Acute and chronic stability of atrial screw-in leads.

The purpose of this study was to evaluate the acute and chronic stability of the atrial screw-in lead. In this study, we used CPI model 4165, 4166, and 4266 porous tip screw-in leads in 32 patients (12 for AAI pacing and 20 for DDD pacing). All of these leads were fixed to the free wall of the right atrium and used as the unipolar type. Acute voltage and current thresholds, lead impedance, P-wave amplitude, and chronic threshold were measured. Early and late complications were also investigated. The average acute stimulation thresholds at 0.6 msec pulse width were 0.82 +/- 0.43 V and 1.1 +/- 0.6 mA. Mean lead impedance was 627.2 +/- 83.1 ohms, and mean P wave amplitude was 3.1 +/- 1.1 mV. After an average follow-up period of 32 months (range: 2-72 months), we found the results of the chronic threshold study to be satisfactory. The thresholds were usually below 0.1 msec pulse width with the nominally programmed pacemaker output. Only one patient required a higher output due to an increased threshold. With regard to complications, neither lead dislodgment nor cardiac perforation was observed. In conclusion, acute and chronic thresholds were satisfactory and no serious complications occurred. Therefore the atrial screw-in lead has long-term reliability and stability.

Androgen regulation of a specific gene in hamster flank organs.

Flank organs of Golden Syrian hamster containing large sebaceous glands are a useful model for studying androgen-dependent gene expression. Recently, we have isolated an androgen-dependent gene from a cDNA library constructed from male mRNAs of flank organs. In the present study, using this gene as a probe, we examined the kinetics of loss and re-expression of the mRNA of this gene. Dot blot hybridization, the current method, can approximately quantify mRNA levels. Castration caused a marked decrease in the mRNA within a few days to undetectable levels. Topical application of testosterone re-activated the mRNA levels, with the earliest activation within 24 h. The results of various topical steroid applications showed a full re-activation of the mRNA by testosterone and dihydrotestosterone, partial re-activation by androstanedione and androstenedione, and no activation by androstanediol or dehydroepiandrosterone. Simultaneous application of testosterone and progesterone inhibited the expression of mRNA but application of dihydrotestosterone and progesterone did not. The current dot blot hybridization technique appears to be a more direct approach for studying androgen action on DNAs than other previously used methods such as morphometry or enzyme assay.