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Biomedical subjects

G Milanesi

Publications and source records attributed to G Milanesi.

At least 73 records · Page 4Linked to original sources
PubMed1981

Analysis of BK virus-transformed cells and BK virus-induced tumors by DNA-DNA reassociation kinetics.

BK virus (BKV)-transformed cells and BKV-induced tumors as well as in vitro derived tumor cell lines were all found to contain BKV DNA sequences when analysed by DNA-DNA reassociation kinetics. In transformed cells the number of viral genome equivalents per diploid cell genome (CG divided by VG) decreased with increasing generations. Likewise, single cell clones had a lower CG divided by VG than parental transformed cells. BKV-induced tumors had a high CG divided by VG. Tumor cells cultivated in vitro and their clones had a lower CG divided by VG than BKV-induced tumors from which they were derived, suggesting a multiclonal origin of tumors. Hamster tumors induced by subcutaneous inoculation of BKV-transformed cells or tumor cell lines had a higher CG divided by VG than cells producing them. Variation in CG divided by VG is discussed in terms of cell selection depending on different in vitro or in vivo conditions of cell growth. In some cases, however, the decrease in CG divided by VG most likely depends on loss on free viral sequences from transformed cells or tumors.

Animals↗
PubMed1981

Lack of association between BK virus and ependymomas, malignant tumors of pancreatic islets, osteosarcomas and other human tumors.

BK virus (BKV) DNA sequences were not detected in 142 human tumors analyzed by DNA-DNA reassociation kinetics and blot hybridization. The investigation was focused mainly on those rare types of human tumors (ependymomas, choroid plexus papillomas, tumors of pancreatic islets and osteosarcomas) that are induced with highest frequency by BKV in experimental animals. In addition, other tumors of the urinary apparatus and of the central nervous system were analyzed. BKV tumor (T) antigen was not detected in neoplastic tissues, and BKV T antibodies were not found in sera and cerebrospinal fluids from patients with neoplasms. Sequences homologous to BKV DNA were found in normal tissue from a kidney carrying a carcinoma. The neoplastic tissue from the same organ, however, had no sequences homologous to BKV DNA. Such DNA does not belong to BKV but probably to another papovavirus related to BKV.

Antibodies, Viral↗
PubMed1980

Integrated and free viral DNA in hamster tumors induced by BK virus.

BK virus (BKV)-induced tumors in hamsters were investigated for the presence of viral DNA by the blot-transfer hybridization technique. Several viral genomes per cell were found in tumor tissues and in their derived cell lines and clones. Most of the detected viral genomes were integrated into the cellular DNA, but some tumors also contained free viral DNA sequences. Integration patterns were different from each other, and many different integration sites were available on the cellular or on the viral DNA or on both. Typical features of integration patterns were found in ependymomas, which were the most frequent (72%) among BKV-induced tumors. Readily detectable viral DNA sequences were only found in neoplastic tissues, but traces of BKV DNA were also present in the apparently normal portion of the brain of an animal that had developed an ependymoma and in the brain (but not in the liver) of another animal 15 days after virus inoculation. A cell line and a single-cell clone derived from a tumor had hybridization patterns considerably simpler that the pattern of the original tumor, lacking several integrated viral genomes and all free viral sequences.

Adenoma, Islet Cell↗
PubMed1979

Transcription of nucleosomal DNA in SV40 minichromosomes by eukaryotic and prokaryotic RNA polymerases.

SV 40 minichromosomes can be transcribed by prokaryotic and eukaryotic RNA polymerases. Size analysis of transcripts indicated that DNA in nucleosomes was accessible for transcription by both enzymes. Sedimentation of the transcription complex showed that minichromosomes which were being transcribed had a full complement of nucleosomes. Strand selection by E. coli RNA polymerase was reduced by the presence of nucleosomes. No region of SV 40 DNA was preferentially transcribed on minichromosomes by either enzyme.

Animals↗
PubMed1978

Minichromosome from BK virus as a template for transcription in vitro.

BK virus DNA can be extracted from virions as a nucleoprotein complex containing about 20 nucleosomes. Transcription of this "minichromosome" with Escherichia coli RNA polymerase indicates that both initiation and elongation of RNA chains are reduced by the presence of nucleosomes. Hybridization analysis of RNA made on the complex shows preferential transcription of one region of BK virus genome. No increase in strand selection is observed with respect to transcription of purified superhelical BK virus DNA.

BK Virus↗
PubMed1978

Restriction fragment analysis of bacteriophage SPP1 in vitro transcription by host RNA polymerase.

In vitro transcription of SPP1 DNA occurred on only one of the two strands, the same which is predominantly transcribed in SPP1-infected cells. Transcripts were distributed in several size classes. Analysis of elongation kinetics and of size distribution, coupled with hybridization to DNA restriction fragments, showed that some regions of the template have more initiation sites than others; some have none. Some regions were transcribed directly, some were transcribed from initiation sites located in other regions, and one was never transcribed. Several transcription initiation sites on SPP1 DNA are located on EcoRI fragment 1; four to five others are distributed among other fragments. Cutting the DNA with EcoRI did not introduce artifactual initiation sites. In vitro transcription units can be localized and oriented with respect to the EcoRI restriction map of SPP1 DNA.

Bacillus subtilis↗
PubMed1974

Template specificity of transcription during sporulation of Bacillus subtilis.

Partially purified extracts from sporulating Bacillussubtilis cultures transcribed different natural DNAs with different efficiencies. This template specificity results in an increased or a decreased synthetic activity with respect to extracts from vegetative cells, depending on the template used. With SPP1 DNA a decrease in activity occurs, whereas with T7 DNA an increased activity was observed, which is due to a higher efficiency of initiation. This is not an intrinsic property of RNA polymerase, but is due to some fraction(s) which can be separated from the enzyme. Together with invivo experiments on transcription and SPP1 phage production during sporulation, these results suggest a possible role of promoter recognition in sporulation.

Bacillus Phages↗
PubMed1972

Transcription after bacteriophage SPP1 infection in Bacillus subtilis.

The role of the host polymerase in Bacillus subtilis infected with phage SPP1 was studied in vivo with regard to production of phage-specific and host-specific ribonucleic acid (RNA) and to phage yield. Evidence is presented that the subunit(s) of B. subtilis RNA polymerase which is sensitive to rifampin and streptolydigin is necessary at all times during infection for phage production. The synthesis of phage RNA and the phage yield in strains resistant to either antibiotic were unaffected by the drug. Host RNA synthesis continued throughout infection; phage-specific RNA never accounted for more than 20% of pulse-labeled RNA at any time during infection.

Anti-Bacterial Agents↗
PubMed1970

Transcriptions of the bacteriophage T4 template in vitro: separation of "delayed early" from "immediate early" transcription.

The synthesis of different early T4 transcripts by E. coli RNA polymerase in vitro can be dissociated in two ways: (1) when T4 DNA is mechanically degraded, it selectively loses the ability to serve as a template for the transcription of delayed early T4 RNA; (2) when initiation of RNA synthesis on intact T4 DNA is limited to a very short time interval immediate early T4 RNA is synthesized at once but delayed early polynucleotide sequences appear only after a time lag. We conclude that initiation sites for T4 early RNA synthesis are closer to immediate early than to delayed early segments of the T4 template and that immediate early and delayed early segments of the T4 chromosome are interspersed. We propose that this interspersing is significant for the programming of transcription during T4 development.

Centrifugation, Density Gradient↗