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1.
Micromanipulation of mammalian embryos: Principles, progress and future possibilities 总被引:1,自引:0,他引:1
Numerous advances in development of techniques for manipulating mammalian embryos outside the maternal environment have been made over the past decade. Some techniques were developed primarily for use in research; others were developed in response to problems of practical livestock production but have proven useful in research as well. Embryo micromanipulation procedures are used often in conjunction with embryo transfer, and interest in these procedures was stimulated by growth of the embryo transfer industry. Included in this review are discussions of procedures for manipulation of gametes and embryos, including sperm injection into oocytes, pronuclear and nuclear transfer, embryo biopsy and splitting, experimental chimera production and isolation of embryonic stem cells. 相似文献
2.
Aphid resistance in Brassica crops: challenges, biotechnological progress and emerging possibilities
Aphids, (Hemiptera: Aphidoidea) a nefarious insect pest of Brassicaceae members including major vegetable and oilseed crops have coevolved with their host plant and emerged as most economically important insect pest of crop Brassicas. Their atypical feeding mechanism and unusual reproductive biology made them intractable to control below economic threshold level of damage to the crops. To a large extent aphid infestation is controlled by spraying agrochemicals of systemic mode of action and rarely by biological control. Use of systemic insecticides is highly cost intensive as well poses bigger threat of their incorporation in dietary chain. Breeding for genetic resistance against aphids has not been possible owing to the non-availability of resistance source within the crossable germplasms and lack of knowledge of the genetics of the trait. Genetic engineering with insect resistant transgenes seems to be the only potential avenue to address this difficult-to-accomplish breeding objective. Some success had been achieved in terms of developing aphid resistant cultivars through genetic engineering however, commercial utilization of such crops are still awaited. Thus protection of crops against aphids necessarily requires more research to identify either more effective insecticidal transgenes or biological phenomenon that can usher to new mechanism of resistance. The present review is an attempt to highlight the current status and possible avenues to develop aphid resistance in Brassicaceae crops. 相似文献
3.
John W. Pohlman 《Hydrobiologia》2011,677(1):33-51
Recent investigations of anchialine caves and sinkholes have identified complex food webs dependent on detrital and, in some
cases, chemosynthetically produced organic matter. Chemosynthetic microbes in anchialine systems obtain energy from reduced
compounds produced during organic matter degradation (e.g., sulfide, ammonium, and methane), similar to what occurs in deep
ocean cold seeps and mud volcanoes, but distinct from dominant processes operating at hydrothermal vents and sulfurous mineral
caves where the primary energy source is mantle derived. This review includes case studies from both anchialine and non-anchialine
habitats, where evidence for in situ chemosynthetic production of organic matter and its subsequent transfer to higher trophic
level metazoans is documented. The energy sources and pathways identified are synthesized to develop conceptual models for
elemental cycles and energy cascades that occur within oligotrophic and eutrophic anchialine caves. Strategies and techniques
for testing the hypothesis of chemosynthesis as an active process in anchialine caves are also suggested. 相似文献
4.
Endocytosis in polarized cells. 总被引:4,自引:0,他引:4
R G Parton 《Seminars in cell biology》1991,2(6):387-395
Recent biochemical and morphological studies using the MDCK cell line have provided insights into the organization of the endocytic pathways in an epithelial cell. The cytoskeletal organization of these cells has been described and evidence for the involvement of microtubules in facilitating endocytic traffic has been obtained. The findings with this model system are compared to results from in vivo studies of the endocytic pathways from the surface domains of specialized epithelial cells and to studies of endocytosis in neurons. 相似文献
5.
