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21.
Clonal abortion of bone marrow T cell precursors: T cells acquire specific antigen reactivity prethymically 总被引:1,自引:0,他引:1
R Chervenak J J Cohen S D Miller 《Journal of immunology (Baltimore, Md. : 1950)》1983,131(4):1688-1692
Lethally irradiated (900 R) mice were reconstituted with bone marrow cells from syngeneic donors that had been tolerized 2 to 3 wk earlier to either DNP or TNP compounds. Five weeks after reconstitution, these animals were tested for their ability to mount a delayed hypersensitivity (DH) response to the tolerizing haptens. Recipient mice were specifically tolerant to the hapten that was used to induce tolerance in the marrow donor. Mixing experiments in which mice were reconstituted with marrow from DNP-tolerant and TNP-tolerant donors showed no indication of active suppression or effective antigen carry-over in this system. This observation held true even in experiments in which mice were reconstituted with a mixture of marrow from tolerant and normal donors at a ratio of 5:1. Thus the reduced responsiveness in recipient mice seemed to be due to the functional elimination of hapten-responsive T cell precursor (pre-T) clones. Recipient unresponsiveness was also shown to be MHC restricted. Maintenance of unresponsiveness appeared to be due to the restricted access of regenerating pre-T cell clones to the maturational influence of the recipient's thymus. 相似文献
22.
A. Cohen A. M. Breure D. J. M. Schmedding R. J. Zoetemeyer J. G. van Andel 《Applied microbiology and biotechnology》1985,21(6):404-408
Summary The effect of partial pre-acidification of carbohydrate containing wastewaters on anaerobic digester performance was investigated. The influent was a 1% (w/v) glucose solution in a mineral salts medium imposing carbon-limited growth conditions. Up to 13% of the Chemical Oxygen Demand (COD) was added as volatile fatty acids (VFA).In all cases, addition of VFA to the glucose medium resulted in significant increases in the maximum specific COD-conversion rates of the sludge (both with respect to continuous feeding and following a shock loading), as compared with values found on digestion of glucose media alone. 相似文献
23.
David L Cohen 《BMJ (Clinical research ed.)》1985,291(6506):1428
24.
Ninety-one patients who had had augmentation mammaplasties were evaluated retrospectively. The intra-implant use of steroids appeared to reduce the incidence of breast firmness--at least over the short follow-up period--but there were complications from this which appear to be dose related (mg of Solu-Medrol/100 cc saline). A long-term evaluation of such patients is desirable. Meanwhile, our limited data strongly suggest that the intra-implant use of steroids should be used only with caution as to the dose and with a careful follow-up. 相似文献
25.
26.
P E Cohen J W Pollard 《BioEssays : news and reviews in molecular, cellular and developmental biology》2001,23(11):996-1009
Meiosis is the process by which diploid germ cells divide to produce haploid gametes for sexual reproduction. The process is highly conserved in eukaryotes, however the recent availability of mouse models for meiotic recombination has revealed surprising regulatory differences between simple unicellular organisms and those with increasingly complex genomes. Moreover, in these higher eukaryotes, the intervention of physiological and sex-specific factors may also influence how meiotic recombination and progression are monitored and regulated. This review will focus on the recent studies involving mouse mutants for meiosis, and will highlight important differences between traditional model systems for meiosis (such as yeast) and those involving more complex cellular, physiological and genetic criteria. 相似文献
27.
Apterous is a LIM-homeodomain protein that confers dorsal compartment identity in Drosophila wing development. Apterous activity requires formation of a complex with a co-factor, Chip/dLDB. Apterous activity is regulated during wing development by dLMO, which competes with Apterous for complex formation. Here, we present evidence that complex formation between Apterous, Chip and DNA stabilizes Apterous protein in vivo. We also report that a difference in the ability of Chip to bind the LIM domains of Apterous and dLMO contributes to regulation of activity levels in vivo. 相似文献
28.
Construction of an ordered overlapping library of bacteriophage P1 DNA in phage vector lambda D69 总被引:1,自引:0,他引:1
A library of bacteriophage P1 DNA was constructed in the phage vector lambda D69. The DNA of some 150 randomly chosen lambda-P1 hybrid phages containing P1 DNA fragments 5-10 kb in size was analyzed by restriction endonuclease digestion using enzymes EcoRI, BglII, and BamHI that cleave P1 DNA at known positions on the physical map of P1. Approximately one third of the phages contained P1 DNA inserts having two or more restriction sites for any one of these enzymes, thus allowing the location of the insert to be determined with respect to the physical map. Genetic tests allowed detection of lambda-P1 hybrid phages possessing inserts with functional P1 ban and CmR genes. A subset of 18 phages was analyzed in more detail; their P1 DNA inserts comprise an ordered collection of overlapping P1 DNA fragments that cover almost 98% of the P1 genome. 相似文献
29.
The comprehensive studies of purine nucleotide metabolism were done in nonstimulated and phytohemagglutinin (PHA)-stimulated human peripheral blood T lymphocytes. Nonstimulated lymphocytes synthesize nucleotides in two alternative pathways: via biosynthesis de novo and salvage pathways. Although synthesis of triphosphonucleosides in unstimulated lymphocytes was the predominant pathway, interconversion of monophosphonucleosides was also active. Exposure of cells to PHA affects differently various pathways of nucleotide metabolism. The most marked changes observed were rapid activation of purine salvage within minutes after exposure to PHA, and significant increase of 5-phosphoribosyl-1-pyrophosphate levels. In addition, significant increases were found in de novo purine biosynthesis, nucleotide interconversions, and RNA and DNA synthesis, whereas catabolism of nucleotides remained unchanged. These results indicate that PHA activation of T lymphocytes causes a rapid synthesis of nucleotides which may be required immediately for increases in energy metabolism and later as the precursors of nucleic acid synthesis. 相似文献
30.
Light induces a rapid and transient increase in inositol-trisphosphate in toad rod outer segments 总被引:1,自引:0,他引:1
J E Brown C Blazynski A I Cohen 《Biochemical and biophysical research communications》1987,146(3):1392-1396
The sub-second time course of changes in the content of [3H]inositol-1,4,5-trisphosphate was determined in rod outer segments from very rapidly frozen Bufo retinas that had been incubated with [3H]inositol. Rod outer segments were cut off frozen specimens with a cryostat microtome and the water soluble extracts were analyzed. The content of [3H]inositol-1,4,5-trisphosphate rose after approximately 250 msec of bright illumination, but returned to the unstimulated level after 1 sec, whether the stimulus remained on or not. That is, there was rapid but transient change in the content of [3H]inositol-1,4,5-trisphosphate after the onset of stimulation. 相似文献