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151.
152.
La Regina M Moros EG Pickard WF Straube WL Baty J Roti Roti JL 《Radiation research》2003,160(2):143-151
This study was designed to determine whether chronic exposure to radiofrequency (RF) radiation from cellular phones increased the incidence of spontaneous tumors in F344 rats. Eighty male and 80 female rats were randomly placed in each of three irradiation groups. The sham group received no irradiation; the Frequency Division Multiple Access (FDMA) group was exposed to 835.62 MHz FDMA RF radiation; and the Code Division Multiple Access (CDMA) group was exposed to 847.74 MHz CDMA RF radiation. Rats were irradiated 4 h per day, 5 days per week over 2 years. The nominal time-averaged specific absorption rate (SAR) in the brain for the irradiated animals was 0.85 +/- 0.34 W/kg (mean +/- SD) per time-averaged watt of antenna power. Antennas were driven with a time-averaged power of 1.50 +/- 0.25 W (range). That is, the nominal time-averaged brain SAR was 1.3 +/- 0.5 W/kg (mean +/- SD). This number was an average from several measurement locations inside the brain, and it takes into account changes in animal weight and head position during irradiation. All major organs were evaluated grossly and histologically. The number of tumors, tumor types and incidence of hyperplasia for each organ were recorded. There were no significant differences among final body weights or survival days for either males or females in any group. No significant differences were found between treated and sham-exposed animals for any tumor in any organ. We conclude that chronic exposure to 835.62 MHz FDMA or 847.74 MHz CDMA RF radiation had no significant effect on the incidence of spontaneous tumors in F344 rats. 相似文献
153.
Barbisan LF Scolastici C Miyamoto M Salvadori DM Ribeiro LR da Eira AF de Camargo JL 《Genetics and molecular research : GMR》2003,2(3):295-308
The effects of crude extracts of the mushroom Agaricus blazei Murrill (Agaricaceae) on both DNA damage and placental form glutathione S-transferase (GST-P)-positive liver foci induced by diethylnitrosamine (DEN) were investigated. Six groups of adult male Wistar rats were used. For two weeks, animals of groups 3 to 6 were treated with three aqueous solutions of A. blazei (mean dry weight of solids being 1.2, 5.6, 11.5 and 11.5 mg/ml, respectively). After this period, groups 2 to 5 were given a single ip injection 200 mg/kg DEN and groups 1 and 6 were treated with 0.9% NaCl. All animals were subjected to 70% partial hepatectomy at week five and sacrificed 4, 24 and 48 h or 8 weeks after DEN or 0.9% NaCl treatments (10th week after the beginning of the experiment). The alkaline comet assay and GST-P-positive liver foci development were used to evaluate the influence of the mushroom extracts on liver cell DNA damage and on the initiation of liver carcinogenesis, respectively. Previous treatment with the highest concentration of A. blazei (11.5 mg/ml) significantly reduced DNA damage, indicating a protective effect against DEN-induced liver cytotoxicity/genotoxicity. However, the same dose of mushroom extract significantly increased the number of GST-P-positive liver foci. 相似文献
154.
Tree size and flowering intensity as affected by nitrogen fertilization in non-bearing orange trees grown under Mediterranean conditions 总被引:1,自引:0,他引:1
Menino MR Carranca C de Varennes A d'Almeida VV Baeta J 《Journal of plant physiology》2003,160(12):1435-1440
A field experiment was conducted in the South of Portugal with young (0-3 years old) non-bearing ‘Lane Late’ orange trees. Five nitrogen (N) rates were used in a randomised block design with three replicates. The 180 g N tree−1 over three years led to the greatest canopy width (176 cm) and volume (2,697 dm3). The greatest rate applied (720 g N tree−1 in the three years) led to the largest flower yield. Nitrogen concentration in the flowers significantly increased with fertilizer N, and also with the flowering period up to the 23rd day, declining thereafter. Flower yield was strongly correlated (r = 0.99, p < 0.001) with flower N concentration. Nutrient composition of flowers and of mature leaves from the spring flush was compared. Significant correlations were found for N (r = 0.47, p <0.01), P (r = -0.49, p <0.01), K (r = 0.44, p <0.05) and Ca (r = 0.87, p <0.001), suggesting that flowers can be used as a tool to diagnose the nutritional status of trees. Canonical analysis (with N treatment as dummy-variables) showed strong relationships between canopy width and N, which were greater at the larger rates of fertilizer application, and strong and inverse relationships between K and Mg, also with the greatest N rates. 相似文献
155.
Exposure of isolated nerve terminals to hydrogen peroxide (25-500 microM) for 10 min produced a partially reversible decrease in the total and reduced glutathione level. No release and resynthesis of glutathione by the oxidant was involved in this effect. Loss of reduced glutathione was associated with elimination of H(2)O(2), which was very quick with >70% of the oxidant eliminated within 5 min. Recovery of both total and reduced glutathione was pronounced after 10 min when the majority of H(2)O(2) was eliminated. Previously we have reported that glutamate metabolism under oxidative stress contributes to the operation of the Krebs cycle, thus to the production of NAD(P)H [J. Neurosci. 20 (2000) 8972]. In the present study we addressed whether metabolism of endogenous glutamate plays a role in the maintenance of glutathione level in nerve terminals. Glutamine and beta-hydroxybutyrate (5mM), alternative metabolites in synaptosomes, were able to decrease the loss of total and reduced glutathione induced by hydrogen peroxide. Metabolic consumption of glutamate was reduced at the same time. In addition an increased demand on the glutathione system by the catalase inhibitor aminotriazole augmented the metabolic consumption of glutamate. It is concluded that under oxidative stress glutamate metabolism contributes to the maintenance of glutathione level, thus to the antioxidant capacity of nerve terminals. 相似文献
156.
