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1.
2.
Groups of male Alderley Park rats were dosed concomitantly with 2-acetylaminofluorene (2AAF) by gavage at doses between 0.01 mg/kg and 40 mg/kg, and livers sampled 2-72 h later. The liver of one group of animals was perfused to yield hepatocytes which were assayed in vitro for unscheduled DNA synthesis (UDS) via incorporation of tritiated thymidine and autoradiography. DNA was extracted from the livers of the other group and DNA adduct levels determined using the 32P-postlabelling technique. The major C-8 2-aminofluorene/guanosine adduct and 3 minor adducts were quantitated, enabling the relative sensitivity of the 2 techniques to be compared. A dose- and time-related UDS response was observed, which, at the most sensitive time-point (12 h) enabled DNA repair to be discerned at a dose level of 0.1-1 mg/kg of 2AAF, a response classified as formally positive at 5 mg/kg 2AAF. Only the C-8 adduct, as determined by 32P-postlabelling, was discernible at 0.01 mg/kg of 2AAF, although other adducts were visible on autoradiograms at higher dose levels. It is concluded that as part of a well-defined dose response, UDS can be discerned with confidence for doses of 2AAF between approximately 0.1 and 5 mg/kg, and DNA adducts for doses of 2AAF between approximately 0.01 and 1 mg/kg. Discernible UDS for 2AAF in the rat liver is apparent at approximately 13 DNA (total) adducts/10(8) nucleotides, or approximately 8 DNA (C-8) adducts/10(8) nucleotides. The presumed C-8 2-acetylaminofluorene/guanosine adduct, prepared by reaction of 2-acetoxy-2-acetylaminofluorene (2AAAF) with DNA, was a significant but unreliable marker of 2AAF/DNA adducts in the rat liver in vivo. DNA repair did not appear to remove DNA adducts selectively, and adducts remained in DNA when discernible DNA repair had ceased. 相似文献
3.
Summary The tumor promotor 12-O-tetradecanoylphorbol-13-acetate (TPA) was examined for its ability to induce endogenous retrovirus from a high-passage clone
of Kirsten sarcoma virus-transformed Balb/c (K-Balb) mouse cells. TPA activated virus in a concentration-dependent manner
(0.0016 to 4.0 μM). Exposure to 1mM actinomycin D inhibited virus induction, suggesting that cellular RNA synthesis is required de novo by this inducer. A broad-spectrum
neutralizing antibody to murine type C virus, gp70, was shown to neutralize the infectivity of the induced virus. The activated
virus had the host range of the xenotropic Balb virus:2, and after removal of the inducer, the activated state decayed rapidly.
TPA stimulated DNA, RNA, and protein synthesis in K-Balb cells, indicating that the mechanism of inducation may be different
from that of previously identified virus inducers. The effects observed using the well-defined K-Balb system offer an opportunity
to study the modulation of retrovirus gene expression by TPA.
This work was conducted while the authors were with the Biological Carcinogenesis Program, Frederick Cancer Research Facility,
Frederick, MD 21701, and was supported under Contract NO1-CO-75380 with the National Cancer Institute, National Institutes
of Health, Bethesda, MD 20205. 相似文献
4.
M E Lefevre D D Joel G Schidlovsky 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1985,179(4):522-528
Conventional and germfree mice ingested a suspension of 2-micron latex particles in drinking water for a 15-day period. Number and distribution of intestinal Peyer's patches did not differ significantly in the two types of mice. Cleared Peyer's patches were compared with regard to size and particle content. The location of particles within Peyer's patch follicles of germfree mice was similar to that of conventional mice, but the latter had significantly larger follicles and greater accumulations of latex particles. Latex concentration varied with patch location. Proximal patches contained the majority of particles in germfree mice, whereas particles were most abundant in distal patches of conventional mice. The results show that particle uptake into Peyer's patches takes place even in the complete absence of bacteria in the gut. 相似文献
5.
Claude Lefevre 《Bulletin of mathematical biology》1983,45(1):11-20
This paper is concerned with a generalization of the simple epidemic model in which the infective population is partitioned
intom classes, each of specific infectiousness. Attention is restricted, however, to the case where all the meeting rates between
two individuals are equal to each other. Both deterministic and stochastic versions are examined. In either case the development
in time of the epidemic process is investigated by exploiting a connection with the standard simple epidemic model. Finally,
it is shown that the technique used also applies to a similar model for the spread of information. 相似文献
6.
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8.
C Lefevre H H Phan A Anteunis G Rosselin 《The journal of histochemistry and cytochemistry》1990,38(9):1257-1266
Transferrin (Tf) and vasoactive intestinal peptide (VIP) were labeled with horseradish peroxidase (HRP) and 125I, respectively. To determine whether two simultaneously incubated ligands are conveyed by the same population of endosomal vesicles in human colon carcinoma cells (HT-29), we used an analysis system derived from the cross-fire method for quantitation of autoradiographic data. This system permitted the collection of data and the statistical calculations required by the double labeling of the cells. HRP-labeled Tf organelles were chosen as reference structures of the endosomal apparatus and taken as the conventional source of the radiolabeling. Our data established from the co-localization hypothesis strongly suggest that after a 30-sec (T 1/2) and a 10-min (T10) internalization at 37 degrees C, VIP and Tf share in major part the same endocytic pathway and even the recycling route to the cell surface. At T10, most of the radiolabeling was located inside the tubulovesicular network, and we also detected slight radiolabeling inside the vesicles recycling Tf. The number of double-labeled endosomes involved in ligand traffic were advantageously observed with our computer-assisted analysis system. 相似文献
9.
Kin Sing Lam Salvatore Forenza Terrence W. Doyle Cedric J. Pearce 《Journal of industrial microbiology & biotechnology》1990,6(4):291-294
Summary Experimental evidence is presented to demonstrate that indolepyruvic acid is an intermediate in the rebeccamycin biosynthetic pathway. [3-14C]Indolepyruvic acid was prepared and efficiently incorporated (8%) into rebeccamycin bySaccharothrix aerocolonigenes. 相似文献
10.
We consider the problem of comparing several nucleic acid sequencesto identify words occurring imperfectly (patterns with no gap)with unusual frequency. Methods for computing, representing,and inspecting interactively the structure of such repeatingmotifs in nucleic acids and more generally any text are described.Multiple sequences are treated as one large concatenate. Ina preprocessing step, a lexical index is created to providerapid string matching for the enumeration of the words matchinga pattern. For given word features (word length, minimal frequency),a sequence profile is displayed. The profile can be inspectedinteractively with on-line algorithms. Applications to the identificationof regulatory elements in DNA regions involved in the controlof gene expression are presented. Our program (DNA-Lexemics)runs on the Macintosh. 相似文献