Cell and tissue research
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Cell and tissue research · Jun 2004
Regrowth of lymphatic vessels following transection of the muscle coat in the rat small intestine.
Regeneration of lymphatic vessels after transection of the muscle coat in the rat jejunum was studied by histochemical methods. The lymphatic regrowth occurred behind the regeneration of blood vessels. Enzyme histochemistry for 5'-nucleotidase (5'-Nase) demonstrated the manner of lymphatic regrowth, which was essentially attributed to vascular sprouting from preexisting lymphatics, and structural changes of the endothelial cells indicating their high migratory potential. ⋯ The expression of 5'-Nase in the regenerating lymphatics was increased in proportion to their growth. VEGF-C, a highly specific lymphangiogenic factor, was highly expressed in a subpopulation of interstitial cells, being close to the regrowing lymphatics with immunoreactivity of its receptor, VEGFR-3, in the regenerative area. The present findings suggest that transection of the intestinal muscle coat affords a useful experimental model for the investigation of lymphatic regeneration in tissue repair and that the interstitium may play a crucial role in lymphangiogenesis.
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Cell and tissue research · Jan 2004
Alpha1beta1-integrin is an essential signal for neurite outgrowth induced by thrombospondin type 1 repeats of SCO-spondin.
In the central and peripheral nervous systems a heterogeneous group of proteins constituting the thrombospondin superfamily provides a cue for axonal pathfinding. They either contain or are devoid of the tripeptide RGD, and the sequence(s) and mechanism(s) which trigger in vitro their neurite-promoting activity have remained unclear. In this study, we reconsider the problem of whether sequences present in the thrombospondin type 1 repeats (TSRs), and independent of the well-known RGD-binding site, may activate integrins and account for their neurite-promoting activity. ⋯ By two different approaches: flow cytometry revealing short-term effects and cell cultures revealing long-term effects, we show that: (a). activation of cell metabolism, (b). changes in cell size and structure, and (c). neurite-promoting activity induced by TSR oligopeptides are inhibited by function-blocking antibodies to beta1-subunit. Using a panel of function-blocking antibodies directed against various integrin alpha-subunits we show that the alpha1-subunit might be the partner of the beta1-subunit in B104 cells. Thus, we demonstrate that an original sequence within a TSR motif from SCO-spondin promotes neurite outgrowth through an intracellular signal driven by integrins, independently of an RGD-binding site.
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Connective tissue growth factor (CTGF) is a potent fibroblast mitogen and angiogenic factor which plays an important role in wound healing, cancerogenesis and fibrotic and vascular disease. Here we explored the regulation and the cellular site of the mRNA synthesis for this growth factor in the developing mouse embryo by in situ hybridisation. ⋯ Very transient but strong expression was observed early during formation of cartilage, in late stages during perichondral ossification, on cerebral neuroepithelium, and in several discrete stages of tooth formation, on mesenchymal precursors of odontoblasts condensing on inner dental epithelium, and later on apposing regions of ameloblast and odontoblast epithelium. Altogether, the current study suggests that CTGF performs a dual role: a continuous function in the cardiovascular system, bone and cartilage-associated mesenchyme and maturing layer VII neurons, but also a more transient function associated with the formation of cartilage, bone, tooth and cerebral nerve cells.
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Cell and tissue research · Mar 2003
Activity-induced and developmental downregulation of the Nogo receptor.
The three axon growth inhibitory proteins, myelin associated glycoprotein, oligodendrocyte-myelin glycoprotein and Nogo-A, can all bind to the Nogo-66 receptor (NgR). This receptor is expressed by neurons with high amounts in regions of high plasticity where Nogo expression is also high. We hypothesized that simultaneous presence of high levels of Nogo and its receptor in neurons confers a locked state to hippocampal and cortical microcircuitry and that one or both of these proteins must be effectively and temporarily downregulated to permit plastic structural changes underlying formation of long-term memory. ⋯ No robust regulation of NgR was observed in the spinal cord following spinal cord injury. Together, our data show that NgR levels in developing and adult neurons are regulated in vivo under different conditions. Strong, rapid and transient downregulation of NgR mRNA in response to kainic acid and after wheel running in cortex and hippocampus suggests a role for NgR and Nogo-A in plasticity, learning and memory.
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Cell and tissue research · Mar 2003
ReviewThe enigma of transmitter-selective receptor accumulation at developing inhibitory synapses.
The control of synaptic inhibition is crucial for normal brain function. More than 20 years ago, glycine and gamma-aminobutyric acid (GABA) were shown to be the two major inhibitory neurotransmitters. They can be released independently from different terminals or co-released from the same terminal to activate postsynaptic glycine and GABA(A) receptors. ⋯ The activation of glycine and/or GABA(A) receptors determines the strength and precise timing of inhibition. Therefore, tight regulation of postsynaptic glycine versus GABA(A) receptor localization is crucial for optimizing synaptic inhibition in neurons. This review focuses on recent findings and discusses questions concerning the specificity of postsynaptic inhibitory neurotransmitter receptor accumulation during inhibitory synapse formation and development.