Photoprotective response of xanthophyll pigments during phytoplankton blooms in Sagami Bay, Japan

The relationship between the xanthophyll pool [diadinoxanthinplus diatoxanthin normalized to chlorophyll (Chl) a] and irradiancewas examined during phytoplankton blooms in Sagami Bay fromthe end of April to July 2000. In the case of Chl a concentrations>2 mg m^-3, a linear correlation was found between the xanthophyllpool and irradiance of the previous day. On the other hand,for Chl a concentrations <2 mg m^-3, the xanthophyll poolremained low and was independent of irradiance of the previousday. The results may indicate that photoprotection by xanthophyllpigments assists the development of phytoplankton blooms underhigh-irradiance conditions.     

Stable genetic transformation of Larix gmelinii L. by particle bombardment of zygotic embryos

We report a new protocol for the stable transformation of Larix gmelinii. Thirty mature zygotic embryos precultured for 3 days on solid medium supplemented with benzyladenine were bombarded with plasmids pUC-GHG (GUS, HPT, and GFP genes) or pBI221-HPT (HPT and GUS genes). After a 2-month culture on selection medium, hygromycin-resistant calli appeared on the surfaces of the necrotic embryos. The frequencies of embryos with resistant calli were 18.4% and 17.4% in the transformations with pUC-GHG and pBI221-HPT DNA, respectively. More than 20 adventitious shoots formed from each of the transgenic calli. Of 17 elongated shoots selected for culturing on a rooting medium, five shoots rooted after 2 months. Expression of the GFP and GUS genes was detected in the resistant tissues by microscopic observations and by a histological GUS activity assay, respectively. PCR and Southern analysis confirmed the stable insertion of the introduced DNA into the genome.     

Cloning and characterization of a cDNA encoding beta-amyrin synthase from petroleum plant Euphorbia tirucalli L

Euphorbia tirucalli L., known as the petroleum plant, produces a large amount of triterpenes, such as beta-amyrin. Degenerate RT-PCR based on the sequences conserved among known beta-amyrin synthases led to cloning of a putative triterpene synthase cDNA, EtAS, from leaves of E. tirucalli. The deduced amino acid sequence of the EtAS cDNA showed the highest identity of 82% to the Panax ginseng beta-amyrin synthase. Heterologous expression of the EtAS ORF in the methylotrophic yeast, Pichia pastoris, resulted in production of beta-amyrin, revealing that the EtAS cDNA codes for a beta-amyrin synthase. This is the first report of a gene involved in the triterpene synthetic pathway from Euphorbiaceae plants.     

Novel matrix metalloproteinase inhibitors: generation of lead compounds by the in silico fragment-based approach

Generation of structurally new matrix metalloproteinase inhibitors was successfully carried out using an in silico technique. In order to identify the small fragment interacting with residues in the S1' pocket of MMP-1 through hydrogen bonds, we performed in silico screening using the LUDI program. As a result, acetyl-L-alanyl-(N-methyl)amide (Ac-L-Ala-NHMe) was selected to link with another fragment, hydroxamic acid that interacted with catalytic zinc. By this approach, the L-glutamic acid derivative 2b was discovered to be a new type of matrix metalloproteinase inhibitor. Further transformation to reduce its peptidic nature and improve activity yielded nonpeptidic lead compounds as inhibitors of MMP-1, -2, -3, and -9.     

Induced synchrony in Cryptococcus neoformans after release from G2-arrest

Cryptococcus neoformans was grown first to OD 4 under moderate aeration, then diluted 2.5 times with fresh medium, and grown under limited aeration for 5 h. Oxygen concentration decreased from 5-6 mg l(-1) to 1.5 mg l(-1) 1 h after the shift to limited aeration, and remained at a similar level thereafter. In all the eleven strains examined the shift caused unbudded G(2)-arrest in more than half of the cells. In three strains more than 80% of the cells were arrested in unbudded G(2), and, therefore they were selected for synchrony experiments. After being shifted to extensive aeration again, the cells resumed growth by synchronous budding, followed by synchronous nuclear division. This method has turned out to be a good tool to prepare synchronized culture in C. neoformans, especially when a large amount of synchronized cells is needed. This is worthy of attention, since synchronous cultures after release from G(2)-arrest have not been reported yet in any yeast species.     

