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Biomedical subjects

M Kress

Publications and source records attributed to M Kress.

101 records · Page 6Linked to original sources
PubMed1979

The influence of fluoro-phenyl-alanine on the synthesis of simian virus 40 DNA and T antigens.

Treatment of Simian Virus 40 (SV40) infected monkey cells with fluorophenylalanine (FPA) resulted in increased uptake of thymidine by the cells, and progressive inhibition of both viral and cellular DNA synthesis. Viral DNA synthesis was more sensitive to inhibition by FPA than cell DNA synthesis. Synthesis of SV40 T antigens was however unaffected by FPA, as judged from immunofluorescence assays. The M.W. of the major polypetides immunoprecipitated from cell extracts by antibodies from tumor bearing hamster sera was similarly unaffected. It is suggested that T antigen synthesized in the presence of FPA is non functional.

Animals↗
PubMed1979

Simian virus 40-transformed cells express new species of proteins precipitable by anti-simian virus 40 tumor serum.

In addition to the virus-coded large-T and small-t antigens, two new classes of proteins were immunoprecipitated by anti-simian virus 40 (SV40) tumor serum from extracts of various SV40-transformed cell lines. These were as follows: (i) proteins (termed "super-T proteins") with an Mr higher than that of large-T antigen (86,000), which were found in many SV40-transformed cell lines derived from mouse and rat cells (super-T proteins and large-T antigen appeared to have closely related structures as judged by the Chromobead elution patterns of their methionine-labeled tryptic peptides); (ii) proteins (termed "55K proteins") with an Mr ranging from 50,000 to 60,000, which were present in all SV40-transformed cell lines examined so far, including those obtained by chromosome-mediated gene transfer. The 55K proteins were not structurally related to large-T antigens, as judged by the Chromobead elution patterns of their methionine-labeled tryptic peptides. Our data are compatible with the assumption that the 55K proteins are largely or totally cell coded.

Animals↗
PubMed1979

Human cytomegalovirus-induced immediate early antigens: analysis in sodium dodecyl sulfate-polyacrylamide gel electrophoresis after immunoprecipitation.

Immediate early antigen (IEA) induced in human lung fibroblasts by human cytomegalovirus was characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis after immunoprecipitation with IEA-positive human sera. Two polypeptides of 76,000 daltons (76K) and 82K were detectable within 90 min after infection. Polypeptides of similar molecular weight were also found in immunoprecipitates of human cytomegalovirus-infected cells nonpermissive for virus replication. IEA is located within the nucleus, although some of the 76K material appears to be located on the outer nuclear membrane. Raising salt concentrations in the extraction buffer increased antigen extraction. The contribution of these IEA polypeptides to IEA nuclear fluorescent staining is discussed.

Animals↗
PubMed1978

Viable deletion mutants in the simian virus 40 early region.

For the purpose of isolating hr-t-like mutants of simian virus 40, we have constructed variants that have lost the unique site for the restriction enzyme Taq I at 0.565. Five mutants have been isolated and characterized by restriction enzyme analysis. All of them produce a normal size T antigen. Four produce a t antigen reduced in size as well as in amount; the fifth one does not seem to make any t antigen at all. The ability of these mutants to transform mouse cells in vitro, as tested by anchorage dependence, is clearly altered; however, the defect is only partial. In the same test, the mutants can complement a tsA mutant for transformation and therefore define a second complementation group in the simian virus 40 early region.

Antigens, Viral↗
PubMed1978

Characterization of two SV40 early mRNAs and evidence for a nuclear "prespliced" RNA species.

Using in vitro translation of sucrose-gradient fractionated cytoplasmic mRNA from SV40-infected cells, we have shown that a deletion in the region mapping between 0.54--0.59 reduced the size of mRNA for small-t but not the size of mRNA for large-T. Mutants with a deletion in this region were shown to produce in vivo either shortened small-t or no small-t, and normal large-T. Similarly, in vitro translation of poly(A)+cytoplasmic RNA from cells infected with these mutants gave the same results. On the other hand in vitro translation of poly(A)+nuclear RNA from the mutants which made no small-t produced a small-t derivative possibly synthesized from a prespliced RNA species. We have also shown that poly(A)+nuclear RNA from mutant dl 2122 produced two small-t related proteins: one of these (MW: 11K) probably represents the product of a "prespliced" RNA, the other (MW: 17K) which is also found in the cytoplasm represents the product of the mutant specific small-t mRNA.

Antigens, Neoplasm↗
PubMed1975

[Induction, by 5-bromo-2'-deoxyuridine, of a "foamy" virus previously undetected in hamster cells transformed by SV40].

TSV5 clone 2 cells in normal conditions of culture contain only an expressed RNA virus (R-type virus). However, exposure of the cells to 5-bromo-2'-deoxyuridine with dexamethasone, induced synthesis of a syncitium-forming ("Foamy") virus. In other hamster cell lines, the same treatment fails to induce a "foamy" virus. The origin of this "foamy" virus is discussed.

Bromodeoxyuridine↗
PubMed1975

Reverse transciptase activity associated with R-type virus-like particles of SV40-transformed hamster cells (TSV5 clone 2).

A line of hamster cells transformed by SV40 (TSV5 clone 2) contains different DNA polymerase activities. One of them has the same template specificity as viral reverse transcriptases. Partial isolation of R-type virus-like particles from TSV5 clone 2 shows that a reverse transcriptase activity is associated with these RNA viruses. This reverse transcriptase was partially purified and its biochemical properties are described.

Animals↗
PubMed1975

[Medial or lateral placement of the graft in myringoplasty comparative studies of both operation techniques using electronic data processing (author's transl)].

After medial placement of the graft in myringoplasty the remaining air-bone gap within the speech range is on an average approximately 10,- dB. This remaining air-bone gap is, according to secured statistics, on an average approximately 10 dB lower than in a lateral placement of the graft. The bone conduction does usually not change in either operation method. The additional support of meatal skin graft on the underlayed fascia does not have any influence on the audiologic finding. The percentage of the reperforations is in type I with a rate of 18% rather high; both operation methods do not significantly differ.

Audiometry↗
PubMedDate not supplied

Alternative RNA splicing in expression of the H-2K gene.

A major role of the classical transplantation antigens (designated class I antigens) is the presentation of virus-infected cells to cytotoxic T cells, a process that leads to the destruction of the cell displaying the viral antigen. Consistent with this function is the finding that these transplantation antigens (encoded by the H-2K, H-2D and H-2L genes in mice) are cell-surface glycoproteins with their amino-termini protruding extracellularly and their carboxy-termini located inside the cell. While the external domain is expected to provide biological specificity required for the associative presentation of viral antigens, the role of the cytoplasmic domain remains obscure. The recent observation that this latter region of the molecule is encoded by three separate DNA exons has suggested a complex role for this portion of the polypeptide chain. We have now obtained evidence for the use of alternative acceptor splice sites in the H-2K gene, resulting in two RNA transcripts that would encode H-2K antigens differing in their carboxy-termini. This is the first demonstration of the use of alternative splice acceptor sites in the same class I gene, and indicates the existence of different functional subsets of antigens encoded by the same gene.

Animals↗