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R Hancock

Publications and source records attributed to R Hancock.

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

Formation of hybrid nucleosomes cantaining new and old histones.

5 mM hydroxyurea (HU) inhibits DNA synthesis in mouse P815 cells by 94-97% in less than 1 hr. Nevertheless, histone synthesis continues and newly-synthesised histones are incorporated into non-replicating chromatin at a rate of about 20% of that in control exponentially-growing cells. To study the organization of these histones in chromatin P815 cells were treated with 5 mM HU in medium containing dense (15N, 13C, 2H) - substituted amino acids. After inhibition of DNA synthesis, newly-synthesised histones were labelled with (3H)-arginine. The cells were harvested 90 min later, and mono- and oligonucleosomes were prepared and analysed on metrizamide-triethanolamine (MA-TEA density gradients. Analysis of the distribution of 3H-labelled histones in these gradients shows that they are incorporated into hybrid mononucleosomes containing both new and old histones. It is also shown that these hybrid nucleosomes are not randomly distributed, but show a certain tendency to be clustered in certain chromatin regions.

Animals↗
PubMed1981

A highly sensitive technique for staining DNA and RNA in polyacrylamide gels using silver.

A technique is described for staining DNA in polyacrylamide gels with silver. It is rapid, requiring about 30 min for whole staining and development procedure, very simple and at least 20 times more sensitive than ethidium bromide for the staining of double-stranded DNA in polyacrylamide gels. This technique can also be applied for the staining of denatured, single-stranded DNA as well as RNA after their electrophoretic separation on polyacrylamide gels, having the same sensitivity as for double-stranded DNA fragments.

Bacteriophage lambda↗
PubMed1981

Characterisation of a chromatin fraction bearing pulse-labelled RNA. 1. Nascent RNA, RNA polymerase B and transcribed DNA sequence content.

We have further characterised a fraction of polynucleosomal chromatin from mouse cells which is enriched in transcribing regions, after separation by multistep partition in a dextran /poly(ethylene glycol) two-phase mixture [Faber, A. J. (1972) Methods Cell Biol. 16, 447--457]. This fraction contains an average of 16% of the total DNA and 63% of the 3-min pulse-labelled RNA in chromatin which, by a number of criteria, represents nascent RNA transcripts. Of the total transcribing RNA polymerase B molecules in chromatin, 52% are found in this fraction by titration with radioactive alpha-amanitin. About 28% of the single-copy DNA sequences in this fraction hybridise to nuclear polyadenylated RNA, compared with only 1.5% of the single-copy sequences in the remaining (nontranscribing) chromatin fraction.

Animals↗
PubMed1981

Characterisation of a chromatin fraction bearing pulse-labelled RNA. 2. Quantification of histones and high-mobility-group proteins.

The histone variants and high-mobility-group (HMG) proteins of a transcribing fraction of chromatin, described in the preceding paper of this journal, have been analysed qualitatively and quantitatively by a combination of one-dimensional and two-dimensional gel electrophoresis. The stoichiometry of the four core histones (all variants included) in this fraction is equimolar and is not detectably different from that in the nontranscribing fraction or in total chromatin. The molar ratio of histone H1 to the core histones is markedly lower, by approximately 72%, than that in the nontranscribing fraction. A minor histone variant identified as M1 (an H2A variant) is detected only in the transcribing fraction, while variant H3.1 is found only in the non-transcribing fraction. Proteins A24, HMG1 and HMG2 are essentially absent from the transcribing fraction; HMG14 is found uniquely in this fraction, while HMG17 occurs at a relatively lower level.

Animals↗
PubMed1980

Transpubic suspension of the bladder neck for urinary incontinence.

We present a modification of the classic Marshall-Marchetti-Krantz procedure in which only 1 pair of sutures is used. Each suture snugs the periurethral tissue of the anterior vaginal wall on each side to the posterior surface of the symphysis pubis and ipsilateral pubic bone by passing the suture through a hole drilled in each respective pubic bone. Complications have been temporary difficulty in voiding after the catheter has been removed and an occasional incisional hernia. Osteitis pubis has not been a problem possibly because of the use of wide-spectrum antibiotics.

Female↗
PubMed1978

Assembly of new nucleosomal histones and new DNA into chromatin.

The assembly of chromatin from newly synthesized nucleosomal histones (labeled with [3H]arginine) and new DNA (density-labeled with [125I]iododeoxyuridine)was studied in growing cultured mouse cells. The nucleosomal histones were specifically examined by dissociating histone H1 and nonhistone proteins from unsheared chromatin either by incubation in 0.6 M NaCl or by digestion with micrococcal nuclease to release nucleosomes. In both cases, the four nucleosomal histones (H2A, H2B, H3, and H4) are essentially the only proteins that remain bound to DNA and that are labeled by [3H]arginine. After formaldehyde fixation, H1-depleted chromatin containing dense DNA can be completely resolved in CsCl buoyant density gradients from that containing unreplicated DNA; separation of nucleosomes is satisfactory although less complete. New DNA and new histones are already assembled into chromatin possessing characteristic nucleosomal structure after 3 min of synthesis (the shortest time studied), as shown by the kinetics of digestion of new DNA by micrococcal nuclease, by the distribution of new DNA and new histones in nucleosomes. However, after 3-30 min of synthesis most new nucleosomal histones are associated with unreplicated DNA rather than with new DNA. It is concluded that new nucleosomes are assembled on DNA at some distance from DNA replication sites, with concomitant migration of preexisting nucleosomes onto new DNA.

Cell Line↗
PubMed1976

Biochemical and electron-microscopic evidence that the subunit structure of Chinese-hamster-ovary interphase chromatin is conserved in mitotic chromosomes.

Biochemical and electron microscopic studies demonstrate that the subunit structure of Chinese hamster ovary cell interphase chromatin is conserved in mititic chromosomes. Digestion of purified chromosomes or nuclei with micrococcal nuclease produces DNA in discrete size classes, as visualized by polyacrylamide gel electrophoresis, which are common to the two materials. Early in digestion the DNA fragments are integral multiples of a monomer approximately 177 base pairs in length, whereas after extensive digestion the remaining DNA fragments migrate ahead of the monomer position. The size of the repeating DNA unit was confirmed as being smaller than that produced by micrococcal nuclease digestion of rat liver nuclei by direct comparison. Electron microscopy of partially unravelled chromosomes at low ionic strength shows tightly packed spheres (nucleosomes) approximately 12 nm in diameter which are often arranged as linear chains. Chromosomal material prepared for electron microscopy after varying extents of micrococcal nuclease digestion is composed of fragments containing pregressively fewer nucleosomes, which parallels the loss of high DNA multimer bands in gel electrophoresis. Material unravelled from chromosomes in the presence of NaCl consists of nucleosomes packed packed in a different configuration which suggests the origin of higher order structures in chromosomes.

Cell Line↗
PubMed1975

Enteric-coated L-dopa (prodopa). A new approach to L-dopa therapy in Parkinson's disease.

Seventeen patients treated for a mean period of 9-4 months with an enteric-coated form of L-dopa (Prodopa), obtained the usual spectrum of benefit as from conventional L-dopa. There was a significant dose-sparing effect with the use of the enteric-coated prepartion of the order of 40% to 50%, whilst reducing gastrointestinal side effects to a minimum, at the same time as achieving optimal clinicl benefit. Enteric-coated L-dopa appears to be a useful and welcome addition to the therapeutic armamentarium for Parkinson's disease.

Female↗