Cerebral arteriovenous malformations: factors influencing the surgical difficulty and outcome.

The outcomes of 151 patients with arteriovenous malformations (AVMs) treated either surgically or conservatively are presented. In terms of long-term survival rate and follow-up results, the patients who underwent total excision had more favorable results than did those treated conservatively. Patient age was the most important clinical factors, with the preoperative level of consciousness being the second most important. A grading system was formulated on the basis of the angiographical factors by using multiregression analysis; the size of the AVM influenced the surgical outcome twice as much as did the location and the pattern of arterial feeding. Thus, a large AVM (greater than or equal to 4 cm) was given 2 points; a small AVM (less than 4 cm) was given 0 points; a deep AVM was given 1 point; a superficial AVM was given 0 points; an AVM supplied by three of more artery systems was given 1 point; and an AVM supplied by one or two artery systems was given 0 points. AVMs were categorized into 5 grades from Grade 0 to 4 by the summation of these points. Predicted Karnofsky scale after surgery was calculated by this grading system and the following equation: predicted Karnofsky scale = 87.2 - 5.6 x Grade. Grade 0 and 1 AVMs showed high rates of total excision (Grade 0, 94%; Grade 1, 82%) and of satisfactory outcome (Grade 0, 90%; Grade 1, 82%) and were classified as "easy" lesions. Grade 2 AVMs are lesions classified as "moderate" and had a total excision rate of 76% and a satisfactory outcome rate of 71%.(ABSTRACT TRUNCATED AT 250 WORDS)

Nonsuture microvascular anastomosis using magnet rings: preliminary report.

An original method of nonsuture microvascular anastomosis was developed using magnet rings and hollow cogwheel-shaped metal devices held together by magnetic power. Only 8.3 minutes was required on average for the anastomosis with a high rate of patency. Histologically, a continuity of vascular wall is noted. This method of simple, rapid and reliable microvascular anastomosis appears to be the best one at present.

N,N-Dimethylformamide-stabilized gold nanoclusters as a catalyst for the reduction of 4-nitrophenol.

In this study, we investigated the catalytic properties of N,N-dimethylformamide (DMF)-stabilized gold nanoclusters (AuNCs) in the reduction of 4-nitrophenol (PNP) to 4-aminophenol by NaBH(4), a well known model reaction to be catalyzed by metal surfaces. The DMF-stabilized AuNCs were prepared in DMF by a surfactant-free method. The DMF-stabilized AuNCs showed high catalytic activity even when used in small quantities (∼10(-7) g). The pseudo-first-order rate constant (k(app)) and activation energy were estimated to be 3 × 10(-3) s(-1) and 31 kJ mol(-1), respectively, with 1.0 µM of the gold catalyst at 298 K. The catalytic activity of the DMF-stabilized AuNCs was strongly influenced by the layer of adsorbed DMF on the Au NCs. This layer of adsorbed DMF prohibited the reactants from penetrating to the surface of the AuNCs via the diffusion at the beginning of the reaction, resulting in an induction time (t(0)) before PNP reduction began. Restructuring of the DMF layer (essentially a form of activation) was the key to achieving high catalytic activity. In addition, atomically monodisperse Au(25)(SG)(18)NCs (SG: glutathione) showed higher catalytic activity in the PNP reduction (k(app) = 8 × 10(-3) s(-1)) even with a low catalyst concentration (1.0 µM), and there was no induction time (t(0)) in spite of the strongly binding ligand glutathione. This suggested that the catalytically active surface sites of the Au(25)(SG)(18)NCs were not sterically hindered, possibly because of the unique core-shell-like structure of the NCs. Retaining these open sites on AuNCs may be the key to making the NCs effective catalysts.

Palladium complex catalyzed acylation of allylic esters with acylsilanes.

Acylation of allylic esters (2) with acylsilanes (1) in the presence of a catalytic amount (5 mol %) of a palladium complex is reported. The reaction proceeds selectively to afford beta,gamma-unsaturated ketones (3) in high yields. [Pd(eta3-C6H5CH=CHCH2)(CF3COO)]2 (4a) showed the best catalytic activity. After the reaction, formation of CF3COOSiMe3 (5a) was confirmed by 29Si NMR measurement of the resulting reaction mixture, indicating the trimethylsilyl moiety effectively traps the CF3COO leaving group from 2. The leaving group of the allylic esters affects the reaction considerably: allylic trifluoroacetate gave the best result, while the corresponding acetates and trichloroacetates did not afford any acylation products at all. Stoichiometric reaction of 4a with 1 gave acylation product 3 with a formation of 5a and Pd(0), whereas no acylation reaction took place with the corresponding acetate complex [Pd(eta3-C6H5CH=CHCH2)(CH3COO)]2 (4b). A DFT calculation suggests that interaction of high-lying HOMO of 1 and low-lying LUMO of eta3-allylpalladium trifluoroacetate intermediate 4 would be indispensable in the catalytic cycle.

Palladium-catalyzed cyanation of propargylic carbonates with trimethylsilyl cyanide

[reaction: see text]An equimolar mixture of propargylic carbonate (1) and trimethylsilyl cyanide (2) in THF under reflux affords cyanoallene (3) in the presence of a catalytic amount (5 mol %) of Pd(PPh3)4. In the reaction, the trimethylsilyl moiety of 2 effectively traps the leaving group of 1. The use of 2 in excess (6 equiv) provides dicyanated products (7 or 8) in high yields.