Purification and characterization of a novel calcium-binding protein, S100C, from porcine heart

A novel Ca(2+)-binding protein, which we have named S100C (Ohta et al. (1991) FEBS Lett. 295, 93-96), was purified to homogeneity from porcine heart by Ca(2+)-dependent dye-affinity chromatography. S100C possesses some properties of S100 proteins, such as self-association and exposure of a hydrophobic site upon binding of Ca2+ but it differs from S100 proteins in forms of its isoelectric point (pI = 6.2), cross-reactivity with antibodies, staining by Stains-all, and its Ca(2+)-dependent interaction with the immobilized dye. S100C bound to cytoskeletal components at physiological concentrations of Ca2+. Moreover, it was found that 125I-labeled S100C interacted with annexin I in a Ca(2+)-dependent manner. S100C also inhibited the phosphorylation of annexin I by protein kinase C. These data suggest that S100C might act to regulate the cytoskeleton in a Ca(2+)-dependent manner via interactions with annexin I.

Correction of motional artifacts in diffusion-weighted MR images using navigator echoes

Patient motion can seriously degrade the quality of diffusion-weighted MR images obtained using standard 2DFT imaging procedures. The main source of error arises from an MR signal phase-shift error which is proportional to the magnitude of the motion. A modified pulse sequence is proposed which uses the phase information from an additional spin echo to correct for patient motion. Application of this technique is demonstrated for a human brain study, which greatly improves the quantification of diffusion values from regions of brain tissue.

Temporal evolution and spatial distribution of the diffusion constant of water in rat brain after transient middle cerebral artery occlusion

The regional distribution and temporal evolution of the diffusion coefficient (Dw) of water in rat brain was measured during and after transient middle cerebral artery (MCA) occlusion. Male Wistar rats (n = 14) were subjected to 2 h of middle cerebral artery occlusion, induced by intracarotid insertion of a filament. Diffusion (n = 14) and perfusion (n = 7) weighted magnetic resonance imaging were performed before, and at various time points after MCA occlusion, ranging from 30 min up to 7 days. Our data demonstrate that the temporal profiles of Dw differ between the severely and the least damaged regions of tissue. In the core of the lesion, where the tissue evolved to necrosis, Dw declined significantly (P < 0.001) within 0.5 h after onset of ischemia, and remained depressed until 24 h after withdrawal of the suture. However, no statistically significant decline in Dw was found in the perifocal regions containing morphologically intact cells. Perfusion MRI qualitatively exhibited a hypoperfusion and reperfusion during, and after 2 h MCA occlusion, respectively. A significant (r > or = 0.71, P < 0.01) correlation was found between delta Dw (the difference in Dw between the ipsilateral ischemic and homologous contralateral control regions) obtained immediately before withdrawal of the suture (2 h of ischemia) and at specific early time points after withdrawal of the suture, and the degree of ischemic cell damage. No significant (P > 0.01) correlation was detected at an early time points of ischemia or at other time points after withdrawal of the suture.(ABSTRACT TRUNCATED AT 250 WORDS)

Histopathological correlations of nuclear magnetic resonance imaging parameters in experimental cerebral ischemia

Changes in the nuclear magnetic resonance (NMR) parameters of spin-lattice relaxation (T1), spin-spin relaxation (T2), proton density (rho), and water diffusion (DNMR) were measured over time together with the histopathological status in three regions of rat brain cortex after permanent middle cerebral artery occlusion (MCA-O). Histological response ranged from severe irreversible damage (necrosis and cavitation) to relatively mild and apparently reversible damage. DNMR was the only NMR parameter which demonstrated a statistically significant change in all three regions of brain studied. Additionally, rho was significantly increased only in the region of brain studied which eventually progressed to necrosis and cavitation. Finally, data are presented which indicate that changes in T2, DNMR, and rho can occur independently of one another.

1H magnetic resonance imaging of normal brain tissue response to photodynamic therapy

1H Magnetic resonance imaging (MRI) was used to study the effects of photodynamic therapy (PDT) on normal rat brain (n = 5) using T1-, T2-, diffusion-, and proton density (rho)-weighted images. Rats received intraperitoneal injections of 12.5 mg/kg of Photofrin II, and 48 hours later the dural area over the frontal cortex was treated with 35 J/cm2 of light (632 +/- 1 nm). The T1-, T2-, and diffusion-weighted images revealed an evolving high contrast region of brain that corresponded to the PDT-treated area. Lesioned brain exhibited significant increases in T1 and T2 relaxation times at 1 day (P less than 0.01) and 3 days (T1, P = 0.018; T2, P less than 0.01) after treatment, compared with the contralateral equivalent volume of nonlesioned brain. Water proton diffusion coefficient (DW) in the lesioned area decreased at 1 day (P = 0.026) and increased at 3 days (P = 0.012) compared with nonlesioned brain. An increase in the proton density ratio (rho D/rho O) from PDT (rho D) versus nonlesioned side (rho O) was found 3 days after PDT treatment (P = 0.03). The data indicate that the biophysical parameters obtained from magnetic resonance imaging scans, T1, T2, DW, and proton density, can be used to monitor changes in an evolving photochemically induced lesion.

Investigation of cerebral ischemia using magnetization transfer contrast (MTC) MR imaging

The effects of cerebral ischemia in rat brain were monitored as a function of time using proton MR imaging. Spin-spin relaxation time (T2), proton density, and magnetization transfer contrast (MTC) were measured by MR imaging at various time intervals during a 1-week period following the induction of ischemic damage. Ischemic injury was characterized by a maximization of both T2 value and MTC appearance at 24 hr postischemic injury. These changes were accompanied by a gradual increase in MR observable water density over the first few days of ischemia. A reduction in the magnetization exchange rate between "free" and "bound" water protons as measured by MTC imaging is at least partially responsible for the elevation in T2 values observed during ischemia, and may accompany breakdown of cellular structure.