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1.
Protein-bound advanced glycation endproducts (AGEs) as bioactive amino acid derivatives in foods 总被引:2,自引:0,他引:2
Henle T 《Amino acids》2005,29(4):313-322
Summary. The Maillard reaction or nonenzymatic browning is of outstanding importance for the formation of flavour and colour of heated
foods. Corresponding reactions, also referred to as “glycation”, are known from biological systems, where the formation of
advanced glycation endproducts (AGEs) shall play an important pathophysiological role in diabetes and uremia. In this review,
pathways leading to the formation of individual protein-bound lysine and arginine derivatives in foods are described and nutritional
consequences resulting from this posttranslational modifications of food proteins are discussed. 相似文献
2.
Garcia RF Gazola VA Barrena HC Hartmann EM Berti J Toyama MH Boschero AC Carneiro EM Manso FC Bazotte RB 《Amino acids》2007,33(1):151-155
Summary. Our purpose was to determine the blood amino acid concentration during insulin induced hypoglycemia (IIH) and examine if the
administration of alanine or glutamine could help glycemia recovery in fasted rats. IIH was obtained by an intraperitoneal
injection of regular insulin (1.0 U/kg). The blood levels of the majority of amino acids, including alanine and glutamine
were decreased (P < 0.05) during IIH and this change correlates well with the duration than the intensity of hypoglycemia. On the other hand,
the oral and intraperitoneal administration of alanine (100 mg/kg) or glutamine (100 mg/kg) accelerates glucose recovery.
This effect was partly at least consequence of the increased capacity of the livers from IIH group to produce glucose from
alanine and glutamine. It was concluded that the blood amino acids availability during IIH, particularly alanine and glutamine,
play a pivotal role in recovery from hypoglycemia. 相似文献
3.
Summary. A randomised, double blind, placebo-controlled study was performed giving 0.5 g · kg−1 · day−1 of undiluted alanyl-glutamine (20%) or saline in a peripheral vein during 4 hours in ICU patients (n = 20). During the infusion
period a steady state in plasma concentration was reached for alanyl-glutamine, but not for alanine, glutamine or glutamate.
On the other hand there was no accumulation of any of the amino acids, as the pre-infusion concentrations were reached within
8 hours after the end of infusion. The half-life of the dipeptide was 0.26 hours (range, 0.15–0.63 h). The distribution volume
of alanyl-glutamine was larger than the extracellular water volume, indicating a rapid hydrolysis of the dipeptide. There
was no detectable alanyl-glutamine in the urine of any of the patients. All patients had excretion of small amounts of amino
acids in urine, but the renal clearance of alanine, glutamine and glutamate were not different between the two groups. 相似文献
4.
Summary. No influence of isotopic substitution in deuterium-substituted tryptophan on the florescence excitation spectrum has previously
been found out. Here, the isotopic effects of electronic excitation of deuterium-substituted tryptophan were experimentally
and theoretically analyzed for first time. It was shown a short-wave shift of the UV-absorption maximum at 220 nm corresponding
to the 360 cal/mol and short-wave shift for fluorescence spectrum corresponding to the 210 cal/mol. To account for this effect,
the quantum chemical calculations of the geometric and electron structure, frequencies of normal vibrations and transition
energies have been performed. The isotopic effects originate from the zero-point energies of ground and excited states. It
was found that isotopic shifts depend on the position of isotope in the molecule and kind of transition. So, it can be utilized
in the analysis of proteins structure and complexation. 相似文献
5.
Summary. Our aim was to determine changes in free amino acid (FAA) and dipeptide (DP) concentrations in probable Alzheimer’s disease
(pAD) subjects compared with control (CT) subjects using liquid chromatography and electrospray ionization tandem mass spectrometry
(LCMS2). We recruited gender- and age-matched study participants based on neurological and neuropsychological assessments. We measured
FAAs and DPs in cerebrospinal fluid (CSF), plasma and urine using LCMS2 with selected reaction monitoring (SRM). Imidazole-containing FAAs (histidine, methyl-histidine), catecholamines (L-DOPA
and dopamine), citrulline, ornithine, glycine and antioxidant DPs (carnosine and anserine) accounted for the major changes
between CT and pAD. Carnosine levels were significantly lower in pAD (328.4 ± 91.31 nmol/dl) than in CT plasma (654.23 ± 100.61 nmol/dl).
