Dynamic relationship between sympathetic nerve activity and renal blood flow: a frequency domain approach

Blood pressure displays an oscillation at 0.1 Hz in humans that is well established to be due to oscillations in sympathetic nerve activity (SNA). However, the mechanisms that control the strength or frequency of this oscillation are poorly understood. The aim of the present study was to define the dynamic relationship between SNA and the vasculature. The sympathetic nerves to the kidney were electrically stimulated in six pentobarbital-sodium anesthetized rabbits, and the renal blood flow response was recorded. A pseudo-random binary sequence (PRBS) was applied to the renal nerves, which contains equal spectral power at frequencies in the range of interest (<1 Hz). Transfer function analysis revealed a complex system composed of low-pass filter characteristics but also with regions of constant gain. A model was developed that accounted for this relationship composed of a 2 zero/4 pole transfer function. Although the position of the poles and zeros varied among animals, the model structure was consistent. We also found the time delay between the stimulus and the RBF responses to be consistent among animals (mean 672 ± 22 ms). We propose that the identification of the precise relationship between SNA and renal blood flow (RBF) is a fundamental and necessary step toward understanding the interaction between SNA and other physiological mediators of RBF

激光探针等离子体质谱用于错石Pb-Pb定年的分析和校正方法的进一步探讨

激光探针等离子体质谱可对错石进行快速准确的Pb一Pb 同位素定年。本文进一步探讨了该方法应用中的几个问题。对不同样品采用不同的聚焦方式可以对U/Pb 分异有一定的控制作用。在一定的条件下, 不连续和连续采样模式都可以得到较高精度和准确度的结果。连续采样模式还可以得到同位素计数的深度剖面。不同的侧量滞留时间会影响测量结果的精度。20Ins 为适合错石ZO7Pb/206Pb 分析的最佳侧量滞留时间。在对侧定结果进行校正时, 可以采用玻璃标样NIST61O 和错石标样两种不同的校正方法。Laser probe-inductively coupled plasma mass spectrometry (LP-ICPMS) provides a rapid,precise and accurate technique for Pb-Pb zircon chronology. Different conditions affect massfractionation during laser ablation. Fixed-focus-mode and active-focus-mode, focus-mode anddefocus-mode, time-average mode (single point method) and time-resolved mode (depth pro-filing method), are compared. Both time-average mode and time-resolved mode can give rel-atively high precise, accurate results, and depth profile can only be obtained by time-resolvedmode. Comparing the results of time-resolved mode using different dwell time, it is found that20 ms is the best dwell time with highest precision and accuracy. It is shown that both NIST610and Zircon Standard give satisfactory calibration results for zircon 207Pb/206Pb isotopic age.Therefore, time resolved mode with dwell time of 20 ms is preferred for zircon analysis.published_or_final_versio

Environmental impacts of mining the giant Panzhihua V-Ti magnetite deposit, SW China

Abstract in http://www.lpi.usra.edu/meetings/gold2001/pdf/3530.pd

Oceanic inside corner detachments of the Limassol Forest area, Troodos ophiolite, Cyprus

Flat-lying extensional detachment faults have been imaged in the inside corner regions of ridge-transform intersections on the Mid-Atlantic Ridge. Exposed detachment surfaces are 10 km or more across, and are corrugated in the direction of spreading, as are continental detachments. Beneath the detachments lie core complexes of peridotite and gabbro; these are overlain by blocks of crustal material. We argue here that similar detachments are an essential component of the Limassol Forest area of the Troodos ophiolite in Cyprus, which lies south of the Arakapas Fault zone, previously recognized as a palaco-transform fault, and here interpreted as a transform fault that evolved into a fracture zone. In the Limassol Forest, core complexes of mantle peridotite can be shown to have been exposed at the sea floor, or to have been covered by overlapping crustal blocks, separated from the peridotite core and from each other by low-angle extensional faults. The extension can be shown to have occured shortly after crustal construction, and the already extended terrain was then intruded by swarms of dykes and plutons. We interpret these relations as arising when crust is constructed in an inside corner area, extended by detachment faulting, deformed further during slip along the transform, and then intruded by new magma as it passes the second spreading centre. The structurally deeper parts of the crustal blocks that overlie the detachment lie broadly towards the west, indicating that the spreading axis lay in that direction. The ophiolite north of the transform is much less extended, and we interpret this as a section of outside corner crust. In this interpretation, the Troodos ophiolite formed to the east (in its current orientation) of a ridge-transform-ridge intersection, in which the transform had a dextral offset and sinistral slip. The part of the ophiolite that forms the Limassol Forest was produced at the western inside corner, and spread eastward until it passed the second spreading axis, at which point the ophiolite north of the Arakapas Fault was created and welded to the Limassol Forest when the transform became a fracture zone.published_or_final_versio

Exogenous and endogenous angiotensin-II decrease renal cortical oxygen tension in conscious rats by limiting renal blood flow

