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1.
Summary. The support vector machine, a machine-learning method, is used to predict the four structural classes, i.e. mainly α, mainly
β, α–β and fss, from the topology-level of CATH protein structure database. For the binary classification, any two structural
classes which do not share any secondary structure such as α and β elements could be classified with as high as 90% accuracy.
The accuracy, however, will decrease to less than 70% if the structural classes to be classified contain structure elements
in common. Our study also shows that the dimensions of feature space 202 = 400 (for dipeptide) and 203 = 8 000 (for tripeptide) give nearly the same prediction accuracy. Among these 4 structural classes, multi-class classification
gives an overall accuracy of about 52%, indicating that the multi-class classification technique in support of vector machines
may still need to be further improved in future investigation. 相似文献
2.
The effect of extractants on degradation of L-glutamate and L-arginine in the course of shaking and filtration at low temperature 总被引:1,自引:0,他引:1
Summary. The effects of demineralized water (DEMI H2O) and 0.5 M ammonium acetate (0.5 M AAc) on losses of L-glutamic acid and L-arginine in the course of shaking and filtration
at low temperature (6 °C) were tested. The concentration of L-glutamic acid decreased by 6.3% in DEMI H2O and by 4.9% in 0.5 M AAc, whereas the L-arginine concentration decreased by 6.0% (DEMI H2O) and 10.7% (0.5 M AAc). We found a significantly (P < 0.05) higher degradation of L-arginine in 0.5 M AAc compared with that of DEMI H2O. 相似文献
3.
Isolation, properties and spatial site analysis of γ subunits of B-phycoerythrin and R-phycoerythrin
Polysiphonia urceolata R-phycoerythrin andPorphyridium cruentum B-phycoerythrin were degraded with proteinaseK, and then the nearly native γ subunits were isolated from the reaction mixture.
The process of degradation of phycocrythrin with proteinaseK showed that the γ subunit is located in the central cavity of
(αβ)6 hexamer of phycoerythrin. Comparative analysis of the spectra of the native phycoerythrin, the phycoerythrin at pH 12 and
the isolated γ subunit showed that the absorption peaks of phycoerythrobilins on α or β subunit are at 535 nm (or 545 nm)
and 565 nm, the fluorescence emission maximum at 580 nm; the absorption peak of phycoerythrobilins on the isolated γ subunit
is at 589 nm, the fluorescence emission peak at 620 nm which overlaps the absorption maximum of C-phycocyanin and perhaps
contributes to the energy transfer with high efficiency between phycoerythrin and phycocyanin in phycobilisome; the absorption
maximum of phycourobilin on the isolated γ subunit is at 498 nm, which is the same as that in native phycoerythrin, and the
fluorescence emission maximum at 575 nm. 相似文献
4.
Infiltrating detached maize (Zeamays L.) leaves with L-galactono-1,4-lactone (L-GAL) resulted in a 4-fold increase in the content of leaf ascorbate. Upon exposure to high irradiance (1000 μmol photons m−2 s−1) at 5 °C, L-GAL leaves de-epoxidized the xanthophyll-cycle pigments faster than the control leaves; the maximal ratio of de-epoxidized
xanthophyll-cycle pigments to the whole xanthophyll-cycle pool was the same in both leaf types. The elevated ascorbate content,
together with the faster violaxanthin de-epoxidation, did not affect the degree of photoinhibition and the kinetics of the
recovery from photoinhibition, assayed by monitoring the maximum quantum efficiency of photosystem II primary photochemistry
(Fv/Fm). Under the experimental conditions, the thermal energy dissipation seems to be zeaxanthin-independent since, in contrast
to the de-epoxidation, the decrease in the efficiency of excitation-energy capture by open photosystem II reaction centers (Fv′/Fm′) during the high-irradiance treatment at low temperature showed the same kinetic in both leaf types. This was also observed
for the recovery of the maximal fluorescence after stress. Furthermore, the elevated ascorbate content did not diminish the
degradation of pigments or α-tocopherol when leaves were exposed for up to 24 h to high irradiance at low temperature. Moreover,
a higher content of ascorbate appeared to increase the requirement for reduced glutathione.