In contrast, L-DOPA levels were higher in pAD (1400.84 ± 253.68) than CT (513.10 ± 121.61 nmol/dl) plasma. These data underscore
the importance of FAA and DP metabolism in the pathogenesis of AD. Since our data show changes in antioxidants, neurotransmitters
and their precursors, or FAA associated with urea metabolism in pAD compared with CT, we propose that manipulation of these
metabolic pathways may be important in preventing AD progression. 相似文献
6.
Nikolic J Stojanovic I Pavlovic R Sokolovic D Bjelakovic G Beninati S 《Amino acids》2007,32(1):127-131
Summary. The existing interrelation in metabolic pathways of L-arginine to polyamines, nitric oxide (NO) and urea synthesis could be
affected in sepsis, inflammation, intoxication and other conditions. The role of polyamines and NO in the toxic effect of
mercury chloride on rat liver function was studied. Administration of mercury chloride for 24 h led to significantly elevated
plasma activities of Alanine transaminase (ALT) and Aspartate transaminase (AST). Malondyaldehyde (MDA) levels were unaffected
(p > 0.05) and arginase activity was significantly decreased (p < 0.05) while nitrate/nitrite production was significantly
elevated (p < 0.001) in liver tissue. Polyamine oxidase (PAO) and diamine oxidase (DAO) activities, enzymes involved in catabolism
of polyamines, were decreased. L-arginine supplementation to intoxicated rats potentiated the effect of mercury chloride on
NO production and it was ineffective on arginase activity.
Results obtained in this study show that mercury chloride-induced toxicity leads to abnormally high levels of ALT and AST
that may indicate liver damage with the involvement of polyamine catabolic enzymes and NO. 相似文献
7.
Summary. Amino acids (AA) are components of protein and precursors of many important biological molecules. To address effects of the
genes associated with metabolism and transport of AA and their derivatives during rat liver regeneration (LR), we firstly
obtained the above genes by collecting databases data and retrieving related thesis, and then analyzed their expression profiles
during LR using Rat Genome 230 2.0 array. The LR-associated genes were identified by comparing the gene expression difference
between partial hepatectomy (PH) and sham-operation (SO) rat livers. It was approved that 134 genes associated with metabolism
of AA and their derivatives and 26 genes involved in transport of them were LR-associated. The initially and totally expressing
number of these genes occurring in initial phase of LR (0.5–4 h after PH), G0/G1 (4–6 h after PH), cell proliferation (6–66 h
after PH), cell differentiation and structure-function reconstruction of liver tissue (72–168 h after PH) were respectively
76, 17, 79, 5 and 162, 89, 564, 195, illustrating that these LR-associated genes were initially expressed mainly in initial
stage, and functioned in different phases. Frequencies of up-regulation and down-regulation of them being separately 564 and
357 demonstrated that genes up-regulated outnumbered those down-regulated. Categorization of their expression patterns into
22 types implied the diversity of cell physiological and biochemical activities. According to expression changes and patterns
of the above-mentioned genes in LR, it was presumed that histidine biosynthesis in the metaphase and anaphase, valine metabolism
in the anaphase, and metabolism of glutamate, glutamine, asparate, asparagine, methionine, alanine, leucine and aromatic amino
acid almost were enhanced in the whole LR; as for amino acid derivatives, transport of neutral amino acids, urea, γ-aminobutyric
acid, betaine and taurine, metabolism of dopamine, heme, S-adenosylmethionine, thyroxine, and biosynthesis of hydroxyproline,
nitric oxide, orinithine, polyamine, carnitine, selenocysteine were augmented during the entire liver restoration. Above results
showed that metabolism and transport of AA and their derivates were necessary in liver regeneration.
Authors’ address: Prof. Dr. C. S. Xu, College of Life Science, No. 46, Jianshe RD, Henan, Xinxiang 453007, China 相似文献
8.
