Objective A number of cardiovascular variables exhibit a circ adian rhythm. Whethe r myocardial contractile response and gene expression of the contractile protein also show changes with a similar period was here investigated. Method Circadi an variabilities in the left ventricular developed pressure (LVP) and contractil ity (LV dp/dt max) were measured in 24 Sprague-Dawley r ats by directly left ve ntricular catheterizing and compared with changes in the gene expression of α- myosin heavy chain (α-MHC) in myocytes obtained from the same animals by dot b lottin g analysis. Results A circadian rhythm was seen in the variabili ty of LVP (P<0.001), LV dp/dt max (P<0.001) and the bio chemically measured expression of the α- MHC gene (P<0.01). As compared to the amplitude of the rhythm i n α-MHC gene exp ression, the amplitude of the contractility rhythm was large (P< 0.01) and the ci rcadian amplitude of the LVP(P<0.001) was the largest, represent ing perhaps a co mposite of intracardiac plus any extracardiac contributions. Conclusion One of factors determing the circadian rhythm of myocardial contractile function is α -MHC gene expression level.

Objective To investigate therapeutic autcomes of using telomerase inhibitors to treat cancer at the presumably most and least opportune circadian stages basing on our earlier study. Methods Twenty-four BALB/C nude mice were synchronized to a regimen of LD12:12 for 4 wk. Hepatic cancer cells (SMMC-7721) were implanted into both flanks of each mouse.Two weeks after transplantation,the hTERT-5'RZ was used to treat the hepatic cancer transplanted into the nude mice daily for two weeks,the injection times being either 9 or 21 HALO.Results The tumorinhibition ratio of mice treated at 21 HALO (65%) was statistically significantly higher than that of mice treated at 9 HALO (48%). Telomerase activity was also reduced to a greater extent in mice treated withhTERT-5'RZ at 21 than at 9 HALO, that was at the time of maximal circadian telomerase activity. Conclusion Injection of ribozyme targeted to telomerase during the tumor's DNA synthesis is associated with a betterinhibition of tumor growth and a better therapeutic outcome in hepaticcancer.