Received: 20 May 1999 / Accepted: 29 October 1999 相似文献
5.
Kocsy G von Ballmoos P Suter M Rüegsegger A Galli U Szalai G Galiba G Brunold C 《Planta》2000,211(4):528-536
The role of glutathione (GSH) in protecting plants from chilling injury was analyzed in seedlings of a chilling-tolerant
maize (Zea mays L.) genotype using buthionine sulfoximine (BSO), a specific inhibitor of γ-glutamylcysteine (γEC) synthetase, the first enzyme
of GSH synthesis. At 25 °C, 1 mM BSO significantly increased cysteine and reduced GSH content and GSH reductase (GR: EC 1.6.4.2)
activity, but interestingly affected neither fresh weight nor dry weight nor relative injury. Application of BSO up to 1 mM
during chilling at 5 °C reduced the fresh and dry weights of shoots and roots and increased relative injury from 10 to almost
40%. Buthionine sulfoximine also induced a decrease in GR activity of 90 and 40% in roots and shoots, respectively. Addition
of GSH or γEC together with BSO to the nutrient solution protected the seedlings from the BSO effect by increasing the levels
of GSH and GR activity in roots and shoots. During chilling, the level of abscisic acid increased both in controls and BSO-treated
seedlings and decreased after chilling in roots and shoots of the controls and in the roots of BSO-treated seedlings, but
increased in their shoots. Taken together, our results show that BSO did not reduce chilling tolerance of the maize genotype
analyzed by inhibiting abscisic acid accumulation but by establishing a low level of GSH, which also induced a decrease in
GR activity.
Received: 9 November 1999 / Accepted: 17 February 2000 相似文献
6.
The physiological properties of transgenic tobacco plants (Nicotiana tabacum L.) with decreased or increased transport capacities of the chloroplast triose phosphate/phosphate translocator (TPT) were
compared in order to investigate the extent to which the TPT controls metabolic fluxes in wild-type tobacco. For this purpose,
tobacco lines with an antisense repression of the endogenous TPT (αTPT) and tobacco lines overexpressing the TPT gene isolated
from the C4 plant Flaveria trinervia (FtTPT) were used. The F. trinervia TPT expressed in yeast cells exhibited transport characteristics identical to the TPT from C3 plants. Neither antisense TPT plants nor FtTPT overexpressors showed a phenotype when grown in a greenhouse in air. Contents
of starch and soluble sugars in upper source leaves were similar in TPT underexpressors and FtTPT overexpressors compared
to the wild type at the end of the photoperiod. The FtTPT overexpressors incorporated more 14CO2 in sucrose than the wild type, indicating that the TPT limits sucrose biosynthesis in the wild type. There were only small
effects on labelling of amino acids and organic acids. The mobilisation of starch was enhanced in αTPT lines but decreased
in FtTPT overexpressors compared to the wild type. Enzymes involved in starch mobilisation or utilisation, such as α-amylase
or hexokinase were increased in αTPT plants and, in the case of amylases, decreased in FtTPT overexpressors. Moreover, α-amylase
activity exhibited a pronounced diurnal variation in αTPT lines with a maximum activity after 8 h in the light. These changes
in starch hydrolytic activities were confirmed by activity staining of native gels. Activities of glucan phosphorylases were
unaffected by either a decrease or an increase in TPT activity. There were also effects of TPT activities on steady-state
levels of phosphorylated intermediates as well as total amino acids and malate. In air, there was no or little effect of altered
TPT transport activity on either rates of photosynthetic electron transport and/or CO2 assimilation. However, in elevated CO2 (1500 μl · l−1) and low O2 (2%) the rate of CO2 assimilation was decreased in the αTPT lines and was slightly higher in FtTPT lines. This shows that the TPT limits maximum
rates of photosynthesis in the wild type.
Received: 26 March 1999 / Accepted: 21 August 1999 相似文献
7.
