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221.
Charles R. Ill Tammy Brehm Bjorn K. Lydersen Rachel Hernandez Karen G. Burnett 《In vitro cellular & developmental biology. Plant》1988,24(5):413-419
Summary Studies with Human x Human (HxH), Human x Mouse (HxM), and Mouse x Mouse (MxM) hybridomas have enabled us to define specific
factors that affect hybridoma growth in a species-specific manner. Three transferrins and three lipophilic iron chelates have
been tested for their ability to support hybridoma proliferation and antibody production. The results of these studies demonstrate
that HxH hybridomas do not respond to bovine transferrin a+ concentrations up to 100 μg/ml and are approximately 100-fold less responsive to mouse transferrin than to human transferrin.
HxM and MxM hybridomas respond equally to human or mouse transferrin but are 100-fold less sensitive to bovine transferrin.
An antibody to the human transferrin receptor inhibited the growth-promoting activity of human or mouse transferrin on HxH
hybridomas but was ineffective on HxM hybridomas. This semonstrated the functionality of the human transferrin receptor in
HxH hybridomas and that human, mouse, and bovine transferrin were interacting through the mouse transferrin receptor in HxM
hybridomas. HxH and HxM hybridomas respond similarly to three different iron chelates exhibiting 80 to 110% of the growth
response to human transferrin. MxM hybridomas fail to respond to the iron chelates at similar concentrations, suggesting that
the human genome present in the other hybridoma species confers a unique ability for utilizing iron when delivered in this
form. 相似文献
222.
223.
A number of experimental and mathematical problems must be solved before high resolution physical maps of mammalian chromosomes can be reliably determined. Such a map might consist of an ordered set of nonsequenced, overlapping DNA fragments 20,000-40,000 bases long, produced by digestion of a chromosome, using two restriction enzymes. Map construction requires assigning a signature to each fragment that differentiates it unambiguously from every other fragment, and then devising a computationally efficient algorithm that will provide a unique ordering of the fragments. In the first part of this paper we present a polynomial time algorithm that yields a unique map, and is largely independent of the method for assigning signatures. In the next section we analyze the distribution of lengths of restriction digest fragments and discuss the implications for the algorithm, including the expected number of map gaps. Finally, we discuss a specific method for assigning signatures proposed by Hans Lehrach, based on which of a panel of probes binds to a given fragment. In particular we examine the effects of fragment length heterogeneity on the theoretical optimum length and number of probes, and the extent to which false signatures might be obtained by nonspecific binding. We conclude that the Lehrach strategy is effective provided the number of probes is >-150, but that each fragment will need testing with at most 25 probes. 相似文献
224.
Definition and identification of homology domains 总被引:3,自引:0,他引:3
A method is described for identifying and evaluating regionsof significant similarity between two sequences. The notionof a homology domain is employed which definesthe boundaries of a region of sequence homology containing noinsertions or deletions. The relative significance of differentpotential homology domains is evaluated using a non-linear similarityscore related to the probability of finding the observed levelof similarity in the region by chance. The sensitivity of themethod is demonstrated by simulating the evolution of homologydomains and applying the method to their detection. Severalexamples of the use of homology domain identification are given.
Received on July 29, 1987; accepted on November 15, 1987 相似文献
225.
Gene amplification at a locus encoding a putative Na+/H+ antiporter confers sodium and lithium tolerance in fission yeast.
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We have identified a new locus, sodium 2 (sod2) based on selection for increased LiCl tolerance in fission yeast, Schizosaccharomyces pombe. Tolerant strains have enhanced pH-dependent Na+ export capacity and sodium transport experiments suggest that the gene encodes an Na+/H+ antiport. The predicted sod2 gene product can be placed in the broad class of transporters which possess 12 hydrophobic transmembrane domains. The protein shows some sequence similarity to the human and bacterial Na+/H+ antiporters. Overexpression of sod2 increased Na+ export capacity and conferred sodium tolerance. Osmotolerance was not affected and sod2 cells were unaffected for growth in K+. In a sod2 disruption strain cells were incapable of exporting sodium. They were hypersensitive to Na+ or Li+ and could not grow under conditions that approximate pH7. The sod2 gene amplification could be selected stepwise and the degree of such amplification correlated with the level of Na+ or Li+ tolerance. 相似文献
226.
