Seedling establishment of deciduous trees in various topographic positions

Abstract. We investigated the effect of topography‐related environmental factors (i.e., ground‐surface stability and soil moisture) on seedling establishment of 8 deciduous tree species. A field experiment was carried out using canopy species, which were classified into 3 groups based on the spatial distribution of adult trees (ridge, slope and valley). Demographic parameters were compared among species during the early stage of seedling establishment among 3 topographic positions in combination with gap and canopy conditions. The percentage of emerging seedlings tended to be lower on the ridge irrespective of the adult topographical distribution patterns. There was no clear trend in seedling emergence among the species groups classified by their spatial distribution. Seedling survival during 2 growing seasons was significantly different among species, topographic positions and light conditions. On the ridge, seedlings of the species dominating ridge tops had greater survival than those of other species, probably due to differences in demand for soil moisture. On the slope, frequent physical damage caused by surface material movement was observed and some species showed greater adaptability to the disturbed slope habitat. Survival of all seedlings was highest in the valley plots. Light conditions were the critical factor for seedling survival in some species. The results of this study suggest that topography creates diverse habitats for the establishment of tree seedlings. In addition to soil moisture, surface material movement may be a significant factor affecting seedling establishment.     

Two flavonoid glucosyltransferases from Petunia hybrida: molecular cloning,biochemical properties and developmentally regulated expression

Two flavonoid glucosyltransferases, UDP-glucose:flavonoid 3-O-glucosyltransferase (3-GT) and UDP-glucose: anthocyanin 5-O-glucosyltransferase (5-GT), are responsible for the glucosylation of anthocyani(di)ns to produce stable molecules in the anthocyanin biosynthetic pathway. The cDNAs encoding 3-GT and 5-GT were isolated from Petunia hybrida by hybridization screening with heterologous probes. The cDNA clones of 3-GT, PGT8, and 5-GT, PH1, encode putative polypeptides of 448 and 468 amino acids, respectively. A phylogenetic tree based on amino acid sequences of the family of glycosyltransferases from various plants shows that PGT8 belongs to the 3-GT subfamily and PH1 belongs to the 5-GT subfamily. The function of isolated cDNAs was identified by the catalytic activities for 3-GT and 5-GT exhibited by the recombinant proteins produced in yeast. The recombinant PGT8 protein could convert not only anthocyanidins but also flavonols into the corresponding 3-O-glucosides. In contrast, the recombinant PH1 protein exhibited a strict substrate specificity towards anthocyanidin 3-acylrutinoside, comparing with other 5-GTs from Perilla frutescens and Verbena hybrida, which showed broad substrate specificities towards several anthocyanidin 3-glucosides. The mRNA expression of both 3-GT and 5-GT increased in the early developmental stages of P. hybrida flower, reaching the maximum at the stage before flower opening. Southern blotting analysis of genomic DNA indicates that both 3-GT and 5-GT genes exist in two copies in P. hybrida, respectively. The results are discussed in relation to the molecular evolution of flavonoid glycosyltransferases.     

RecFOR and RecOR as distinct RecA loading pathways

The molecular role of the RecF protein in loading RecA protein onto single-stranded DNA (ssDNA)-binding protein-coated ssDNA has been obscured by the facility with which the RecO and RecR proteins alone perform this function. We now show that RecFOR and RecOR define distinct RecA loading functions that operate optimally in different contexts. RecFOR, but not RecOR, is most effective when RecF(R) is bound near an ssDNA/double-stranded (dsDNA) junction. However, RecF(R) has no enhanced binding affinity for such a junction. RecO and RecR proteins are both required under all conditions in which the RecFOR pathway operates. The RecOR pathway is uniquely distinguished by a required interaction between RecO protein and the ssDNA binding protein C terminus. The RecOR pathway is more efficient for RecA loading onto ssDNA when no proximal dsDNA is available. A merger of new and published results leads to a new model for RecFOR function.     

Involvement of aquaporin in thromboxane A2 receptor-mediated, G12/13/RhoA/NHE-sensitive cell swelling in 1321N1 human astrocytoma cells

The physiological role of the thromboxane A₂ (TXA₂) receptor expressed on glial cells remains unclear. We previously reported that 1321N1 human astrocytoma cells pretreated with dibutyryl cyclic AMP (dbcAMP) became swollen in response to U46619, a TXA₂ analogue. In the present study, we examined the detailed mechanisms of TXA₂ receptor-mediated cell swelling in 1321N1 cells. The cell swelling caused by U46619 was suppressed by expression of p115-RGS, an inhibitory peptide of Gα_12/13 pathway and C3 toxin, an inhibitory protein for RhoA. The swelling was also inhibited by treatment with Y27632, a Rho kinase inhibitor and 5-(ethyl-N-isopropyl)amiloride (EIPA), a Na⁺/H⁺-exchanger inhibitor. Furthermore, cell swelling was suppressed by the pretreatment with aquaporin inhibitors mercury chloride or phloretin in a concentration-dependent manner, suggesting that aquaporins are involved in U46619-induced 1321N1 cell swelling. In fact, U46619 caused [³H]H₂O influx into the cells, which was inhibited by p115-RGS, C3 toxin, EIPA, mercury chloride and phloretin. This is the first report that the TXA₂ receptor mediates water influx through aquaporins in astrocytoma cells via TXA₂ receptor-mediated activation of Gα_12/13, Rho A, Rho kinase and Na⁺/H⁺-exchanger.     

