技术资料

Taxol stabilizes microtubules,prevents tubulin depolymerization,and promotes tubulin bundling and is one of the most effective drugs for the treatment of metastatic breast and ovarian cancer. Although its interaction with tubulin has been well characterized,the mechanism by which taxol induces growth arrest and cytotoxicity is not well understood. Herein,we show that taxol induced dose- and time-dependent accumulation of the cyclin inhibitor p21WAF1 in both p53 wild-type and p53-null cells,although the degree of induction was greater in cells expressing wild-type p53. In MCF7 cells,wild-type p53 protein was also induced after taxol treatment,and this induction was mediated primarily by increased protein stability. Taxol induced both p21WAF1 and wild-type p53 optimally in MCF7 cells after 20-24-h exposure with an EC50(3) of 5 nM. In p53-null PC3M cells,p21WAF1 was similarly induced after 24-h exposure to taxol. Coincident with these biochemical effects,taxol altered the electrophoretic mobility of c-raf-1 and stimulated mitogen activated protein kinase. Previous depletion of c-raf-1 inhibited both the p21WAF1- and p53-inducing properties of taxol,as well as the activation of MAP kinase. These data suggest that induction of p21WAF1 by taxol requires c-raf-1 activity,but that it is not strictly dependent on wild-type p53. Furthermore,the ability of taxol to both induce wild-type p53 in MCF7 cells and activate MAP kinase is also dependent on c-raf-1 expression. View Publication

Hypoxia-inducible factor 1 (HIF-1) is found in mammalian cells cultured under reduced O2 tension and is necessary for transcriptional activation mediated by the erythropoietin gene enhancer in hypoxic cells. We show that both HIF-1 subunits are basic-helix-loop-helix proteins containing a PAS domain,defined by its presence in the Drosophila Per and Sim proteins and in the mammalian ARNT and AHR proteins. HIF-1 alpha is most closely related to Sim. HIF-1 beta is a series of ARNT gene products,which can thus heterodimerize with either HIF-1 alpha or AHR. HIF-1 alpha and HIF-1 beta (ARNT) RNA and protein levels were induced in cells exposed to 1% O2 and decayed rapidly upon return of the cells to 20% O2,consistent with the role of HIF-1 as a mediator of transcriptional responses to hypoxia. View Publication

We have investigated the potential of stirred suspension cultures to support hematopoiesis from starting innocula of normal human bone marrow cells. Initial studies showed that the short-term maintenance of both colony-forming cell (CFC) numbers and their precursors,detected as long-term culture-initiating cells (LTC-IC),could be achieved as well in stirred suspension cultures as in static cultures. Neither of these progenitor cell populations was affected in either type of culture when porous microcarriers were added to provide an increased surface for adherent cell attachment. Supplementation of the medium with 10 ng/ml of Steel factor (SF) and 2 ng/ml of interleukin-3 (IL-3) resulted in a significant expansion of LTC-IC,CFC and total cell numbers in stirred cultures. Both the duration and ultimate magnitude of these expansions were correlated with the initial cell density and after 4 weeks the number of LTC-IC and CFC present in stirred cultures initiated with the highest starting cell concentration tested reflected average increases of 7- and 22-fold,respectively,above input values. Stirred suspension cultures offer the combined advantages of homogeneity and lack of dependence on the formation and maintenance of an adherent cell layer. Our results suggest their applicability to the development of scaled-up bioreactor systems for clinical procedures requiring the production of primitive hematopoietic cell populations. In addition,stirred suspension cultures may offer a new tool for the analysis of hematopoietic regulatory mechanisms. View Publication

Normal murine bone marrow (BM) cells were sorted on the basis of low forward and orthogonal light scatter properties,Sca-1 expression (Sca-1+),lack of staining with a cocktail of mature hematopoietic lineage markers (Lin-),and binding of wheat germ agglutinin (WGA+). This approach allowed the reproducible isolation of a very small subpopulation (0.037% +/- 0.023% of all nucleated BM cells) that was approximately 400-fold enriched in cells capable of reconstituting both lymphoid and myeloid lineages in lethally irradiated recipients. Transplantation of 30 or 10 of these Sca-1+Lin-WGA+ cells resulted in textgreater or = to 20% donor-derived nucleated peripheral blood cells 3 months posttransplantation in 100% and 22% of the recipients,respectively. When Sca-1+Lin-WGA+ cells were cultured in serum-free medium supplemented with Steel factor,interleukin-6 (IL-6),and erythropoietin (with or without IL-3),a large increase in total cell number,including cells with an Sca-1+Lin-WGA+ phenotype was observed. Single cell cultures showed that 90% to 95% of the input cells underwent at least one division during the first 2 weeks and the remainder died. Interestingly,this proliferative response was not accompanied by a parallel increase in the number of cells with both lymphoid and myeloid repopulating potential in vivo,as quantitation of these by limiting dilution analysis showed they had decreased slightly (1.3-fold) but not significantly below the number initially present. These results demonstrate that Sca-1+Lin-WGA+ cells with long-term repopulating potential can be maintained for 2 weeks in a serum- and stroma cell-free culture,providing a simple in vitro system to study their behavior under well-defined conditions. The observed expansion of Sca-1+Lin-WGA+ cells in vitro without a concomitant increase in reconstituting cells also shows that extensive functional heterogeneity exists within populations of cells with this surface phenotype. View Publication