A mutation outside the two zinc fingers of ADR1 can suppress defects in either finger. 总被引:2,自引:2,他引:0
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A second-site mutation that restored DNA binding to ADR1 mutants altered at different positions in the two zinc fingers was identified. This mutation (called IS1) was a conservative change of arginine 91 to lysine in a region amino terminal to the two zinc fingers and known from previous experiments to be necessary for DNA binding. IS1 increased binding to the UAS1 sequence two- to sevenfold for various ADR1 mutants and twofold for wild-type ADR1. The change of arginine 91 to glycine decreased binding twofold, suggesting that this arginine is involved in DNA binding in the wild-type protein. The increase in binding by IS1 did not involve protein-protein interactions between the two ADR1 monomers, nor did it require the presence of the sequences flanking UAS1. However, the effect of IS1 was influenced by the sequence of the first finger, suggesting that interactions between the region amino terminal to the fingers and the fingers themselves could exist. A model for the role of the amino-terminal region based on these results and sequence homologies with other DNA-binding motifs is proposed. 相似文献
227.
Summary Neuron populations in the retina of the toad, Bufo marinus, were labelled with a monoclonal antibody raised against microtubule-associated protein 2 (MAP2). A subpopulation of cones, probably corresponding to the blue-sensitive small single cones, large diameter amacrine cells in the most proximal row of the inner nuclear layer and some large ganglion cells in the ganglion cell layer were labelled. Double labelling experiments were carried out to establish the colocalisation of MAP2 with known putative transmitter substances of the anuran amacrine cells. MAP2 was colocalised in a subpopulation of serotonin-immunoreactive and in all tyrosine hydroxylase-immunoreactive amacrine cells. The results indicate, that the MAP2 content in the neurons of the anuran retina can be correlated with other well-defined neurochemical and/or physiological properties.On leave from Department of Zoology, Attlia József University, Szeged, Hungary 相似文献
228.
Daniel R. Vlock Beth Arnold Jeannette Humpierres Donald R. Schwartz Shan R. Baker Charles J. Krause Neil Swanson Thomas E. Carey 《Cancer immunology, immunotherapy : CII》1992,34(5):329-336
Summary In previous studies we evaluated the incidence and specificity of autologous antibody reactivity against squamous cell carcinoma of the head and neck (SCCHN). We were able to demonstrate that autologous antibody reactivity is present in native sera but was usually of too low a titer to allow further analysis. Dissociation of immune complexes by acidification and ultrafiltration of serum augmented autologous antibody reactivity in nine out of nine autologous systems tested. Native antibody and antibody derived from immune complexes produced by the host and reactive with autologous tumor cells may be directed against physiologically relevant antigens. Therefore, correlations of antibody titers with clinical course may provide insight into the nature of the host response to cancer. In the present analysis, serological studies of six patients with SCCHN were performed with serum samples obtained over many months. Results of serial serological assays were correlated to tumor progression and clinical course. Fluctuations in autologous antibody reactivity were noted over time. In four cases, rises in autologous antibody titers preceded the clinical diagnosis of recurrence by several months. Drops in autologous antibody reactivity were noted in two cases following surgery or radiation therapy. In two cases of long-term survivors, no correlation between antibody reactivity and clinical course was noted. Specificity analysis of the six autologous systems demonstrated reactivity against autologous and allogeneic SCCHN as well as melanoma cell lines. These sera did not react with glioma, neuroblastoma, renal cell, breast, bladder and colon carcinoma cell lines nor with fetal calf serum, pooled lymphocytes, red blood cells and platelets. Autologous serial serological studies may provide a means by which to evaluate the host/tumor relationship in patients with SCCHN. 相似文献
229.
Phyllis W. Speisere Maria I. New Grace M. Tannin Donald Pickering Soo Young Yang Perrin C. White 《Human genetics》1992,88(6):647-648
Summary An A-to-G transition in the second intron was the sole mutation detected in four Yupik Eskimo patients with salt-wasting congenital adrenal hyperplasia due to steroid 21-hydroxylase deficiency. Allele-specific hybridization should be an efficient means of performing prenatal diagnosis of the disease in this highly inbred population. 相似文献
230.
Bacterial flagellar diversity and significance in pathogenesis 总被引:4,自引:0,他引:4
Bacterial flagella are structurally diverse, ranging from the thoroughly investigated model examples found in Escherichia coli and Salmonella typhimurium to the more exotic sheathed flagella of, for example, Helicobacter pylori, and the complex multi-flagellin endoflagella found in many spirochaetes. We summarize some of the emerging structural and genetic findings relating to these more novel flagellar types, and outline their possible significance in the pathogenicity of some medically important bacteria. 相似文献