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1.
We have recently demonstrated that atopic T lymphocytes have decreased sensitivity to prostaglandin E2 (PGE2). In order to determine whether this decreased sensitivity was reflected at the receptor level, we have employed a radioligand binding assay utilizing [3H]PGE2. We have demonstrated a single specific reversible binding site for [3H]PGE2 on normal T cells (N = 10) with a mean KD (+/-SD) of 32.2 (+/-25.0) nM, a binding capacity of 20.2 (+/-13.0) pM, and a mean of 1004 (+/-118) receptors per cell. Atopic T cells (N = 10) were also found to have a single specific binding site for [3H]PGE2 with a mean KD of 24.9 (+/-17.8) nM, a binding capacity of 7.1 (+/-10.1) pM, and a mean of 372 (+/-61) receptors per cell. These radioligand binding studies were correlated with functional studies in the same subjects. Phytohemagglutinin-stimulated protein synthesis ([3H]leucine uptake) was suppressed in a dose-dependent fashion by PGE2 (10(-6)-10(-12) M). The maximal effect of PGE2 on normal T cells was 10(-6) M PGE2 with an IC50 of 10(-12) M. Atopic T cells responded quantitatively less than normal T cells to PGE2. Further, the maximum suppression of protein synthesis by PGE2 occurred at 10(-6) M with an IC50 of 10(-10) to 10(-11) M. These studies suggest that part of the decreased sensitivity of atopic T cells to PGE2 may result from a reduction in PGE2 binding sites. 相似文献
2.
Rob J.M. Moormann Johan T. den Dunnen Leon Mulleners Peter Andreoli Hans Bloemendal John G.G. Schoenmakers 《Journal of molecular biology》1983,171(4):353-368
Two complementary DNA clones pRLγ-2 and pRLγ-3 of different rat lens γ-crystallin messenger RNAs have been used to identify γ-crystallin gene sequences in rat genomic DNA. Subsequently, the DNA present in the 18,000 to 20,000 bases region of the EcoRI digest, giving rise to a strong doublet hybridization signal, was cloned in λ phage Charon-4A. One of the clones, λRCHγ-3, carrying an insert of 17,500 bases has been characterized in detail. From analysis at the restriction enzyme level with 5′-, “middle” and 3′-specific subprobes of pRLγ-3 it could be deduced that λRCHγ-3 contains only one γ-crystallin gene. The coding sequences of this gene are interrupted by intronic DNA. The primary structure of this gene and its flanking regions have been established by sequencing the relevant regions of a subclone of λRCHγ-3, designated pRCHγ-3.1. The sequence data show that the γ-crystallin gene extends over 2700 bases of rat genomic DNA. The gene is split by two introns, one of 87 base-pairs after the third translation codon and a large one of 1880 base-pairs after codon 84. The mosaic structure of the gene is strictly co-linear with the structure of the γ-crystallin polypeptide in that the large intron is positioned in a region which specifies the so-called “connecting peptide” and which links the two highly symmetrical and homologous protein domains. Although expected from the cDNA and protein sequence no introns were observed between the coding regions in the DNA specifying the two homologous folding motifs present in each protein domain. The relevance of this phenomenon in terms of the evolution of the mature γ-crystallin gene is discussed. 相似文献
3.
Rob J. De Boer Alan S. Perelson Ioannis G. Kevrekidis 《Bulletin of mathematical biology》1993,55(4):781-816
Two types of behavior have been previously reported in models of immune networks. The typical behavior of simple models, which
involve B cells only, is stationary behavior involving several steady states. Finite amplitude perturbations may cause the
model to switch between different equilibria. The typical behavior of more realistic models, which involve both B cells and
antibody, consists of autonomous oscillations and/or chaos. While stationary behavior leads to easy interpretations in terms
of idiotypic memory, oscillatory behavior seems to be in better agreement with experimental data obtained in unimmunized animals.
Here we study a series of models of the idiotypic interaction between two B cell clones. The models differ with respect to
the incorporation of antibodies, B cell maturation and compartmentalization. The most complicated model in the series has
two realistic parameter regimes in which the behavior is respectively stationary and chaotic. The stability of the equilibrium
states and the structure and interactions of the stable and unstable manifolds of the saddle-type equilibria turn out to be
factors influencing the model's behavior. Whether or not the model is able to attain any form of sustained oscillatory behavior,
i.e. limit cycles or chaos, seems to be determined by (global) bifurcations involving the stable and unstable manifolds of
the equilibrium states. We attempt to determine whether such behavior should be expected to be attained from reasonable initial
conditions by incorporating an immune response to an antigen in the model. A comparison of the behavior of the model with
experimental data from the literature provides suggestions for the parameter regime in which the immune system is operating. 相似文献
4.
Dog-DAT: a direct agglutination test using stabilized, freeze-dried antigen for the serodiagnosis of canine visceral leishmaniasis 总被引:2,自引:0,他引:2
Linda Oskam Rob J. Slappendel Eef G.M. Beijer Nel C.M. Kroon Cor W. van Ingen Seray Özensoy Yusuf Özbel Wiepko J. Terpstra 《FEMS immunology and medical microbiology》1996,16(3-4):235-239
Abstract We have evaluated the use of an improved direct agglutination test (DAT) based on stable, freeze-dried antigen for the detection of anti- Leishmania antibodies in canine serum samples. With a cut-off value of 1:640, the sensitivity of the DAT was shown to be 100% and the specificity of the test was 98.8%. 相似文献
5.
