[Effects of NaCl stress on the exogenous gene expression in transgenic poplar plants].

The expressions of BtCry1Ac insect-resistance genes and rhizogenesis genes and their response to NaCl stress were studied using tissue culture plants of high transgenic insect-resistant 'poplar 741' and transpolygenes 741 (insect-resistant genes and T-DNA of Ri plasmid). The results showed that IAA and GA contents increased quickly, plant root number increased and root length reduced after rhizogenesis and hormone synthesis related gene in Ri T-DNA were inserted into the genome of poplar (Figs.2, 3, 8 and 9). Plant height, root number, chlorophyll content, IAA and GA contents decreased gradually with an increase in NaCl stress intensity (Figs.1, 2, 4-6, 8 and 9). Apiece index change extent of transgenic rol gene plant was smaller than transgenic Bt gene plant and non-transgenic plant. Bt toxin protein content of transgenic rol gene plant increased significantly under NaCl stress (Fig.7). Our results indicate that the expressions of the foreign genes changed with the changes of the environmental conditions.

Effects of ischemic preconditioning on blood-brain barrier permeability and MMP-9 expression of ischemic brain.

The study was designed to investigate the effects of ischemic preconditioning (IP) on permeability of blood-brain barrier (BBB) and expression of matrix metalloproteinase-9 (MMP-9) in subsequent ischemic hemisphere. Rats were divided into four groups, one group was used as control, and the other three groups were given three different pretreatments: the first group received a saline injection into the right internal carotid artery (SI), the second group underwent both left and right carotid arteries occlusion (BCAO), and the third group was treated with BCAO and SI simultaneously (BS). After 24 hours of pretreatments, the focal cerebral ischemia was induced by inserting a thread into the right middle cerebral artery causing occlusion (MCAO). Brain water content, BBB permeability and MMP-9 expression of ischemic hemisphere brains were measured at 24 and 48 hours after MCAO. After 24 and 48 hours MCAO, averages for brain water content were 82.92 and 83.12% in BS group, 85.19 and 85.73% in SI group and 86.06 and 85.88% in BCAO group. Evans blue content of ischemic hemispheres were 14.01 and 11.74 microg/mm(3) at 24 and 48 hours after MCAO in BS group, which were lower than the other two groups, 16.22, 15.01 and 16.61, 15.58 microg/mm(3), respectively (p<0.01). The expression levels of MMP-9 in ischemic hemisphere in BS were lower than that in other two groups (p<0.01). Therefore, ischemic preconditioning could ameliorate brain edema and BBB disruption caused by subsequent cerebral ischemia. Ischemic preconditioning could decrease MMP-9 protein and mRNA expression, which may be an important mechanism of cerebral ischemic tolerance.