PubMed Health⌕ Search

Biomedical subjects

B C Wu

Publications and source records attributed to B C Wu.

At least 19 recordsLinked to original sources
PubMed2006

Suspended aggregates as an immobilization mode for high-density perfusion culture of HEK 293 cells in a stirred tank bioreactor.

Cells of the human embryonic kidney cell line (HEK 293) grown in repeated suspension and perfusion systems were characterized and described. Cell aggregates that formed immediately after the HEK 293 cells were inoculated in stirred vessels in serum-containing Dulbecco's modified Eagle's medium (D-MEM)/F-12 medium. The mean diameter of the cell aggregates reflecting the aggregate size increased with culture time, shifting from 63 to 239 mum after 1 and 8 days of culture in spinner flasks, respectively. No significant differences in cell performance were observed between HEK 293 cell populations grown as suspended aggregates and those grown as anchored monolayers. Replacing the D-MEM/F-12 with CD 293 medium caused the compact spherical cell aggregates to dissociate into single cells and small irregular aggregates without any apparent effect on cell performance. Moreover, the spherical cell aggregates could reform from individual cells and small aggregates when exposed to the serum-containing D-MEM/F-12 dominant medium. Perfusion culture of HEK 293 cells grown as suspended aggregates in a 7.5-l stirred tank bioreactor for 17 days resulted in a maximum viable cell density of 1.2 x 10(7) cells ml(-1). These results demonstrate the feasibility and proof-of-concept for using aggregates as an immobilization system in large-scale stirred bioreactors because a small-scale culture can be used as easily as the inoculum for larger bioreactors.

Bioreactors↗
PubMed2001

Salicylates inhibit flavivirus replication independently of blocking nuclear factor kappa B activation.

Flaviviruses comprise a positive-sense RNA genome that replicates exclusively in the cytoplasm of infected cells. Whether flaviviruses require an activated nuclear factor(s) to complete their life cycle and trigger apoptosis in infected cells remains elusive. Flavivirus infections quickly activate nuclear factor kappa B (NF-kappaB), and salicylates have been shown to inhibit NF-kappaB activation. In this study, we investigated whether salicylates suppress flavivirus replication and virus-induced apoptosis in cultured cells. In a dose-dependent inhibition, we found salicylates within a range of 1 to 5 mM not only restricted flavivirus replication but also abrogated flavivirus-triggered apoptosis. However, flavivirus replication was not affected by a specific NF-kappaB peptide inhibitor, SN50, and a proteosome inhibitor, lactacystin. Flaviviruses also replicated and triggered apoptosis in cells stably expressing IkappaBalpha-DeltaN, a dominant-negative mutant that antagonizes NF-kappaB activation, as readily as in wild-type BHK-21 cells, suggesting that NF-kappaB activation is not essential for either flavivirus replication or flavivirus-induced apoptosis. Salicylates still diminished flavivirus replication and blocked apoptosis in the same IkappaBalpha-DeltaN cells. This inhibition of flaviviruses by salicylates could be partially reversed by a specific p38 mitogen-activated protein (MAP) kinase inhibitor, SB203580. Together, these results show that the mechanism by which salicylates suppress flavivirus infection may involve p38 MAP kinase activity but is independent of blocking the NF-kappaB pathway.

Animals↗
PubMed1997

Aneuploid marker assignment in hexaploid oat with the C genome as a reference for determining remnant homoeology.

Nullisomic lines of hexaploid oat Avena sativa L. (2n = 6x - 2 = 40, AACCDD) cultivar Sun II were used to assign 134 DNA sequences to 10 chromosome-associated syntenic groups. A limited set of ditelosomic lines allowed localization of subsets of these sequences to six chromosome arms. Advantages of using such aneuploids in mapping are in the assignment of gene families, monomorphic RFLP sequences, and oat linkage groups to chromosomes. The published hexaploid oat RFLP linkage map has 38 linkage groups, 17 more than expected on the basis of the haploid chromosome number. Using nullisomics, eight linkage groups were assigned to five physical chromosomes; using ditelosomics, three of these linkage groups were assigned to their respective chromosome arms. The A- and D-genome chromosome sets of oat are indistinguishable from each other based on different staining and genomic in situ hybridization techniques, while C-genome chromosomes are distinct. Because chromosomal rearrangements such as translocations and inversions have played an important role in the evolution of hexaploid oat, the distinction of C-genome chromosomes can be used to determine remnant homoeologous segments that exist in the other two genomes. Among the 10 syntenic groups identified, six chromosomes showed sequence homoeology believed to represent segmental homoeologous regions. Owing to various evolutionary forces, segmental homoeology instead of whole chromosome homoeology appears to best describe the genome organization in hexaploid oat.