Presence and stability of an unusual phycoerythrin (PE) characteristically similar to R-PE are described in a terrestrial,
desiccation-tolerant cyanobacterium, Lyngbya arboricola. Extraction and purification of the PE by using acetone precipitation, gel filtration and ion-exchange chromatography resulted
in achieving a purity index (A560/A280) of up to 5.2. SDS-PAGE of the PE showed presence of 18 kDa, 20 kDa and 32 kDa bands corresponding to α, β and γ subunits
of R-PE without any other contaminating phycobiliproteins (PBPs). The absorption spectrum of the PE was distinguished by two
major peaks at 499 and 559 nm. The maximum fluorescence emission at room temperature was 578 nm. Spectroscopic and electrophoresis
characteristics of PE in the dry mats on storage at 25 ± 1°C over silica gel for 2 years remained almost unaffected. Quantitatively,
storage stability of the PE was in the order of dry mats > lyophilized > liquid state and the impact of temperature on loss
of PE was in the order of 25°C > −20°C > 4°C. The relevance of L. arboricola for production of stable unusual PE is discussed. 相似文献
8.
Summary. Heat shock proteins (HSPs) are synthesised by cells subsequent to a stress exposure and are known to confer protection to
the cell in response to a second challenge. HSP induction and decay are correlated to thermotolerance and may therefore be
used as a biomarker of thermal history. The current study tested the temperature-dependent nature of the heat shock response
and characterised its time profile of induction. Whole blood from 6 healthy males (Age: 26 ± (SD) 2 yrs; Body mass 74.2 ±
3.8 kgs; VO2max: 49.1 ± 4.0 ml·kg−1·min−1) were isolated and exposed to in vitro heat shock (HS) at 37, 38, 39, 40, and 41 °C for a period of 90 min. After HS the
temperature was returned to 37 °C and intracellular HSP70 was quantified from the leukocytes at 0, 2, 4, and 6 h after heat
treatment. The concentration of HSP70 was not different between temperatures (P > 0.05), but the time-profile of HSP70 synthesis appeared temperature-dependent. At control (37 °C) and lower temperatures
(38–39 °C) the mean HSP70 concentration increased up to 4 h post HS (P < 0.05) and then returned towards baseline values by 6 h post HS. With in vitro hyperthermic conditions (40–41 °C), the time-profile
was characterised by a sharp rise in HSP70 levels immediately after treatment (P < 0.05 for 40 °C at 0 h), followed by a progressive decline over time. The results suggest a temperature-dependent time-profile
of HSP70 synthesis. In addition, the temperature at which HSP70 is inducted might be lower than 37 °C. 相似文献
9.
Using the crystal structure of allophycocyanin from cyanobacterium Spirulina platensis (APC-SP) as a search model, the crystal structure of allophycocyanin from red algae Porphyra yezoensis (APC-PY) has been studied by molecular replacement methods. The APC-PY crystals (Form 3) belong to the space group of R32, cell dimensions a = b = 10.53 nm, c = 18.94 nm, α =β = 90°, γ= 120°; there is one αβ monomer in each crystallographic asymmetric unit in the cell. The translation function search gave a unique peak with a correlation coefficient (Cc) of 67.0% and an R-factor of 36.1 % for reflection data from 1.0 to 0.4 nm. Using the results by molecular replacement, the initial model of APC-PY was built, and the coincidence of the chromophore in APC-PY initial model with its 2Fo-FC OMIT map further confirms the results by molecular replacement. 相似文献
10.
The entry of calcium and magnesium from external sources into mycorrhizal roots of 3-year-old Norway spruce trees (Piceaabies [L.] Karst.) was monitored. Roots of intact plants were exposed for various periods of time, ranging from 2 min to 48 h,
to nutrient solutions which contained the stable-isotope tracers 25Mg and 44Ca. After labelling, samples of roots were excised from the plants, shock-frozen, cryosubstituted and embedded. The resulting
isotope composition in this material was analysed by a laser-microprobe-mass-analyser (LAMMA) at relevant positions within
cross-sections of the roots. For both elements, we determined (i) the fractions of the isotopes originating from the plant
prior to labelling, and (ii) the fraction of isotopes originating from the corresponding tracer that penetrated into the root.
