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991.
Richard H. Stadler Jovanka Markovic Robert J. Turesky 《Biological trace element research》1995,47(1-3):299-305
The anti- and pro-oxidative effects of phenolic compounds and antioxidants were studied in two different in vitro model systems
utilizing ethyl linoleate and 2′-deoxyguanosine (2′-dG) as oxidative substrates, and a Fenton reaction (H2O2, Fe2+) to initiate oxidation. Oxidation of the biomolecules in both model systems exhibited dose dependency. In the 2′-dG assay,
oxidation was closely related to H2O2 generation, which occurred during autoxidation of the phenolics. Hydroxylating activity was greatly enhanced by Mn2+ and Cu2+, but not by Zn2+ or Co2+. Ethyl linoleate peroxidation was inhibited by low concentrations of catechol, quercitin, and instant coffee. However, peroxidation
was promoted by high concentrations of the same compounds, probably by recycling of chelated inactive Fe3+ to the active Fe2+ state. 相似文献
992.
Shigeko Ishimatsu Toshihiro Kawamoto Koji Matsuno Yasushi Kodama 《Biological trace element research》1995,49(1):43-52
In this study, eight kinds of nickel (Ni) compounds were orally administered to Wistar male rats and the distribution of each
compound was investigated 24 h after the administration. The Ni compounds used in this experiment were nickel metal [Ni−M],
nickel oxide (green) [NiO(G)], nickel oxide (black) [NiO(B)], nickel subsulfide [Ni3S2], nickel sulfide [NiS], nickel sulfate [NiSO4], nickel chloride [NiCl2], and nickel nitrate [Ni(NO3)2]. The solubilities of the nickel compounds in saline solution were in the following order; [Ni(NO3)2>NiCl2>NiSO4]≫[NiS>Ni3S2]>[NiO(B)>Ni−M>NiO(G)]. The Ni level in the visceral organs was higher in the rats given soluble Ni compounds; Ni(NO3)2, NiCl2, NiSO4, than that in the rats receiving other compounds. In the rats to which soluble Ni compounds were administered, 80–90% of
the recovered Ni amounts in the examined organs was detected in the kidneys. On the other hand, the Ni concentration in organs
administered scarcely soluble Ni compounds; NiO(B), NiO(G), and Ni−M were very low. The estimated absorbed fraction of each
Ni compounds was increased with the increase of the solubility. These results suggest that the kinetic behavior of Ni compounds
administered orally is closely related with the solubility of Ni compounds, and that the solubility of Ni compounds is one
of the important factors for determining the health effect of Ni compounds. 相似文献
993.
Innovation in wild chimpanzees (Pan troglodytes) 总被引:5,自引:0,他引:5
Christophe Boesch 《International journal of primatology》1995,16(2):1-16
Innovations of behavior have major implications for the concept of culture in animals. Innovation has rarefy been documented
in wild animal populations. The chimpanzees of the Ta? National Park, C?te d’Ivoire, spontaneously included new patterns of
behavior in their repertoire during our study. Some innovations were incorporated into a minority of the group members’ repertoire,
whereas others, such as building day nests in trees and on the ground more frequently, became general behaviors. Similarly,
new contexts for use of leaf- clipping behavior and novel ways of feeding on some leaves appeared and rapidly became part
of the behavior of most group members. The environmental parameters were too stable to explain these new forms of behavior,
as most of them took place within 1 month during the same dry season. In a similar way, leaf- grooming acquired a new function
in Gombe chimpanzees. A process similar to social conventions could explain the emergence of these new functions for an existing
behavior in a way rather similar to human “fashion. ” Three major characteristics of human culture — the absence of individual
variations in the performance of the behavior, the general use of the behavior by group members, and the ability to modify
the function of a behavior — characterize leaf-clipping in Ta? chimpanzees and leaf- grooming in Gombe chimpanzees. 相似文献
994.
