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  • 1
    Electronic Resource
    Electronic Resource
    Modulation of mRNA levels in the presence of thymocytes and genome mapping for a set of genes expressed in mouse thymic epithelial cells (1997)
    Springer
    Immunogenetics 46 (1997), S. 142-151 
    Details
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Modulation of gene expression in mouse thymic epithelium upon culture in the presence of thymocytes (coculture) was studied by comparison of hybridization signatures on a set of nearly 5000 mouse thymus cDNA clones. Forty-nine differentially expressed clones (usually down-regulated in coculture) were characterized by tag sequencing. Many of them corresponded to entities that had not been described previously in the mouse, and were further characterized by genome mapping. This set of genes appears to be involved in growth regulation and differentiation within the thymus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050253
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  • 2
    Electronic Resource
    Electronic Resource
    Differential gene expression in CD3e- and RAG1-deficient thymuses: definition of a set of genes potentially involved in thymocyte maturation (1999)
    Springer
    Immunogenetics 50 (1999), S. 255-270 
    Details
    ISSN: 1432-1211
    Keywords: Key words Thymus ; T lymphocytes ; Gene regulation ; Chemokines ; Thymic stroma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  A set of 3000 mouse thymus cDNAs was analyzed by extensive measurement of expression using complex-probe hybridization of DNA arrays ("quantitative differential screening"). The complex probes were initially prepared using total thymus RNA isolated from C57BL/6 wild-type (WT), CD3e- and RAG1-deficient mice. Over 100 clones displaying over- or under-expression by at least a factor of two between WT and knockout (KO) thymuses were further analyzed by measuring hybridization signatures with probes from a wide range of KO thymuses, cell types, organs, and embryonic thymuses. A restricted set of clones was selected by virtue of their expression spectra (modulation in KO thymuses and thymocytes, lymphoid cell specificity, and differential expression during embryonic thymus development), sequenced at one extremity, and compared to sequences in databases. Clones corresponding to previously identified genes (e.g., Tcrβ, Tcf1 or CD25) showed expression patterns that were consistent with existing data. Ten distinct clones corresponding to new genes were subjected to further study: Northern blot hybridization, in situ hybridization on thymus sections, and partial or complete mRNA sequence determination. Among these genes, we report a new serine peptidase highly expressed in cortical epithelial cells that we have named thymus-specific serine peptidase (TSSP), and an acidic protein expressed in thymocytes and of unknown function that we have named thymus-expressed acidic protein (TEAP). This approach identifies new molecules likely to be involved in thymocyte differentiation and function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050601
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  • 3
    Electronic Resource
    Electronic Resource
    Ultraviolet-B-induced stress and changes in gene expression in Arabidopsis thaliana: role of signalling pathways controlled by jasmonic acid, ethylene and reactive oxygen species (1999)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 22 (1999), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Treatment with supplementary UV-B resulted in decreases in transcripts of the photosynthetic genes Lhcb and psbA and concomitant increase in transcripts of two pathogen-related genes, PR-1 and PDF1·2, in Arabidopsis thaliana. UV-B exposure caused increases in jasmonic acid (JA) levels and ethylene production. UV-B treatment of jar1 and etr1-1 mutants, which are insensitive to JA and ethylene, respectively, showed that the increase in PR-1 transcripts was dependent on ethylene and PDF1·2 transcripts on both JA and ethylene. In contrast, the down-regulation of photosynthetic transcripts was independent of both compounds. Previous studies have indicated a role for reactive oxygen species (ROS) in the UV-B-induced down-regulation of the photosynthetic genes and up-regulation of PR-1 genes. Here we have shown that ROS are also required for the UV-B-induced up-regulation of PDF1·2 genes. The results indicate that the effects of UV-B on the three sets of genes are mediated through three distinct signal transduction pathways which are similar, but not identical, to pathways initiated in response to pathogen infection. In addition, the increased sensitivity of both jar1 and etr1-1 mutants to UV-B radiation, as compared with wild-type plants, indicated that intact JA and ethylene signal pathways are required for defence against UV-B damage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1999.00499.x