Summary. Amino acids analysis in single wheat embryonic protoplast was performed using capillary electrophoresis equipped with laser-induced
fluorescence (CE-LIF), combination with tissue culture technique. Reagent fluorescein isothiocyanate (FITC) was introduced
into living protoplasts by electroporation for intracellular derivatization. A special osmotic buffer (0.6 mol/L mannitol,
5 mmol/L CaCl2) was used to keep the osmotic balance of embryonic protoplasts during the protoplasts derivatization. After completion of
the derivatization reaction in the protoplasts, a single protoplast was drawn into the capillary tip by electroosmotic flow.
Then a 0.1 M NaOH lysing solution was injected by diffusion. The derivatized amino acids were separated by capillary electrophoresis
and detected by laser-induced fluorescence detection after the protoplast was lysed Nine amino acids were quantitatively and
qualitatively determined and compared in lysate and single protoplast of wheat embryonic cells respectively, with mean concentrations
of amino acids ranging from 2.68×10−5 mol/L to 18.18×10−5 mol/L in single protoplast. 相似文献
9.
Mesophyll cells (MCs) and bundle-sheath cells (BSCs) of leaves of the C4 plant maize (Zea mays L.) were separated by cellulase digestion to determine the relative proportion of the glutamine synthetase (GS; EC 6.3.1.2)
or the NADH-glutamate dehydrogenase (GDH; EC 1.4.1.2) isoforms in each cell type. The degree of cross-contamination between
our MC and BSC preparations was checked by the analysis of marker proteins in each fraction. Nitrate reductase (EC 1.6.6.1)
proteins (110 kDa) were found only in the MC fraction. In contrast, ferredoxin-dependent glutamate synthase (Fd-GOGAT; EC
1.4.7.1) proteins (160 kDa) were almost exclusively present in the BSC fraction. These results are consistent with the known
intercellular distribution of nitrate reductase and Fd-GOGAT proteins in maize leaves and show that the cross-contamination
between our MC and BSC fractions was very low. Proteins corresponding to cytosolic GS (GS-1) or plastidic GS (GS-2) were found
in both the MC and BSC fractions. While equal levels of GS-1 (40 kDa) and GS-2 (44 kDa) polypeptides were present in the BSC
fraction, the GS-1 protein level in the MC fraction was 1.8-fold higher than the GS-2 protein pool. Following separation of
the GS isoforms by anion-exchange chromatography of MC or BSC soluble protein extracts, the relative GS-1 activity in the
MC fraction was found to be higher than the relative GS-2 activity. In the BSC fraction, the relative GS-1 activity was very
similar to the relative GS-2 activity. Two isoforms of GDH with apparent molecular weights of 41 kDa and 42 kDa, respectively,
were detected in the BSC fraction of maize leaves. Both GDH isoenzymes appear to be absent from the MC fraction. In the BSCs,
the level of the 42-kDa GDH isoform was 1.7-fold higher than the level of the 41-kDa GDH isoform. A possible role for GS-1
and GDH co-acting in the synthesis of glutamine for the transport of nitrogen is discussed.
Received: 25 January 2000 / Accepted: 30 March 2000 相似文献
10.
The dye FM1-43 was used alone or in combination with measurements of the membrane capacitance (Cm) to monitor membrane changes in protoplasts from Viciafaba L. guard cells. Confocal images of protoplasts incubated with FM1-43 (10 μM) at constant ambient osmotic pressure (πo) revealed in confocal images a slow internalisation of FM1-43-labelled membrane into the cytoplasm. As a result of this process
the relative fluorescence intensity of the cell interior (fFM,i) increased with reference to the total fluorescence (fFM,t) by 7.4 × 10−4 min−1. This steady internalisation of dye suggests the occurrence of constitutive endocytosis under constant osmotic pressure.