PD 098059 has been shown previously to inhibit the dephosphorylated form of mitogen-activated protein kinase kinase-1 (MAPKK1) and a mutant MAPKK1(S217E,S221E),which has low levels of constitutive activity (Dudley,D. T.,Pang,L.,Decker,S. J.,Bridges,A. J.,and Saltiel,A. R. (1995) Proc. Natl. Acad. Sci. U.S.A. 92,7686-7689). Here we report that PD 098059 does not inhibit Raf-activated MAPKK1 but that it prevents the activation of MAPKK1 by Raf or MEK kinase in vitro at concentrations (IC50 = 2-7 microM) similar to those concentrations that inhibit dephosphorylated MAPKK1 or MAPKK1(S217E,S221E). PD 098059 inhibited the activation of MAPKK2 by Raf with a much higher IC50 value (50 microM) and did not inhibit the phosphorylation of other Raf or MEK kinase substrates,indicating that it exerts its effect by binding to the inactive form of MAPKK1. PD 098059 also acts as a specific inhibitor of the activation of MAPKK in Swiss 3T3 cells,suppressing by 80-90% its activation by a variety of agonists. The high degree of specificity of PD 098059 in vitro and in vivo is indicated by its failure to inhibit 18 protein Ser/Thr kinases (including two other MAPKK homologues) in vitro by its failure to inhibit the in vivo activation of MAPKK and MAP kinase homologues that participate in stress and interleukin-1-stimulated kinase cascades in KB and PC12 cells,and by lack of inhibition of the activation of p70 S6 kinase by insulin or epidermal growth factor in Swiss 3T3 cells. PD 098059 (50 microM) inhibited the activation of p42MAPK and isoforms of MAP kinase-activated protein kinase-1 in Swiss 3T3 cells,but the extent of inhibition depended on how potently c-Raf and MAPKK were activated by any particular agonist and demonstrated the enormous amplification potential of this kinase cascade. PD 098059 not only failed to inhibit the activation of Raf by platelet-derived growth factor,serum,insulin,and phorbol esters in Swiss 3T3 cells but actually enhanced Raf activity. The rate of activation of Raf by platelet-derived growth factor was increased 3-fold,and the subsequent inactivation that occurred after 10 min was prevented. These results indicate that the activation of Raf is suppressed and that its inactivation is accelerated by a downstream component(s) of the MAP kinase pathway. View Publication

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Autografts using untreated or in vitro manipulated bone marrow and peripheral blood stem cells represent promising approaches to the treatment of malignant diseases. In this work,the collagen gel culture technique was compared with agar and methylcellulose for its capacity to permit the growth of human granulomonocytic (day 14 CFU-GM; collagen vs agar or MTC) or erythroblastic (day 7 CFU-E and day 14 BFU-E; collagen versus methylcellulose) colonies in autologous transplantation products. Our results show that the collagen culture system always gave as many or more colonies than the other techniques. It also allowed harvesting of gels onto glass slides and subsequent May-Grünwald-Giemsa,cytochemical or immunocytochemical staining. We suggest that the collagen assay represents an interesting alternative to the widely used agar or methylcellulose systems for the culture of hematopoietic progenitors because of the equal or higher number of colonies detected,the easy phenotypical identification of colonies in stained gels,and the ability to store high-quality documentation. This technique is particularly attractive for use in the quality control of autologous bone marrow transplantation procedures. View Publication

Ionomycin,a new polyether antibiotic with a high affinity for calcium ions,is obtained in pure form from fermentation broths of Streptomyces conglobatus sp. nov. Trejo by solvent extraction. It is unique amongst known polyether antibiotics in that it has a UV absorption maximum at 300 nm. thereby distinguishing it from other antibiotics of its class. The Ca salt has the molecular formula C41H70O9Ca. Ionomycin is a narrow spectrum antibiotic being active against Gram-positive bacteria. View Publication

By using immunoelectron microscopy,we have localized the binding site on 50S Escherichia coli ribosomal subunits for puromycin,an antibiotic that interacts with the ribosomal peptidyltransferase center. This was achieved by affinity-labeling 50S subunits with N-bromoacetyl puromycin and treating the labeled subunits with an antibody specific for the N6,N6-dimethyladenosine moiety of puromycin. The position of the puromycin binding site was then revealed by localizing the attachment sites of the IgG molecules on the surfaces of the 50S subunits under the electron microscope: it was located at the interface between the subunits,on and around the wider lateral protuberance of the 50S subunit. This localizes directly the peptidyl transferase center on the surface of the large ribosomal subunit. View Publication

A method has been described for the long-term culture of human bone marrow cells in liquid medium. Hematopoiesis,as measured by the production of granulocytic-macrophage progenitor cells (CFUc),continued for at least 20 weeks and was dependent upon the presence of a marrow-derived adherent layer of cells. As in the case of murine marrow liquid cultures,the adherent layer consisted of mononuclear phagocytic cells,endothelial cells,and lipid-laden adipocytes,the latter being essential for long-term hematopoiesis. Optimal growth conditions included McCoy's medium supplemented with fetal bovine serum,horse serum,and hydrocortisone and incubation at 33 degrees C. Horse serum in conjunction with hydrocortisone appeared essential for the growth of adipocytes. View Publication

Serotonin receptor affinity and photelectron spectral data were obtained on a number of substituted N,N-dimethyltryptamines. Evidence is presented that electron-donating substituents in the 5-position lead to enhanced behavioral disruption activity and serotonin receptor affinity as compared to unsubstituted N,N-dimethyltryptamine and analogues substituted in the 4- or 6-position. Some correlation was found between ionization potentials and behavioral activity,which may have implications concerning the mechanism of receptor binding. View Publication

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