A 44-month retrospective analysis was performed on 666 pacemakers implanted at Mt. Sinai Medical Center. Mapping techniques and endocardial waveform analyses were used during lead positioning to ensure the best electr...
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A 44-month retrospective analysis was performed on 666 pacemakers implanted at Mt. Sinai Medical Center. Mapping techniques and endocardial waveform analyses were used during lead positioning to ensure the best electrical environment. The optimal pacing lead type was selected based on the clinical situation. Follow-up evaluations were rigorous. Patient population ranged in age from 28 to 103 with a mean of 78 years at time of implant. Seventy percent of the patients received DDD pacemakers with an 81% survival incidence at 44 months, of the WI population (30% of the implants), there was a 62% survival incidence. Most problems associated with the pacing systems were related to the atrial channel. Loss of atrial sensing occurred in 7.5% of the population and was corrected noninvasively in 5.8%. Due to chronic loss of atrial sensing, 1.7% of the population remained programmed to DVI/VVI. A total of 7.7% were chronically reprogrammed from DDD to WI, 5.6% secondary to atrial fibrillation. Reoperations were necessary in 1.2% of the malfunctioning systems that could not be corrected by reprogramming. The following conclusions were reached: (1) maximizing hemodynamic benefits and minimizing pacemaker complications permitted a survival rate equal to or better than that of the general population, and (2) chronic problems related to the atrial lead and malfunctions of the pacing system were minimized by careful patient selection, appropriate pacemaker and lead selection, endocardial waveform analysis, and thorough follow-up.
Changes in the mRNA population of the mesonotal epidermal cells were investigated inGalleria mellonella during the first 48 h after pupation. Total RNA was extracted and assayed by in vitro translation. The translatio...
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Changes in the mRNA population of the mesonotal epidermal cells were investigated inGalleria mellonella during the first 48 h after pupation. Total RNA was extracted and assayed by in vitro translation. The translational products were separated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and visualized by autoradiography. The changing banding pattern of the in vitro synthesized proteins indicates changes in the cellular pattern of mRNAs, most of which occur between 6 h and 18 h after pupal ecdysis. These changes mostly consist in the decrease or disappearance of bands. The injection of juvenile hormone (JH) immediately after pupal ecdysis does not qualitatively influence mRNA changes, but does alter their time course, for they are postponed for 6–12 h. After the injection of 20-hydroxyecdysone (20HE) the same changes can again be seen, but they are greatly accelerated. A comparison of these results with known data on the time course of reprogramming and ecdysteroid titre leads to the conclusion that the mRNA changes in the epidermal cells are a prerequisite for the renewed expression of a developmental programme. This is independent of whether, in the absence of JH, a new programme is determined or whether, under the influence of JH, the previous programme is restored. 20HE does not have any effect on the change in the developmental programme. The change seems to occur as an active and autonomous process in the epidermal cells, in accordance with a genetically fixed developmental programme.
The epidermal cell cycle of the pupal mesonotum of Galleria was investigated by the determination of mitotic indices, [3H]thymidine incorporation and flow-cytophotometric analysis during the first 48 h after pupation....
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The epidermal cell cycle of the pupal mesonotum of Galleria was investigated by the determination of mitotic indices, [3H]thymidine incorporation and flow-cytophotometric analysis during the first 48 h after pupation. Immediately after the pupal ecdysis nearly all epidermal cells are arrested in G2 [post synthetic period]. Thereafter only a few mitoses occur, leading to a slow increase in the number of G1 [presynthetic period] nuclei. With the onset of a mitotic wave at a pupal age of 21 h this increase becomes more rapid. On day 2, the cell population reaches a plateau in the number of G1 (resp. G2) cells, reflecting a steady state between mitotic activity and DNA synthesis. A comparison of these cell cycle changes with known data of the time course of reprogramming and ecdysteroid titer leads to the conclusion that there is no causal relationship between DNA synthesis and cellular determination in the sense of a quantal cell cycle, and that DNA synthesis can precede the definite rise in ecdysteroid titer.
Sensitivity to juvenile hormone and to 20-hydroxyecdysone was investigated during the last-larval stages of T. molitor. Topical applications of a juvenile hormone analog (K-421d) showed that the sensitive period, occu...
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Sensitivity to juvenile hormone and to 20-hydroxyecdysone was investigated during the last-larval stages of T. molitor. Topical applications of a juvenile hormone analog (K-421d) showed that the sensitive period, occurring before apolysis, is relatively short (< 4 days in a 3-wk instar) and divided into 2 phases. Treatment during the 1st and longest phase induced a delay in development and then an increase in larval molt percentage. Treatment during the 2nd phase induced several abnormal molts (prothetelic larvae and larval-pupal intermediates). Injections of massive doses of 20-hydroxyecdysone (10 .mu.g/animal) also evidenced a period of disturbance of the morphogenetic program, beginning before pupal apolysis but continuing several days after. Comparison of the sensitive periods to both hormones suggests that a very important and rapid step of the larval-pupal program change is controlled hormonally just before pupal apolysis.
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