Steady internalisation of FM1-43 labelled membrane caused a prominent staining of a ring-like structure located beneath the
plasma membrane. Abrupt elevation of πo by 200 mosmol kg−1 caused, over the first minutes of incubation, a rapid internalisation of FM1-43 fluorescence into the cytoplasm concomitant
with a decrease in cell perimeter. Within the first 5 min the cell perimeter decreased by 7.9%. Over the same time fFM,i/fFM,t increased by 0.13, reflecting internalisation of fluorescent label into the cytoplasm. Combined measurements of Cm and total fluorescence of a protoplast (fFM,p) showed that an increase in πo evoked a decrease in Cm but no change in fFM,p. This means that surface contraction of the protoplast is due to retrieval of excess membrane from the plasma membrane and
internalisation into the cytoplasm. Further inspection of confocal images revealed that protoplast shrinking was only occasionally
associated with internalisation of giant vesicles (median diameter 2.7 μm) with FM1-43-labelled membrane. But, in all cases,
osmotic contraction was correlated with a diffuse distribution of FM1-43 label throughout the cytoplasm. From this, we conclude
that endocytosis of small vesicles into the cytoplasm is the obligatory process by which cells accommodate an osmotically
driven decrease in membrane surface area.
Received: 4 May 1999 / Accepted: 19 August 1999 相似文献
11.
Summary. The stability of felinine, an amino acid present in feline urine, was investigated. Synthetic felinine was unstable in the
urine of a selection of mammals. Felinine was found to stable in feline urine in which urea had been degraded. Synthetic felinine
was found to react specifically with urea and did not react with urea analogues such as biuret or thiourea or other nucleophilic
compounds such as ammonia which is more nucleophilic or acetamide and water which are less nucleophilic than urea. The reaction
of urea and felinine was independent of pH over the range of 3–10. Urea did not react with N-acetyl-felinine suggesting a felinine N-terminal interaction with urea. Mass spectral analysis of the reaction products showed
the presence of carbamylated felinine and fragmentation ions derived from carbamyl-felinine. The physiological relevance of
felinine carbamylation is yet to be determined. 相似文献
12.
Almost all about citrulline in mammals 总被引:2,自引:0,他引:2
Curis E Nicolis I Moinard C Osowska S Zerrouk N Bénazeth S Cynober L 《Amino acids》2005,29(3):177-205
Summary. Citrulline (Cit, C6H13N3O3), which is a ubiquitous amino acid in mammals, is strongly related to arginine. Citrulline metabolism in mammals is divided
into two fields: free citrulline and citrullinated proteins. Free citrulline metabolism involves three key enzymes: NO synthase
(NOS) and ornithine carbamoyltransferase (OCT) which produce citrulline, and argininosuccinate synthetase (ASS) that converts
it into argininosuccinate. The tissue distribution of these enzymes distinguishes three “orthogonal” metabolic pathways for
citrulline. Firstly, in the liver, citrulline is locally synthesized by OCT and metabolized by ASS for urea production. Secondly,
in most of the tissues producing NO, citrulline is recycled into arginine via ASS to increase arginine availability for NO
production. Thirdly, citrulline is synthesized in the gut from glutamine (with OCT), released into the blood and converted
back into arginine in the kidneys (by ASS); in this pathway, circulating citrulline is in fact a masked form of arginine to
avoid liver captation. Each of these pathways has related pathologies and, even more interestingly, citrulline could potentially
be used to monitor or treat some of these pathologies. Citrulline has long been administered in the treatment of inherited
urea cycle disorders, and recent studies suggest that citrulline may be used to control the production of NO. Recently, citrulline
was demonstrated as a potentially useful marker of short bowel function in a wide range of pathologies. One of the most promising
research directions deals with the administration of citrulline as a more efficient alternative to arginine, especially against
underlying splanchnic sequestration of amino acids. Protein citrullination results from post-translational modification of
arginine; that occurs mainly in keratinization-related proteins and myelins, and insufficiencies in this citrullination occur
in some auto-immune diseases such as rheumatoid arthritis, psoriasis or multiple sclerosis. 相似文献
13.
Summary. This study examined 10 wks of resistance training and the ingestion of supplemental protein and amino acids on muscle performance
and markers of muscle anabolism. Nineteen untrained males were randomly assigned to supplement groups containing either 20 g
protein (14 g whey and casein protein, 6 g free amino acids) or 20 g dextrose placebo ingested 1 h before and after exercise
for a total of 40 g/d. Participants exercised 4 times/wk using 3 sets of 6–8 repetitions at 85–90% of the one repetition maximum.
