[Construction of thr461 --> Asn461 and Ile462 --> Val462 mutation vector of P4501A1 gene].

OBJECTIVE: To construct Thr461 --> Asn461 and Ile462 --> Val462 mutation vector of P4501A1 gene and to provide scientific base for deeply researching on the function of cytochrome 1A1 gene (CYP1A1) and the mechanism of carcinogenesis. METHODS: According to cDNA sequence of human CYP1A1 gene, universal primers (Pm3/Pm4) and mutant primers (Pt15/Pt16 and Pt17/Pt18) containing restriction enzyme site and mutation site were designed. The first set of primers involving Pm3/Pt16 and Pm3/Pt18 amplified a forward 1.5kb fragment from pGEM-T-CYP1A1 plasmid. The second set of primers involving Pt15/Pm4 and Pt17/Pm4 amplified a reverse 177-bp fragment from 10ng pGEM-T-CYP1A1 plasmid. The third set of primers involving Pm3/Pm4 amplified a 1.5kb fragment from the fomer PCR amplifications. The third PCR products were separated, purified and recovered from 1% agarose gel, then inserted into pMD-T vector. Subsequently the conjunct products were transformed into E. coil strain DH-5alpha., then the single clone was screened out and plasmids were extracted from such clone finally verified by restriction endonuclease analysis and sequencing. RESULTS: A 1.5kb fragment of tricycle PCR amplifications were digested by restriction endonucleases (BamHI and SailI) and sequenced bidirectionally by universal primers(T7p and SP6). The results verified that the cloned fragment including Asn461 and Val462 mutant site had 99.9% homology with the human cDNA of CYP1A1 gene in Genebank. CONCLUSION: The objective fragment containing Asn461 and Va462 mutant site with cDNA of the CYP1A1 gene has been successfully constructed in this experiment.

[Impact of low-level lead exposure on neural cell adhesion molecule expression of primarily cultured hippocampal neurons].

OBJECTIVE: To study the impact of low-level lead exposure on neural cell adhesion molecule (NCAM) expression of primarily cultured hippocampal neurons. METHODS: Wistar rats gestated at 18th day were anaesthetized and paunched to get the pups, the hippocampi of the pups were separated and the hippocampal neurons were primarily cultured. After co-cultivated with different dosage of PbCl(2), the NCAM expression of the neurons were tested with Western blotting at different culture time. RESULTS: Normally, the expression of NCAM at the 1st culture day was very low and its integral obsorbency density was 14; the climax expression time of NCAM of the cultured hippocampal neurons was 3rd to 5th cultured day, and their integral obsorbency density were 2 542 to 2 580; henceforth, the NCAM expression declined. NCAM expression was inhibited significantly by lead during the 2nd to 4th cultured day, and dose-response relationship was observed. The inhibition of lead weakened along with the cultured time prolonged, at 5th cultured day, it disappeared, and the NCAM expression of 10(-2), 10(-3) and 10(-4) mmol/L groups even exceeded the control groups. After that, the expression of NCAM in all groups began to decline, and the dose-response relationship of lead to the NCAM expression was observed again. CONCLUSION: Low-level lead might significantly inhibit the NCAM expression of the primarily cultured Wistar rats' hippocampal neurons, and might delay the climax NCAM expression time.

Aluminum-induced apoptosis in cultured cortical neurons and its effect on SAPK/JNK signal transduction pathway.

Aluminum exposure and apoptotic cell death has been implicated in several neurodegenerative diseases. The mechanisms by which aluminum interacts with the nervous system are only partly understood. In this study, we used cultured cortical neurons to investigate the ability of aluminum to induce the apoptosis of neurons and to explore the role of SAPK/JNK (stress-activated protein kinase or c-jun N-terminal kinase) signal transduction pathway on the apoptosis induced by aluminum. We found that aluminum-induced degeneration of cortical neurons involved the DNA fragmentation characteristic of apoptosis, and staining of aluminum-treated neurons with the DNA-binding fluorochrome Hoechst 33258 revealed the typical apoptotic condensation and fragmentation of chromatin. The rate of apoptosis increased significantly (from 4.9 to 13.1, 21.4, and 59.8%, P<0.01), which was measured by TdT-mediated dUTP nick end labeling. Western blot analysis showed that SAPK/JNK activities of cortical neurons varies when the exposure time of AlCl(3) were different. The phosphorylation levels were 4.2, 3.3, 1.9 and 1.1 times greater compared to control cultures for 6, 12, 24, and 48 h, respectively (P<0.01). Furthermore, a JNK pathway inhibitor, CEP-11004 (KT8138) inhibited the activation of SAPK/JNK to protect cortical neurons from apoptosis induced by aluminum chloride. Our study demonstrates that aluminum can induce the apoptosis of cortical neurons and SAPK/JNK signal transduction pathway may play an important role in the apoptosis.