Effect of smooth muscle tone on morphometry and residual strain in rat duodenum, jejunum and ileum

It is difficult to measure gastrointestinal smooth muscle (SM) tone except in sphincter regions. Since tone affects the biomechanical properties, the aim of the present study was to evaluate intestinal SM tone by studying the morphometry and biomechanical properties with and without muscle tone. Circumferential rings of 0.8-1mm in width were cut from the rat duodenum, jejunum and ileum. Sectors were obtained by cutting the rings opposite to the mesentery. The rings and the sectors were immersed in physiological Krebs solution in order to maintain the tone and into Krebs solution without Ca(++) and with EGTA to abolish the tone. The circumferences, area, the circularity and residual strain of the mucosal and serosal surfaces, opening angle, and opening angle tone/non-tone ratio were measured or computed. The tone affects the opening angle and residual strain in the intestinal sectors. The opening angle in the tissue sectors with tone was smaller (P<0.05) than those without tone in all three segments. The opening angle tone/non-tone ratio was 0.40+/-0.05, 0.43+/-0.06 and 0.36+/-0.11 for duodenum, jejunum and ileum, respectively, and did not differ among the three intestinal segments. The residual strain between sectors with and without SM tone differed in duodenal and jejunal mucosa and in the serosa of all three segments (P<0.05). The intestinal rings with tone showed axial variation for luminal area (P<0.001), for wall area (P<0.05), and for the mucosal and serosal residual strains (P<0.05). In conclusion, the intestinal mechanical properties are affected by intestinal SM tone. The tone can be evaluated by measuring the opening angle and residual strains of sectors in intestinal segments with and without SM tone.     

A shared epitope of the interphotoreceptor retinoid-binding protein recognized by the CD4+ and CD8+ autoreactive T cells

We previously demonstrated that cultures of rat uveitogenic T cells rapidly become dominated by CD4+ cells, but activation of CD8+ autoreactive T cells also occurred during the in vitro culture of in vivo-primed T cells. In the present study, we show that the commonly used uveitogenic peptide, interphotoreceptor retinoid-binding protein (IRBP) 1-20, generated both CD4+ and CD8+ autoreactive T cells in the C57BL/6 (B6) mouse and that this 20-mer contains at least two distinct antigenic epitopes. To determine whether the CD8 response was Ag-specific and whether CD4+ and CD8+ IRBP1-20-specific T cells recognize distinct antigenic epitopes, we prepared highly purified CD4+ and CD8+ T cells from IRBP1-20-primed mice and tested their proliferative response to a large panel of truncated peptides derived from IRBP1-20. The results showed that both CD4+ and CD8+ T cells recognized the same spectrum of peptides. In addition, peptides P10-18 were found to bind effectively to CD8+ IRBP1-20-specific T cells when complexed with recombinant H-2K(b) and also stimulate the proliferation and cytokine production of CD4+ IRBP1-20-specific T cells. Our results document for the first time that CD8+ and CD4+ autoreactive T cells display characteristic epitope recognition and they both recognize the same core epitope.     

2000年间野生稻和栽培稻(O.sativa.L)分布区逆向分离的过程及动力Ⅰ.古今野生稻和栽培稻(O.sativa.L)的分布与人口分布的关系

２０００ａ间,中国境内野生稻分布区域由２４９５５７５ｋｍ２缩减至１３７１０９４ｋｍ２,减少了４５．０６％;分布纬度北界由３８°３′Ｎ南移至２８°１４′Ｎ,南移９°４９′、１１４０ｋｍ;中国境内栽培稻分布区域由４０８１８６０ｋｍ２增加至９６０００００ｋｍ２,增加了１３５．００％;分布北界由３８°Ｎ北移至５３°２９′Ｎ,北移１５°２９′、１７００ｋｍ。人口分布重心主要在黄河流域和长江流域,对该区域野生稻的生存产生不利影响。而促进栽培稻的发展,必须建立野生稻自然保护区。     

N-Acetyl-d-glucosamine 2-epimerase from Anabaena sp. CH1 contains a novel ATP-binding site required for catalytic activity

ATP is required as a structural activator for the reversible epimerization of N-acetyl-d-glucosamine to N-acetyl-d-mannosamine by N-acetyl-d-glucosamine 2-epimerase (AGE); however, the ATP-binding site on AGE has not been clearly identified. This study aimed to investigate the specific region of Anabaena sp. CH1 AGE (bAGE) that is required for ATP binding. In the absence of ATP, tryptic digest of bAGE resulted in the production of 2 segments of 17 and 26 kDa, while in the presence of 1 mM ATP, the enzyme was resistant to trypsin. ADP also displayed protective effects against trypsin digestion. A trypsin-mediated ATP-footprinting assay identified a deviant ATP-protected region, 156-GKYTK-160, which is located within the flexible loop of bAGE. Site-directed mutagenesis of residues in the loop region was performed, and both K151A and K160A variants greatly decreased the enzymatic activity as well as the ATP-binding ability of bAGE, indicating that residues K151 and K160 may be critical for ATP binding. This study demonstrated that the ATP-binding site (151-KDNPKGKYTK-160) of bAGE was a novel rather than a classical Walker motif A. This is the first ATP-binding site reported for AGEs.