Differential effects of salt on renal hemodynamics and potential pressure transmission in stroke-prone and stroke-resistant spontaneously hypertensive rats

Salt-supplemented stroke-prone spontaneously hypertensive rats (SHRsp) develop more severe hypertension-induced renal damage (HIRD) compared with their progenitor SHR. The present studies were performed to examine whether in addition to increasing the severity of hypertension salt also enhanced the transmission of such hypertension to the renal vascular bed in the SHRsp. "Step" and "dynamic" renal blood flow (RBF) autoregulation (AR) were examined in ~12-wk-old SHR and SHRsp after 3-5 days of an 8% NaCl diet. During step AR under anesthesia (n = 8-11), RBF was significantly higher in the SHRsp at all perfusion pressures (P < 0.01), but AR capacity was not different. Similarly, in separate conscious chronically instrumented rats (n = 8 each), both blood pressure (BP) and RBF were modestly but significantly higher at baseline before salt in the SHRsp (P < 0.05). However, transfer function analysis did not show significant differences in the admittance gain parameters. However, after 3-5 days of salt, although average BP was not significantly altered in either strain, RBF increased further in the SHRsp and there was a significantly greater transfer of BP into RBF power in the SHRsp. This was reflected in the significantly higher admittance gain parameters at most frequencies including the heartbeat frequency (P < 0.05 maximum). These differential hemodynamic effects of salt have the potential to enhance BP transmission to the renal vascular bed and also contribute to the more severe HIRD observed in the salt-supplemented SHRsp

Characterization of dynamics in renal autoregulation using Volterra models

The dynamics of renal autoregulation are modeled using a modified Volterra representation called the fixed pole expansion technique (FPET). A data dependent procedure is proposed for selecting the pole locations in this expansion that enables a reduction in model complexity compared to standard Volterra models. Furthermore, a quantitative characterization of frequency dependent features of the renal autoregulatory response is enabled via the model's pole locations. The utility of this approach is demonstrated by applying the modeling technique to renal blood pressure and renal blood flow measurements in conscious rats. The model is used to characterize the myogenic autoregulatory response in control rats and rats whose renal autoregulation has been impaired by calcium channel blockers. © 2006 IEEE.Office of Academic Affiliations, Department of Veterans Affairs National Institute of Diabetes and Digestive and Kidney Diseases: DK-40426, DK-61653Manuscript received September 17, 2004; revised April 30, 2006. This work was supported in part by National Institutes of Diabetes and Digestive and Kidney Diseases under Grant DK-40426 and Grant DK-61653 and in part by the Office of Research and Development of the Department of Veterans Affairs. Asterisk indicates corresponding author. *R. Hacıog^lu was with the Department of Electrical and Computer Engineering, Illinois Institute of Technology Chicago, IL 60616 USA. He is now with the Department of Electrical and Electronics Engineering, Zonguldak Karaelmas University, Zonguldak 67100, Turkey (e-mail: [email protected])

Geochemistry and Petrogenesis of Late Ediacaran Rare-metal Albite Granites of the Arabian-Nubian Shield

The Abu Dabbab albite granite (ADAG), in the central Eastern Desert of Egypt, hosts the most significant rare metal ore deposit in the northern part of the Neoproterozoic Arabian‐Nubian Shield. Here, we report detailed field, petrographic, mineralogical and geochemical investigation of the ADAG, an isolated stock‐like granitic body with sharp intrusive contacts against metamorphic country rocks, probably emplaced at about 600 Ma. The fine‐grained porphyritic upper unit is a preserved remnant of the shallowly‐emplaced apex of the magma chamber, whereas the medium‐grained lower unit crystallized at deeper levels under subvolcanic conditions. The peraluminous leucocratic ADAG shares common geochemical characteristics with post‐collisional intraplate A‐type magmas. In addition to the conspicuous enrichment in Na_2O, the ADAG is remarkable for its anomalous concentrations of Ta, Nb, Li, Hf, Ga, Sn, Zn and heavy rare‐earth elements. Nb‐Ta minerals in the ADAG are mixed with Fe‐Mn oxides, forming black patches that increase in abundance toward of the base of the intrusion. Columbite–tantalite, cassiterite and wolframite are the most important ore minerals. Pronounced negative Eu anomalies (Eu/Eu* = 0.10–0.24) reflect extreme magmatic fractionation and perhaps the effects of late fluid‐rock interaction. The ADAG was most likely generated by partial melting of the juvenile middle crust of the ANS as the geotherm was elevated by erosional uplift following lithospheric delamination and it was emplaced at the intersection of lineations of structural weakness. Although formation of the ADAG and its primary enrichment in rare metals are essentially due to magmatic processes, late‐stage metasomatism caused limited redistribution of rare metals. Fluid‐driven subsolidus modification was limited to the apex of the magma chamber and drove development of greisen, amazonite, and quartz veins along fracture systems