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  • 4
    Electronic Resource
    Electronic Resource
    Ultraviolet-B-induced responses in Arabidopsis thaliana: role of salicylic acid and reactive oxygen species in the regulation of transcripts encoding photosynthetic and acidic pathogenesis-related proteins (1998)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 21 (1998), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Supplementary UV-B was shown to lead to a decrease in transcripts encoding the photosynthetic genes Lhcb and psbA and a concomitant increase in transcripts encoding three acid-type pathogenesis-related proteins, PR-1, PR-2 and PR-5, in Arabidopsis thaliana. UV-B radiation has been reported to lead to the generation of reactive oxygen species (ROS). Here we report that ROS are required for UV-B-induced down-regulation of the photosynthetic genes and up-regulation of PR genes, as the addition of antioxidants before UV-B treatment resulted in a marked reduction in the effect of UV-B on both sets of genes. Rises in ROS are frequently accompanied by increases in salicylic acid (SA) accumulation. UV-B treatment of transgenic NahG Arabidopsis plants, which are unable to accumulate SA, showed that the increase in PR transcripts, but not the decrease in photosynthetic transcripts, was dependent on the increase in SA. In addition, a 3 d exposure to UV-B radiation resulted in a 7-fold increase in SA levels. Oxidant treatment of NahG plants indicated that ROS could not up-regulate PR genes in the absence of SA accumulation; however, the down-regulation of photosynthetic transcripts was unchanged from that in wild-type plants. The results indicate that the effects of UV-B on the two sets of genes are mediated through two distinct signal tranduction pathways. One pathway is ROS-dependent but SA-independent and mediates the down-regulation of photosynthetic genes. The other is SA- and ROS-dependent and mediates the up-regulation of the acidic-type PR genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1998.00325.x
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  • 5
    Electronic Resource
    Electronic Resource
    Multivariate analysis of intraspecific responses to UV-B radiation in white clover (Trifolium repens L.) (2001)
    Oxford, UK : Blackwell Science Ltd.
    Plant, cell & environment 24 (2001), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: White clover (Trifolium repens L.) is experiencing increased levels of ultraviolet-B (UV-B) radiation in temperate pastures due to the depletion of the stratospheric ozone layer. Based on 17 morphological, morphogenetic and physiological attributes, this study analysed the consequences of enhanced UV-B on 26 white clover populations using principal components analysis (PCA). After 18 d of exposure to 13·3 kJ m−2 d−1 UV-B in controlled environments, UV-B significantly decreased above-ground and below-ground plant growth attributes, epidermal cell surface area and maximum quantum efficiency of photosystem II photochemistry (Fv/Fm). Aspects of cell division and cell expansion both were negatively affected by UV-B. Stomatal density, specific leaf mass, root-to-shoot ratio and levels of UV-B-absorbing compounds increased in response to UV-B. In the multivariate analysis, the main dimension of UV-B sensitivity was characterized by changes in plant growth attributes. Alterations in partitioning within and between plant organs constituted a secondary tier of UV-B responsiveness. Plant characteristics related to UV-B tolerance included lower growth rate, smaller epidermal cell surface area and higher UV-B-induced levels of UV-B-absorbing compounds. The results suggest overall UV-B tolerance for slower-growing populations from less productive habitats with higher natural UV-B irradiance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2001.00749.x
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  • 6
    Electronic Resource
    Electronic Resource
