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991.
Yildirim G Baştuğ M Akçil IE Fiçicilar H Koç E Zaloğlu N 《Biological trace element research》2000,78(1-3):7-12
The platelet-activating factor (PAF) is an inflammatory mediator and it may exert some of its effects by reactive oxygen species
(ROS). We investigated the effects of PAF and hyperbaric oxygenation (HBO) on copper (Cu) and zinc (Zn) levels in plasma and
the intracellular antioxidant enzyme activities of rats. PAF administration caused a decrease in erythrocyte catalase (CAT)
and glutathione peroxidase (GPx) activities and in the plasma zinc level. Following PAF administration, exposure to HBO also
caused a decrease in erythrocyte GPx activity. These results support the hypothesis that PAF may produce free oxygen radicals
and HBO enhances this effect. The enzyme activities of the antioxidant defense system were found to be affected by these oxidative
processes. This is likely to be the result of excessive production of ROS or overutilization and/or inhibition of the antioxidant
enzymes. 相似文献
992.
The aim of this study was to assess the effects of cold-restraint stress on blood and the other tissue levels of trace elements.
The experiment was performed on male Swiss albino rats. The animals were divided to two groups: control and stressed groups.
In the stressed group, the rats were subjected to immobilization for 4 h at 4°C. At the end of the experimental period, blood
and tissue samples were collected from all of the animals. The levels of zinc, copper, magnesium, and manganese were measured
using flame and graphite furnace atomic absorption spectrometry. In rats subjected to stress, the zinc levels of serum were
increased, whereas in the duodenum and brain, zinc was found to decrease when compared to the control. The magnesium content
of both the stomach and duodenum were reduced, but the manganese levels of the liver, kidneys, and brain significantly increased
because of stress. In conclusion, cold-restraint stress may affect the metabolic process by changing the distributions of
zinc, magnesium, and manganese in tissues. 相似文献
993.
994.
To evaluate the importance and fate of organic matter inputs in forested streams, we determined the litterfall inputs and
the benthic coarse particulate organic matter (CPOM) in one headwater stream flowing through a mixed deciduous forest, during
one year. Both vertical traps and the stream bottom were sampled monthly. The material collected was sorted into four main
categories: leaves, fruits and flowers, twigs and debris. Litter production was 715 g m−2 y−1 and seasonal, with 73% of the
annual total during October–December (autumn). Leaves comprised the largest litter component. Benthic organic matter was 1880
g m−2 y−1, and was also seasonal. Highest accumulation was attained in spring, and twigs and branches comprised the major
component.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
995.
Influence of Precursor Availability on Alkaloid Accumulation by
Transgenic Cell Line of Catharanthus roseus 总被引:7,自引:0,他引:7 下载免费PDF全文
Serap Whitmer Camilo Canel Didier Hallard Cecilia Gon?alves Robert Verpoorte 《Plant physiology》1998,116(2):853-857
We have used a transgenic cell line of Catharanthus roseus (L.) G. Don to study the relative importance of the supply of biosynthetic precursors for the synthesis of terpenoid indole alkaloids. Line S10 carries a recombinant, constitutively overexpressed version of the endogenous strictosidine synthase (Str) gene. Various concentrations and combinations of the substrate tryptamine and of loganin, the immediate precursor of secologanin, were added to suspension cultures of S10. Our results indicate that high rates of tryptamine synthesis can take place under conditions of low tryptophan decarboxylase activity, and that high rates of strictosidine synthesis are possible in the presence of a small tryptamine pool. It appears that the utilization of tryptamine for alkaloid biosynthesis enhances metabolic flux through the indole pathway. However, a deficiency in the supply of either the iridoid or the indole precursor can limit flux through the step catalyzed by strictosidine synthase. Precursor utilization for the synthesis of strictosidine depends on the availability of the cosubstrate; the relative abundance of these precursors is a cell-line-specific trait that reflects the metabolic status of the cultures. 相似文献
996.
François Barrieu Dominique Thomas Danièle Marty-Mazars Maryse Charbonnier Francis Marty 《Planta》1998,204(3):335-344
The vacuolar membrane (tonoplast) of plant cells contains aquaporins, protein channels that facilitate the selective transport
of water. These tonoplast intrinsic proteins (TIPs) of 23–29 kDa belong to the ancient major intrinsic protein (MIP) family.
A monospecific polyclonal antiserum directed against a 26 kDa intrinsic protein from the tonoplast of meristematic cells from
cauliflower (Brassica oleracea L. var. botrytis) was used to screen a cDNA library. Two distinct cDNAs have been isolated. Both clones, c26-1 and c26-2, encode closely related TIPs. The c26-1 insert, consisting of 933 bp upstream of the poly(A) tail, is a full-length cDNA with an open reading frame encoding a protein
of 251 amino acids with a calculated Mr of 25 500. The c26-2 insert is a 5′ truncated cDNA. The two cDNAs share 90.5% sequence identity within their overlapping coding regions but only
35% sequence identity in the 3′␣untranslated regions, indicating that highly related TIP-encoding genes are expressed in meristematic
cells. Although TIPs have previously been found in a variety of cell types, they have not been found in meristems. The derived
amino acid sequences (BobTIP26-1 and BobTIP26-2, respectively) closely resemble the aquaporin γ-TIP from Arabidopsis thaliana. Northern blot analysis and in situ hybridization show that BobTIP26 mRNAs preferentially accumulate in highly meristematic cells, mostly before and during cell enlargement, and in the living
cells of the xylem. This differential pattern of expression is also found by immunodetection of BobTIP26 polypeptides. The
gene expression patterns are discussed with respect to the probable function of the gene products.