Double PHD Fingers Protein DPF2 Recognizes Acetylated Histones and Suppresses the Function of Estrogen-related Receptor α through Histone Deacetylase 1

Estrogen-related receptor α (ERRα) is a member of the nuclear receptor superfamily and regulates many physiological functions, including mitochondrial biogenesis and lipid metabolism. ERRα enhances the transactivation function without endogenous ligand by associating with coactivators such as peroxisome proliferator-activated receptor γ coactivator 1 α and β (PGC-1α and -β) and members of the steroid receptor coactivator family. However, the molecular mechanism by which the transactivation function of ERRα is converted from a repressive state to an active state is poorly understood. Here we used biochemical purification techniques to identify ERRα-associated proteins in HeLa cells stably expressing ERRα. Interestingly, we found that double PHD fingers protein DPF2/BAF45d suppressed PGC-1α-dependent transactivation of ERRα by recognizing acetylated histone H3 and associating with HDAC1. DPF2 directly bound to ERRα and suppressed the transactivation function of nuclear receptors such as androgen receptor. DPF2 was recruited to ERR target gene promoters in myoblast cells, and knockdown of DPF2 derepressed the level of mRNA expressed by target genes of ERRα. These results show that DPF2 acts as a nuclear receptor-selective co-repressor for ERRα by associating with both acetylated histone H3 and HDAC1.     

Stem turnover strategy of multiple-stemmed woody plants

We have investigated stem turnover strategy for Lindera umbellata, an understory shrub that sprouts from its rootstock under natural conditions to replace constituent stems, on the basis of the hypothesis that the multiple-stemmed form of woody species is an adaptation enabling efficient reproduction in high-stress environments. We tested the hypothesis that the timing of stem replacement maximizes sexual reproduction for the shrub. We developed a model for the time of optimum replacement of a stem by a daughter stem which maximizes the sexual reproduction of a shrub and tested the model using L. umbellata growing in the field. From the model, the optimum time of replacement of a stem with a daughter stem is when cumulative sexual reproduction per unit time for the stem is maximum. In practice, this will be the last age (t _opt) at which annual sexual reproduction in a stem can potentially exceed cumulative sexual reproduction per unit time for the stem. Half of the stems died at almost t _opt and had sexually mature daughter stems at that time. Other stems, however, died at times more remote from t _opt when daughter stems were sexually immature. It is thought that normal replacement of the latter stems was prevented by accidents such as breakage. We conclude that clumps of L. umbellata achieve efficient sexual reproduction by stem replacement at the optimum time, although accidents can, to some extent, determine when the stem actually dies.     

Sex difference in body weight gain and leptin signaling in hypocretin/orexin deficient mouse models

Recent studies in human and animal models of narcolepsy have suggested that obesity in narcolepsy may be due to deficiency of hypocretin signaling, and is also under the influence of environmental factors and the genetic background. In the current study, using two hypocretin/orexin deficient narcoleptic mouse models (i.e. preproorexin knockout (KO) and orexin/ataxin-3 transgenic (TG) mice) with cross-sectional assessments, we have further analyzed factors affecting obesity. We found that both KO and TG narcoleptic mice with mixed genetic backgrounds (N4-5, 93.75-96.88% genetic composition of C57BL/6) tended to be heavier than wild type (WT) mice of 100-200 days old. The body weight of heterozygous mice was intermediate between those of KO and WT mice. Obesity was more prominent in females in both KO and TG narcoleptic mice and was associated with higher serum leptin levels, suggesting a partial leptin resistance. Obesity is less prominent in the congenic TG narcoleptic mice, but is still evident in females. Our results confirmed that hypocretin/orexin ligand deficiency is one of the critical factors for the obese tendency in narcolepsy. However, multiple factors are also likely to affect this phenotype, and a sex difference specific alteration of leptin-hypocretin signaling may be involved.     

Surgical influence of pancreatectomy on the function and count of circulating dendritic cells in patients with pancreatic cancer

Background: Dendritic cells (DCs) are important for an immune surveillance. Myeloid DCs (DC1) are important for an effective antitumor immune system. The function and count of circulating DC1 (cDC1) in hosts with a malignant tumor would be defective. This study focused on analyzing the immunological features of cDC1 in patients with pancreatic cancer during the perioperative period. Materials and methods: Thirty-two pancreatic cancer patients who underwent pancreatectomy and 18 age-matched healthy individuals as controls were enrolled in this study. The perioperative cDC count, the stimulatory capacity of cDC1 against allogeneic T cells and TGF-β1 level in the serum were measured. The cDC count was measured at 12 months after the operation. Results: The preoperative cDC1/cDC2 ratio, cDC1 count, and stimulatory capacity of cDC1 were impaired in patients in comparison to controls (P<0.05). The serum TGF-β1 level was significantly higher in patients than controls (P<0.001). The stimulatory capacity of cDC1 recovered after pancreatectomy (P<0.05). The serum TGF-β1 level significantly decreased after the operation (P<0.05); however, they were still significantly higher than controls (P<0.05). Although the cDC1/cDC2 ratio and the cDC1 count did not increase after the pancreatectomy, they recovered as the controls’ level at 12 months after the pancreatectomy in disease-free patients (P<0.05) and the serum TGF-β1 level in those patients at 12 months after the operation significantly decreased compared with those at the postoperative period (P<0.05). Conclusion: Surgical resection of pancreatic cancer could be associated with improved cDC1 function. When a patient remained disease free, the recovery of cDC1 counts was observed approximately 12 months after pancreatectomy. Further strategy will be needed to improve immune function in patients with pancreatic cancer.