Dido Vassilacopoulou James A. Ripellino Nikolaos Tezapsidis Vivian Y. H. Hook Nikolaos K. Robakis 《Journal of neurochemistry》1995,64(5):2140-2146
Abstract: The amyloid β peptide (Aβ) of Alzheimer disease is derived from the proteolytic processing of the amyloid precursor proteins (APPs), which are considered type I transmembrane proteins. Here we report that the soluble fraction of isolated adrenal medullary chromaffin granules (CG), a model neuronal secretory vesicle system, contains an antigen that immunochemically and on sodium dodecyl sulfate-polyacrylamide gel electrophoresis was indistinguishable from full-length APP. A truncated APP fragment with intact Aβ sequence was also detected in the soluble fraction of CG. In vitro experiments showed that full-length APP was solubilized from CG membranes at 37°C as a function of pH, with a peak of activity between pH 8.5 and pH 9.0. Solubilization of full-length APP was inhibited by several protease inhibitors, including aprotinin, cystatin, and iodoacetamide, by the divalent cations Ca2+ and Zn2+ , and by preheating of the membranes. These results are consistent with and suggest the involvement of an enzymatic mechanism in the solubilization of potentially amyloidogenic full-length APP. Production of Aβ from a transmembrane APP predicts a proteolytic cleavage within the lipid bilayer, a site relatively inaccessible to proteases. Thus, the detected soluble, potentially amyloidogenic, full-length APP may be a substrate for the proteases producing Aβ. The detection of soluble APP with intact Aβ sequence in secretory vesicles is consistent with the extracellular topology of amyloid depositions. 相似文献
995.
996.
Semicontinuously grown wild carrot ( Daucus carota L.) cells were used in an investigation of the effect of culture medium pH on ammonium uptake in suspension cultures as a first step in exploring the relationship between pH and anthocyanin biosynthesis. In contrast to published data showing decreasing uptake rates with decreasing culture medium pH, ammonium-limited, semicontinuous carrot cell cultures showed a 25% greater ammonium uptake rate at pH 4.5 than at pH 5.5. When cells that had been grown semicontinuously in medium with a pH of 4.5 or 5.5 were grown in batch cultures at pH 4.5, 5.5 or 6.5 the ammonium uptake rates were those of the semicontinuous cultures, indicating that the pH of the batch culture medium had no effect on ammonium uptake rates over 7 days. The cell culture was composed of very small aggregates when it was grown semicontinuously in medium at pH 4.5, but was composed of large aggregates when it was grown semicontinuously in medium at pH 5.5. The aggregation/disaggregation of the cells was pH dependent, as changing the pH of the semicontinuous culture medium altered the extent of the aggregation. We conclude that the change in culture medium pH caused the cells to aggregate or disaggregate which in turn decreased or increased the rate of ammonium uptake from the medium. 相似文献
997.
Spring wheat plants were grown in a 137Cs labelled nutrient solution, either in the presence or absence of NH4 as a secondary N source. Between 11 and 64 days after sowing (DAS), plants were harvested on nine occasions. The plants supplied with NH4 and NO3 had lower root 137Cs Activity Concentrations (AC) than those supplied with NO3 only. Shoot AC were equal in both nutrition treatments. Shoot and root 137Cs AC (dry weight basis) showed the same trends with plant age in both nutrition treatments. Shoot AC almost doubled between 11 and 28 DAS after which they gradually decreased concomitant with a similar decrease in K concentrations. Root AC were always higher than shoot AC and increased to a maximum at 35 DAS after which they fluctuated. Expressed on a tissue water basis, the 137Cs AC varied less during plant age than did dry weight based AC. Furthermore, root and shoot AC expressed on a tissue water basis were almost equal. It is shown that the initial increase in 137Cs AC in both root and shoot can largely be explained by the initial dilution of absorbed 137Cs in the unlabelled seedling tissues. No correlation was found between K and 137Cs distribution among ears, leaves, stems and roots in 64 old wheat plants. NH4 as a secondary N source in a nitrate nutrient solution marginally affected 137Cs distribution.Abbreviations AC
activity concentrations
- DAS
days after sowing
FAX no corresponding author: +3216321997 相似文献
998.
