Regulation of CD8+ T cell development by thymus-specific proteasomes

Proteasomes are responsible for generating peptides presented by the class I major histocompatibility complex (MHC) molecules of the immune system. Here, we report the identification of a previously unrecognized catalytic subunit called beta5t. beta5t is expressed exclusively in cortical thymic epithelial cells, which are responsible for the positive selection of developing thymocytes. Although the chymotrypsin-like activity of proteasomes is considered to be important for the production of peptides with high affinities for MHC class I clefts, incorporation of beta5t into proteasomes in place of beta5 or beta5i selectively reduces this activity. We also found that beta5t-deficient mice displayed defective development of CD8(+) T cells in the thymus. Our results suggest a key role for beta5t in generating the MHC class I-restricted CD8(+) T cell repertoire during thymic selection.     

Wichtige forstschädliche Insekten Japans

SummaryO. Eichhorn and K. Kanamitsu: Important forest insect pests of Japan The paper deals with the life histories, the damage and the limiting factors (parasites, diseases) of a number of forest insects which are considered to be severe pests in Japanese forest.Special regard is devoted to the pine shoot moth complex and to a group of bark and wood boring insects, which cause severe damage in the pine forests of southern Japan.

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RésuméO. Eichhorn et K. Kanamitsu: Importants insectes nuisibles aux forêts du Japon Ce travail traite du cycle biologique, des dégâts et des facteurs qui limitent la multiplication (parasites, maladies) d'un grand nombre d'insectes qui sont considérés comme très nuisibles aux forêts japonaises.Une attention spéciale est accordée au complexe des tordeuses des pousses du pin, et à un groupe d'insectes creusant l'écorce et le bois, qui produisent d'importants dégâts dans les forêts au sud du Japon.

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Den Herren Professor M. Nitto und Dr. C. Nishiguchi (Institute of Forest Zoology, Tokyo University) und K. Katagiri (Government Forestry Experiment Station Shikoku) danken wir für die Durchsicht des Manuskriptes.

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Den Herren Professor M. Nitto und Dr. C. Nishiguchi (Institute of Forest Zoology, Tokyo University) und K. Katagiri (Government Forestry Experiment Station Shikoku) danken wir für die Durchsicht des Manuskriptes.     

Tyrosinase inhibitory activity of proanthocyanidins from woody plants

Flavanol values, molecular weight distributions, polyphenolic patterns, and tyrosinase inhibitions of proanthocyanidins (PACs) from karamatsu (Larix sp.) bark, acacia Morishima (Acacia mearnsii) bark, and commercial quebracho (Schinopsis lorentzii) extracts were examined to investigate the relation between the structures of PACs from woody plants and tyrosinase inhibitory activities. Aqueous acetone (70%) extracts of acacia showed high flavanol contents and strong tyrosinase inhibition. On the other hand, the quebracho extracts inhibited tyrosinase activity slightly despite its high flavanol content. Phenyl nucleus analysis by the nucleus exchange reaction provided information that karamatsu, quebracho, and acacia extracts consist of procyanidin, profisetinidin, and prorobinetinidin, respectively. The relation between the phenolic hydroxylation pattern and tyrosinase inhibition suggested that the PACs with a 5,7-dihydroxyphenyl structure in the A-ring and a 3,4,5-trihydroxyphenyl structure in the B-ring have potent tyrosinase inhibitory activity.Part of this paper was presented at the 49th Annual Meeting of the Japan Wood Research Society, Tokyo, April 1999     

Immunolocalization of an anionic peroxidase in differentiating poplar xylem

Peroxidases are the major candidate enzymes involved in dehydrogenative polymerization of monolignols. Peroxidases have the signal sequence at their N-terminus and this suggests that they are transported to extracellular spaces or developing cell walls. In this study, we focused on an anionic peroxidase isozyme encoded by prxA3a, which seems to be related to lignification. To investigate the localization of peroxidase in differentiating xylem cells of poplar (Populus sieboldii × Populus grandidentata), anti-PRX3 antibody was raised against the anionic peroxidase. Western blotting and peroxidase activity inhibition assay showed specificity of the antibody. Labeling by anti-PRX3 antibody was localized in vessels and fibers during the secondary wall formation and was observed along the plasma membrane beside the microtubules. The labeling was not seen in the cell wall, where localization of peroxidases was expected during lignification. The peroxidase isozyme, which is suggested to be involved in monolignol polymerization, is localized on the plasma membrane and its localization might be regulated by microtubules.     

Carotenoids in three species of Corbicula Clams, Corbicula japonica, Corbicula sandai, and Corbicula sp. (Chinese Freshwater Corbicula Clam)

Carotenoids were investigated in three species of corbicula clams, Corbicula japonica, Corbicula sandai, and Corbicula sp. (Chinese freshwater corbicula clam). Forty-three carotenoids were isolated. Among them, 7,8-didehydro-beta-cryptoxanthin (12), peridininol 5,8-furanoxide (38), pyrrhoxanthin 5,8-furanoxide (40), and pyrrhoxanthinol 5,8-furanoxide (43) are newly reported as naturally occurring carotenoids. Their structures were characterized on the basis of UV-vis, FAB-MS including MS/MS experiments, and 1H NMR spectroscopic data. The total carotenoid contents in C. japonica, C. sandai, and Chinese freshwater corbicula clam were found to be 5.3, 2.6, and 0.3 mg/100 g in the edible part (wet weight), respectively. Peridinin (34) and its derivatives were found to be major carotenoids in C. japonica, which inhabits brackish water. On the other hand, lutein (13) was found to be the major carotenoid in C. sandai and Chinese corbicula clams, which inhabit freshwater. These patterns well reflected the carotenoids in their dietary algae. 7',8'-Didehydrodeepoxyneoxanthin (19), corbiculaxanthin (21), corbiculaxanthin 3'-acetate (22), and 6-epiheteroxanthin (24) were found in all three species of corbicula clams and have not previously been found in other shellfishes. They were assumed to be peculiar carotenoids in corbicula clams.     

