Evolution and Construction Differentiation Pattern of African Railway Network

Since the new century, countries in Africa have started a new round of rail network planning and construction which brings the completed different features together with the spatial organization of the railway network during the colonial period. Along with the strategic layout of “going out” with China’s railways, the organizational structure of the African railway network will make a tremendous change for the construction market, network organization, and gauge structure of the African railways. Based on the literature reviews, we analyzed and forecasted the evolution of railway network in Africa and discussed the spatial differentiation of the future construction market of the railways from the view of country and enterprise. The results show that the development of the African railway networks will experience three stages: 1850–1960, 1960–2010 and 2010–2050, and that the organization pattern of the African railway network has evolved from the “Hinterland-Port” model to the “Continental Integration” model. The development of railway technical standards tends to be integrated, the gauge type is changed from complicated to single, the gauge distribution is changed from broken to uniform. The contractor countries of the railway changed from English-French dominated to China dominated. The application of railway technical standards is influenced by technology dependence and path dependence and is mainly reflected in the two characteristics of “Chinese standard implantation” and “local standard retention”. The contractor enterprises of railway have a monopoly on the market of a country, CCECC and CRCC are leading, and the contractor enterprises are spatially characterized by four spatial distribution modes: single, continuous, jumping and comprehensive.

CD66e Enrichment Enhances Repopulation of Human Long-Term Hematopoietic Stem Cells

Gene-modified hematopoietic stem cells (HSCs) therapy has demonstrated remarkable success for the treatment of inherited blood disorders. As the origin of hematologic hierarchy, HSCs play an essential role in sustaining life-long hematopoiesis. HSCs identification via reliable and robust bio-markers could facilitate the development of HSC gene therapy. Previous studies showed that long-term hematopoietic stem cells (LT-HSCs) were enriched in the Lin -CD34 +CD38 -CD45RA -CD90 +CD49f + population which could support long-term hematopoietic reconstitution. However, several of these surface markers proved to be unreliable when ex vivo culturing, such as CD38 and CD49f. Thus, HSCs characterization is still hindered by lacking bona-fide bio-markers, and consequently identification of long-term HSCs still needs time-consuming in vivo transplantation. To this end, we performed in vitro screening and comprehensive functional evaluation to identify a novel surface marker of human HSCs. During initial screening, a cell surface antigen screen panel (including 242 human cell surface markers) and human CD34 and CD90 antibodies were used to perform flow cytometry analysis on CD34 + HSPCs enriched from umbilical cord blood. Compared with CD34 + cell population, we found that CD66 (a,c,d,e), CD200 and CD48 positive cells were more enriched in CD34 +CD90 + subset. Previous studies indicated that HSCs cannot be maintained during in vitro culturing. By tracking these candidate surface markers based on this principle, CD66e was selected as the potential HSCs bio-marker. Next, we examined the in vivo hematologic repopulating potential of HSCs by limiting dilution assay (LDA) on immune-deficient mouse model. We sorted CD66e + and CD66e - subsets from CD34 +CD90 +CD45RA - subpopulation, and transplanted into irradiated NOD-scid Il2rg −/− (NPG) mice respectively. At week16 post-transplantation, in contrast to the CD66e - group, CD66e + cells exhibited significantly higher reconstitution in peripheral blood (PB), bone marrow (BM) and spleen. Engraftment dynamics revealed that the CD66e - group were only capable of reconstitution 4 weeks post transplantation, even at the highest initial cell dose. Moreover, the CD66e - group displayed impaired multi-lineage differentiation pattern, especially in PB and BM samples, while the CD66e + group presented a robust multi-lineage reconstitution. Notably, LDA results showed that the CD66e + cells within CD34 +CD90 +CD45RA - population contained 1 out of 529 SCID repopulating cells (SRC), almost 60-fold greater than the CD66e - fraction. To further investigate the long-term repopulating potential of the CD66e + cells, we performed the secondary transplantation collected from the BM cells of primary recipients. CD66e + cells presented significant higher repopulating activity than CD66e- subset in the secondary recipients. These findings reveal that the major cells with homing and long-term reconstitution capacity among CD34 +CD90 +CD45RA - cells were CD66e positive. In order to determine the transcriptional profile of CD66e + cells, we performed RNA-sequencing analysis using the population of CD34 + cells, CD34 +CD90 +CD45RA - cells, CD66e + and CD66e - cells within CD34 +CD90 +CD45RA - subset. Remarkably, compared with other groups, the CD66e + cells displayed a bias toward the signature of HSC and early progenitors such as LMPP and CLP. Moreover, gene set enrichment analysis showed that hematopoietic lineage and long-term potentiation-related genes were highly enriched in the CD66e + cells. Further qRT-PCR experiment confirmed that several HSC-related genes were significantly higher expressed in CD34 +CD90 +CD45RA -CD66e + cells, compared to CD66e - population or CD34 + HSPCs, suggesting that the gene expression profile of CD66e + cells is reminiscent of HSC signature. Altogether, we demonstrate that CD66e is a robust functional HSC bio-marker that CD66e-positive population among CD34 +CD90 +CD45RA - cells exhibit typical HSC signature, enhanced in vivo engraftment potential and robust multilineage differentiation pattern, which will provide an invaluable tool to investigate the origin of human HSCs, paving the way for the therapeutic application. Figure 1 Figure 1. Disclosures Fang: EdiGene, Inc.: Current Employment.