6.
Ronald J. Ash Gary A. Flynn Rob M.J. Liskamp Harry C.J. Ottenheijm 《Biochemical and biophysical research communications》1984,125(2):784-789
Sparsomycin, ScRs configuration, was the most potent of the four possible stereoisomers as a competitive inhibitor of peptide bond formation. In addition, the configuration of the two chiral centers dictated whether the compound exhibited time- and temperature-dependent inhibition of peptidyl transferase when incubated with polysomes prior to enzyme assay. The data corroborate the thesis that a peptidyl transferase-mediated acylation of the pivotal sulfoxide moiety and subsequent Pummerer rearrangement play a significant role in the inhibitory properties of sparsomycin. 相似文献
7.
Agrobacterium and plant genetic engineering 总被引:27,自引:0,他引:27
Erratum
Agrobacterium and plant genetic engineering 相似文献8.
Knowiedge on community structure of North Sea meiofauna has greatly increased recently. A quasisynoptic picture of meiofauna
densities and copepod community structure from 171 stations of the southern North Sea, sampled in April–May 1986, has been
obtained during the North Sea Benthos Survey. Latitudinal patterns in meiofauna abundance and copepod weight, abundance and
diversity exist in an area between 51°30′N and 58°30′N. Using TWINSPAN-classification five major groups of copepod species
can be recognized which are related to sediment type, latitude and depth. The part of the meiofauna in total benthic energy
flow, their role in the benthic food web and in biogeochemical cycles is discussed based on existing literature. There are
still considerable gaps in knowledge and the field is not progressing rapidly.
Publication no. 599 Netherlands Institute of Ecology, Centre for Estuarine and Coastal Ecology, Yerseke, The Netherlands. 相似文献
9.
Priscilla Y. L. Tng Leonela Z. Carabajal Paladino Michelle A. E. Anderson Zach N. Adelman Rennos Fragkoudis Rob Noad Luke Alphey 《PLoS neglected tropical diseases》2022,16(6)
Aedes aegypti and Ae. albopictus are the main vectors of mosquito-borne viruses of medical and veterinary significance. Many of these viruses have RNA genomes. Exogenously provided, e.g. transgene encoded, small RNAs could be used to inhibit virus replication, breaking the transmission cycle. We tested, in Ae. aegypti and Ae. albopictus cell lines, reporter-based strategies for assessing the ability of two types of small RNAs to inhibit a chikungunya virus (CHIKV) derived target. Both types of small RNAs use a Drosophila melanogaster pre-miRNA-1 based hairpin for their expression, either with perfect base-pairing in the stem region (shRNA-like) or containing two mismatches (miRNA-like). The pre-miRNA-1 stem loop structure was encoded within an intron; this allows co-expression of one or more proteins, e.g. a fluorescent protein marker tracking the temporal and spatial expression of the small RNAs in vivo. Three reporter-based systems were used to assess the relative silencing efficiency of ten shRNA-like siRNAs and corresponding miRNA-like designs. Two systems used a luciferase reporter RNA with CHIKV RNA inserted either in the coding sequence or within the 3’ UTR. A third reporter used a CHIKV derived split replication system. All three reporters demonstrated that while silencing could be achieved with both miRNA-like and shRNA-like designs, the latter were substantially more effective. Dcr-2 was required for the shRNA-like siRNAs as demonstrated by loss of inhibition of the reporters in Dcr-2 deficient cell lines. These positive results in cell culture are encouraging for the potential use of this pre-miRNA-1-based system in transgenic mosquitoes. 相似文献
10.
The biochemical mechanisms underlying thidiazuron (TDZ)-induced regeneration in plant cells have not been clearly elucidated.
Exposure of leaf explants of Echinacea purpurea to a medium containing TDZ results in undifferentiated cell proliferation and differentiated growth as mixed shoot organogenesis
and somatic embryogenesis. The current studies were undertaken to determine the potential roles of auxin, indoleamines, and
ion signaling in the dedifferentiation and redifferentiation of plant cells. E. purpurea leaf explants were found to contain auxin and the related indoleamine neurotransmitters, melatonin, and serotonin. The levels
of these endogenous indoleamines were increased by exposure to TDZ associated with the induction of regeneration. The auxin-transport
inhibitor 2,3,5-triiodobenzoic acid and auxin action inhibitor, p-chlorophenoxyisobutyric acid decreased the TDZ-induced regeneration but increased concentrations of endogenous serotonin
and melatonin. As well, inhibitors of calcium and sodium transport significantly reduced TDZ-induced morphogenesis while increasing
endogenous indoleamine content. These data indicate that TDZ-induced regeneration is the manifestation of a metabolic cascade
that includes an initial signaling event, accumulation, and transport of endogenous plant signals such as auxin and melatonin,
a system of secondary messengers, and a concurrent stress response. 相似文献