日本

现在来看看G7成员国之一、亚洲的传统科技领袖——日本的表现.二战后,日本的重建进展迅猛,人口激增,在整个国家工业化环境塑造下的婴儿潮一代成长为推动上世纪六七十年代日本经济快速发展的中坚力量.日本以生产高质量创意工业产品为基础建立起良好的声誉,并在80年代达到经济巅峰,然而随后便进入了被称之为“丢失的10年”的发展停滞期...     

Androgen regulation of cell proliferation and expression of viral sequences in mouse mammary tumour cells

The role of steroids in promoting cell proliferation is well established but the molecular mechanisms are not clear. The S115 mouse mammary tumour cell line provides a model system for molecular studies in vitro in that it exhibits in tissue culture both a positive proliferative response to androgens and a change from a transformed phenotype in the presence of androgen to a normal phenotype when androgen is removed. We have considered here the possible involvement of mouse mammary tumour virus (MMTV) in these processes. We have demonstrated the presence in S115 cells of MMTV-related sequences which are transcribed into RNA only in the long-term presence of androgen. Prolonged culture in the absence of androgen, which results in loss of proliferative response to androgen, is accompanied by loss of MMTV-related RNA and increased methylation of MMTV-related sequences.     

Reactivity of HTLV-transformed human T-cell lines to MHC class II antigens

T-cell lines established from individuals infected with human T-cell leukaemia virus (HTLV) or generated by co-cultivation of normal human T cells with HTLV-infected T-cells, express class II (HLA-D/DR or Ia) antigens of the major histocompatibility complex (MHC) and interleukin-2 (IL-2) receptors. Because the expression of these markers characterizes the differentiation of immunologically activated T cells, we have now explored the possibility that HTLV- infected T cells might be primed to autologous or allogeneic Ia antigens expressed by the infecting cells. Our studies on the capacity of HTLV-infected T cells to display responses on mixed lymphocyte culture indicate that such T cells as well as single-cell clones derived from them, react non-discriminatively to all known allelic variants of human HLA-D/DR antigens, including those expressed by the responding cells. This reaction is inhibited by antibody to human Ia and is not triggered by Ia-negative T-leukaemia cells. The structure recognized seems to be a common epitope determinant of human Ia antigens, as (HTLV-infected) T cells primed in vitro to one HLA-D/DR specificity display amplified responses to all other HLA-D/DR antigens. We therefore believe that autostimulation by a self-Ia determinant may trigger the clonal expansion of HTLV-infected T cells and potentiate autoimmune processes.     

The effect of alkylation on the antimicrobial activities of 7-hydroxy- and 4-hydroxycoumarins

Zusammenfassung Es wird der Einfluss einer Alkylierung auf die antimikrobielle Wirkung von 7-Hydroxy- und 4-Hydroxy-Cumarin dargestellt.     

Electron-microscopic mapping of the hinge region of myosin

Summary The trypsin-sensitive sites in the labile hinge region of the myosin molecule are located with heightened accuracy (±2 nm) by electron microscopy as lying at 70, 85, 95, and 103 nm from the C-terminus of the rod section of the molecule.I thank Dr.Michael Young for valuable advice and encouragement, Drs.Jerome Gross andRomaine R. Bruns for use of their electron microscope, and Mrs.Muriel H. Blanchard for excellent technical assistance. This work was supported by the American Heart Association, The John A. Hartford Foundation, Inc., and the National Institutes of Health.     

Backbone structure of the infectious epsilon15 virus capsid revealed by electron cryomicroscopy

A half-century after the determination of the first three-dimensional crystal structure of a protein, more than 40,000 structures ranging from single polypeptides to large assemblies have been reported. The challenge for crystallographers, however, remains the growing of a diffracting crystal. Here we report the 4.5-A resolution structure of a 22-MDa macromolecular assembly, the capsid of the infectious epsilon15 (epsilon15) particle, by single-particle electron cryomicroscopy. From this density map we constructed a complete backbone trace of its major capsid protein, gene product 7 (gp7). The structure reveals a similar protein architecture to that of other tailed double-stranded DNA viruses, even in the absence of detectable sequence similarity. However, the connectivity of the secondary structure elements (topology) in gp7 is unique. Protruding densities are observed around the two-fold axes that cannot be accounted for by gp7. A subsequent proteomic analysis of the whole virus identifies these densities as gp10, a 12-kDa protein. Its structure, location and high binding affinity to the capsid indicate that the gp10 dimer functions as a molecular staple between neighbouring capsomeres to ensure the particle's stability. Beyond epsilon15, this method potentially offers a new approach for modelling the backbone conformations of the protein subunits in other macromolecular assemblies at near-native solution states.     

The genome of the choanoflagellate Monosiga brevicollis and the origin of metazoans

Choanoflagellates are the closest known relatives of metazoans. To discover potential molecular mechanisms underlying the evolution of metazoan multicellularity, we sequenced and analysed the genome of the unicellular choanoflagellate Monosiga brevicollis. The genome contains approximately 9,200 intron-rich genes, including a number that encode cell adhesion and signalling protein domains that are otherwise restricted to metazoans. Here we show that the physical linkages among protein domains often differ between M. brevicollis and metazoans, suggesting that abundant domain shuffling followed the separation of the choanoflagellate and metazoan lineages. The completion of the M. brevicollis genome allows us to reconstruct with increasing resolution the genomic changes that accompanied the origin of metazoans.     

The early Miocene onset of a ventilated circulation regime in the Arctic Ocean

Deep-water formation in the northern North Atlantic Ocean and the Arctic Ocean is a key driver of the global thermohaline circulation and hence also of global climate. Deciphering the history of the circulation regime in the Arctic Ocean has long been prevented by the lack of data from cores of Cenozoic sediments from the Arctic's deep-sea floor. Similarly, the timing of the opening of a connection between the northern North Atlantic and the Arctic Ocean, permitting deep-water exchange, has been poorly constrained. This situation changed when the first drill cores were recovered from the central Arctic Ocean. Here we use these cores to show that the transition from poorly oxygenated to fully oxygenated ('ventilated') conditions in the Arctic Ocean occurred during the later part of early Miocene times. We attribute this pronounced change in ventilation regime to the opening of the Fram Strait. A palaeo-geographic and palaeo-bathymetric reconstruction of the Arctic Ocean, together with a physical oceanographic analysis of the evolving strait and sill conditions in the Fram Strait, suggests that the Arctic Ocean went from an oxygen-poor 'lake stage', to a transitional 'estuarine sea' phase with variable ventilation, and finally to the fully ventilated 'ocean' phase 17.5 Myr ago. The timing of this palaeo-oceanographic change coincides with the onset of the middle Miocene climatic optimum, although it remains unclear if there is a causal relationship between these two events.