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51.
Rapidly expanding development and practice of gene therapy requires the availability of large quantities of high titer retroviral supernatants. One way to achieve high retroviral titers is through improved understanding of the kinetics of retroviral production and decay, and the subsequent development of improved cell culture methods. In the present study we investigated the effects of different operational modes on the retroviral production of the NIH 3T3 fibroblast derived amphotropic murine retroviral producing cell line pMFG/CRIP. Semi-continuous culture (exchange of 50% of medium volume daily) was found to promote cell growth and enhance retroviral production. The rapid medium exchange resulted in significantly larger amounts of high titer supernatants and an extended production phase as compared to the batch control cultures. The specific viral productivity of the pMFG/CRIP cells was in the range of 10 to 40 infectious viruses produced per thousand producer cells per day. The CV-1 African Green Monkey kidney cell line was used as the infection target. Lowering the serum level form 20% to 10% improved retroviral production slightly. However, at lower serum levels (1%, 5% and 10% (v/v)) growth of the producer cell line, and thus retroviral production, was directly proportional to the serum level. The half-life of the virus at 37°C was found to be 5.5 hours. Promoting the growth of producer cell lines can improve retroviral vectors titers and viral production. High cell density systems that allow for rapid cell growth and waste product removal are likely to be used to generate high-titer retroviral supernatants. 相似文献
52.
53.
Bernhard Kraus 《Experimental & applied acarology》1994,18(7):435-443
Reproducing Varroa jacobsoni obtained from brood cells of Apis mellifera L. with 13–16 day old bees (pupae) and Varroa mites kept on adult bees for at least 8 days were simultaneously tested for their choice in three host types. Comparisons were made of attractiveness of Varroa jacobsoni to nurse bees, pollen foragers as to larvae from nearly capped brood cells. Host choices were observed in Petri dishes and in an Y-shaped olfactometer. Varroa jacobsoni obtained from capped brood cells showed a stronger preference for nurse bees in Petri dish simultaneous choice tests with pollen foragers or larvae than did mites which were previously kept on adult bees. In olfactometer simultaneous choice tests, the two mite test groups showed no clear difference in preferences for bees of different ages. The preference of Varroa jacobsoni for bees of different ages is therefore not only influenced by host factors but also by intrinsic factors in female mites that depend on the mite's reproductive stage. 相似文献
54.
55.
Michel Monod Giuseppe Togni Bernhard Hube Dominique Sanglard 《Molecular microbiology》1994,13(2):357-368
The secreted aspartic proteinases (SAP) of Candida sp. are presumed to be potential virulence factors. In the opportunistic pathogen Candida albicans the proteinase genes identified to date, SAP1, SAP2, SAP3 and SAP4, constitute a multigene family. Before addressing the possible role of each proteinase in virulence, we sought to isolate all the members of this multigene family by screening a genomic library with a SAP1 probe for additional C. albicans SAP genes using low-stringency hybridization conditions. Three putative new members, SAP5, SAP6 and SAP7 were isolated and sequenced. The N-terminal segments of the deduced amino acid sequences of SAP5 and SAP6 contained secretion signal sequences similar to those of other Candida SAPs. Upon comparison and alignment with the other reported SAP amino acid sequences, SAP7 is not only the most divergent protein but also exhibits a much longer putative pro-sequence with a single Lys-Lys putative processing site. Using SAP1 to SAP7 as probes, the overall number of SAP genes in C. albicans was tentatively estimated by low-stringency hybridization to EcoRI-digested genomic DNA. While each isolated SAP gene could be assigned to distinct EcoRI bands, the existence of two additional genes not isolated after screening of the C. albicans gene library was inferred. Furthermore, evidence was obtained for the existence of SAP muttigene families in other Candida species such as C. tropicalis, C. parapsilosis and C. guiller-mondii. 相似文献
56.
Bernhard M. Riegl Samuel J. Purkis Peter Houk Genevieve Cabrera Richard E. Dodge 《Coral reefs (Online)》1994,13(1):40-40
International Society for Reef Studies 相似文献
57.
Frank Bernhard David L. Coplin Klaus Geider 《Molecular & general genetics : MGG》1993,239(1-2):158-168
A large ams gene cluster required for production of the acidic extracellular polysaccharide (EPS) amylovoran by the fire blight pathogen Erwinia amylovora was cloned. Tn5 mutagenesis and gene replacement were used to construct chromosomal ams mutants. Five complementation groups, essential for amylovoran synthesis and virulence in E. amylovora, were identified and designated amsA-E. The ams gene cluster is about 7 kb in size and functionally equivalent to the cps gene cluster involved in EPS synthesis by the related pathogen Erwinia stewartii. Mucoidy and virulence were restored to E. stewartii mutants in four cps complementation groups by the cloned E. amylovora ams genes. Conversely, the E. stewartii cps gene cluster was able to complement mutations in E. amylovora ams genes. Correspondence was found between the amsA-E complementation groups and the cpsB-D region, but the arrangement of the genes appears to be different. EPS production and virulence were also restored to E. amylovora amsE and E. stewartii cpsD mutants by clones containing the Rhizobium meliloti exoA gene. 相似文献
58.
Sieghart Sopper Susanne Hemm Jürgen Meixensberger Cheik Coulibaly Christiane Stahl-Hennig Gerhard Hunsmann Bernhard Fleckenstein Volker ter Meulen Rüdiger Drries 《Journal of medical primatology》1993,22(2-3):138-146
Paired sera and CSF samples were collected from SIVmac-infected macaques. Animals infected with SIVmac251 maintained low gag and high env-specific antibody levels in plasma. Increasing env-specific antibody titers in CSF were associated in one animal with strong intrathecal synthesis. SIVmac239-infected monkeys revealed high antibody titers of gag and env-specificity, in one animal accompanied by weak intrathecal synthesis of virus-specific antibodies. In all animals, the CD4/CD8 ratio in CSF decreased faster compared to blood. 相似文献
59.
Bernd Johannsen Bernhard Noll Peter Leibnitz Günter Reck Steffi Noll Hartmut Spies 《Inorganica chimica acta》1993,210(2)
The reaction of mercaptoacetyl diglycine (MAG2) with technetium(V) gluconate in aqueous solution produced [TcO(MAG2)]−. A single X-ray structure determination was carried out for the tetraphenylarsonium salt. The dark brown crystals are monoclinic, space group P2(1)/n, with a=12.478(5), b=14.922(5), c=17.183(9) Å and Z=4. The [TcO(MAG2)]− ion has a square pyramidal geometry with the technetium atom displaced by 0.756 Å towards the oxo ligand from the plane formed by the equatorial S,N,N,O atoms. The rhenium complex AsPh4[ReO(MAG2)] was prepared analogously starting from Re(V) gluconate and characterized. 相似文献
60.
The preparation and X-ray structure of [Ag(9-EtGH-N7)2]NO3·H2O(9-EtGH=neutral 9-ethylguanine) is reported. The compound crystallizes in the triclinic system, space group P
with a=7.063(6), b=7.153(3), c=11.306(10) Å, α=83.36(6), β=76.66(7), γ=81.44(6)°. The cation is centrosymmetric with Ag(I) coordinated via two N7 positions and Ag---N7 bond lengths of 2.11(1) Å. Applying 109Ag NMR spectroscopy, complex formation constants for both the 1:1 complex (log β1=0.6) and the title compound (log β2=1.6) in Me2SO have been determined. 相似文献