HLA molecules, the transmission of these mutants results in the accumulation of escape mutants in the population. However, whether escape mutant-specific CTLs are definitively not elicited in new hosts sharing donor HLA molecules still remains unclear. A previous study showed that a Y-to-F substitution at the second position (2F) of the Nef138-10 epitope is significantly detected in HLA-A*2402⁺ hemophilic donors. Presently, we confirmed that this 2F mutant was an escape mutant by demonstrating strong and weak abilities of Nef138-10-specific CTL clones to suppress replication of the wild-type and 2F mutant viruses, respectively. We demonstrated the existence of the 2F-specific CTLs in three new hosts who had been primarily infected with the 2F mutant. The 2F-specific CTL clones suppressed the replication of both wild-type and mutant viruses. However, the abilities of these clones to suppress replication of the 2F virus were much weaker than those of wild-type-specific and the 2F-specific ones to suppress replication of the wild-type virus. These findings indicate that the 2F mutant is conserved in HIV-1-infected donors having HLA-A*2402, because the 2F-specific CTLs failed to completely suppress the 2F mutant replication and effectively prevented viral reversion in new hosts carrying HLA-A*2402.     

Local Delivery of Mesenchymal Stem Cells with Poly-Lactic-Co-Glycolic Acid Nano-Fiber Scaffold Suppress Arthritis in Rats

Mesenchymal stem cells (MSC) have been used recently for the treatment of autoimmune diseases in murine animal models due to the immunoregulatory capacity. Current utilization of MSC requires cells in certain quantity with multiple courses of administration, leading to limitation in clinical usage. Here we efficiently treated collagen-induced arthritis rats with a single local implantation with reduced number of MSC (2∼20% of previous studies) with nano-fiber poly-lactic-co-glycolic acid (nano-fiber) scaffold. MSC seeded on nano-fiber scaffold suppressed arthritis and bone destruction due to inhibition of systemic inflammatory reaction and immune response by suppressing T cell proliferation and reducing anti- type II collagen antibody production. In vivo tracing of MSC demonstrated that these cells remained within the scaffold without migrating to other organs. Meanwhile, in vitro culture of MSC with nano-fiber scaffold significantly increased TGF-β1 production. These results indicate an efficient utilization of MSC with the scaffold for destructive joints in rheumatoid arthritis by a single and local inoculation. Thus, our data may serve as a new strategy for MSC-based therapy in inflammatory diseases and an alternative delivery method for bone destruction treatment.