The micronucleus test with mouse peripheral blood on N-methyl-N'-nitro-N-nitrosoguanidine and mitomycin C.

The micronucleus test using mouse peripheral blood was conducted with N-methyl-N'-nitro-N-nitro-soguanidine (MNNG) and mitomycin C (MMC) as part of the 5th collaborative study supported by the Environmental Mutagen Society of Japan (CSGMT/MMS.JEMS). Male CD-1 mice were intraperitoneally injected once with 12.5-100 mg/kg of MMC. Peripheral blood was drawn at different intervals after treatment, placed on slides previously coated with acridine orange and the numbers of reticulocytes with micronuclei (MNRETs) were scored. The experiments indicated that the maximum effect of both MNNG and MMC was found about 48 h after treatment, and that the micronucleus test using peripheral blood is useful for the screening of chemicals throughout the experimental period in a single animal.     

Colorectal Advanced Neoplasms Occur through Dual Carcinogenesis Pathways in Individuals with Coexisting Serrated Polyps

Background

Individuals with serrated polyps (SP) are at higher risk for synchronous colorectal advanced neoplasms (AN) and cancers. However, it remains unclear whether there is a unique involvement of the serrated pathway and/or the classical adenoma-carcinoma sequence in this setting.

Methods

Colorectal ANs, which include tubular adenomas ≥10 mm, adenomas with villous histology, high-grade intraepithelial neoplasms, and cancers, were collected retrospectively. The groups included ANs with (AN+SP) or without (AN-only) coexisting SPs. Clinicopathological findings were compared between groups. BRAF and KRAS mutations in ANs and SPs, and methylation levels at long interspersed element-1 (LINE-1) in adjacent mucosa were determined by pyrosequencing.

Results

Seventy-five ANs from 40 patients in the AN+SP group, and 179 ANs from 119 patients in the AN-only group were analyzed. There were no significant differences in clinicopathological findings between the two groups, except that intraepithelial neoplasia in the AN+SP group was more likely to be located in the right colon (P = 0.018). BRAF mutations were significantly more frequent in the AN+SP group (P = 0.003), while KRAS mutations showed no significant differences between groups (P = 0.142). The majority of high-grade intraepithelial neoplasms in both groups showed a contiguous component of conventional adenoma. Individuals with large and right-sided SPs had significantly more conventional adenomas compared to those without such SPs (P = 0.027 and P = 0.031, respectively). Adjacent mucosa from individuals with multiple and large SPs showed significantly lower methylation levels at LINE-1 compared to individuals without such associated SPs (P = 0.049 and P = 0.015, respectively).

Conclusion

Our data suggest that both the adenoma-carcinoma sequence and the serrated pathway are operational in individuals with coexisting ANs and SPs. The reduced methylation levels at LINE-1 in the background mucosa suggest the possibility of an underlying ‘field defect’.     

Pacific-wide contrast highlights resistance of reef calcifiers to ocean acidification

Ocean acidification (OA) and its associated decline in calcium carbonate saturation states is one of the major threats that tropical coral reefs face this century. Previous studies of the effect of OA on coral reef calcifiers have described a wide variety of outcomes for studies using comparable partial pressure of CO₂ (pCO₂) ranges, suggesting that key questions remain unresolved. One unresolved hypothesis posits that heterogeneity in the response of reef calcifiers to high pCO₂ is a result of regional-scale variation in the responses to OA. To test this hypothesis, we incubated two coral taxa (Pocillopora damicornis and massive Porites) and two calcified algae (Porolithon onkodes and Halimeda macroloba) under 400, 700 and 1000 μatm pCO₂ levels in experiments in Moorea (French Polynesia), Hawaii (USA) and Okinawa (Japan), where environmental conditions differ. Both corals and H. macroloba were insensitive to OA at all three locations, while the effects of OA on P. onkodes were location-specific. In Moorea and Hawaii, calcification of P. onkodes was depressed by high pCO₂, but for specimens in Okinawa, there was no effect of OA. Using a study of large geographical scale, we show that resistance to OA of some reef species is a constitutive character expressed across the Pacific.     

Decreased Amyloid-β Pathologies by Intracerebral Loading of Glycosphingolipid-enriched Exosomes in Alzheimer Model Mice

Elevated levels of amyloid-β peptide (Aβ) in the human brain are linked to the pathogenesis of Alzheimer disease. Recent in vitro studies have demonstrated that extracellular Aβ can bind to exosomes, which are cell-secreted nanovesicles with lipid membranes that are known to transport their cargos intercellularly. Such findings suggest that the exosomes are involved in Aβ metabolism in brain. Here, we found that neuroblastoma-derived exosomes exogenously injected into mouse brains trapped Aβ and with the associated Aβ were internalized into brain-resident phagocyte microglia. Accordingly, continuous intracerebral administration of the exosomes into amyloid-β precursor protein transgenic mice resulted in marked reductions in Aβ levels, amyloid depositions, and Aβ-mediated synaptotoxicity in the hippocampus. In addition, we determined that glycosphingolipids (GSLs), a group of membrane glycolipids, are highly abundant in the exosomes, and the enriched glycans of the GSLs are essential for Aβ binding and assembly on the exosomes both in vitro and in vivo. Our data demonstrate that intracerebrally administered exosomes can act as potent scavengers for Aβ by carrying it on the exosome surface GSLs and suggest a role of exosomes in Aβ clearance in the central nervous system. Improving Aβ clearance by exosome administration would provide a novel therapeutic intervention for Alzheimer disease.