Both divalent cations rapidly penetrated across the cortical apoplast and reached the endodermis. After 2 min of exposure
to the labelling solution, an initial transient gradient of the tracers could be observed within the root cortex. Subsequently,
calcium as well as magnesium equilibrated between the apoplast of the entire cortex and the external tracer with a half-time,
t1/2, of about 3 min. In contrast, the kinetics of radial movement into the vascular stele showed a delay with a t1/2 of 100–120 min. We take this as strong evidence that there exists a free apoplastic path for divalent cations in the cortex
and that the endodermis is a major barrier to the further passage of Mg and Ca into the xylem. While 25Mg in the labelling solution exchanged rapidly with Mg in the cortical apoplast, the exchange across the plasma membrane with
Mg present in the protoplasm of the same cortical cells was almost 2 orders of magnitude slower. The kinetics of Ca and Mg
entry at +6 °C were similar to those obtained at a root temperature of +22 °C.
Received: 23 December 1998 / Accepted: 17 September 1999 相似文献
11.
T. M. Falk W. Villwock L. Renwrantz 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(1):9-16
Haemoglobins of five tilapiine species of the genera Oreochromis and Sarotherodon were investigated. By gel filtration chromatography a molecular weight of 67–69 kDa was determined for the tetrameric molecules
which remained stable between pH 5.0 and pH 9.1. When subjected to sodium dodecyl sulphate-Urea-polyacrylamide gel electrophoresis
(PAGE), haemoglobins of all species each were split into monomers of three different molecular weights ranging between 16.3
kDA and 17.6 kDa. Subsequently, isoelectric focusing separated haemolysates into about 23 differently charged tetrameric haemoglobins
that were arranged in species-specific patterns. This diversity was shown to result from the occurrence of different types
of globin chains. By acidic urea PAGE a total of seven major α-globins and five major β-globins were detected and species-characteristic
chain variants were identified. To determine the globin chain composition of particular haemoglobin tetramers, 26 bands were
isolated by isoelectric focusing and analysed by acidic urea PAGE. Tetramers consisted of doublets of identical α- and identical
β-chains (α2β2, symmetric tetramers), or combinations of three (α2ββ*; αα*β2) or four (αα*ββ*) distinct chains (asymmetric tetramers). Finally, globin chains of Oreochromis niloticus were subjected to partial N-terminal amino acid sequencing. Differences in the composition of the three major β-chains could
be shown, whereas the α-chains were N-terminally blocked.
Accepted: 12 September 1997 相似文献
12.
The α1 subunit coding for the human brain type E calcium channel (Schneider et al., 1994) was expressed in Xenopus oocytes in the absence, and in combination with auxiliary α2δ and β subunits. α1E channels directed with the expression of Ba2+ whole-cell currents that completely inactivated after a 2-sec membrane pulse. Coexpression of α1E with α2bδ shifted the peak current by +10 mV but had no significant effect on whole-cell current inactivation. Coexpression of α1E with β2a shifted the peak current relationship by −10 mV, and strongly reduced Ba2+ current inactivation. This slower rate of inactivation explains that a sizable fraction (40 ± 10%, n= 8) of the Ba2+ current failed to inactivate completely after a 5-sec prepulse. Coinjection with both the cardiac/brain β2a and the neuronal α2bδ subunits increased by ≈10-fold whole-cell Ba2+ currents although coinjection with either β2a or α2bδ alone failed to significantly increase α1E peak currents. Coexpression with β2a and α2bδ yielded Ba2+ currents with inactivation kinetics similar to the β2a induced currents, indicating that the neuronal α2bδ subunit has little effect on α1E inactivation kinetics. The subunit specificity of the changes in current properties were analyzed for all four β subunit
genes. The slower inactivation was unique to α1E/β2a currents. Coexpression with β1a, β1b, β3, and β4, yielded faster-inactivating Ba2+ currents than currents recorded from the α1E subunit alone. Furthermore, α1E/α2bδ/β1a; α1E/α2bδ/β1b; α1E/α2bδ/β3; α1E/α2bδ/β4 channels elicited whole-cell currents with steady-state inactivation curves shifted in the hyperpolarized direction. The
β subunit-induced changes in the properties of α1E channel were comparable to modulation effects reported for α1C and α1A channels with β3≈β1b > β1a≈β4≫β2a inducing fastest to slowest rate of whole-cell inactivation.
Received: 27 March 1997/Revised: 10 July 1997 相似文献
13.
