Polysilanes on surfaces

For chain-like polymers on surfaces, the relationship between chain topology and inherent physical properties has long been puzzling due to the lack of proper models and detection systems with ultrahigh sensitivity and high accuracy. Among various chain-like polymers, soluble organopolysilane is one suitable model for elucidating the uniqueness of chain-like polymers on surfaces because of its (1) controllable molecular length, polydispersity, stiffness, and terminal group by an adequate molecular design, a careful synthesis, and a precise purification, and (2) highly luminescent chromophore due to Siσ-Siσ* transition of the Si main chain. This review comprehensively covers the works on (i) molecular imaging with scanning probe microscopy, (ii) tethering on surfaces by a grafting-to approach, (iii) self-assembly, (iv) structural phase transition, (v) orientational phase transition, and (vi) chiroptical switching, memory and amplification in single and double layer films deposited on solid surfaces. This knowledge and understanding may stimulate advanced studies on polymer-based nanoscience, nanotechnology, and nanofabrication as well as in traditional surface chemistry and polymer physics.

Nitric oxide synthase and NMDA receptor expressions in cavernoma tissues with epileptogenesis

OBJECTIVES

To investigate the contribution of nitric oxide (NO) and the glutamate systems to epileptogenicity of cavernoma (CA).

METHODS

Using immunohistochemistry we examined NO synthases (NOS; neuronal, inducible and endothelial) and N-methyl-D-aspartate (NMDA) receptor subunits 1(NR1) and 2A/B (NR2A/B) in tissues, with and without hemosiderin deposits, adjacent to CA resected from temporal (seven patients) and frontal (one patient) lobes.

RESULTS

All isoforms of NOS, especially iNOS expression, was significantly upregulated in company with NR2A/B expression, not only in declining neuronal cells but also in reactive astrocytes in the tissue, with hemosiderin deposits, adjacent to CA and moreover the degree of iNOS expression was significantly correlated with seizure frequency.

CONCLUSIONS

These preliminary results sustain a speculation that excessive NO may generate in the tissue surrounding CA with repeated microhaemorrhaging and seizures. The neuronal loss and reactive glial proliferation induced by iron or NO may play a role in epileptogenesis.

Spontaneous chronic head and spinal subdural haematoma

Spinal chronic subdural haematomas (SSDH) are extremely rare. We report a case of a SSDH combined with intracranial SDH. After tapping the SSDH in addition to the evacuation of SDH, the clinical symptoms dramatically improved. SSDH are considered to have an uncertain prognosis; however, good results can be obtained with an early diagnosis and prompt treatment.

Overlapping free bone graft with galea-pericranium in reconstruction of the anterior skull base to prevent CSF leak and sequestrum formation

Background. Reconstruction of the skull base after resection of a tumour is important to prevent postoperative complications such as infectionsand cerebrospinal fluid (CSF) leakage. Several reconstructive methods of the anterior skull base have been reported but, their long-term results are not clear. Methods. We describe a technique used after removal of an olfactory neuroblastoma with infiltration of the skull base. The reconstructed dura was covered with a galeal patch, a replicated galeal-pericranial flap, a graft from the inner table of skull, and a vascularised galeal-pericranial flap placed on the skull base defect. All layers were fixed with fibrin glue. Conclusion. Three dimensional computed tomography (3D-CT) at bone window settings demonstrated the bone graft covered the bone defect and was not absorbed and after 11 years there have been no signs of tumour regrowth or complications.

Instantaneous inclusion of a polynucleotide and hydrophobic guest molecules into a helical core of cationic beta-1,3-glucan polysaccharide

