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Cycle Rate (cycle + rate)
Selected AbstractsReentrant Ventricular Tachycardia Originating from the Aortic Sinus Cusp:JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2004A Case Report We report a case of idiopathic reentrant ventricular tachycardia (VT) originating from the left aortic sinus cusp. A prepotential preceding the QRS complex by 58 ms was recorded from the posterior right ventricular (RV) outflow tract. During VT entrainment observed by pacing from the midseptal RV, it initially was orthodromically captured with a long conduction time but then antidromically captured as the pacing cycle rate was increased. Pacing at that site failed to show concealed entrainment despite a postpacing interval similar to the VT cycle length. Radiofrequency catheter ablation abolished the VT in the left aortic sinus cusp where a prepotential preceding the QRS complex by 78 ms with a postpacing interval similar to the VT cycle length was recorded in addition to concealed entrainment. The findings suggest that, in this VT, a critical slow conduction zone is partially present extending from the left aortic sinus cusp to the posterior right ventricular outflow tract. The patient has remained free from VT recurrence after 5-month follow-up. [source] On the reliability of 13C metabolic modeling with two-compartment neuronal-glial modelsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 15 2007Alexander A. Shestov Abstract Metabolic modeling of 13C NMR spectroscopy (13C MRS) data using two-compartment neuronal-glial models enabled non-invasive measurements of the glutamate-glutamine cycle rate (VNT) in the brain in vivo. However, the reliability of such two-compartment metabolic modeling has not been examined thoroughly. This study uses Monte-Carlo simulations to investigate the reliability of metabolic modeling of 13C positional enrichment time courses measured in brain amino acids such as glutamate and glutamine during [1- 13C]- or [1,6- 13C2]glucose infusion. Results show that the determination of VNT is not very precise under experimental conditions typical of in vivo NMR studies, whereas the neuronal TCA cycle rate VTCA(N) is determined with a much higher precision. Consistent with these results, simulated 13C positional enrichment curves for glutamate and glutamine are much more sensitive to the value of VTCA(N) than to the value of VNT. We conclude that the determination of the glutamate-glutamine cycle rate VNT using 13C MRS is relatively unreliable when fitting 13C positional enrichment curves obtained during [1- 13C] or [1,6- 13C2]glucose infusion. Further developments are needed to improve the determination of VNT, for example using additional information from 13C- 13C isotopomers and/or using glial specific substrates such as [2- 13C]acetate. © 2007 Wiley-Liss, Inc. [source] Mathematical modeling of 13C label incorporation of the TCA cycle: The concept of composite precursor functionJOURNAL OF NEUROSCIENCE RESEARCH, Issue 15 2007Kai Uffmann Abstract A novel approach for the mathematical modeling of 13C label incorporation into amino acids via the TCA cycle that eliminates the explicit calculation of the labeling of the TCA cycle intermediates is described, resulting in one differential equation per measurable time course of labeled amino acid. The equations demonstrate that both glutamate C4 and C3 labeling depend in a predictible manner on both transmitochondrial exchange rate, VX, and TCA cycle rate, VTCA. For example, glutamate C4 labeling alone does not provide any information on either VX or VTCA but rather a composite "flux". Interestingly, glutamate C3 simultaneously receives label not only from pyruvate C3 but also from glutamate C4, described by composite precursor functions that depend in a probabilistic way on the ratio of VX to VTCA: An initial rate of labeling of glutamate C3 (or C2) being close to zero is indicative of a high VX/VTCA. The derived analytical solution of these equations shows that, when the labeling of the precursor pool pyruvate reaches steady state quickly compared with the turnover rate of the measured amino acids, instantaneous labeling can be assumed for pyruvate. The derived analytical solution has acceptable errors compared with experimental uncertainty, thus obviating precise knowledge on the labeling kinetics of the precursor. In conclusion, a substantial reformulation of the modeling of label flow via the TCA cycle turnover into the amino acids is presented in the current study. This approach allows one to determine metabolic rates by fitting explicit mathematical functions to measured time courses. © 2007 Wiley-Liss, Inc. [source] Bed rest versus free mobilisation following embryo transfer: a prospective randomised studyBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 11 2004Zouhair O. Amarin Objective To evaluate the efficacy of two clinical methods of post-embryo transfer protocols in patients undergoing in vitro fertilisation. Design Prospective, randomised clinical trial. Setting Hospital-based clinic for reproductive medicine. Sample Women under 40 years of age who were undergoing in vitro fertilisation with GnRH pituitary down-regulation and controlled ovarian hyperstimulation. Methods Patients were randomised to rest for either 1 or 24 hours after embryo transfer. Main outcome measure Clinical pregnancy per cycle rate (the percentage of cycles started that demonstrated a live fetus on ultrasound examination performed at six or seven weeks of gestation). Results The clinical pregnancy rates were 21.5% for the 1-hour and 18.2% for the 24-hour post-embryo transfer groups. The implantation rate per embryo was significantly higher in the 1-hour group (14.4%) than in the 24-hour group (9%). Conclusion One-hour and 24-hour rest post-embryo transfer result in comparable rates of clinical pregnancy. However, 24-hour rest results in reduced implantation rate per embryo. [source] | ||||||||||