Casali EA de Souza LF Gelain DP Kaiser GR Battastini AM Sarkis JJ 《Molecular and cellular biochemistry》2003,247(1-2):111-119
Sertoli cell maturation is a complex process involving both morphological and biochemical changes. These cells have previously been shown to be targets for extracellular purine structures such as ATP and adenosine. These compounds evoke responses in rat Sertoli cells through the purinoceptor families, P2X and P2Y and PA1. The signals to purinoceptors are usually terminated by the action of ectonucleotidases. In a previous work, we demonstrated that rat Sertoli cells have ecto-ATPdiphosphohydrolase (EC 3.6.1.5), ecto-5-nucleotidase (EC 3.1.3.5) and ecto-adenosine deaminase (ecto-ADA) (EC 3.5.4.4) activities. Here we investigated whether some changes occur during rat Sertoli cell maturation in these activities. Rat Sertoli cells obtained from rats of different ages representing the pre pubertal, mid pubertal and young adult (10-, 18- and 35-day-old, respectively) were cultured and used for different assays. The nucleotide hydrolysis was estimated by measuring the Pi released using a colorimetric method and by HPLC analysis. ATP and ADP hydrolysis was increased 3-fold during sexual maturation. AMP hydrolysis increased 4-fold in 10- to 35-day-old Sertoli cells. Similar results were obtained when we used other substrates to measure the extracellular hydrolysis of nucleotides (GTP, GDP, GMP and IMP). The ecto-ADA activity showed a 2-fold increase in the specific activity (18- to 35-day-old Sertoli cells). The termination of the purine cascade by adenosine degradation was faster in the 35- than in 18-day-old Sertoli cells. Follicle Stimulating Hormone (FSH) influences on the ectonucleotidase activities were investigated in 10- and 18-day-old Sertoli cells and a significant increase in the ATP and ADP hydrolysis was observed. Our results show an increase in the extracellular purine cascade during the Sertoli cell development, indicating a rise in the purine communication inside the seminiferous tubules with rat sexual maturation. 相似文献
157.
Paulina Juszczyk Regina Kasprzykowska Aleksandra S. Koodziejczyk 《Letters in Peptide Science》2003,10(2):79-82
Sodium bis(2-methoxyethoxy)aluminum hydride, NaAlH2(OCH2CH2OCH3)2, commercially known as Vitride® or Red-Al®, enables rapid synthesis of pure optically active N-protected amino alcohols and peptide alcohols in very high yields. The method is very simple and attractive, as it does not require an additional step of N-protected amino acid derivatization and proceeds without the loss of enantiomeric homogeneity. 相似文献
158.
Bicalho B Gonçalves RA Zibordi AP Manfio GP Marsaioli AJ 《Zeitschrift für Naturforschung. C, Journal of biosciences》2003,58(9-10):746-751
The production of antimicrobial compounds by fungi associated with Clusia spp. pollinating bees (Trigona sp., Trigonini) was investigated in order to approach natural mechanisms of microbial density control within nest environment. By using a bioassay-guided approach based on bioautography and minimal inhibitory concentration (MIC), known alpha,beta-dehydrocurvularin and curvularin were isolated from Curvularia eragrostidis (CCT 5634) and Curvularia pallescens (CCT 5654), and known cochlioquinone A and isocochlioquinone A were isolated from Drechslera dematioidea (CCT 5631). 相似文献
159.
Wiesner J Kettler K Sakowski J Ortmann R Jomaa H Schlitzer M 《Bioorganic & medicinal chemistry letters》2003,13(3):361-363
We have developed the [5-(4-nitrophenyl)-2-furyl]acrylic acid substituted benzophenone 4g as a novel lead for anti-malarial agents. Here, we demonstrated that the acyl residue at the 2-amino group of the benzophenone core structure has to be a phenylacetic acid substructure substituted in its para-position with methyl or other substituents of similar size. The trifluoromethyl substituted derivative displayed an IC(50) of 47 nM against the multi-drug resistant Plasmodium falciparum strain Dd2. 相似文献
160.
Amyloidosis is characterized by extracellular deposits of protein fibrils with a high content of β-sheets in secondary structure. The protein forms together with proteoglycans amyloid fibrils causing organ damage and serious morbidity. Intact apolipoprotein A-I (apoA-I) is an important protein in lipid metabolism regulating the synthesis and catabolism of high density lipoproteins (HDL). Usually, apoA-I is not associated with amyloidosis. However, four naturally occuring mutant forms of apoA-I are known so far resulting in amyloidosis. The most important feature of all variants is the very similar formation of N-terminal fragments which were found in the amyloid deposits (residues 1–83 to 1–94). The new insights in the understanding of the association of apoA-I with HDL, its metabolism, and its hypothesized structural findings may explain a common mechanism for the genesis of apoA-I induced amyloidosis. Here we summarized the specific features of all known amyloidogenic variants of apoA-I and speculate about its metabolic pathway, which may have general implications for the metabolism of apoA-I. 相似文献