Summary. The condensation reactions of sodium trimetaphosphate with single amino acids, namely glycine, L-alanine, β-alanine and γ-aminobutyric
acid or pairs of these amino acids were reinvestigated by electrospray ion-trap mass spectrometry and high performance liquid
chromatography. It was found when mixtures were treated by sodium trimetaphosphate only in the presence of α-amino acid dipeptides
were formed. Without addition of α-amino acids, the β-amino acid or γ-aminobutyric acid could not form peptide either by themselves
or with their mixtures under the same conditions. From the data it is concluded that phosphate might select α-amino acids
to produce the peptides being important precursors for the origin of life.
Authors’ address: Dr. Pengxiang Xu, The Key Laboratory for Chemical Biology of Fujian Province, Department of Chemistry, Xiamen
University, Xiamen 361005, China 相似文献
14.
Summary. Glutamine is one of the most abundant free amino acid found in raw food. In this study, the contribution of free glutamine
to nonenzymatic browning and fluorescence was investigated using an aqueous model system with methylglyoxal. The results indicated
that glutamine contributed to the Maillard reaction via two pathways. First, the hydrolysis of the amide bond of glutamine
led to the release of ammonia which was implicated in the formation of brown color and fluorescence. Among other nitrogen
donors tested (asparagine, glutamic acid and urea) our results demonstrated that free glutamine was a major source of ammonia
during heating. When heated at 120 and 180 °C, 100% of ammonia was released from glutamine after 60 and 10 min, respectively.
The second pathway involved a direct Maillard reaction with the α-amino group of glutamine. Both pathways led to a rapid and
complete destruction of glutamine when heated in the model systems. With reference to the Maillard browning (absorbance at
420 nm) glutamine turned out to be the most reactive amine, followed by asparagine, glutamate, ammonia and urea. Maximum fluorescence
(excitation and emission wavelengths at 330 and 450 nm, respectively) was also observed with glutamine followed by urea and
ammonia. Overall this study suggested that free glutamine predominantly contributes to the color and fluorescence formations
of foodstuffs. 相似文献
15.
Tomohiro Yamaguchi Youichi Suzuki Ryuichi Katakura Takusaburo Ebina Junkichi Yokoyama Yoshiaki Fujimiya 《Cancer immunology, immunotherapy : CII》1998,47(2):97-103
γδT cells play a regulatory role in both primary and metastatic tumor growth in humans. The mechanisms responsible for the
activation and proliferation of circulating γδT cells should be fully understood prior to their adoptive transfer to cancer
patients. We have examined in vitro functional effects of interleukin-15 (IL-15) on highly purified γδT cells isolated from
glioblastoma patients. γδT cells constitutively express the heterotrimeric IL-2 receptor (IL-2R) αβγ, but the levels of IL-2Rβ
or γ expression were not increased by incubation with saturating amounts of IL-15. IL-15 was shown to induce a maximal γδT
cell proliferation, although at much higher concentrations (at least 2000 U/ml) than IL-2 (100 U/ml). Submaximal concentrations
of IL-15 plus low concentrations of IL-2 produced an additive proliferative response. In contrast to the IL-2-induced response,
this activity was completely or partially abrogated by anti-IL-2Rβ, or anti-IL-2Rγ antibodies, but not by anti-IL-2Rα antibodies.
Incubation of γδT cells in the presence of IL-15 resulted not only in the appearance of NK and LAK activity, but also in specific
autologous tumor cell killing activity, an additive effect being seen with IL-15 and IL-2. This IL-15-induced tumor-specific
activity could be significantly blocked by anti-IL-2Rγ and anti-IL-2R-β mAb, but not by anti-IL-2Rα mAb. Thus, in contrast
to IL-2, IL-15 activates tumor-specific γδT cells through the components of IL-2Rβ and IL-2Rγ, but not IL-2Rα. These enhanced
in vitro tumor-specific and proliferative responses of γδT cells seen with IL-15 suggest a rational adjuvant imunotherapeutic
use of γδT cells in cancer patients.
Received: 23 January 1998 / Accepted: 20 May 1998 相似文献
16.
