High-resolution MR vessel wall imaging in determining the stroke aetiology and risk stratification in isolated middle cerebral artery disease.

PURPOSE: High-resolution MR vessel wall imaging (HRVWI) can characterise vessel wall pathology affecting intracranial circulation and helps in differentiating intracranial vasculopathies. The aim was to differentiate intracranial pathologies involving middle cerebral artery (MCA) in patients with ischemic stroke and characterise the high-risk plaques in intracranial atherosclerotic disease (ICAD) using HRVWI. METHODS: Patients with ischemic stroke with isolated MCA disease with ≥ 50% luminal narrowing by vascular imaging were enrolled within 2 weeks of onset and underwent high-resolution (3 T) intracranial vessel wall imaging (VWI). The pattern of vessel wall thickening, high signal on T1-weighted images, juxtaluminal hyperintensity, pattern and grade of enhancement were studied. The TOAST classification before and after HRVWI and the correlation of the recurrence of ischemic events at 3 months with imaging characteristics were analysed. RESULTS: Of the 36 patients, the mean age was 49.53 ± 15.61 years. After luminal imaging, by TOAST classification, 12 of 36 patients had stroke of undetermined aetiology. After vessel wall imaging, lesions in MCA were analysed. Of them, 23 patients had ICAD, 8 had vasculitis, and 2 had partially occlusive thrombus in MCA. The ability of HRVWI to bring a change in diagnosis was significant (p = 0.031). Of the 23 patients with ICAD, 12 patients had recurrent strokes within 3 months. The presence of grade 2 contrast enhancement (p = 0.02) and type 2 wall thickening (p = 0.03) showed a statistically significant association with recurrent ischemic events. CONCLUSION: High-resolution MRVWI can help in identifying the aetiology of stroke. The HRVWI characteristics in ICAD can help in risk stratification.

Vessel Wall Thickening and Enhancement in High-Resolution Intracranial Vessel Wall Imaging: A Predictor of Future Ischemic Events in Moyamoya Disease.

BACKGROUND AND PURPOSE: Very few data are available with regard to high-resolution intracranial vessel wall imaging characteristics of Moyamoya disease and their relation to ischemic stroke risk. We investigated the high resolution imaging characteristics of MMD and its correlation with recent ischemic events. MATERIALS AND METHODS: Patients with Moyamoya disease confirmed by DSA, including patients after revascularization, were enrolled. All the patients underwent high-resolution intracranial vessel wall imaging. Vessel wall thickening, enhancement, and the remodeling index of the bilateral distal ICA and proximal MCA were noted. The patients were followed up at 3 months and 6 months after high-resolution intracranial vessel wall imaging and the association of ischemic events with imaging characteristics was assessed. RESULTS: Twenty-nine patients with Moyamoya disease were enrolled. The median age at symptom onset was 12 years (range, 1-51 years). A total of 166 steno-occlusive lesions were detected by high-resolution intracranial vessel wall imaging. Eleven lesions with concentric wall thickening (6.6%) were noted in 9 patients. Ten concentric contrast-enhancing lesions were observed in 8 patients, of which 3 patients (4 lesions) showed grade II enhancement. The presence of contrast enhancement (P = .01) and wall thickening (P ≤ .001) showed a statistically significant association with ischemic events within 3 months before and after the vessel wall imaging. Grade II enhancement showed a statistically significant (P = .02) association with ischemic events within 4 weeks of high-resolution intracranial vessel wall imaging. The mean ± standard deviation outer diameter of the distal ICA (right, -3.3 ± 0.68 mm; left, 3.4 ± 0.60 mm) and the remodeling index (right, 0.71 ± 0.13; left, 0.69 ± 0.13) were lower in Moyamoya disease. CONCLUSIONS: High-resolution intracranial vessel wall imaging characteristics of concentric wall thickening and enhancement are relatively rare in our cohort of patients with Moyamoya disease. The presence of wall thickening and enhancement may predict future ischemic events in patients with Moyamoya disease.

Experimental and first-principles investigation of the adsorption and entrapping of guanine with SiO2 clusters of sol-gel silicate material for understanding DNA photodamage.

