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De Novo Formation (de + novo_formation)
Selected AbstractsMultiple Mechanisms Of Early Hyperglycaemic Injury Of The Rat Intestinal MicrocirculationCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 1-2 2002H Glenn Bohlen SUMMARY 1. Hyperglycaemia in the vast majority of humans with diabetes mellitus is the end result of profound insulin resistance secondary to obesity. For patients in treatment, hyperglycaemia is usually not sustained but, rather, occurs intermittently. In in vivo studies of the rat intestinal microcirculation, endothelial impairment occurs within 30 min at D -glucose concentrations , 300 mg/dL. Endothelial-dependent dilation to acetylcholine and constriction to noradrenaline is impaired. Vasodilation to exogenous nitric oxide (NO) remains normal. 2. When initiated before hyperglycaemia, suppression of oxygen radicals by both scavenging and pretreatment with cyclo-oxygenase blockade to prevent oxygen radical formation minimized endothelial impairments during hyperglycaemia. Neither treatment was effective in restoring endothelial function once it was damaged by hyperglycaemia. 3. A mechanism that may initiate the arachidonic acid, oxygen radical process is activation of specific isoforms of protein kinase C (PKC). De novo formation of diacylglycerol during hyperglycaemia activates PKC. Blockade of the ,II PKC isoform with LY-333531 prior to hyperglycaemia protected NO formation within the arteriolar wall, as judged with NO-sensitive microelectrodes. Furthermore, once suppression of endothelial dilation was present in untreated animals, PKC blockade could substantially restore endothelial-dependent dilation. 4. These results indicate that acute hyperglycaemia is far from benign and, in the rat, causes rapid endothelial impairment. Both oxygen radical scavenging and cyclo-oxygenase blockade prior to bouts of hyperglycaemia minimize endothelial impairment with limited side effects. Blockade of specific PKC isozymes protects endothelial function both as a pre- or post-treatment during moderately severe hyperglycaemia. [source] Transient concentration of a ,-tubulin-related protein with a pericentrin-related protein in the formation of basal bodies and flagella during the differentiation of Naegleria gruberiCYTOSKELETON, Issue 2 2002Mi Ra Suh Abstract The distribution of two proteins in Naegleria gruberi, N-,TRP (Naegleria ,-tubulin-related protein) and N-PRP (Naegleria pericentrin-related protein), was examined during the de novo formation of basal bodies and flagella that occurs during the differentiation of N. gruberi. After the initiation of differentiation, N-,TRP and N-PRP began to concentrate at the same site within cells. The percentage of cells with a concentrated region of N-,TRP and N-PRP was maximal (68%) at 40 min when the synthesis of tubulin had just started but no assembled microtubules were visible. When concentrated tubulin became visible (60 min), the region of concentrated N-,TRP and N-PRP was co-localized with the tubulin spot and then flagella began to elongate from the region of concentrated tubulin. When cells had elongated flagella, the concentrated N-,TRP and N-PRP were translocated to the opposite end of the flagellated cells and disappeared. The transient concentration of N-,TRP coincided with the transient formation of an F-actin spot at which N-,TRP and ,-tubulin mRNA were co-localized. The concentration of N-,TRP and formation of the F-actin spot occurred without the formation of microtubules but were inhibited by cytochalasin D. These observations suggest that the regional concentration of N-,TRP and N-PRP is mediated by actin filaments and might provide a site of microtubule nucleation for the assembly of newly synthesized tubulins into basal bodies and flagella. Cell Motil. Cytoskeleton 52:66,81, 2002. © 2002 Wiley-Liss, Inc. [source] Muscle stem cells and model systems for their investigationDEVELOPMENTAL DYNAMICS, Issue 12 2007Nicolas Figeac Abstract Stem cells are characterized by their clonal ability both to generate differentiated progeny and to undergo self-renewal. Studies of adult mammalian organs have revealed stem cells in practically every tissue. In the adult skeletal muscle, satellite cells are the primary muscle stem cells, responsible for postnatal muscle