Our understanding of the mechanisms underlying the role of hypoxia in the initiation and progression of renal disease remains rudimentary. We have developed a method that allows wireless measurement of renal tissue oxygen tension in unrestrained rats. This method provides stable and continuous measurements of cortical tissue oxygen tension (PO2) for more than 2 weeks and can reproducibly detect acute changes in cortical oxygenation. Exogenous angiotensin-II reduced renal cortical tissue PO2 more than equi-pressor doses of phenylephrine, probably because it reduced renal oxygen delivery more than did phenylephrine. Activation of the endogenous renin-angiotensin system in transgenic Cyp1a1Ren2 rats reduced cortical tissue PO2; in this model renal hypoxia precedes the development of structural pathology and can be reversed acutely by an angiotensin-II receptor type 1 antagonist. Angiotensin-II promotes renal hypoxia, which may in turn contribute to its pathological effects during development of chronic kidney disease. We hypothesised that both exogenous and endogenous angiotensin-II (AngII) can decrease the partial pressure of oxygen (PO2) in the renal cortex of unrestrained rats, which might in turn contribute to the progression of chronic kidney disease. Rats were instrumented with telemeters equipped with a carbon paste electrode for continuous measurement of renal cortical tissue PO2. The method reproducibly detected acute changes in cortical oxygenation induced by systemic hyperoxia and hypoxia. In conscious rats, renal cortical PO2 was dose-dependently reduced by intravenous AngII. Reductions in PO2 were significantly greater than those induced by equi-pressor doses of phenylephrine. In anaesthetised rats, renal oxygen consumption was not affected, and filtration fraction was increased only in the AngII infused animals. Oxygen delivery decreased by 50% after infusion of AngII and renal blood flow (RBF) fell by 3.3 ml min(-1) . Equi-pressor infusion of phenylephrine did not significantly reduce RBF or renal oxygen delivery. Activation of the endogenous renin-angiotensin system in Cyp1a1Ren2 transgenic rats reduced cortical tissue PO2. This could be reversed within minutes by pharmacological angiotensin-II receptor type 1 (AT1 R) blockade. Thus AngII is an important modulator of renal cortical oxygenation via AT1 receptors. AngII had a greater influence on cortical oxygenation than did phenylephrine. This phenomenon appears to be attributable to the profound impact of AngII on renal oxygen delivery. We conclude that the ability of AngII to promote renal cortical hypoxia may contribute to its influence on initiation and progression of chronic kidney diseas

Deterministic Chaos in Blood Pressure Signals During Different Physiological Conditions

Several coupled and nonlinear controlling mechanisms are involved in the regulation of blood pressure. The possible presence of chaos in physiological signals has been the subject of some research. In this study, blood pressure signals were analysed using a range of nonlinear time series analysis techniques. Individual effectors of blood pressure were either experimentally removed or enhanced, so that the controlling mechanisms that are responsible for the chaotic nature of the signals may be identified by chaotic analysis of the signals. The level of chaos varied across the different experimental conditions, showing a distinct decrease from control conditions to all other experimental conditions

Deterministic Chaos in Blood Pressure Signals During Different Physiological Conditions

Several coupled and nonlinear controlling mechanisms are involved in the regulation of blood pressure. The possible presence of chaos in physiological signals has been the subject of some research. In this study, blood pressure signals were analysed using a range of nonlinear time series analysis techniques. Individual effectors of blood pressure were either experimentally removed or enhanced, so that the controlling mechanisms that are responsible for the chaotic nature of the signals may be identified by chaotic analysis of the signals. The level of chaos varied across the different experimental conditions, showing a distinct decrease from control conditions to all other experimental conditions

'VEEP' in children with Hodgkin's disease--a regimen to decrease late sequelae.

In an attempt to decrease the risk of second malignancies and future infertility in children with Hodgkin's disease (HD) while retaining acceptable remission rates, an anthracycline based regimen containing no alkylating agent has been devised. VEEP contains vincristine, epirubicin, etoposide and prednisolone given at 3 weekly intervals. Forty-four patients, aged 2-15 years, have been treated: ten relapsed patients and 34 previously untreated with chemotherapy (including three relapsed stage I treated initially with radiotherapy). The median follow up for all patients is 25 months (range 6-52 months). The response rate in previously treated patients was 80% (95% CI 44-97%) and five remain alive in remission. The response rate in untreated patients was 88% (95% CI 72-97%) with 62% CR + CR(u) (uncertain/unconfirmed) (95% CI 44-77%). Of four patients who had a final response of CR(u) three have relapsed at 9, 16 and 38 months. Two of the children in CR have relapsed at 6 and 16 months. The relapse free rate at 3 years is 67% (95% CI 17-82%). In this pilot study the event free survival appears somewhat poorer than conventional combinations and further follow up is required to confirm the salvagability of relapsed patients