Structural Requirements for the Intestinal Mucosal-Cell Peptide Transporter: The Need for N-Terminal α-Amino Group

The requirement for a free -amino group for the intestinal peptide carrier-mediated transport was investigated. A series of dipeptide analogues without the N-terminal -amino group [including phenyl-propionylproline, phenylacetylproline, N-benzoylproline, phenylacetyl--methyldopa, and hippuric acid (N-benzoylglycine)] were studied in the perfused rat intestinal segment. The absorption of phenylpropionylproline, phenylacetyl--methyldopa, and N-benzoylproline was concentration dependent. The transport parameters (mean ± SD) of phenylpropionylproline and N-benzoylproline were as follows: J_max*, 0.037 (±0.019) mM; K _m, 0.045 (±0.027) mM; P _c*, 0.830 (±0.130); and P _m*, 0.673 ± 0.049; and J _max*, 1.34 (±0.24) mM; K _m, 1.31 (±0.30) mM; P _c*, 1.02 (±0.11); and P _m* 0; respectively. The intestinal permeabilities of phenylpropionylproline, phenylacetylproline, N-benzoylproline, and hippuric acid (N-benzoylglycine) were significantly reduced by dipeptides and ceph-radine. These results strongly suggest that these dipeptide analogues, without an -amino group, are transported by the peptide carrier and provide more direct evidence that a free -amino group is not absolutely essential for the mucosal-cell peptide carrier-mediated transport.     

肝细粒棘球蚴病超声影象的病理基础探讨

对98例原发性肝细粒棘球蚴病人,149个肝包虫囊肿进行了超声影象学分型和组织病理学观察。结果表明,超声分型基本上可反映肝细粒棘球蚴囊肿发展阶段的病理特征,可看出随着患者年龄增长,包虫囊肿有由Ⅰ型至Ⅴ型转化的趋势。组织学观察表明,这一转化过程伴随着细粒棘球蚴囊肿自身损伤的逐渐加重。反映了肝细粒棘球蚴囊肿发生、发展和衰亡的规律。结果还表明,在肝细粒棘球蚴病例中,活力基本正常、损伤和死亡的囊肿约各占1/3。上述结果可供肝细粒棘球蚴病化疗中评价疗效时参考。