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741.
The production of activated oxygen species by an interaction of methemoglobin with ascorbate 总被引:5,自引:0,他引:5
U Benatti A Morelli L Guida A De Flora 《Biochemical and biophysical research communications》1983,111(3):980-987
Ascorbate reacts with methemoglobin to produce reactive oxygen species, most probably hydroxyl radicals. The main features of this system are: a) disappearance of ascorbate; b) consumption of oxygen with an ascorbate/O2 stoichiometry of 2:1; c) requirement of unliganded heme iron; d) formation of H2O2. The proposed mechanism involves an ascorbate-mediated interconversion of methemoglobin and oxy-hemoglobin, resulting in the production of H2O2. This product is decomposed by hemoglobin to produce hydroxyl radicals according to a Fenton-like reaction in which ascorbate recycles methemoglobin to hemoglobin. Alternative pathways of formation and of decomposition of H2O2 in this system appear to play a minor role. 相似文献
742.
Roumen M. Balansky Penka M. Blagoeva Zwetanka I. Mircheva Silvio De Flora 《Journal of cellular biochemistry》1994,56(4):449-454
A series of 16 experiments, using a total of 2,000 BD6 rats, was designed in order to assess the ability of 8 individual agents or their combinations to modulate the liver and oesophageal carcinogenesis induced by multiple doses of diethylnitrosamine (DEN). Of the antioxidants tested, sodium selenite, ascorbic acid, and butylated hydroxytoluence generally exhibited protective effects on both types of tumors. In contrast, retinoic acid behaved as a promoter of DEN hepatocarcinogenesis, but this effect could be eliminated by its combination with either selenite or butylated hydroxytoluene. Caffeine and theophyline, when individually assayed, were devoid of significant protective effects, and the later methylxanthine stimulated oesophageal tumorigenesis when administered afer exposure to the carcinogen. Caffeine tended to decrease tje multiplicityof tumors and potentiated the inhibitory effect of selenite in the liver. Irrespective of combination with caffeine, treatment with phwnobarbital before each DEN injection tended to reduce the multiplicity of both liver and oesophageal tumors. On the other hand, the metabolic inhibitoe diethyldithiocarbamate, given after each DEN injection, dramatically enhancedd the incidence and multiplicity of oesophageal tumors. Thus, on the whole, modulation of DEN carcinogenesis varied depending on test agents, their conbinations, dosages, treatment schedules, and target organ. 相似文献
743.
It has been repeatedly suggested that mammalian cranial sutures act not only to allow growth but also to reduce the levels of strain experienced by the skull during feeding. However, because of the added complexity they introduce, sutures are rarely included in finite element (FE) models, despite their potential to influence strain results. Because sutures present different morphologies and with differing degrees of internal fusion, many different methods of modeling may be necessary to accurately measure strain environments. Alternatively, these variables may exert very little influence on the scale of a whole‐skull model. To validate suture modeling methods, four alternative ways of including a suture in 3D FE models of the pig zygomatic arch were considered and compared with ex vivo experimental data from digital speckle pattern interferometry (DSPI). The use of DSPI rather than traditional strain gauge techniques allows strain gradients around the suture as well as the motions of the two bones to be observed. Results show that the introduction of 3D elements assigned more compliant material properties than the surrounding bone, is the most effective way of modeling both morphologies of suture, both in tension and compression. However, models containing no suture are almost indistinguishable from these compliant suture models, beyond the high strain gradient immediately adjacent to the suture. Conversely, modeling the suture as an open break in the mesh, or with spring elements assigned suture properties, fails to reproduce the experiment. Thus, although a solid but flexible model of sutures is preferred, the similarity between these models and those without sutures tentatively suggests that such extra detail may be unnecessary in pigs if the behavior of the whole skull is of interest. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc. 相似文献
744.
745.
Details of the life of João Barbosa Rodrigues, early explorer of the Amazon, renowned specialist on Brazilian orchids and palms, and director of the “Jardim Botânico” of Rio de Janeiro from 1890 to 1909, are presented. Several of his illustrations are reproduced here for the first time. 相似文献
746.
João Paulo C de Oliveira Flora Fernandes Angela K Cruz Viviane Trombela Elisângela Monteiro Anamaria A Camargo Aldina Barral Camila I de Oliveira 《Kinetoplastid biology and disease》2007,6(1):5
Background
Leishmania (Leishmania) amazonensis infection in man results in a clinical spectrum of disease manifestations ranging from cutaneous to mucosal or visceral involvement. In the present study, we have investigated the genetic variability of 18 L. amazonensis strains isolated in northeastern Brazil from patients with different clinical manifestations of leishmaniasis. Parasite DNA was analyzed by sequencing of the ITS flanking the 5.8 S subunit of the ribosomal RNA genes, by RAPD and SSR-PCR and by PFGE followed by hybridization with gene-specific probes. 相似文献747.
Flora Doffe Vincent Carbonnier Manon Tissier Bernard Leroy Isabelle Martins Johanna S. M. Mattsson Patrick Micke Sarka Pavlova Sarka Pospisilova Jana Smardova Andreas C. Joerger Klas G. Wiman Guido Kroemer Thierry Soussi 《Cell death and differentiation》2021,28(5):1477
Infrequent and rare genetic variants in the human population vastly outnumber common ones. Although they may contribute significantly to the genetic basis of a disease, these seldom-encountered variants may also be miss-identified as pathogenic if no correct references are available. Somatic and germline TP53 variants are associated with multiple neoplastic diseases, and thus have come to serve as a paradigm for genetic analyses in this setting. We searched 14 independent, globally distributed datasets and recovered TP53 SNPs from 202,767 cancer-free individuals. In our analyses, 19 new missense TP53 SNPs, including five novel variants specific to the Asian population, were recurrently identified in multiple datasets. Using a combination of in silico, functional, structural, and genetic approaches, we showed that none of these variants displayed loss of function compared to the normal TP53 gene. In addition, classification using ACMG criteria suggested that they are all benign. Considered together, our data reveal that the TP53 coding region shows far more polymorphism than previously thought and present high ethnic diversity. They furthermore underline the importance of correctly assessing novel variants in all variant-calling pipelines associated with genetic diagnoses for cancer.Subject terms: Tumour-suppressor proteins, Genetics research 相似文献
748.
The micropylar apparatus (MA) in Rhagoletis cerasi (Diptera, Tephritidae) is located at the anterior pole of the egg and consists of two parts: an outer chorion and an inner vitelline membrane. Sperm entry takes place through the micropylar canal, 2.0–2.5 μm in diameter, which penetrates the micropylar endochorion and terminates in the thick vitelline membrane, thus forming the “pocket.” The pore of the micropylar canal, i.e., the micropyle, is covered by the exochorionic tuft. The formation of the MA is accomplished by 40 micropylar cells during oogenesis. These cells secrete the successive eggshell layers: the vitelline membrane, the wax layer, the innermost chorionic layer, the micropylar endochorion, and the exochorion. Two among 40 micropylar cells differentiate and form two tightly connected projections. The latter contain a bundle of parallel microtubules and participate in the formation of the micropylar canal and the pocket. At the tip of the projections there are two thin extensions full of microfilaments. In late developmental stages the two projections and the extensions degenerate and leave the canal and the pocket behind. We also discuss the structural features of the MA in relation to its physiology among Diptera. 相似文献