M. Loui Thomas Rajan A. Badwe Ramakant K. Deshpande Urmila C. Samant Shubhada V. Chiplunkar 《Cancer immunology, immunotherapy : CII》2001,50(4):218-225
The mechanism responsible for tissue specific localization of γδ T cell subsets is not well understood. In order to explain
the sequestration of specific γδ T cell subsets in the peripheral blood and tumor tissue of patients with esophageal cancer,
we examined the function and expression of adhesion molecules on these cells. A hierarchy in the expression of adhesion molecules
was observed. In vitro activated γδ T cells showed dominant expression of LFA-1 (CD11a), VLA-α4 (CD49d), intermediate expression
of VLA-α5 (CD49e) and L-selectin (CD62L), but low expression of CD44v6 and αEβ7 (CD103). It was observed that the γδ T cells use LFA-1, L-selectin and CD44v6 to bind to squamous cell carcinoma (SCC) cells,
whereas they adhere to fibroblast cells using LFA-1, VLA-α4 and VLA-α5. Vδ1 T cell subsets from the peripheral blood γδ T
cells utilize a larger array of adhesion molecules, namely LFA-1, VLA-α4, VLA-α5, L-selectin and αEβ7, to bind to SCC cells compared to the restricted usage of LFA-1, L-selectin and CD44v6 by the Vδ2 T cells. Flow cytometric
analysis of tumor infiltrating lymphocytes from the esophageal tumors confirmed the selective accumulation of Vδ1+γδ T cells in the tumor compartment. It thus appears that adhesion molecules expressed on these lymphocytes play an important
role in the recruitment and retention of Vδ1 T cells in the tumor milieu.
Received: 27 November 2000 / Accepted: 1 March 2001 相似文献
17.
Density-dependent pollen germination and tube growth in vitro is a well-documented phenomenon, termed the pollen population
effect, but far less is known about its molecular basis. We present evidence to support phytosulfokine-α [Y(SO3H)IY(SO3H)TQ; PSK-α] as a native bioactive factor contributing to this effect. Mature pollen grains of Nicotiana tabacum L. var.macrophylla were incubated in liquid medium for 2 h. Pollen germination frequency increased in a density-dependent manner from 625 to
46,000 grains/ml. Conditioned medium, obtained from the medium of pollen cultured at a density of 10,000 pollen grains/ml
for 12 h, promoted the germination of pollen cultured at a low density (625 grains/ml). A rabbit antiserum against PSK-α specifically
inhibited the promotive effect of conditioned medium. Quantification by enzyme-linked immunosorbent assay showed that the
conditioned medium contained 0.4 nM of PSK-α. Exogenous PSK-α also stimulated pollen germination in the low-density culture.
These results indicate that PSK-α is an important regulator involved in the pollen population effect.
Received: 15 March 2000 / Accepted: 24 May 2000 相似文献
18.
Summary. Glutathione (reduced form GSH and oxidized form GSSG) constitutes an important defense against oxidative stress in the brain,
and taurine is an inhibitory neuromodulator particularly in the developing brain. The effects of GSH and GSSG and glycylglycine,
γ-glutamylcysteine, cysteinylglycine, glycine and cysteine on the release of [3H]taurine evoked by K+-depolarization or the ionotropic glutamate receptor agonists glutamate, kainate, 2-amino-3-hydroxy-5-methyl-4-isoxazolepropionate
(AMPA) and N-methyl-D-aspartate (NMDA) were now studied in slices from the hippocampi from 7-day-old mouse pups in a perfusion system.
All stimulatory agents (50 mM K+, 1 mM glutamate, 0.1 mM kainate, 0.1 mM AMPA and 0.1 mM NMDA) evoked taurine release in a receptor-mediated manner. Both
GSH and GSSG significantly inhibited the release evoked by 50 mM K+. The release induced by AMPA and glutamate was also inhibited, while the kainate-evoked release was significantly activated
by both GSH and GSSG. The NMDA-evoked release proved the most sensitive to modulation: L-Cysteine and glycine enhanced the
release in a concentration-dependent manner, whereas GSH and GSSG were inhibitory at low (0.1 mM) but not at higher (1 or
10 mM) concentrations. The release evoked by 0.1 mM AMPA was inhibited by γ-glutamylcysteine and cysteinylglycine, whereas
glycylglycine had no effect. The 0.1 mM NMDA-evoked release was inhibited by glycylglycine and γ-glutamylcysteine. In turn,
cysteinylglycine inhibited the NMDA-evoked release at 0.1 mM, but was inactive at 1 mM. Glutathione exhibited both enhancing
and attenuating effects on taurine release, depending on the glutathione concentration and on the agonist used. Both glutathione
and taurine act as endogenous neuroprotective effectors during early postnatal life.
