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Articles by M Bendayan
Total Records ( 2 ) for M Bendayan
  M Bendayan , I Londono , B. E Kemp , G. D Hardie , N Ruderman and M. Prentki
 

Immunogold cytochemistry was applied to reveal the intracellular location of AMP-activated protein kinase (AMPK) subunits in liver tissue of normal rats fed ad libitum. AMPK and β subunits were located both in the cytosol and in close association with rosettes of glycogen particles ( particles). To reveal their true in situ association with glycogen, particular tissue processing conditions that retain glycogen in the cells were required. These included fixation with a combination of glutaraldehyde and paraformaldehyde, followed by postfixation with osmium tetroxide and lead citrate and embedding in Epon. Processing by less-stringent fixation conditions and embedding in Lowicryl led to the extraction of the glycogen deposits, which in turn resulted in the absence of any labeling. This indicates that the loss of glycogen deposits leads to the loss of closely associated proteins. Labeling for the 1 and 2 subunits of AMPK was found to be about 2-fold greater over glycogen than over cytosol, whereas labeling for β1 was 8-fold higher over the glycogen particles than over the cytosol. Immunogold combined with morphometric analysis demonstrated that the β1 subunits are located at the periphery of the glycogen rosettes, consistent with a recent hypothesis developed via biochemical approaches. (J Histochem Cytochem 57:963–971, 2009)

  S. Y Kim , S Lee , S. W Hong , B. H Min , K. U Lee , M Bendayan and I. S. Park
 

Nestin, which was initially identified as a marker of neural stem cells, has been reported in regenerating pancreas as well as in early embryonic stem (ES) cell derivatives. However, little is known about its specific roles in stem cells as a functional regulator. We investigated the source of the action of nestin in ES and adult pancreatic ductal stem (PDS) cells in regard to the neogenesis of insulin-secreting β-cells. In ES cells, suppression of nestin by gene silencing led to an increased expression of the pluripotency-associated genes, including Oct 4, Nanog, and SSEA-1, before embryoid body (EB) formation, whereas it reduced endodermal and pancreatic transcription factors in EBs. Inhibition of nestin expression in adult PDS cells caused a low expression of pancreatic transcription factors and islet hormones, leading to poor β-cell development and insulin secretion. These data may indicate not only that nestin is a simple stem cell marker, but also that it constitutes a functional factor at the time of stem cell differentiation. We suggest that nestin plays pivotal roles as an intermediate regulator governing both stemness and differentiation of stem cells in the process of their differentiation into insulin-secreting cells. (J Histochem Cytochem 58:567–576, 2010)

 
 
 
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