Unravelling cell wall formation in the woody dicot stem

Populus is presented as a model system for the study of wood formation (xylogenesis). The formation of wood (secondary xylem) is an ordered developmental process involving cell division, cell expansion, secondary wall deposition, lignification and programmed cell death. Because wood is formed in a variable environment and subject to developmental control, xylem cells are produced that differ in size, shape, cell wall structure, texture and composition. Hormones mediate some of the variability observed and control the process of xylogenesis. High-resolution analysis of auxin distribution across cambial region tissues, combined with the analysis of transgenic plants with modified auxin distribution, suggests that auxin provides positional information for the exit of cells from the meristem and probably also for the duration of cell expansion. Poplar sequencing projects have provided access to genes involved in cell wall formation. Genes involved in the biosynthesis of the carbohydrate skeleton of the cell wall are briefly reviewed. Most progress has been made in characterizing pectin methyl esterases that modify pectins in the cambial region. Specific expression patterns have also been found for expansins, xyloglucan endotransglycosylases and cellulose synthases, pointing to their role in wood cell wall formation and modification. Finally, by studying transgenic plants modified in various steps of the monolignol biosynthetic pathway and by localizing the expression of various enzymes, new insight into the lignin biosynthesis in planta has been gained.     

Structure of a new 2-deoxy-2-[(R)-3-hydroxybutyramido]-D-glucose-containing O-specific polysaccharide from the lipopolysaccharide of Citrobacter gillenii PCM 1542

The O-specific polysaccharide of Citrobacter gillenii PCM 1542 from serotype O-12a,12 b is composed of one residue each of D-glucose, D-GlcNAc, 2-deoxy-2-[(R)-3-hydroxybutyramido]-D-glucose (D-GlcNAcyl) and two GalNAc residues. On the basis of sugar and methylation analyses of the intact and Smith degraded polysaccharides, along with 1D and 2D 1H and 13C NMR spectroscopy, the following structure of the branched pentasaccharide repeating unit of the O-specific polysaccharide was established:This structure differs significantly from that of the O-specific polysaccharide of C. gillenii PCM 1544 from the same serotype O-12a,12 b, which has been established earlier (Kübler-Kielz.shtsls;b, J. et al. Carbohydr. Res. 2001, 331, 331-336). Serological studies confirmed that the two O-antigens are not related and suggested that strains PCM 1542 and 1544 should be classified into different O-serogroups.     

Integrative nuclear FGFR1 signaling (INFS) pathway mediates activation of the tyrosine hydroxylase gene by angiotensin II,depolarization and protein kinase C

The integrative nuclear FGFR1 signaling (INFS) pathway functions in association with cellular growth, differentiation, and regulation of gene expression, and is activated by diverse extracellular signals. Here we show that stimulation of angiotensin II (AII) receptors, depolarization, or activation protein kinase C (PKC) or adenylate cyclase all lead to nuclear accumulation of fibroblast growth factor 2 (FGF-2) and FGFR1, association of FGFR1 with splicing factor-rich domains, and activation of the tyrosine hydroxylase (TH) gene promoter in bovine adrenal medullary cells (BAMC). The up-regulation of endogenous TH protein or a transfected TH promoter-luciferase construct by AII, veratridine, or PMA (but not by forskolin) is abolished by transfection with a dominant negative FGFR1TK-mutant which localizes to the nucleus and plasma membrane, but not by extracellularly acting FGFR1 antagonists suramin and inositolhexakisphosphate (IP6). Mechanism of TH gene activation by FGF-2 and FGFR1 was further investigated in BAMC and human TE671 cultures. TH promoter was activated by co-transfected HMW FGF-2 (which is exclusively nuclear) but not by cytoplasmic FGF-1 or extracellular FGFs. Promoter transactivation by HMWFGF-2 was accompanied by an up-regulation of FGFR1 specifically in the cell nucleus and was prevented FGFR1(TK-) but not by IP6 or suramin. The TH promoter was also transactivated by co-transfected wild-type FGFR1, which localizes to both to the nucleus and the plasma membrane, and by an exclusively nuclear, soluble FGFR1(SP-/NLS) mutant with an inserted nuclear localization signal. Activation of the TH promoter by nuclear FGFR1 and FGF-2 was mediated through the cAMP-responsive element (CRE) and was associated with induction of CREB- and CBP/P-300-containing CRE complexes. We propose a new model for gene regulation in which nuclear FGFR1 acts as a mediator of CRE transactivation by AII, cell depolarization, and PKC.     

Yeast-like fungi as etiologic agents of blood infections in patients hospitalized in 1998-1999

The aim of the study was the analysis of frequency of yeast-like fungi as etiological agents of fungemias in patients hospitalized in operative and conservative wards of Medical Academy Central Clinical Hospital in Warsaw in 1998-1999. Peripheral blood samples and collected from vascular catheters were incubated in BacT/Alert system(Organon Teknika, USA). Positive blood samples were inoculated on Sabouraud medium with chloramphenicol (bioMerieux, France) (the time of cultivation from 48 h to 7 days at 30 C) and on chromogenic medium BBL CHROMagar Candida (Becton Dickinson, USA). Fungal strains were identified by standard mycological procedures using ID 32 C strips (ATB system, bioMerieux, France) and tests of Sanofi Diagnostics Pasteur (France). The total number of positive blood cultures was 1724. Fifty eight fungal strains were isolated from blood samples (3.36%). Strains belonged to 4 genera: Candida (55), Trichosporon (1), Saccharomyces (1) and Pichia (1). Thirty eight fungal strains were isolated from peripheral blood samples. Forty seven fungal strains were cultured from patients hospitalized in operative wards. Among fungi isolated from peripheral blood samples C. albicans (10), C. glabrata (9) and C. parapsilosis (5) strains dominated. From blood samples collected from vascular catheters most often C. albicans (7), C. glabrata (4) and C. parapsilosis (3) were isolated.     