Identification of ovalbumin phenotypes of the Asian indigenous chicken populations using polymerase chain reaction-restriction fragment length polymorphism

Three electrophoretic variations (AA, BB and AB) of ovalbumin controlled by codominant alleles Ov^A and Ov^B have been observed in various chicken populations. We compared nucleotide sequences of the open reading frame between two alleles of ovalbumin gene. The difference between the two alleles was found as a non‐synonymous substitution of asparagine to aspartic acid as a result of AAT to GAT point mutation at position 8032–8034 in exon 8. We developed polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP) protocol in combination with Mbo I restriction endnuclease mapping for the detection of this substitution. By the PCR‐RFLP the allelic frequency of the Ov^B was estimated to be within the range of 0.000–0.150 in 11 Asian indigenous chicken populations and 0.000 in four improved breeds used in the present study. Gene frequency, estimated by PCR‐RFLP in the present study, paralleled that obtained by protein polymorphisms of egg white. Thus, this study provides, for the first time, information of the occurrence of ovalbumin allele Ov^A and Ov^B in Asian indigenous chicken populations.     

Mercapturic acid formation from lindane in rats

4-Chloro-, 2,4-dichloro-, 3,4-dichloro-, 2,3,5-trichloro-, and 2,4,5-trichlorophenylmercapturic acids were identified as main metabolites of lindane, γ-isomer of 1,2,3,4,5,6-hexachloro-cyclohexane, in rat urine. Pathways to these metabolites were shown to include $\text{(}\text{36}\text{45}\text{)-}\text{hexachlorocyclohexene}$ as the most important intermediary metabolite. $\text{(}\text{346}\text{5}\text{)-}\text{Pentachlorocyclohexene}$ and $\text{(}\text{346}\text{5}\text{)-}\text{tetrachlorocyclohexene}$ also seem to be involved in these pathways, while $\text{(}\text{36}\text{45}\text{)-}\text{pentachlorocyclohexene}$ plays a minor role in the pathway. Glutathione conjugation, using the rat liver soluble fraction, occurred directly on the polychlorocyclohexenes, not on their further transformed products. In in vivo biodegradation, $\text{(}\text{36}\text{45}\text{)-}\text{hexachlorocyclohexene}$ may be dechlorinated and dehydrochlorinated at the endoplasmic reticulum before it undergoes the glutathione conjugation in cytosol, although other polychlorocyclohexenes generally react in a manner similar to that in the in vitro reaction.     

Serum adenosine deaminase activity in bovine liver diseases

A total of 60 cattle were examined for the presence of pathological liver lesions. The liver lesions were classified as glycogen degeneration, liver abscess, sawdust liver and fatty degeneration. The value of serum adenosine deaminase (ADA) activity was investigated as a pilot study for diagnosing liver diseases in cattle. Serum ADA activity was significantly higher in cases with glycogen degeneration (9.8 +/- 3.8 U/l) , liver abscess (10.4 +/- 3.2 U/l), sawdust liver (11.5 +/- 7.3 U/l) and fatty degeneration (20.8 +/- 7.7 U/l) than in the controls. The results indicate that ADA activity increases with the degree of hepatocellular damage. We concluded that serum ADA activity may be of value in bovine liver disease diagnosis.     

Pesticide residues in food--acute dietary exposure

Consumer risk assessment is a crucial step in the regulatory approval of pesticide use on food crops. Recently, an additional hurdle has been added to the formal consumer risk assessment process with the introduction of short-term intake or exposure assessment and a comparable short-term toxicity reference, the acute reference dose. Exposure to residues during one meal or over one day is important for short-term or acute intake. Exposure in the short term can be substantially higher than average because the consumption of a food on a single occasion can be very large compared with typical long-term or mean consumption and the food may have a much larger residue than average. Furthermore, the residue level in a single unit of a fruit or vegetable may be higher by a factor (defined as the variability factor, which we have shown to be typically x3 for the 97.5th percentile unit) than the average residue in the lot. Available marketplace data and supervised residue trial data are examined in an investigation of the variability of residues in units of fruit and vegetables. A method is described for estimating the 97.5th percentile value from sets of unit residue data. Variability appears to be generally independent of the pesticide, the crop, crop unit size and the residue level. The deposition of pesticide on the individual unit during application is probably the most significant factor. The diets used in the calculations ideally come from individual and household surveys with enough consumers of each specific food to determine large portion sizes. The diets should distinguish the different forms of a food consumed, eg canned, frozen or fresh, because the residue levels associated with the different forms may be quite different. Dietary intakes may be calculated by a deterministic method or a probabilistic method. In the deterministic method the intake is estimated with the assumptions of large portion consumption of a 'high residue' food (high residue in the sense that the pesticide was used at the highest recommended label rate, the crop was harvested at the smallest interval after treatment and the residue in the edible portion was the highest found in any of the supervised trials in line with these use conditions). The deterministic calculation also includes a variability factor for those foods consumed as units (eg apples, carrots) to allow for the elevated residue in some single units which may not be seen in composited samples. In the probabilistic method the distribution of dietary consumption and the distribution of possible residues are combined in repeated probabilistic calculations to yield a distribution of possible residue intakes. Additional information such as percentage commodity treated and combination of residues from multiple commodities may be incorporated into probabilistic calculations. The IUPAC Advisory Committee on Crop Protection Chemistry has made 11 recommendations relating to acute dietary exposure.