Aneuploidy↗
PubMed1981

Comparison of nuclear proteins of several human tumors and normal cells by two-dimensional gel electrophoresis.

Using isoelectric focusing and sodium dodecyl sulfate two-dimensional gel electrophoresis, 9 M urea-extractable nuclear proteins from four human tumor cells (HeLa, Namalwa, acute myelogenous leukemia, and lymphoma) and four normal human cells (IMR-90, WI-38, liver, and lymphocytes) were compared. Two protein spots, 140/7.7 and 54/6.6, were found in all four tumor cells but not in the four normal cells studied. Two protein spots, 56/6.7 and 56/6.9, were found in all four normal cells but not in any of the tumors studied. None of these proteins was common to those found in the earlier studies on rat tumors (H. Takami et al., Cancer Res., 39: 2096-2105, 1979).

Cell Nucleus↗
PubMed1980

Chronic herpes simplex infection in cutaneous T-cell lymphomas.

Therapeutically unresponsive erosive or ulcerative lesions caused by the herpes simplex virus developed in five patients with advanced cutaneous T-cell lymphoma. The chronic progressive character of the herpetic infection probably was the consequence of immunosuppression resulting from advanced lymphoma or its treatment. Herpes simplex infection should be considered in the differential diagnosis of cutaneous ulcerations in patients with cutaneous T-cell lymphomas.

Aged↗
PubMed1979

Characteristics of infection of B and T lymphocytes from mice after inoculation with cytomegalovirus.

Viremia was produced by inoculating intravenously BALB/c mice with murine cytomegalovirus. Virus was detected in plasma and granulocytes only during the first 8 days after infection. Lymphocyte-associated viremia, detectable by cocultivation on syngeneic or allogeneic fibroblasts, persisted for at least 4 weeks. Eight to 10 days after infection, sonicated lymphocytes had no demonstrable free virus. When whole lymphocytes with no demonstrable free virus were enclosed in a Millipore chamber and placed on a fibroblastic feeder layer, T cells produced free virus but B cells did not. Compared to normal calf serum, specific hyperimmune serum reduced B cell-associated infectious centers by 74% and T cell-associated infectious centers by only 38%. Normal mouse sera reduced by 36% and 30% infectious center production by B cells and T cells, respectively. Lymphocytes enriched with Fc receptor-positive cells produced significantly more infectious centers than receptor-negative cells.

Animals↗
PubMed1978

Isolation and characterization of a cytosol protein (64/7.2) present in large amounts in rapidly growing hepatomas.

Protein 64/7.2 (molecular weight/isoelectric point) is present in the cytosol of several hepatomas including the Novikoff hepatoma and Morris hepatomas 9618A, 7794A, and 3924A, but it is not present in liver or 18-hr regenerating liver. Quantitatively, its concentration was highest in Novikoff hepatoma (150 microgram/g tissue) and Morris hepatoma 3924A (550 microgram/g tissue), which are rapid-growing tumors, less in Morris hepatoma 7794A (72 microgram/g tissue), which is of intermediate growth rate, and least in the slow-growing Morris hepatoma 9618A (25 microgram/g tissue). Protein 64/7.2 was isolated from Novikoff hepatoma ascites cells in high purity as shown by its migration as a single band on one-dimensional acid-urea-polyacrylamide gels and a single spot on two-dimensional isoelectric focusing sodium dodecyl sulfate-polyacrylamide gels. Its amino acid composition has an acidic to basic amino acid ratio of 1.6. Its amino-terminal amino acid is lysine, and its carboxyl-terminal amino acid is glycine. Interestingly, the amino acid composition is strikingly similar to that of the phosphorylated Novikoff hepatoma chromatin Protein Cg', partially characterized in our laboratory.

