Factors Associated with Early and Late Seizure Related to Aneurysmal Subarachnoid Hemorrhage.

Post-stroke epilepsy may occur after aneurysmal subarachnoid hemorrhage (aSAH). Both early and late seizures could cause severe neurocognitive deficits if administration of appropriate antiseizure medication is delayed. Therefore, it is important to elucidate the risk factors for early and late seizures, which could be shared with medical teams to promptly manage seizures. There are aspects of both hemorrhage and ischemia in aSAH, and thus, numerous risk factors are considered for early and late seizures. We examined factors associated with aSAH-related early and late seizures. Among 297 patients who had aSAH and underwent direct or endovascular surgery, 25 had early seizures and 20 had late seizures. Patients who did not experience any seizures in at least 2-years of follow-up (n = 81) were used as the control group. Early seizures were associated with older age and acute severe nonneurological infection, whereas late seizures were associated with intraparenchymal lesion volume >10 mL and shunt placement. In patients with late seizures, consistency was frequently observed between electroencephalogram and the presence of intraparenchymal lesions. The frontopolar electrode on electroencephalogram was highly sensitive to abnormality in early seizures. Early seizures were induced by the patient's systemic factors, which may lower the threshold for cortical excitability. Patients with intraparenchymal lesions who undergo shunt placement should be carefully followed up for late seizures.

Solid-state 13C NMR study of cholesteric liquid crystals.

We investigated the structural behavior of cholesteric liquid crystals of 4-(hexyloxy)-4'-cyanobiphenyl (6OCB) in an 11.7 T magnetic field by solid-state (13)C nuclear magnetic resonance. Five 6OCB cholesteric liquid crystal systems were prepared with 4-methoxyphenyl 3,4-O-isopropylidene-2,6-bis-O-(4-methylbenzoyl)-ß-d-galactopyranoside (CR), in which 6OCB was doped with 0.51, 1.00, 2.34, 5.60, and 6.47 mol % CR, giving products with helical twisting powers (HTPs) of 0.28, 0.54, 1.27, 3.05, and 3.52 µm(-1), respectively. Analyses of the alignment-induced shifts showed that the liquid crystals directors in pure 6OCB and 6OCB doped with 0.51 and 1.00 mol % CR become aligned with the 11.7 T magnetic field direction. However, 6OCB doped with 2.34, 5.60, and 6.47 mol % CR retained their cholesteric structures when the magnetic field was applied. The critical HTP value for resisting realignment by magnetic field was estimated to be approximately 1.27 µm(-1). A biaxiality of the phase was partially considered during spectral simulations, although the molecular shape of 6OCB can be defined as cylinderical when it is rotating rapidly. Our current understanding is that the order parameters in the cholesteric structures are not uniform; i.e., the molecular directors already aligned almost perpendicular to the magnetic field are significantly perturbed by the external field.

Stacking of bacteriochlorophyll c macrocycles in chlorosome from Chlorobium limicola as revealed by intermolecular 13C magnetic-dipole correlation, X-ray diffraction, and quadrupole coupling in 25Mg NMR.

The stacking of the bacteriochlorophyll (BChl) c macrocycles and the role of water in forming an aggregate sheet, in chlorosome, were examined by means of (13)C NMR spectroscopy, the measurement of the X-ray diffraction pattern, and (25)Mg NMR spectroscopy. (1) The stacking of the macrocycles, i.e., weakly overlapped dimers forming displaced layers, was selected out of six different kinds of stacking so far identified in the aggregates of isomeric BChl c in solution and in the solid aggregate of an isomeric mixture of BChl c extracted from Chlorobium limicola. The selection was based on the comparison of the intermolecular (13)C...(13)C magnetic-dipole correlations with the nearest-neighbor carbon-to-carbon close contacts simulated for the above six different stackings. It has turned out that the stacking of the macrocycles in chlorosome is basically the same as that in the in vitro solid aggregate. (2) The crucial role of water in stabilizing the aggregate structure in chlorosome was shown by tracing the dehydration processes and by comparison with the solid aggregate using the X-ray diffraction pattern. Possible binding sites of water molecules were located, by structural simulation, based on the particular stacking structure. (3) The dimer-based stacking of the macrocycles was evidenced by (25)Mg NMR spectroscopy, which exhibited a pair of signals showing different quadrupole coupling, due to the presence or absence of a water molecule in the axial position.

Fullerene as a standard sample for adjusting the NMR spectral resolution in multiple-quantum magic-angle-spinning experiments.

A method using fullerene for adjusting the NMR spectral resolution for multiple quantum magic angle spinning (MQMAS) experiments is proposed. To observe its (13)C MAS signal, it is not necessary to apply (1)H decoupling, unavailable with single-resonance MQMAS probes. Although (13)C T(1) of fullerene is rather long, a recycle time of 5 s in shimming yields its signal with sufficiently high sensitivity if setting the appropriate Ernst angles corresponding to magnetic fields. It is demonstrated that so-adjusted high resolution is reflected in the (87)Rb MQMAS spectra of RbNO(3).