growth, hypertrophy, and regeneration. In the past decade, several molecular markers have been found that identify satellite cells in quiescent and activated states. However, despite their prime importance, surprisingly little is known about the biology of satellite cells, as their analysis was for a long time hampered by a lack of genetically amenable experimental models where their properties can be dissected. Here, we review how the embryonic origin of satellite cells was discovered using chick and mouse model systems and discuss how cells from other sources can contribute to muscle regeneration. We present evidence for evolutionarily conserved properties of muscle stem cells and their identification in lower vertebrates and in the fruit fly. In Drosophila, muscle stem cells called adult muscle precursors (AMP) can be identified in embryos and in larvae by persistent expression of a myogenic basic helix,loop,helix factor Twist. AMP cells play a crucial role in the Drosophila life cycle, allowing de novo formation and regeneration of adult musculature during metamorphosis. Based on the premise that AMPs represent satellite-like cells of the fruit fly, important insight into the biology of vertebrate muscle stem cells can be gained from genetic analysis in Drosophila. Developmental Dynamics 236:3332,3342, 2007. © 2007 Wiley-Liss, Inc. [source] VEGF signaling is required for the assembly but not the maintenance of embryonic blood vesselsDEVELOPMENTAL DYNAMICS, Issue 3 2002W. Scott Argraves Abstract Here we investigated the importance of vascular endothelial growth factor (VEGF) signaling to the de novo formation of embryonic blood vessels, vasculogenesis, as opposed to the maintenance of blood vessels. We found that antagonizing the activity of the VEGF signaling pathway by using soluble VEGF receptor 1 (sFlt1) or VEGF antibodies inhibited vasculogenesis that occurs in embryos and in cultures of 7.5 days postcoitus prevascular mesoderm. Antagonist treatment resulted in the formation of clusters of endothelial cells not normally observed during vasculogenesis. In contrast, when embryos with established vasculatures or cultures of vascularized mesoderm were treated with sFlt1 or VEGF antibodies, no discernible alterations to the preexisting blood vessels were observed. These observations indicate that, although VEGF signaling is required to promote the mesenchymal to epithelial transition by which angioblasts assemble into nascent endothelial tubes, it is not required by endothelial cells to maintain their organization as an endothelium. © 2002 Wiley-Liss, Inc. [source] On the origin of intrinsic matrix of acellular extrinsic fiber cementum: Studies on growing cementum pearls of normal and bisphosphonate-affected guinea pig molarsEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 3 2002Chantha K. Jayawardena Cementum pearls (CPs) belong to a type of acellular extrinsic fiber cementum (AEFC) that form on the maturing enamel of guinea pig molars. This study aimed to elucidate the forming process of intrinsic matrix of AEFC using the CPs of normal and bisphosphonate-affected guinea pig molars as experimental models. A group of guinea pigs were subjected to continuous administration of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) for 2 wk to inhibit mineralization of growing CPs. Fenestration of the enamel organ and migration of periodontal cells on to the exposed surface of maturing enamel appeared to be unaffected by HEBP, whereas de novo formation as well as growth of pre-existing CPs did not proceed under the same conditions. Immunoreactions for osteopontin were located exclusively on the mineralized matrix of preformed CPs, implying the absence of additional deposition or accumulation of putative intrinsic cementum matrix on the affected CPs, where the propagation of mineral phase had been arrested. In both normal and HEBP-treated groups, distinct enzymatic reactions for alkaline phosphatase appeared on the cells of the periodontal ligament associated closely with the sites of CP formation, and along the mineralization front of CPs. These observations suggest that the mineralization process per se plays a central role in the deposition of AEFC matrix and that alkaline phosphatase of periodontal cells penetrating through the enamel organ to the maturing enamel surface