切片剥離法による細胞壁層のフィビリル傾角計測法

細胞壁のフィブリル傾角は木材の物性に非常に影響するので, これまで種々の方法で測定されてきた。偏光顕微鏡法は手軽で精度の高い測定を可能とするが, この測定に必須である細胞壁のsingle wall化が困難なために, 未だ充分には活用されてはいない。そこで極めて簡単な操作で, 各種の木材細胞壁のsingle wallを得る方法を考案した。その概略はまず細胞直径程度の厚さの縦断切片を乾燥し, その両面に透明なエポキシ樹脂液を塗布して2枚のスライドガラスに挟み, 圧締しながら硬化させる。この時, 孔をあけたポリエチレンフィルムで切片を囲んでおく。この2枚のスライドを剥すと切片に含まれていたdouble wallは両側に引き剥されてsingle wallとなる。この時, S_1とS_2との境界で剥離する場合もある。剥離面に再び樹脂液を塗布して同様の操作を繰り返していくと, 細胞壁はさらに薄片化しS_1, S_2, S_3などの個々の細胞断層を単離できる。そして剥離面をカナダバルサムで封入し偏光顕微鏡観察に供する。その結果, 細胞壁各部での消光位から壁の平均フィブリル傾角が容易に測定される。これに加えて, 剥離の際にフィブリルに平行な条線が多数発生した。これらは背景となる細胞壁を対角位にすると明瞭に観察できるので、個々の壁層のフィブリル傾角を非常に能率的に計測することが可能となった。For measurement of fibril angle using the polarizing microscope, a very effective method was devised. Longitudinal wood sections are sandwiched with epoxy resin between two glass slides, and splitted with the glass slides after curring. By this very simple preparation, a series of single walls and even respective wall layers could be obtained. These splitted-sections were shown to be really suitable in measurement of both average fibril angle and individual one of various wall layers. The former was estimated by the extinction position under crossed polars, while the latter became possible at the diagonal position to be determined from many striations along microfibrils occurred during the sample preparation

Mining prokaryotic genomes for unknown amino acids: a stop-codon-based approach

<p>Abstract</p> <p>Background</p> <p>Selenocysteine and pyrrolysine are the 21st and 22nd amino acids, which are genetically encoded by stop codons. Since a number of microbial genomes have been completely sequenced to date, it is tempting to ask whether the 23rd amino acid is left undiscovered in these genomes. Recently, a computational study addressed this question and reported that no tRNA gene for unknown amino acid was found in genome sequences available. However, performance of the tRNA prediction program on an unknown tRNA family, which may have atypical sequence and structure, is unclear, thereby rendering their result inconclusive. A protein-level study will provide independent insight into the novel amino acid.</p> <p>Results</p> <p>Assuming that the 23rd amino acid is also encoded by a stop codon, we systematically predicted proteins that contain stop-codon-encoded amino acids from 191 prokaryotic genomes. Since our prediction method relies only on the conservation patterns of primary sequences, it also provides an opportunity to search novel selenoproteins and other readthrough proteins. It successfully recovered many of currently known selenoproteins and pyrrolysine proteins. However, no promising candidate for the 23rd amino acid was detected, and only one novel selenoprotein was predicted.</p> <p>Conclusion</p> <p>Our result suggests that the unknown amino acid encoded by stop codons does not exist, or its phylogenetic distribution is rather limited, which is in agreement with the previous study on tRNA. The method described here can be used in future studies to explore novel readthrough events from complete genomes, which are rapidly growing.</p

Early endovascular stenting for extracranial carotid artery dissection with angiographic flow stasis: A series of four cases

Extracranial carotid artery dissection is a major cause of ischemic stroke in young patients. Progressive stroke or recurrent ischemic symptoms may occur despite adequate medical treatment. Our treatment policy for these conditions is based on the fact that immediate vascular reconstruction is necessary in the cases with angiographic flow stasis in the true lumen beyond the dissection site. We report our experiences with four consecutive extracranial carotid artery dissections successfully treated with early endovascular stenting and discuss the indication of this treatment with a special emphasis on the angiographic findings

Preconcentration of Arsenic Species in Environmental Waters by Solid Phase Extraction Using Metal-loaded Chelating Resins

Joint Research on Environmental Science and Technology for the Earth『Annual Report of FY 2002, The Core University Program between Japan Society for the Promotion of Science (JSPS) and National Centre for Natural Science and Technology (NCST)』pp.20-23, Core University Program Office, Fujita Laboratory, Dept. of Environmental Engineering, Osaka University, 200