Lymphangiogenesis, an important initial step in tumor metastasis and transplant sensitization, is mediated by the action of VEGF-C and -D on VEGFR3. In contrast, VEGF-A binds VEGFR1 and VEGFR2 and is an essential hemangiogenic factor. We re-evaluated the potential role of VEGF-A in lymphangiogenesis using a novel model in which both lymphangiogenesis and hemangiogenesis are induced in the normally avascular cornea. Administration of VEGF Trap, a receptor-based fusion protein that binds and neutralizes VEGF-A but not VEGF-C or -D, completely inhibited both hemangiogenesis and the outgrowth of LYVE-1+ lymphatic vessels following injury. Furthermore, both lymphangiogenesis and hemangiogenesis were significantly reduced in mice transgenic for VEGF-A164/164 or VEGF-A188/188 (each of which expresses only one of the three principle VEGF-A isoforms). Because VEGF-A is chemotactic for macrophages and we demonstrate here that macrophages in inflamed corneas release lymphangiogenic VEGF-C/VEGF-D, we evaluated the possibility that macrophage recruitment plays a role in VEGF-A–mediated lymphangiogenesis. Either systemic depletion of all bone marrow–derived cells (by irradiation) or local depletion of macrophages in the cornea (using clodronate liposomes) prior to injury significantly inhibited both hemangiogenesis and lymphangiogenesis. We conclude that VEGF-A recruitment of monocytes/macrophages plays a crucial role in inducing inflammatory neovascularization by supplying/amplifying signals essential for pathological hemangiogenesis and lymphangiogenesis
Leaf senescence is an active process involving remobilization of nutrients from senescing leaves to other parts of the plant. Whereas senescence is accompanied by a decline in leaf cytokinin content, supplemental cytokinin delays senescence. Plants that overexpress isopentenyl transferase (ipt), a cytokinin-producing gene, or knotted1 (kn1), a homeobox gene, have many phenotypes in common. Many of these phenotypes are characteristic of altered cytokinin physiology. The effect of kn1 on leaf senescence was tested by driving its expression using the promoter of the senescence-associated gene SAG12. SAG:kn1 tobacco plants showed a marked delay in leaf senescence but otherwise developed normally. The delay in senescence was revealed by an increase in chlorophyll content in SAG:kn1 leaves relative to leaves of the control plants and by a decrease in the number of dead leaves. Senescence was also delayed in detached leaves of SAG:kn1 plants. Delayed senescence was accompanied by increased leaf cytokinin content in older leaves expressing kn1. These experiments extend the current understanding of kn1 function and suggest that in addition to mediating meristem maintenance, kn1 is capable of regulating the onset of senescence in leaves.
The feasibility of maintaining a single-mode optical fiber interferometer in quadrature is demonstrated using a servo driven piezoelectrically stretched coiled fiber. The controller has a range of ~10(-5)-1000 rad with a stress voltage coefficient of ~27pi rad/V.
A review of recent progress in signal processing, sensor developments and multiplexing techniques for fibre optic low-coherence interferometry is presented, with an emphasis on the new developments in this field which have the potential to be exploited for practical applications.Yun-jiang Rao was born in Yunnan, China. He received his MEng and PhD degrees in Optoelectronics at the University of Chongqing, China, in 1986 and 1990, respectively. In 1988 he was employed as a lecturer at the University of Chongqing, where he led a research team to develop the first fully automatic single-mode fibre arc-fusion splicing machine in China. From 1991 to 1992 he worked on allfibre optically-addressed silicon microresonator sensors as a Postdoctoral Research Fellow at the University of Strathclyde in Scotland. In 1992 he joined the Department of Physics at the University of Kent at Canterbury as a Research Fellow, where he has been working on fibre-optic low coherence interferometry, development of fibre-optic pressure and temperature sensors, advanced fibre-optic sensor multiplexing techniques and in-fibre Bragg grating sensors. He had developed a universal fibre-optic point sensor system for quasi-static absolute measurements of multiparameters based on low-coherence interrogation. His current research interests are intrinsic and extrinsic singlemode fibre-based sensors, multiplexing techniques, fibreoptic interferometry and in-fibre Bragg grating sensors. He has authored or co-authored over 60 journal and conference papers.
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