    Ultraviolet-B effects on transcript levels for photosynthetic genes are not mediated through carbohydrate metabolism (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 20 (1997), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The relationship between UV-B-induced changes in gene expression and carbohydrate levels in pea seedlings has been investigated. The effect of supplementary UV-B radiation on the transcript abundance for two photosynthetic genes, photosynthesis, respiration and the levels of carbohydrates was determined in fully expanded leaves of 17-d-old pea seedlings under high (HL: 350 μmol m−2 s−1) and low (LL: 150 μmol m−2 s1) light. Supplementary UV-B caused down regulation of the photosynthetic genes in green leaves under LL and to a lesser extent under HL. In contrast to previous studies, UV-B radiation resulted in a decrease in glucose levels rather than an increase under LL. Sucrose and starch levels were not affected until longer exposure. Effects of UV-B on carbohydrate levels were, however, minimal under HL. The effects on transcript levels were most marked under LL and therefore could not be attributed to elevated carbohydrate levels. Comparison of UV-B effects on carbohydrates in source (leaf) and sink (green buds) organs indicated that changes in carbohydrates in response to UV-B are probably indirect and arise from effects of UV-B on photosynthesis in source organs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1997.d01-39.x
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  • 7
    Electronic Resource
    Electronic Resource
    Ultraviolet-B-induced DNA lesions and their removal in wheat (Triticum aestivum L.) leaves (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 19 (1996), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Monoclonal antibodies were used in an enzyme-linked immunosorbent assay (ELISA) to detect the induction and removal of cyclobutane pyrimidine dimers (CPDs) and (6-4) photoproducts in DNA isolated from ultraviolet B (UV-B)-exposed primary wheat (Triticum aestivum L. cv. Chinese Spring) leaf tissue. The accumulation of lesions in the primary leaves of 6-d-old wheat seedlings was followed during the exposure of the leaf to an approximate dose of 3.6×10−1 W m−2 UV-B (Caldwell weighting). Significant increases in the levels of both CPDs and (6-4) photoproducts were detected in wheat leaves exposed to UV-B in the absence of other light However, only an increase in (6-4) photoproduct levels could be measured in wheat leaves exposed to the same UV-B source in the presence of supplemental white light. The removal of CPD antibody binding sites in the DNA after irradiation was rapid under conditions of high light intensity in contrast to the removal of (6-4) photoproduct antibody binding sites, which was significantly slower. The removal of CPDs appeared to be light dependent, this rate of removal decreasing with decreasing light fluences. The removal of (6-4) photoproducts also appeared light dependent, but to a lesser extent than the removal of CPDs, under the conditions studied here. Gene expression in the primary wheat leaf was measured and showed an up-regulation of chalcone synthase expression and a reduction in expression of chlorophyll a/b-binding protein (cab) in response to supplementary UV-B. No effect was seen on the expression of the other photosynthetic genes studied (the genes coding for the enzymes sedoheptu-lose 1,7-bisphosphatase and fructose 1,6-bisphosphatase). Measurement of the levels of DNA lesions in this same tissue showed that the observed changes in gene expression accompanied the appearance of UV-B induced lesions in the form of (6-4) photoproducts in the wheat leaf genome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1996.tb00238.x
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  • 8
    Electronic Resource
    Electronic Resource
    The effect of ultraviolet-B radiation on gene expression and pigment composition in etiolated and green pea leaf tissue: UV-B-induced changes are gene-specific and dependent upon the developmental stage (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 17 (1994), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect of ultraviolet-B radiation (UV-B: 280–320nm) on gene expression and pigment composition has been investigated in pea tissue at different stages of development. Pea (Pisum sativum L., cv. Feltham First) seedlings were grown for 17d and then exposed to supplementary UV-B radiation. Chlorophyll a per unit fresh weight decreased by more than 20% compared with control levels after exposure to UV-B radiation for 7d. In contrast, chlorophyll b content remained the same or increased slightly. Leaf protein biosynthesis, as determined by 35S-methionine incorporation, was rapidly inhibited by UV-B radiation, although the steady-state levels of proteins were either unchanged or only slightly altered. RNA transcripts for the chlorophyll a/b binding protein (cab) were also rapidly reduced to low or even undetectable levels in the expanded third leaf or younger leaf bud tissue after exposure to UV-B radiation. In contrast, cab RNA transcripts were either low or undetectable in etiolated pea tissue, but increased substantially in light and during exposure to UV-B radiation. The cab RNA transcripts were still present at control levels in pea plants after 7d of greening