Authors’ address: Prof. Simo S. Oja, Brain Research Center, Medical School, FI-33014 University of Tampere, Finland 相似文献
19.
Merentie M Uimari A Pietilä M Sinervirta R Keinänen TA Vepsäläinen J Khomutov A Grigorenko N Herzig KH Jänne J Alhonen L 《Amino acids》2007,33(2):323-330
Summary. The markers of oxidative stress and inflammation were studied in acute pancreatitis in transgenic rats exhibiting activated
polyamine catabolism. In addition, the effect of bismethylspermine (Me2Spm) pretreatment, preventing pancreatitis in this model, on these mediators was investigated. Lipid peroxidation was increased
at 6 and 24 h after induction of pancreatitis. These changes as well as the markedly decreased superoxide dismutase activity
at 24 h were abolished by Me2Spm pretreatment. Glutathione level and catalase activity changed transiently, and the effect of Me2Spm was clear at 24 h. Serum inflammatory cytokine levels increased already at 4 h whereas NF-κB was distinctly activated
only at 24 h. Me2Spm prevented the increase in TNF-α and IL-6 while it had no effect on NF-κB activation. These results show that typical inflammatory
and, to a lesser degree, some oxidative stress mediators are involved and beneficially affected by the disease-ameliorating
polyamine analogue in our pancreatitis model. 相似文献
20.
Maize (Zea mays L.) cell cultures incorporated radioactivity from [14C]cinnamate into hydroxycinnamoyl-CoA derivatives and then into polysaccharide-bound feruloyl residues. Within 5–20 min, the
CoA pool had lost its 14C by turnover and little or no further incorporation into polysaccharides then occurred. The system was thus effectively a
pulse–chase experiment. Kinetics of radiolabelling of diferulates (also known as dehydrodiferulates) varied with culture age.
In young (1–3 d) cultures, polysaccharide-bound [14C]feruloyl- and [14C]diferuloyl residues were both detectable within 1 min of [14C]cinnamate feeding. Thus, feruloyl residues were dimerised <1 min after their attachment to polysaccharides. For at least
the first 2.3 h after [14C]cinnamate feeding, polysaccharide-bound [14C]diferuloyl residues remained almost constant at ≈7% of the total polysaccharide-bound [14C]ferulate derivatives. Since feruloyl residues are attached to polysaccharides <1 min after the biosynthesis of the latter,
and >10 min before secretion, the data show that extensive feruloyl coupling occurred intra-protoplasmically. Exogenous H2O2 (1 mM) caused little additional feruloyl coupling; therefore, wall-localised coupling may have been peroxidase-limited. In
older (e.g. 4 d) cultures, less intraprotoplasmic coupling occurred: during the first 2.5 h, polysaccharide-bound [14C]diferuloyl residues were a steady 1.4% of the total polysaccharide-bound [14C]ferulate derivatives. In contrast to the situation in younger cultures, exogenous H2O2 induced a rapid 4- to 6-fold increase in all coupling products, indicating that coupling in the walls was H2O2-limited. In both 2- and 4-d-old cultures, polysaccharide-bound 14C-trimers and larger coupling products exceeded [14C]diferulates 3- to 4-fold, but followed similar kinetics. Thus, although all known dimers of ferulate can now be individually
quantified, it appears to be trimers and larger products that make the major contribution to cross-linking of wall polysaccharides
in cultured maize cells. We argue that feruloyl arabinoxylans that are cross-linked before and after secretion are likely
to loosen and tighten the cell wall, respectively. The consequences for the control of cell expansion and for the response
of cell walls to an oxidative burst are discussed.
Received: 19 January 2000 / Accepted: 13 April 2000 相似文献