Secondary xylem development in Arabidopsis: a model for wood formation

Our understanding of the molecular controls regulating the identity of the vascular cambium and the development of secondary xylem and phloem have not yet benefited much from the use of Arabidopsis as a genetic system. Under appropriate growth conditions Arabidopsis undergoes extensive secondary growth in the hypocotyl, with the development of both a vascular and a cork cambium. The secondary xylem of the hypocotyl develops in two phases, an early phase in which only vessel elements mature and a later stage in which both vessel elements and fibres are found. During this second phase the secondary xylem of Arabidopsis closely resembles the anatomy of the wood of an angiosperm tree, and can be used to address basic questions about wood formation. The development of the vascular cambium and secondary growth in Arabidopsis hypocotyl is described and its utility as a model for wood formation in trees is considered.     

Further studies on the Paramecium aurelia species complex in Greece

The strains collected in Athens and the city of Egina, the Island of Egina were identified as P. primaurelia. This is the first information about finding of P. primaurelia in Greece.     

A comparison of the in vitro genotoxicity of anticancer drugs idarubicin and mitoxantrone

Idarubicin is an anthracycline antibiotic used in cancer therapy. Mitoxantrone is an anthracycline analog with presumed better antineoplastic activity and lesser toxicity. Using the alkaline comet assaywe showed that the drugs at 0.01-10 microM induced DNA damage in normal human lymphocytes. The effect induced by idarubicin was more pronounced than by mitoxantrone (P < 0.001). The cells treated with mitoxantrone at 1 microM were able to repair damage to their DNA within a 30-min incubation, whereas the lymphocytes exposed to idarubicin needed 180 min. Since anthracyclines are known to produce free radicals, we checked whether reactive oxygen species might be involved in the observed DNA damage. Catalase, an enzyme inactivating hydrogen peroxide, decreased the extent of DNA damage induced by idarubicin, but did not affect the extent evoked by mitoxantrone. Lymphocytes exposed to the drugs and treated with endonuclease III or formamidopyrimidine-DNA glycosylase (Fpg), enzymes recognizing and nicking oxidized bases, displayed a higher level of DNA damage than the untreated ones. 3-Methyladenine-DNA glycosylase II (AlkA), an enzyme recognizing and nicking mainly methylated bases in DNA, increased the extent of DNA damage caused by idarubicin, but not that induced by mitoxantrone. Our results indicate that the induction of secondary malignancies should be taken into account as side effects of the two drugs. Direct strand breaks, oxidation and methylation of the DNA bases can underlie the DNA-damaging effect of idarubicin, whereas mitoxantrone can induce strand breaks and modification of the bases, including oxidation. The observed in normal lymphocytes much lesser genotoxicity of mitoxantrone compared to idarubicin should be taken into account in planning chemotherapeutic strategies.     

Molecular basis of inherited predispositions for tumors

On the basis of literature data and own experience the authors review the current knowledge about the molecular basis of inherited predispositions for tumors. They hypothesize that in the near perspective 5-10 years studies using existing registry data/material and the latest novel technology will allow the identification of the molecular background for the majority of hereditary cancers which will have enormous practical consequences especially for the prevention of malignancies.     

Stoichiometry of the photosynthetic apparatus and phycobilisome structure of the cyanobacterium Plectonema boryanum UTEX 485 are regulated by both light and temperature

The role of growth temperature and growth irradiance on the regulation of the stoichiometry and function of the photosynthetic apparatus was examined in the cyanobacterium Plectonema boryanum UTEX 485 by comparing mid-log phase cultures grown at either 29 degrees C/150 micromol m(-2) s(-1), 29 degrees C/750 micromol m(-2) s(-1), 15 degrees C/150 micromol m(-2) s(-1), or 15 degrees C/10 micromol m(-2) s(-1). Cultures grown at 29 degrees C/750 micromol m(-2) s(-1) were structurally and functionally similar to those grown at 15 degrees C/150 micromol m(-2) s(-1), whereas cultures grown at 29 degrees C/150 micromol m(-2) s(-1) were structurally and functionally similar to those grown at 15 degrees C/10 micromol m(-2) s(-1). The stoichiometry of specific components of the photosynthetic apparatus, such as the ratio of photosystem (PS) I to PSII, phycobilisome size and the relative abundance of the cytochrome b(6)/f complex, the plastoquinone pool size, and the NAD(P)H dehydrogenase complex were regulated by both growth temperature and growth irradiance in a similar manner. This indicates that temperature and irradiance may share a common sensing/signaling pathway to regulate the stoichiometry and function of the photosynthetic apparatus in P. boryanum. In contrast, the accumulation of neither the D1 polypeptide of PSII, the large subunit of Rubisco, nor the CF(1) alpha-subunit appeared to be regulated by the same mechanism. Measurements of P700 photooxidation in vivo in the presence and absence of inhibitors of photosynthetic electron transport coupled with immunoblots of the NAD(P)H dehydrogenase complex in cells grown at either 29 degrees C/750 micromol m(-2) s(-1) or 15 degrees C/150 micromol m(-2) s(-1) are consistent with an increased flow of respiratory electrons into the photosynthetic intersystem electron transport chain maintaining P700 in a reduced state relative to cells grown at either 29 degrees C/150 micromol m(-2) s(-1) or 15 degrees C/10 micromol m(-2) s(-1). These results are discussed in terms of acclimation to excitation pressure imposed by either low growth temperature or high growth irradiance.