Data were analyzed with two-way ANOVA (p < 0.05). The protein supplement resulted in greater increases in total body mass, fat-free mass, thigh mass, muscle strength,
serum IGF-1, IGF-1 mRNA, MHC I and IIa expression, and myofibrillar protein. Ten-wks of resistance training with 20 g protein
and amino acids ingested 1 h before and after exercise is more effective than carbohydrate placebo in up-regulating markers
of muscle protein synthesis and anabolism along with subsequent improvements in muscle performance. 相似文献
14.
Taranukhin AG Taranukhina EY Saransaari P Djatchkova IM Pelto-Huikko M Oja SS 《Amino acids》2008,34(1):169-174
Summary. Taurine is a sulphur-containing amino acid abundant in the nervous system. It protects cells from ischemia-induced apoptosis,
but the mechanism underlying this is not well established. The aim of our study was to explore the effects of taurine on two
main pathways of apoptosis induced by ischemia: receptor-mediated and mitochondrial cell death. Brain slices containing the
supraoptic (SON) and paraventricular (PVN) nuclei of the hypothalamus were incubated in vitro under control and simulated
ischemic (oxygen-glucose deprivation for 30 min) conditions in the absence and presence of 20 mM taurine. Brain slices were
harvested after the 180-min “postischemic” period and fixed in 4% paraformaldehyde. To estimate apoptosis, immunostaining
was done for caspase-8 and caspase-9 in paraffin-embedded sections. Immunoreactive caspase-8 and caspase-9 cells were observed
in SON and PVN in all experimental groups, but in the “ischemic” group the expression of caspase-8 and caspase-9 and the number
of immunoreactive cells was significantly increased in both hypothalamic nuclei. Addition of taurine (20 mM) to the incubation
medium induced a marked decrease in caspase-8 and caspase-9 immunoreactivity after ischemia in SON and PVN when compared with
the taurine-untreated “ischemic” group. Taurine reduces ischemia-induced caspase-8 and caspase-9 expression, the key inductors
of apoptosis in SON and PVN.
Authors’ address: Dr. Andrey Taranukhin, Tampere Brain Research Center, Medical School, University of Tampere, FI-33014 Finland 相似文献
15.
Non-photochemical quenching of chlorophyll fluorescence (NPQ) and quantum yield of photosystem II (PSII) were studied with
intact mesophyll chloroplasts of maize (Zea mays L.) during the initial minutes of illumination using the pulse-modulated chlorophyll fluorescence technique. Non-photochemical
quenching was rapidly reversible in the dark at any point during illumination, which is indicative of energy-dependent dissipation
of energy (mediated via thylakoid ΔpH changes and ascorbate-dependent synthesis of zeaxanthin). In chloroplasts suspensions
including 15 mM ascorbate in the medium, with addition of oxaloacetate and pyruvate, the PSII yield, rate of reduction of
oxaloacetate and phosphorylation of pyruvate reached a maximum after approximately 2 min of illumination. Under these conditions,
which promote phosphorylation and a decreased ΔpH across the thylakoid membrane, NPQ rose to a maximum after 2–3 min of illumination,
dropped to a minimum after about 6 min, and then increased to a steady-state level. A rather similar pattern was observed
when leaves were illuminated following a 30-min dark period. Providing chloroplasts with higher levels of ascorbate (60 mM),
prevented the transient drop in NPQ. Anaerobic conditions or addition of potassium cyanide caused a decrease in PSII yield,
providing evidence for operation of the ascorbate-dependent Mehler-peroxidase reaction. These conditions also strongly suppressed
the transient drop in NPQ. Dithiothreitol, an inhibitor of violaxanthin de-epoxidase, caused a large drop in NPQ even in the
presence of high levels of ascorbate. The results suggest that the decline of NPQ occurs in response to an increase in lumen
pH after initiation of phosphorylation, that this decline can be suppressed by conditions where ascorbate is not limiting
for violaxanthin de-epoxidase, and that the increase of NPQ after such a decline is the result of development of energy dissipation
in PSII reaction centers.