Received: 27 March 1997 / Accepted: 20 May 1997 相似文献
997.
Yin-Shan Yang Laurent Guignard André Padilla François Hoh Marie-Paule Strub Marc-Henri Stern Jean-Marc Lhoste Christian Roumestand 《Journal of biomolecular NMR》1998,11(3):337-354
The human oncoprotein p13
MTCP1
is coded by the MTCP1 gene, a gene involved in chromosomal translocations associated with T-cell prolymphocytic leukemia, a rare form of human leukemia with a mature T-cell phenotype. The primary sequence of p13
MTCP1
is highly and only homologous to that of p14
TCL1
, a product coded by the gene TCL1 which is also involved in T-cell prolymphocytic leukemia. These two proteins probably represent the first members of a new family of oncogenic proteins. We present the three-dimensional solution structure of the recombinant p13
MTCP1
determined by homonuclear proton two-dimensional NMR methods at 600 MHz. After proton resonance assignments, a total of 1253 distance restraints and 64 dihedral restraints were collected. The solution structure of p13
MTCP1
is presented as a set of 20 DYANA structures. The rmsd values with respect to the mean structure for the backbone and all heavy atoms for the conformer family are 1.07 ± 0.19 and 1.71 ± 0.17 Å, when the structured core of the protein (residues 11–103) is considered. The solution structure of p13
MTCP1
consists of an orthogonal -barrel, composed of eight antiparallel -strands which present an original arrangement. The two -pleated loops which emerge from this barrel might constitute the interaction surface with a potential molecular partner. 相似文献
998.
Bruno Chauffert Marie-Thérèse Dimanche-Boitrel Carmen Garrido Mikael Ivarsson Monique Martin François Martin Eric Solary 《Cytotechnology》1998,27(1-3):225-235
Kinetic resistance plays a major role in the failure of chemotherapy towards many solid tumors. Kinetic resistance to cytotoxic
drugs can be reproduced in vitro by growing the cells as multicellular spheroids (Multicellular Resistance) or as hyperconfluent
cultures (Confluence-Dependent Resistance). Recent findings on the cell cycle regulation have permitted a better understanding
why cancer cells which arrest in long quiescent phases are poorly sensitive to cell-cycle specific anticancer drugs. Two cyclin-dependent
kinase inhibitors (CDKI) seem particularly involved in the cell cycle arrest at the G1 to S transition checkpoint: the p53-dependent
p21cip1 protein which is activated by DNA damage and the p27kip1 which is a mediator of the contact inhibition signal. Cell quiescence could alter drug-induced apoptosis which is partly
dependent on an active progression in the cell cycle and which is facilitated by overexpression of oncogenes such as c-Myc
or cyclins. Investigations are yet necessary to determine the influence of the cell cycle on the balance between antagonizing
(bcl-2, bcl-XL...) or stimulating (Bax, Bcl-XS, Fas...) factors in chemotherapy-induced apoptosis. Quiescent cells could also be protected from toxic agents by an enhanced
expression of stress proteins, such as HSP27 which is induced by confluence. New strategies are required to circumvent kinetic
resistance of solid tumors: adequate choice of anticancer agents whose activity is not altered by quiescence (radiation, cisplatin),
recruitment from G1 to S/G2 phases by cell pretreatment with alkylating drugs or attenuation of CDKI activity by specific
inhibitors.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
999.
1000.
Anne Schoendorf Roberte Bronner Jean Broadhvest François Bernier 《Sexual plant reproduction》1998,11(3):140-147
In the tobacco (Nicotiana tabacum) Appendix mutant, anthers are tipped by a miniature style and stigma. The outgrowth appears on the anther when it is already
differentiating and follows the developmental timing of the central carpel. The Appendix mutation thus represents a late homeotic
transformation suggesting that the APPENDIX (APX) gene either could be a misregulated organ identity gene or could be involved in regulating the expression of such genes.
RFLP analysis with two class B (TM6 and NTGLO) and a class C (NAG) probes revealed that the Appendix phenotype is not caused by a mutation in one of these genes. However, in situ hybridization
showed important changes in the expression of NTGLO and NAG in the mutant when compared with wild-type tobacco. Surprisingly, although no phenotypic alteration other than the style
and stigma outgrowth is observed in the Appendix mutant, changes in class B and class C gene expession were not restricted
to the anther tip cells from which the outgrowth originates. As expected, NAG was expressed in the Appendix outgrowth but it was also overexpressed in the normal third and fourth whorl organs at the
time the outgrowth, as well as the central styles and stigmas, differentiated. Overexpression of a class C gene is probably
responsible for the Appendix phenotype. In normal and mutant flowers, NTGLO was expressed in the second, third and fourth whorls up to the time of carpel fusion. Expression of this class B gene then
ceased in the fourth whorl organs but was reactivated at later stages only in the styles and stigmas as well as in the outgrowths
of the mutant. It thus seems that the function of the APX gene is either to regulate the late expression of organ identity genes or to control cell proliferation in such a way that,
in the mutant, some cells are in a state where they respond in an unusual way to developmental signals.
Received: 17 October 1997 / Revision accepted: 24 March 1998 相似文献