Amino Acids↗
PubMed1978

Fiberoptic esophagogastroscopy, brushings, and biopsy in rabbits (Oryctolagus cuniculus).

The esophagus and stomach of rabbits were examined with a pediatric fiberoptic endoscope. The procedure involved general anesthesia and placement of an endotracheal airway followed by endoscopy. Photography, biopsies, and brushings for histology, cytology, and microbiological cultures were accomplished using this procedure. Rabbits were endoscoped and brushed repetitively on successive days without inducing esophagitis.

Animals↗
PubMed1977

Comparative studies on the '5'-cap' and in vitro translational activity of cytoplasmic and nuclear poly A(+) RNA1.

The translational activities of cytoplasmic poly A(+)RNA of normal rat liver and Novikoff hepatoma cells in the wheat germ cell free system were found to be approximately 15-20 times greater than tose of the corresponding nuclear poly A(+) RNA. The translationsl activities were 85 and 62 pmoles 3H-leucine incorporated/micron g cytoglasmic poly A(+) RNA for the liver and tumor respectively and 3-4 pmoles 3H-leucine incoporated/micron g nuclear poly A(+)RNA. Inasmuch as intergity of the '5'-cap' of mRNA is essential for its translational activity, quantitative comparisons were made of its content in these RNA fractions. Of the total 32P incorporated into the tumor cytoplasmic poly A(+) RNA, 0.41% was in the '5'-cap'; in nuclear poly A(+) RNA, the '5'-cap' contained 0.11%. After periodate oxidation and labeling with KB3H4, m7 guanosine, the 5'-terminal nucleoside in both liver and Novikoff hepatoma nuclear poly A(+) RNA contained approximately 20% as much isotope as in the cytoplasmic poly A(+) RNA. These results suggest the lower translational activity of nuclear poly A(+) RNA is partly related to its lower content of the '5'-cap'. Molecular selection of poly A(+) RNA for transport out of the nucleus or further cytoplasmic processing may account for the higher percentage of the '5-cap' and the greater translational activity of the cytoplasmic poly A(+) RNA. During these studies, it was also found that the m7 guanosine of the '5'-cap' was not removed during translation of the mRNA in the wheat germ system; this result suggests that the '5'-cap' may associate with allosteric binding sites of initiation factor(s).

Animals↗
PubMed1977

Evidence for coupled synthesis of mRNA for ribosomal proteins and rRNA.

Two-dimensional gel electrophoresis revealed quantitative differences in the 35S-methionine labeled proteins synthesized in vitro in the wheat germ system containing poly A(+) mRNA of normal liver, regenerating liver or Novikoff hepatoma cells. A group of low molecular weight proteins which comigrated with proteins of 40S ribosomal subunits were synthesized in a much greater concentration with the poly A(+) mRNA from the latter two sources. This correlates with increased synthesis of ribosomal proteins in regenerating liver or tumors which is temporally coupled with the increased nucleolar synthesis of rRNA precursors.

Animals↗
PubMed1977

Enhancement of murine cytomegalovirus infection during graft-vs.-host reaction.

A mouse model was used for elucidation of the role of a graft-vs-host reaction in promoting cytomegalovirus infection. F1 (DBA/2 X C3H/He) hybrid mice were infected with murine cytomegalovirus. Five weeks later, a graft-vs.-host reaction was produced in the chronically infected animals by the administration of multiple doses of DBA/2 parental splenocytes. Cytomegalovirus was recovered more often from the organs of mice undergoing graft-vs.-host reaction than from those of control animals (P less than 0.001). These results indicate that the graft-vs.-host reaction alone can enhance murine cytomegalovirus infection in a chronically infected host and may help explain the high incidence of cytomegalovirus infection after bone marrow allograft transplantation in man.

Animals↗
PubMed1976

Dimethylnitrosamine-demethylase: absence of increased enzyme catabolism and multiplicity of effector sites in repression. Hemoprotein involvement.