Received: 13 August 1999 / Accepted: 17 September 1999 相似文献
16.
Mühling J Burchert D Langefeld TW Matejec R Harbach H Engel J Wolff M Welters ID Fuchs M Menges T Krüll M Hempelmann G 《Amino acids》2007,33(3):511-524
Summary. We examined the effects of DON [glutamine-analogue and inhibitor of glutamine-requiring enzymes], alanyl-glutamine (regarding
its role in neutrophil immunonutrition) and alanyl-glutamine combined with L-NAME, SNAP, DON, β-alanine and DFMO on neutrophil
amino and α-keto acid concentrations or important neutrophil immune functions in order to establish whether an inhibitor of
•NO-synthase [L-NAME], an •NO donor [SNAP], an analogue of taurine and a taurine transport antagonist [β-alanine], an inhibitor
of ornithine-decarboxylase [DFMO] as well as DON could influence any of the alanyl-glutamine-induced effects. In summary,
irrespective of which pharmacological, metabolism-inhibiting or receptor-mediated mechanisms were involved, our results showed
that impairment of granulocytic glutamine uptake, modulation of intracellular glutamine metabolisation and/or de novo synthesis
as well as a blockade of important glutamine-dependent metabolic processes may led to significant modifications of physiological
and immunological functions of the affected cells. 相似文献
17.
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
18.
Summary. New bioinorganic complexes of the aspartic acid with the antimony or bismuth triiodide were synthesized by a direct solid–solid
reaction at room temperature. The formula of the complex is MI3[OOCCH2CH(NH2)CO]2.5 · 2.5H2O (M = Sb, Bi). The complex may be a dimer with bridge structure. The crystal structure of the complexes belongs to a triclinic
system. The lattice parameters are a = 0.9883 nm, b = 1.4284 nm, c = 2.0114 nm, α = 94.46°, β = 99.76° and γ = 100.1° for
the complex of antimony and a = 0.9756 nm, b = 1.4560 nm, c = 1.9875 nm, α = 94.18°, β = 97.25° and γ = 101.16° for the complex
of bismuth. The infrared spectra and thermal analyses can demonstrate the complex formation between the aspartic acid and
the antimony or bismuth ion. 相似文献
19.
Guz G Oz E Lortlar N Ulusu NN Nurlu N Demirogullari B Omeroglu S Sert S Karasu C 《Amino acids》2007,32(3):405-411
Summary. Ischemia-reperfusion (I/R) injury is one of the most common causes of renal dysfunction. Taurine is an endogenous antioxidant
and a membrane-stabilizing, intracellular, free beta-amino acid. It has been demonstrated to have protective effects against
I/R injuries to tissues other than kidney. The aim of this study was to determine whether taurine has a beneficial role in
renal I/R injury. Forty Wistar-Albino rats were allocated into four groups as follows: sham, taurine, I/R, and I/R + taurine.
Taurine 7.5 mg/kg was given intra-peritoneally to rats in the groups taurine and I/R + taurine. Renal I/R was achieved by
occluding the renal arteries bilaterally for 40 min, followed by 6 h of reperfusion. Immediately thereafter, blood was drawn
and tissue samples were harvested to measure 1) serum levels of BUN and creatinine; 2) serum and/or tissue levels of malondialdehyde
(MDA), glutathione (GSH), glucose 6-phosphate dehydrogenase (G-6PD), 6-phosphogluconate dehydrogenase (6-PGD) and glutathione
reductase (GSH-red); 3) renal morphology; and 4) immunohistochemical staining for P-selectin. Taurine administration reduced
I/R-induced increases in serum BUN and creatinine, and serum and tissue MDA levels (p < 0.05). Additionally, taurine lessened
the reductions in serum and tissue glutathione levels secondary to I/R (p < 0.05). Taurine also attenuated histopathologic
evidence of renal injury, and reduced I/R-induced P-selectin immunoreactivity (p < 0.05). Overall, then, taurine administration
appears to reduce the injurious effects of I/R on kidney. 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