Sandra L. Schmid Alexander Sorkin Marino Zerial 《Cold Spring Harbor perspectives in biology》2014,6(12)
Endocytosis may have been a driving force behind the evolution of eukaryotic cells. It plays critical roles in cell biology (e.g., signal transduction) and in organismal physiology (e.g., tissue morphogenesis).Endocytosis, the process of cellular ingestion, may have been the driving force behind evolution of the eucaryotic cell (de Duve 2007). Acquiring the ability to internalize macromolecules and digest them intracellularly would have allowed primordial cells to move out from their food sources and pursue a predatory existence; one that might have led to the development of endosymbiotic relationships with mitochondria and plastids. Thus, it is fitting that endocytosis was first discovered and named as the processes of cell “eating” and “drinking.” In 1883, the developmental biologist Ilya Metchnikoff coined the term phagocytosis, from the Greek “phagos” (to eat) and “cyte” (cell), after observing motile cells in transparent starfish larva surround and engulf small splinters that he had inserted (Tauber 2003). Decades later, in 1931, Warren H. Lewis, one of the earliest cell “cinematographers” coined the term pinocytosis, from the Greek “pinean” (to drink), after observing the uptake of surrounding media into large vesicles in cultured macrophages, sarcoma cells, and fibroblasts by time-lapse imaging (Lewis 1931; Corner 1967).Importantly, these pioneering studies also revealed that the function of endocytosis goes well beyond eating and drinking. Indeed, Metchnikoff, considered one of the founders of modern immunology, realized that the phagocytic behavior of the mesodermal amoeboid cells he had observed under the microscope could serve as a general defense system against invasive parasites, in the larva as in man. This revolutionary concept, termed the phagocytic theory, earned Metchnikoff the 1908 Nobel Prize in Physiology or Medicine for his work on phagocytic immunity, which he shared with Paul Ehrlich who discovered the complementary mechanisms of humoral immunity that led to the identification of antibodies (Vaughan 1965; Tauber 2003; Schmalstieg and Goldman 2008). The phagocytic theory was a milestone in immunology and cell biology, and formally gave birth to the field of endocytosis.Key discoveries over the intervening years, aided in large part by the advent of electron microscopy, revealed multiple pathways for endocytosis in mammalian cells that fulfill multiple critical cellular functions (Fig. 1). These mechanistically and morphologically distinct pathways, and their discoverers, include clathrin-mediated endocytosis (Roth and Porter 1964), caveolae uptake (Palade 1953; Yamada 1955), cholesterol-sensitive clathrin- and caveolae-independent pathways (Moya et al. 1985; Hansen et al. 1991; Lamaze et al. 2001), and, more recently, the large capacity CLIC/GEEC pathway (Kirkham et al. 2005). In place of Metchnikoff’s splinters, many of these discoveries resulted from the detection and tracking of internalized HRP-, ferritin-, or gold-conjugated ligands by electron microscopy. These electron-dense tracers allowed researchers to identify cellular structures associated with the uptake and intracellular sorting of receptor-bound ligands. A particularly striking example is the pioneering work of Roth and Porter, who in 1964 observed the uptake of yolk proteins into mosquito oocytes. To synchronize uptake, they killed female mosquitos at timed intervals after a blood feed and observed the sequential appearance of electron-dense yolk granules in coated pits, coated and uncoated vesicles, and progressively larger vesicles. Their remarkable observations accurately described coated vesicle budding, uncoating, homo- and heterotypic fusion events, as well as the emergence of tubules from early endosomes (Fig. 2), all of which are now known hallmarks of the early endocytic trafficking events.Open in a separate windowFigure 1.Time line for discoveries of endocytic pathways and their discoverers. Boxes are color-coded by pathway. *, Nobel laureate. HRP, horseradish peroxidase; CCVs, clathrin-coated vesicles; CCPs, clathrin-coated pits; EGFR, epidermal growth factor receptor; PM, plasma