Comparison of Differentiation Pattern and WNT/SHH Signaling in Pluripotent Stem Cells Cultured under Different Conditions

Pluripotent stem cells (PSCs) are characterized by the ability to self-renew as well as undergo multidirectional differentiation. Culture conditions have a pivotal influence on differentiation pattern. In the current study, we compared the fate of mouse PSCs using two culture media: (1) chemically defined, free of animal reagents, and (2) standard one relying on the serum supplementation. Moreover, we assessed the influence of selected regulators (WNTs, SHH) on PSC differentiation. We showed that the differentiation pattern of PSCs cultured in both systems differed significantly: cells cultured in chemically defined medium preferentially underwent ectodermal conversion while their endo- and mesodermal differentiation was limited, contrary to cells cultured in serum-supplemented medium. More efficient ectodermal differentiation of PSCs cultured in chemically defined medium correlated with higher activity of SHH pathway while endodermal and mesodermal conversion of cells cultured in serum-supplemented medium with higher activity of WNT/JNK pathway. However, inhibition of either canonical or noncanonical WNT pathway resulted in the limitation of endo- and mesodermal conversion of PSCs. In addition, blocking WNT secretion led to the inhibition of PSC mesodermal differentiation, confirming the pivotal role of WNT signaling in this process. In contrast, SHH turned out to be an inducer of PSC ectodermal, not mesodermal differentiation.

P2X7 receptor signaling is not required but can enhance Th17 differentiation

The purinergic receptor P2X7 (P2X7R) is important in inflammasome activation and generally considered to favor proinflammatory Th17 immune responses. However, several studies utilizing P2rx7-/- mice did not observe impaired inflammation, on the contrary, these reports demonstrate that P2rx7-/- mice can have more sever inflammation compared to WT controls. To begin to clarify this discrepancy, the impact of P2X7R signaling on primary Th17 and Th1 cell responses was examined. Initially, utilizing a global knockout approach, we found that P2rx7-/- mice develop comparable Th17 and Th1 responses to those of WT mice. However, indepth in vitro and in vivo investigations revealed differences in the immune response outcome depending on which cell type expresses P2X7R. In this regard, DC-specific P2X7R deficient chimeras demonstrate a comparable Th17 differentiation pattern with that of WT chimeras but display a significantly enhanced Th1 response. However, P2rx7-/- T cells have a suppressed Th17 differentiation profile while developing a similarly enhanced Th1 response as observed in DC-specific P2X7R deficient chimeras. Finally, P2X7R expression induces more T cell death in vivo, attributed to its cytotoxicity, which results in a similar total number of WT Th17 and P2rx7-/- Th17 cells and remarkably higher amounts of P2rx7-/- Th1 cells. Collectively, our findings establish that P2X7R expression on CD4+ T cells is necessary for Th17 differentiation while inhibiting Th1 development.

Metapopulation Structure of Diatom-associated Marine Bacteria

Marine bacteria-phytoplankton interaction ultimately shapes ecosystem productivity. The biochemical mechanisms underlying their interactions become increasingly known, yet how these ubiquitous interactions drive bacterial evolution has not been illustrated. Here, we sequenced genomes of 294 bacterial isolates associated with 19 coexisting diatom cells. These bacteria constitute eight genetically monomorphic populations of the globally abundant Roseobacter group. Six of these populations are members of Sulfitobacter, arguably the most prevalent bacteria associated with marine diatoms. A key finding is that populations varying at the intra-specific level have been differentiated and each are either associated with a single diatom host or with multiple hosts not overlapping with those of other populations. These closely related populations further show functional differentiation; they differ in motility phenotype and they harbor distinct types of secretion systems with implication for mediating organismal interactions. This interesting host-dependent population structure is even evident for demes within a genetically monomorphic population but each associated with a distinct diatom cell, as shown by a greater similarity in genome content between isolates from the same host compared to those from different hosts. Importantly, the intra- and inter-population differentiation pattern remains when the analyses are restricted to isolates from intra-specific diatom hosts, ruling out distinct selective pressures and instead suggesting coexisting microalgal cells as physical barriers of bacterial gene flow. Taken together, microalgae-associated bacteria display a unique microscale metapopulation structure, which consists of numerous small populations whose evolution is driven by random genetic drift.

Histologic features of hair follicle neoplasms and cysts in dogs and cats: a diagnostic guide

Hair follicle neoplasms occur in many different species, including humans. In domestic animals, they are most common in dogs. Most hair follicle tumors are benign, but malignant neoplasms can also occur. To diagnose hair follicle neoplasms, a thorough knowledge of follicular anatomy is important, given that follicular tumors are classified according to the differentiation pattern seen in the corresponding part of the normal hair follicle. This review focuses on the key diagnostic features of hair follicle tumors and follicular cysts in dogs and cats.