The metabolic significance of Se in plants is not well documented, though the presence of many selenoenzymes in bacteria and
the essentiality of Se in higher animals is established. Since germination is an active process in plant growth and metabolism,
the effect of Se was investigated in germinatingVigna radiata L, a nonaccumulating Sedeficient legume. Growth and protein were enhanced in seedlings supplemented with selenium (Se) as
sodium selenite in the medium up to 1 μg/mL. The pattern of uptake of75Se in the differentiating tissues and the subcellular distribution were investigated. The percentage of incorporation of75Se was greater in the mitochondria at the lowest level (0.5 μg/mL) of Se supplementation compared to higher levels of Se exposure.
Proteins precipitated from the postmitochondrial supernatant fractions, when separated by means of polyacrylamide gel electrophoresis
(PAGE), indicated a major selenoprotein in the seedlings germinated at 2.0 μg/mL Se. In seedlings grown with supplemented
Se, enhanced respiratory control ratio and succinate dehydrogenase activity were observed in the mitochondria of tissues,
indicative of a role for Se in mitochondrial membrane functions. 相似文献
999.
Pigment analysis was performed by means of normal phase HPLC on a number of bacteriochlorophyll a and b containing species of purple bacteria that contain a core antenna only. At least 99% of the bacteriochlorophyll in Rhodobacter sphaeroides R26, Rhodopseudomonas viridis and Thiocapsa pfennigii was esterified with phytol (BChl a
p and BChl b
p, respectively). Rhodospirillum rubrum contained only BChl a esterified with geranyl-geraniol (BChl a
GG). Rhodospirillum sodomense and Rhodopseudomonas marina contained, in addition to BChl a
p, small amounts of BChl a
GG, and presumably also of BChl a esterified with dihydro and tetrahydro geranyl-geraniol (2,10,14-phytatrienol and probably 2,14-phytadienol). In all species bacteriopheophytin (BPhe) esterified with phytol was present. The BChl/BPhe ratio indicated that in these species a constant number of 25 ± 3 antenna BChls is present per reaction centre. This number supports a model in which the core antenna consists of 12 - heterodimers surrounding the reaction centre. Determination of the in vivo extinction coefficient of BChl in the core-reaction centre complex yielded a value of ca. 140 mM–1 cm–1 for BChl a containing species and of 130 mM–1 cm–1 for Rhodopseudomonas viridis.Abbreviations BChl
bacteriochlorophyll
- BPhe
bacteriopheophytin
- GG
geranyl-geraniol
- LHI and LHII
core and peripheral antenna complexes
- P
phytol
- RC
reaction centre
Dedicated to the memory of Professor D.I. Arnon. 相似文献
1000.
A cDNA clone encoding Brassica calmodulin 总被引:2,自引:0,他引:2
A 834 bp cDNA encoding calmodulin (CaM) has been isolated from Brassica juncea. On Northern analysis this cDNA hybridises this cDNA to mRNAs of about 0.9 kb in leaf, silique and peduncle. Genomic Southern analysis indicates the presence of a CaM multigene family in Brassica juncea. Comparison of the predicted amino acid sequence of Brassica CaM with that of Arabidopsis CaM ACaM-2 and ACaM-3 showed 100% homology, which is not unusual, since both plants belong to the family Cruciferae. In situ hybridisation studies on Brassica seedlings using a digoxigenin-labelled RNA probe showed that high levels of CaM mRNA were detected in the leaf primordia and the shoot apical meristem, and to a lesser degree, in the zone of root elongation of the root tip. The occurrence of a higher rate of cell division and growth in these regions than its surrounding tissue may possibly be related to higher levels of CaM mRNA. 相似文献