Evidence is presented that the previously observed decrease of the Vmax of hepatic microsomal demethylation of dimethylnitrosamine (DMN), following pretreatment of rats with 3-methylcholanthrene (MC), is not due to increase in the rate of breakdown but to decrease of de novo synthesis. Determinations of Vmax at time intervals in the transition from the high steady-state level induced by a carbohydrate-devoid casein diet, down to the low steady-state level of carbohydrate-containing basal diet, yielded two consecutive slopes; descent from the basal diet level to the lower steady-state level following pretreatment with MC yielded one slope. Plotting these slopes against the initial Vmax values gave a typical exponential curve (or straight line if the logs of slopes are used) indicating that the rate of enzyme decay in the MC-treated animals is not greater than that expected from normal enzyme catabolism. A multiplicity of effector sites appears to be involved in the repressor action of different structural types; for example, repression by MC (46.6%) and by phenobarbital (23.9%) in combination are approximately additive (62.0%), rather than competitive, indicating that the two agents act at different sites. A P-450 type cytochrome is involved in the demethylation of DMN. DMN-demethylase is inhibited by carbon monoxide, but the susceptibility to CO is far greater than that observed previously with 3,4-benzopyrene hydroxylation; inhibition of DMN-demethylase as a function of CO concentration follows typical enzyme kinetics. However, while both phenobarbital and MC powerfully repress the DMN-demethylase, we have confirmed that they are strong inducers of the synthesis of P-450 and P-448, respectively, as estimated from the difference spectra.

Animals↗
PubMed1976

Antigenically active nonhistone chromatin proteins in cancer cells.

Two-dimensional polyacrylamide gel electrophoresis shows that in nuclei of Novikoff hepatoma ascites cells there are approximately 75 proteins in the chromatin fraction soluble in 3 M NaCl:7 M urea. Dialysis of this fraction to an ionic strength of 0.15 produces a soluble fraction and a precipitate. The proteins in the soluble fraction have been reported to be active in gene control. Antibodies to the soluble fraction distribute diffusely throughout the nucleus, and antibodies to the precipitate localized primarily in the nucleolus and the nuclear ribonucleoprotein network. The nucleolar proteins differ from the extranucleolar proteins in antigenicity and labeling patterns. The development of methods for isolation, purification, and identification of nuclear proteins provided the opportunity for analysis of chromatin antigens in tumor cells. Utilizing two-dimensional preparative polyacrylamide gel techniques as well as conventional procedures, several nuclear proteins have been isolated in electrophoretically homogeneous states including protein A-24, a histone-like nonhistone protein; C-14, a protein that stimulates nucleolar RNA polymerase; and a chromatin antigen soluble in 3 M NaCl:7 M urea that remains soluble after dialysis to 0.15 M NaCl to precipitate the histones and the DNA. This antigen has been found in the chromatin of both the Novikoff hepatoma and the Walker 256 carcinosarcoma but not in the chromatin of either normal or regenerating liver. It is a nonhistone nuclear protein as indicated by its amino acid analysis in which the ratio of the number of acidic to basic amino acids is approximately 1.4. Further studies are in progress on the function and structure of this chromatin protein. As an approach to analysis of relative rates of synthesis of this antigen and otherproteins, the products of translation of messenger RNA of Novikoff hepatoma and normal liver are being analyzed by autoradiography of two-dimensional electrophoretic gels.

Animals↗
PubMed1975

Enhancement of mouse cytomegalovirus infection during host-versus-graft reaction.

C3H/He mice chronically infected with murine cytomegalovirus were given skin allografts from histoincompatible BALB/c donors. A significant increase in cytomegalovirus titers occurred within 3 days after placement of the graft in the spleens and kidneys of the allograft recipients as compared with control animals. No significant changes in virus titers were detected in the salivary gland, lung, liver, or blood of allograft recipients. These results indicate that the host-versus-graft reaction alone can enhance murine cytomegalovirus in a chronically infected host and may help explain the high incidence of cytomegalovirus infection seen after renal and other allograft transplantation in man.

Animals↗