Experimental and clinicopathologic study on the relationship between transcription factor Egr-1 and esophageal carcinoma.

AIM: To observe the growth suppression effect of exogenous introduction of early growth response gene-1 (Egr-1 gene) on esophageal carcinoma tissue as well as on esophageal carcinoma cell line Eca109 and to explore the potential application of Egr-1 gene in gene therapy of tumor. METHODS: Eukaryotic expression vector of PCMV-Egr-1 plasmid was introduced into Eca109 cell line which expressed no Egr-1 protein originally with lipofectamine transfection method. The introduction and expression of PCMV-Egr-1 plasmid into Eca109 cell line was confirmed by G418 selection culture, PCR amplification of neogene contained in the vector, Western blot analysis and immunocytochemical analysis. The cell growth curve, soft agar colony formation rate and tumorigenicity in SCID mice were examined to demonstrate the growth suppression effect of exogenous Egr-1 gene on Eca109 cell line. The Egr-1 mRNA and Egr-1 protein were also detected in 50 surgical specimens of esophageal carcinoma by in situ hybridization and immunohistochemistry. RESULTS: Exogenous Egr-1 gene was introduced successfully into Eca109 cell line and expressed Egr-1 protein stably. The transfected Eca109 cell line grew more slowly than control Eca109 as shown by cell growth curves, the soft agar colony formation rate (4.0% vs 6.9%, P < 0.01) and the average growth rate of tumor in SCID mice (35.5 +/- 7.6 vs 65.8 +/- 7.6, P < 0.05). The expression level of Egr-1 mRNA and protein significantly increased in dysplastic epithelia adjacent to cancer rather than in cancer tissues (65.8% vs 20.0% by ISH and 57.9% vs 0.01). CONCLUSION: Exogenous Egr-1 gene shows the strong effect of growth inhibition in Eca109 cell line. Egr-1 in the cancer tissue shows down-regulated expression that supports the inhibited function of Egr-1 in cancer growth and suggests Egr-1 may have an important role in gene therapy of esophageal carcinoma.

[Molecular mapping of the S-a locus for F1 pollen sterility in cultivated rice (Oryza sativa L.)].

F1 pollen sterility in cultivated rice (Oryza sativa L.) was found to be caused by at least six loci of F1 pollen sterility genes. At the S-a locus, one of the six loci for F1 pollen sterility, the allelic interaction of S-ai and S-aj causes the male gametes carrying S-aj allele abortive. To map the S-a locus, Taichung 65(T65), a Keng (japonica) variety with S-aj/S-aj, its isogenic F1 sterile line TISL4 with S-ai/S-ai from Chin-tsao, a Hsien (indica) variety, and the F2 population from cross T65 x TISL4 were used as materials. The polymorphism between T65 and TISL4 detected by RFLP and RAPD analysis was less than 1%. This result indicated that short segments from Chin-tsao were introgressed into the isogenic F1 sterile line, since the TISL4 was developed by repeatedly backcrossing for thirteen times. By linkage analysis of S-a and the marker loci, the S-a locus was mapped on chromosome 1. The genetic distances between S-a and RFLP markers CDO548 and RG146 are 6.4 cM and 7.2 cM respectively, and those between S-a and RAPD markers O11-1000 and Y13-500 are 6.8 cM and 11.2 cM respectively. The mapping of the S-a locus is an important step towards marker-aided selection for overcoming the hybrid sterility in rice.

A reevaluation of the critical membrane potential of the effective refractory period in guinea pig ventricular fibres.

The traditional critical membrane potential (CMP), -55(-)-60 mV, which corresponds to effective refractory period (ERP), was anew investigated in guinea pig ventricular muscle fibres. The electrical and contractile responses to the stimulus during repolarization of action potential (AP), particularly from +10 to -60 mV, were observed. One third of 35 tested cells displayed testing action potential (TAP) and local response at > or = -54 mV when they were stimulated by testing pulses in 37 degrees C normal Tyrode's solution. Potential level of TAP which occurred earliest was at -30 mV and that of local response which appeared earliest was at 0 mV during repolarization among 95 systematic tests. Most of the TAPs belonged to the slow response potential type. The ratio of TAP evoked at > or = -54 mV initial membrane potential (IMP) was as high as 86% when the experiment was carried out in 37 degrees C 1.5 mmol KC1/L Tyrode's solution. In view of distribution of IMPs of TAPs, the CMP of ERP in guinea pig ventricular muscle fibres was more positive than traditional CMP measured by Hoffman et al. in dog, sheep Purkinje fibres and had a quite changeable range. The CMP of every cell in ventricular muscle was not all the same, and their CMPs approximated to normal distribution. There was no sharp line separating ERP from relative refractory period in myocardium. Higher temperature and low [K]0 were the important factors elevating CMP of ERP.

Effects and mechanism of low [K]o on the critical potential of effective refractory period in guinea pig ventricular muscle cells.

1.5 mM KCl Tyrode's solution enabled the critical potential (-55-60 mV) of effective refractory period to shift in a positive direction in guinea pig ventricular muscle cells. In 1.5 mM KCl Tyrode's solution, the probability of testing AP's initial potential positive to -54 mV in the repolarizing phase was as high as 80% (n = 10), but the percentage in 4.5 mM [K]o group was only 11% (n = 35). The mean value of the positive shift was 30.2 +/- SD 17 mV. Testing APs had higher values of overshoots (mean = 23 +/- 13.8 mV); their mean Vmax was 98 V/s. Early after depolarization and positive inotropic effects appeared. 13.5 mM KCl, in contrast to 1.5 mM KCl, produced contrary effects. Phenomena indicated that early after depolarization in low [K]o was associated with the positive shift of critical potential of effective refractory period. Above-mentioned effects of 1.5 mM KCl could not be completely eliminated by verapamil, but could be abolished by an inactivation promoting agent of sodium channel, lidocaine 7.4 x 10(-5) M (n = 10). The results suggest that accelerating recovery time and shifting recovery potential in the positive direction of inactivated sodium channel might be the principal reasons for the effects of low [K]o. The role of the Na+ pump inhibitor, ouabain, was not similar to that of 1.5 mM KCl Tyrode's solution except for positive inotropic effect.