plays a key role in the mineralization process of CPs. [source] Proteomic Analysis of Shear Stress-Mediated Protection from TNF-, in Endothelial CellsMICROCIRCULATION, Issue 4 2010Julie K. Freed Microcirculation (2010) 17, 259,270. doi: 10.1111/j.1549-8719.2010.00031.x Abstract Previous studies have shown that physiological levels of shear stress can protect endothelial cells (ECs) from apoptotic stimuli. Here, we differentiate between acute and chronic protection and demonstrate the use of proteomic technologies to uncover mechanisms associated with chronic protection of ECs. We hypothesized that changes in abundance of proteins associated with the TNF-, signaling cascade orchestrate shear stress-mediated protection from TNF-, when cells are preconditioned with shear prior to the exposure of apoptotic stimuli. Detection of cleaved caspase 3 through Western blot analysis confirmed chronic shear stress-mediated protection from TNF-,. In the presence of the nitric oxide synthase inhibitor, LNMA (N, -monomethyl- l -arginine), chronic protection remained. Treatment with a de novo protein synthesis inhibitor, cycloheximide, eliminated this protective effect. Isotopic-labeling experiments, coupled with LC,MS/MS (liquid chromatography,tandem mass spectrometry) of isolated components of the TNF-, pathway revealed that CARD9, a known activator of the NF-,B pathway, was increased (60%) in sheared cells versus nonsheared cells. This result was confirmed through Western blot analysis. Our data suggest that de novo formation of proteins is required for protection from TNF-, in ECs chronically exposed to shear stress, and that CARD9 is a candidate protein in this response. [source] Polerovirus protein P0 prevents the assembly of small RNA-containing RISC complexes and leads to degradation of ARGONAUTE1THE PLANT JOURNAL, Issue 3 2010Tibor Csorba Summary RNA silencing plays an important role in plants in defence against viruses. To overcome this defence, plant viruses encode suppressors of RNA silencing. The most common mode of silencing suppression is sequestration of double-stranded RNAs involved in the antiviral silencing pathways. Viral suppressors can also overcome silencing responses through protein,protein interaction. The poleroviral P0 silencing suppressor protein targets ARGONAUTE (AGO) proteins for degradation. AGO proteins are the core component of the RNA-induced silencing complex (RISC). We found that P0 does not interfere with the slicer activity of pre-programmed siRNA/miRNA containing AGO1, but prevents de novo formation of siRNA/miRNA containing AGO1. We show that the AGO1 protein is part of a high-molecular-weight complex, suggesting the existence of a multi-protein RISC in plants. We propose that P0 prevents RISC assembly by interacting with one of its protein components, thus inhibiting formation of siRNA/miRNA,RISC, and ultimately leading to AGO1 degradation. Our findings also suggest that siRNAs enhance the stability of co-expressed AGO1 in both the presence and absence of P0. [source] Viral Infection Induces De Novo Lesions of Coronary Allograft Vasculopathy Through a Natural Killer Cell-Dependent PathwayAMERICAN JOURNAL OF TRANSPLANTATION, Issue 11 2009J. A. Graham Viral infections including those due to cytomegalovirus have been associated with accelerated cardiac allograft vasculopathy (CAV) in clinical trials and some animal models. Evidence demonstrating a direct causal relationship between such infections and de novo formation of coronary vascular lesions is lacking. Heterotopic murine cardiac transplants were performed in a parental to F1 combination in animals lacking both T- and B-lymphocytes (RAG,/,). Coronary vasculopathy developed almost exclusively in the presence of recipient infection with lymphocytic choriomeningitis virus but not in uninfected controls. This process was also dependent upon the presence of natural killer (NK) cells as depletion of NK cells abrogated the process. These data show that a viral infection in its native host, and not previously implicated in the production of CAV, can contribute to the development of advanced coronary vascular lesions in cardiac allotransplants in mice. These data also suggest that virus-induced CAV can develop via an NK-cell-dependent pathway in the absence of T- and B-lymphocytes. [source] | |||||||||||||