membrane; ER, endoplasmic reticulum; CLIC/GEEC, clathrin-independent carriers/GPI-enriched endocytic compartments.Open in a separate windowFigure 2.Fiftieth anniversary of the discovery of clathrin-mediated endocytosis by Roth and Porter (1964). The image is the hand-drawn summary of observations made by electron microscopic examination of the trafficking of yolk proteins in a mosquito oocyte. Note the many details, later confirmed and mechanistically studied over the intervening 50 years. These include the growth, invagination, and pinching off of coated pits (1,2), which concentrate cargo taken up by coated vesicles (3), the rapid uncoating of nascent-coated vesicles (4), homotypic fusion of nascent endocytic vesicles in the cell periphery (5), the formation of tubules from early endosomes (7), and changes in the intraluminal properties of larger endosomes (6). Finally, yolk proteins are stored in granules as crystalline bodies (8). (From Roth and Porter 1964; reprinted, with express permission, from Rockefeller University Press © 1964, The Journal of Cell Biology
20: 313–332, doi: 10.1083/jcb.20.2.313.)Another milestone in the field of endocytosis was the discovery of the lysosome by Christian de Duve (Appelmans et al. 1955). Whereas the finding of phagocytosis and other endocytic pathways was possible through microscopy, the discovery of lysosomes originated from a biochemical approach (Courtoy 2007), which benefited from the invention of the ultracentrifuge. de Duve and coworkers observed that preparations of acid phosphatase obtained by subcellular fractionation had an unusual behavior: contrary to most enzymatic activities, the activity of acid phosphatase increased rather than decreased with time, freezing–thawing of the fractions and the presence of detergents. Interestingly, the same was true for other hydrolases, which depended on acidic pH for their optimal activity. This led him to postulate that the acid hydrolases were contained in acidified membrane-bound vesicles. In collaboration with Alex Novikoff, he visualized these vesicles, the lysosomes, by electron microscopy (Beaufay et al. 1956) and later showed their content of acid phosphatase (Farquhar et al. 1972). In 1974, de Duve was awarded the Nobel Prize for Physiology or Medicine for his seminal finding of the lysosomes and peroxisomes. He shared it with Albert Claude and George E. Palade “for their discoveries concerning the structural and functional organization of the cell.” The importance of this work lies also in the significant therapeutic applications that followed. The discovery by Elizabeth Neufeld and collaborators of uptake of lysosomal enzymes by cells provided the foundation for enzyme replacement therapy for lysosomal storage disorders (Neufeld 2011).In the 1970s, research in endocytosis entered the molecular era. Using de Duve and Albert Claude-like methods of subcellular fractionation, Barbara M. Pearse purified clathrin-coated vesicles from pig brain (Pearse 1975). A year later, she isolated a major protein species of 180 kDa, which she named clathrin “to indicate the lattice-like structures which it forms” (Pearse 1976). It was a breakthrough that inaugurated the molecular dissection of clathrin-mediated endocytosis.Over the intervening years, the continued application of microscopy (which now spans from electron cryotomography to live cell, high-resolution fluorescence microscopy), genetics (in particular, in yeast, Caenorhabditis elegans and Drosophila melanogaster), biochemistry (including cell-free reconstitution of endocytic membrane trafficking events), as well as molecular and structural biology have revealed a great deal about the cellular machineries and mechanisms that govern trafficking along the endocytic pathway. A partial, and because of space limitations, necessarily incomplete list of milestones (Year Mechanistic milestones Discoverers 1973 Identification of shibirets (dynamin) mutant in Drosophila D. Suzuki and C. Poodry 1974–1976 Zipper mechanism for phagocytosis S. Silverstein 1975–1976 Isolation of CCVs, purification of clathrin B. Pearse 1982–1984 Phosphomannose, M6PR, and lysosomal targeting W. Sly, S. Kornfeld, E. Neufeld, G. Sahagian 1983–1984 Isolation