under supplementary UV-B radiation or UV-B alone. The protein composition changed significantly over the 7d of greening, but no differences could be detected between the light treatments. The increase in chlorophyll content was slightly greater during de-etiolation under supplementary UV-B radiation than under control irradiance. Under UV-B radiation alone, chlorophyll was synthesized at a greatly reduced rate. Changes in protective pigments were also determined. Anthocyanins did not change in either etiolated or green tissue exposed to UV-B radiation. However, other flavonoids increased substantially in either tissue during exposure to light and UV-B radiation. The RNA levels for chalcone synthase were measured in green and etiolated tissue exposed to UV-B radiation. The chs RNA transcripts were present in low or undetectable amounts in control tissues. In green leaf tissue exposed to supplementary UV-B, a transient increase was detected. The transcripts for chs reached a maximum level after approximately 8 h UV-B exposure, and then declined to lower levels over subsequent days of diurnal photoperiods. However, a constant increase in chs was found after continuous exposure to UV-B for up to 30 h. In etiolated tissue, either white-light, supplementary UV-B or UV-B alone gave small increases in chs, only 8 h of UV-B radiation alone gave any substantial increase in chs expression. Overall, these results clearly demonstrate that the response to increased levels of UV-B radiation is dependent upon the developmental stage of the tissue and involves complex changes in gene expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1994.tb00264.x
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  • 9
    Electronic Resource
    Electronic Resource
    Changes in mRNA levels and polypeptide subunits of ribulose 1,5-bisphosphate carboxylase in response to supplementary ultraviolet-B radiation (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 15 (1992), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Pea plants (Pisum sativum L., cv. Greenfeast) were grown for 17d (150 μmol photons m−2 s−1; 12h light/12 h dark) and then exposed to moderate levels of supplementary ultraviolet-B radiation (UV-B: 280–320 nm) during the light cycle. The total soluble leaf protein, maximum Rubisco activity, polypeptide and mRNA transcript levels for Rubisco subunits were then determined in the mature third leaf pair from the base of the plants. Total soluble protein per unit leaf area showed little change after 1 d but declined by 33% during 3d of UV-B exposure. However, there was no change on a unit chlorophyll basis. Total RNA per unit area declined by 15% and 37% after 1 or 3d of UV-B treatment, respectively. Maximum Rubisco activity declined by 38% after 1 d and 71% after 3d of UV-B exposure. Rubisco polypeptide subunits showed some decrease (∼16%) after 1d exposure, but declined by 56% over 3d. The decrease in Rubisco is probably the major reason for the reduction in soluble protein. In contrast to the relatively slow decline in total soluble protein and Rubisco, the level of the mRNA transcripts for both rbc L and rbc S showed a dramatic decrease within hours of UV-B exposure. The mRNA transcripts for rbc S were reduced to 〉20% of control values after 4h of UV-B exposure, while the rbc L transcripts were reduced by 60% after 8h. Further exposure to UV-B reduced the mRNA transcripts to either trace or undetectable levels. The decrease in rbc S mRNA levels with the UV-B exposure can be partially ameliorated by higher photosynthetically active irradiance during the period of UV-B exposure. Plants that were exposed to supplementary UV-B radiation for short periods (4h or 8h) and returned to control conditions, showed no recovery after 24h. However, after a further 2d, the rbc L and rbc S mRNA transcripts had recovered to ca. 60% of the control values, showing that the effect upon the mRNA transcripts is a reversible response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1992.tb01461.x
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  • 10
    Electronic Resource
    Electronic Resource
    Murine cells expressing an HLA molecule are specifically lysed by HLA-restricted antiviral human T cells (1986)
    [s.l.] : Nature Publishing Group
    Nature 319 (1986), S. 153-154 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Murine cells expressing HLA-A2 or HLA-A11 molecules have been obtained by transfection of P815-HTR cells9 with genomic clones of well-established HLA specificities described previously10'11. These cells were infected with the A/Texas (AT) human influenza A virus and successful infection was ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/319153a0
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