We succeeded in the quantitative and selective introduction of an ammonium cationic group into the C6 position of Curdlan (CUR) by "Click Chemistry", and the obtained cationic Curdlan (CUR-N+) showed good solubility in water. ORD studies suggested that CUR-N+ adopts a single-stranded structure, different from a right-handed, triple-stranded helical structure of beta-1,3-glucan polysaccharides in water. It has been revealed that the polymeric complexes of CUR-N+ with polymeric guest molecules, such as polycytidylic acid (poly(C)), permethyldecasilane (PMDS), and single-walled carbon nanotubes (SWNTs), can be easily obtained by just mixing them in water with sonication. The characterization of the resultant CUR-N+-poly(C) complexes by UV-vis, CD spectroscopic measurements, and AFM and TEM observations revealed that they have stoichiometric, nanosized fibrous structures. From these experimental results as well as our precedent studies (e.g., refs 6 and 23), we propose that the complexation would be driven by the cooperative action of (1) the hydrogen-bonding interaction between the OH group at the C2 position and hydrogen-bonding sites of the cytosine ring (ref 6d), (2) the electrostatic interaction between the ammonium cation and the phosphate anion (ref 23), as well as (3) the background hydrophobic interaction. In addition, the complexed polynucleotide chain showed a strong resistance against enzymatic hydrolysis. Likewise, the dispersion of PMDS and SWNTs in water by CUR-N+ and the fibrous structures of the complexes were confirmed by spectroscopic measurements as well as microscopic observations. These binding properties of CUR-N+, which can proceed spontaneously in water, clearly differ from those of schizophyllan (SPG), which inevitably require a denature-renature process corresponding to a conversion of a triple strand to single strands induced by DMSO or base for inclusion of polymeric guest molecules.

The relationship between paired pulse magnetic MEP and surgical prognosis in patients with intractable epilepsy

PURPOSE

To assess whether paired pulse magnetic motor evoked potential (MEP) can predict surgical prognosis in patients with intractable epilepsy.

METHODS

MEP of the unilateral hand muscles were recorded following paired pulse transcranial magnetic stimulation (TMS) of the motor cortex. The interstimulus intervals of paired stimulation were 1-16 ms with a conditioning stimulus that was 90% active motor threshold. Subjects were six patients with temporal lobe epilepsy (TLE) scheduled for anterior temporal lobectomy and three patients with myoclonic or head-drop seizures scheduled for anterior corpus callosotomy, resulting in the unilateralization of epileptic discharges. The hemisphere showing unilateral discharges was defined as the affected hemisphere. The intracortical inhibition and facilitation curve was drawn based on MEP before and after surgery and the relationship between MEP and surgical prognosis was investigated.

RESULTS

In five patients with TLE showing class I surgical results (Engel's classification), the affected hemisphere showing cortical hyperexcitability preoperatively was almost normalized after surgery. However, in a patient with class III, the unaffected hemisphere showed cortical hyperexcitability before and after surgery. In the callosotomy group, two patients with excellent outcomes showed the same results as TLE group with class I.

CONCLUSIONS

Paired pulse magnetic MEP may provide predictive value in terms of surgical outcome in those patients with intractable epilepsy.

Circular dichroism of optically active poly(dialkylsilane) aggregates in microcapsules

Poly[n-hexyl-(S)-3-methylpentylsilane] aggregates confined in microcapsules to keep the aggregation number and ranging in average polymer mass m(p) in a microcapsule from 2 x 10(-)(16) to 2 x 10(-)(14) g were studied by circular dichroism measurements in ethanol (a nonsolvent) and tetrahydrofuran (an associative solvent at low temperature) at various temperatures. The weight-average molecular weight M(w) and the polydispersity index (the ratio of M(w) to the number-average molecular weight) of the polysilane sample were 6.6 x 10(4) and 1.07, respectively, and the average number of polymer molecules in each capsule was estimated to be 1.9 x 10(3) for m(p) = 2 x 10(-)(16) g and 1.7 x 10(5) for m(p) = 2 x 10(-)(14) g. The size of each aggregate did not affect the optical activity because the circular dichroism thus obtained was proportional to m(p) under the same conditions in the investigated m(p) range; on the other hand, the peak height of the circular dichroism in tetrahydrofuran had a significant hysteresis between 0 and 25 degrees C. Moreover, the circular dichroism appreciably reflected the prepared method, that is, the temperature and solvent; in other words, the aggregates memorized the initial conditions in their stacking structures.

Notable norbornene (NBE) incorporation in ethylene–NBE copolymerization catalysed by nonbridged half-titanocenes: better correlation between NBE incorporation and coordination energy

CpTiCl2(N=CtBu2) exhibits both remarkable catalytic activity and efficient norbornene (NBE) incorporation for ethylene-NBE copolymerization: the NBE incorporation by Cp'TiCl2(X) (X = N=CtBu2, O-2,6-iPr2C6H3; Cp' = Cp, C5Me5, indenyl) was related to the calculated coordination energy after ethylene insertion.