of clathrin adapters/localization to distinct membranes J. Keen, B. Pearse, M. Robinson 1986 Isolation of endocytosis mutants (End) in yeast H. Riezman 1986–1987 Isolation of vacuolar protein sorting mutants in yeast S. Emr, T. Stevens 1986 Endosome fusion in vitro J. Gruenberg and K. Howell 1986 EGF and insulin receptor signaling from endosomes J. Bergeron and B. Posner 1986 Macropinocytosis induced in stimulated cells D. Bar-Sagi and J. Feramisco 1987 Endocytic sorting motifs (FxNPxY, YxxF) M. Brown and J. Goldstein, I. Trowbridge, T. McGraw 1987–1989 Cloning of CHC, CLC, AP2 T. Kirchhausen, M. Robinson 1988 Isolation of biochemically distinct early and late endosomes S. Schmid and I. Mellman 1989–1991 Clathrin-mediated endocytosis reconstituted in vitro E. Smythe, G. Warren, S. Schmid 1990 Localization of endosomal Rab5 and Rab7 P. Chavrier, R. Parton, M. Zerial 1991 Endosome to trans-Golgi network (TGN) transport reconstituted in vitro S. Pfeffer 1992 Rab5 and Rab4 as early endocytic regulators in vivo M. Zerial, R. Parton, I. Mellman 1992–1995 Caveolin/VIP21 identified as caveolar coat protein R. Anderson, T. Kurzchalia, R. Parton, K. Simons 1992 Vacuolar fusion reconstituted in vitro W. Wickner 1992–1994 Trigger mechanism for phagocytosis of bacteria S. Falkow, J. Galán, J. Swanson 1993 Actin’s role in endocytosis in yeast H. Riezman 1993 Isolation of autophagy mutants (Atg) in yeast Y. Ohsumi 1993 PI3 kinase activity (PI3P) and endosome function S. Emr 1993 Dynamin’s role in clathrin-mediated endocytosis R. Vallee, S. Schmid 1995 Dynamin assembles into rings S. Schmid, P. De Camilli 1996 Clathrin-mediated endocytosis requirement for signaling S. Schmid 1996 Long distance retrograde transport of signaling endosomes in neurons W. Mobley 1996 PI5 phosphatase activity (PI(4,5)P2) and clathrin-mediated endocytosis P. De Camilli 1996 Ubiquitin-dependent sorting in endocytosis R. Haguenauer-Tsapis; L. Hicke and H. Riezman 1997 AP3 and endosomal/lysosomal sorting J. Bonifacino, S. Robinson 1998 FYVE fingers bind to PI3P H. Stenmark 1998 LBPA in MVB biogenesis T. Kobayashi, R. Parton, J. Gruenberg 1997–1998 Sorting nexins G. Gill, S. Emr 1998 Structural basis for Y-based sorting signal recognition D. Owen 1998 Retromer coat and endosome to TGN sorting S. Emr 1998 β-Propeller structure of clathrin heavy chain terminal domain T. Kirchhausen and S. Harrison 1998 Cargo-specific subpopulations of clathrin-coated pits M. von Zastrow 1999 Structure of the clathrin coat protein superhelical motifs J. Ybe and F. Brodsky 1999 Imaging green fluorescent protein–clathrin in living cells J. Keen 1999 Biochemical purification of Rab5 effectors S. Christoforidis and M. Zerial 1999 Genetic screen for endocytosis mutants in C. elegans B. Grant 2000 Role of endocytosis in establishing morphogenic gradients M. Gonzalez-Gaitan, S.M. Cohen 2000 Identification of GGA coats and lysosomal sorting J. Bonifacino, S. Kornfeld, M. Robinson 2000 Identification of endosomal sorting complex required for transport (ESCRT) machinery for multivesicular body (MVB) formation S. Emr 2001 Ubiquitin-dependent sorting into MVBs R. Piper, S. Emr, H. Pelham 2002 Structure of the AP2 core D. Owen 2003 Lipid conjugation of LC3/Atg8 Y. Ohsumi 2003–2004 siRNA studies of endocytic components S. Robinson, E. Ungewickell, A. Sorkin 2004 BAR domains and membrane curvature generation H. McMahon, P. De Camilli 2004 8-Å structure of a complete clathrin coat T. Kirchhausen and S. Harrison 2005 Modular design of yeast endocytosis machinery D. Drubin and M. Kaksonen 2005 Kinome-wide RNAi analysis of clathrin-mediated endocytosis (CME) and clathrin-independent endocytosis (CIE) M. Zerial and L. Pelkmans 2006–2008 Reconstitution of dynamin-mediated membrane fission A. Roux, P. De Camilli, S. Schmid, J. Zimmerberg, V. Frolov 2007 Glycosphingolipid-induced endocytosis L. Johannes 2009 Reconstitution of Rab- and SNARE-dependent vacuolar and endosome fusion from purified components W. Wickner, M. Zerial 2010 Cavins as major caveolae coat components R. Parton; B. Nichols 2010 Reconstitution of ESCRT-dependent internal vesicle formation T. Wollert and J. Hurley 2012 Reconstitution of CCV formation from minimal components E. Ungewickell