We report a first principles density functional theoretical (DFT) investigation of guanine (G) adsorption onto SiO2 clusters, viz., Si2O4, Si3O6, Si4O8 and Si5O10 in terms of geometry, binding energy (EB), binding site, energy gap (Eg), and electronic and spectral properties. Guanine entrapped within a Si9O18 cluster was also studied in terms of geometry, energy gap (Eg), electronic and spectral properties. We observed that the most stable forms of the cluster were Si5O10 and Si9O18. Guanine adsorbed onto SiO2 (G-SiO2) and guanine entrapped within SiO2 (GE-SiO2) were analyzed by the B3LYP/LanL2DZ method. The HOMO-LUMO energies illustrate that charge transfer from ligand to metal (L → M) occurs in G-SiO2 clusters as guanine to SiO2. The composite of guanine with nanostructured silica material was prepared by simple precipitation and chemical sol-gel processes. The prepared G-SiO2 and GE-SiO2 composites were characterized by FT-IR and FE-SEM with EDX analysis. The resulting experimental evidence is included for better understanding the guanine adsorption and entrapment. The adsorption and entrapping of G-SiO2 and GE-SiO2 was also confirmed by UV-vis spectroscopy. Experimental results are compared with the DFT results. Furthermore, the sol-gel silicate material used to protect the DNA base (guanine) from UVA-irradiation has been highlighted.

Surface enhanced vibrational spectroscopy and first-principles study of L-cysteine adsorption on noble trimetallic Au/Pt@Rh clusters.

The Rh shell of the Au/Pt/Rh trimetallic nanoparticles induces a wide variety of interesting surface reactions by allowing the adsorption of amino acids like L-cysteine (L-Cys). We present a snapshot of theoretical and experimental investigation of L-Cys adsorption on the surface of noble trimetallic Au/Pt@Rh colloidal nanocomposites. Density functional theoretical (DFT) investigations of L-Cys interaction with the Rhodium (Rh) shell of a trimetallic Au/Pt@Rh cluster in terms of geometry, binding energy (E(B)), binding site, energy gap (E(g)), electronic and spectral properties have been performed. L-Cys establishes a strong interaction with the Rh shell. It binds to Rh by the S1-site, which makes a stable L-Cys-Rh surface complex. DFT can be taken as a valuable tool to assign the vibrational spectra of the adsorption of L-Cys on trimetallic Au/Pt@Rh colloidal nanocomposites and mono-metallic Rh nanoparticles. Surface-enhanced infrared spectroscopy (SEIRS) with L-Cys on a Rh6 cluster surface has been simulated for the first time. Experimental information on the L-Cys-Rh surface complex is included to examine the interaction. The experimental spectral observations are in good agreement with the simulated DFT results. Characterization of the synthesized trimetallic Au/Pt@Rh colloidal nanocomposites has been done by high-resolution transmission electron microscopy (HR-TEM) with selected area electron diffraction (SAED) pattern, energy dispersive X-ray (EDX) spectroscopy, dynamic light scattering (DLS) measurements, zeta potential, zeta deviation analysis and UV-visible (UV-Vis) spectroscopic studies.

Experimental and first-principles study of guanine adsorption on ZnO clusters.

Theoretical investigation of guanine, DNA base adsorption on the ZnO model clusters, viz., Zn2O2, Zn3O3, Zn4O4 ring (R) and Zn4O4 wurtzite (W) in terms of geometry, binding site, binding energy (EB), energy gap (Eg), electronic and spectral properties were studied by a density functional theory (DFT) method. The guanine adsorption on the ZnO (G-ZnO) clusters is modeled by the B3LYP/LanL2DZ method. The calculated binding energy (EB) and energy gap (Eg) of the guanine molecule are highly dependent on the nature of the cluster size and vary with the size of the clusters. Physisorption proceeded via formation of the NZn bond between guanine and the active Zn(2+) site on ZnO. The HOMO-LUMO energies show that charge transfer occurs in the G-ZnO clusters, from ZnO to guanine to better understand the interaction. The Mulliken charges are computed. The electronic properties of ZnO and G-ZnO clusters were compared with different basis sets (B3LYP/6-31G, B3LYP/6-311G, MP2/6-31G and MP2/LanL2DZ). Experimental information like microscopic and spectroscopic evidence is also included for understanding the guanine-ZnO interactions. The G-ZnO composite was prepared by a precipitation method and characterized by SEM with EDX, FT-IR and FT-RAMAN analysis. The interaction of guanine with ZnO nanoparticles was observed by UV-vis spectroscopy. The experimental results are compared with the DFT results in the light of these new insights.