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Biomedical subjects

P Collis

Publications and source records attributed to P Collis.

13 recordsLinked to original sources
PubMed1995

Rapid changes in human immunodeficiency virus type 1 RNA load and appearance of drug-resistant virus populations in persons treated with lamivudine (3TC).

The effect of the appearance of drug-resistant human immunodeficiency virus type 1 (HIV-1) on viral RNA load was studied in patients treated with the reverse transcriptase inhibitor lamivudine. During the first 12 weeks of treatment, HIV-1 RNA concentrations and amino acid changes in codon 184, causing high-level resistance to lamivudine, were determined in longitudinal serum samples from HIV-1 p24 antigen-positive and -negative patients. A marked decline in the amount of HIV-1 RNA (approximately 95% below baseline) and HIV-1 p24 antigen was observed within 2 weeks, followed by a rise that coincided with the appearance of lamivudine-resistant viruses in serum (isoleucine mutants initially, which were subsequently replaced by valine variants). After 12 weeks, a partial antiviral effect was observed despite the presence of a complete codon 184 mutant virus population in serum. This study shows that the rapid appearance of drug-resistant virus in serum is followed by an increase in viral RNA load.

CD4 Lymphocyte Count↗
PubMed1990

DNaseI hypersensitive sites 1, 2 and 3 of the human beta-globin dominant control region direct position-independent expression.

The human beta-globin dominant control region (DCR) which flanks the multigene beta-globin locus directs high level, site of integration independent, copy number dependent expression on a linked human beta-globin gene in transgenic mice and stably transfected mouse erythroleukemia (MEL) cells. We have assayed each of the individual DNaseI hypersensitive regions present in the full 15kb DCR for position independence and copy number dependence of a linked beta-globin gene in transgenic mice. The results show that at least three of the individual DNaseI hypersensitive site regions (sites 1, 2 and 3), though expressing at lower levels than the full DCR, are capable of position independent, copy number dependent expression. Site 2 alone directs the highest level of expression of the single site constructs, producing nearly 70% of the level of the full DCR. Sites 1 and 3 each provide 30% of the full activity. Deletion of either site 2 or 3 from the complete set significantly reduces the level of expression, but does not effect position independence or copy number dependence. This demonstrates that sites 2 and 3 are required for full expression and suggests that all the sites are required for the full expression of even a single gene from this multigene locus.

Animals↗
PubMed1990

Definition of the minimal requirements within the human beta-globin gene and the dominant control region for high level expression.

The human beta-globin dominant control region (DCR) was previously identified as a region from the 5' end of the human beta-globin locus which directs high level, site of integration-independent, copy number-dependent expression on a linked human beta-globin gene in transgenic mice and stably transfected mouse erythroleukaemia (MEL) cells. We have now analysed the elements comprising the DCR by systematic deletion mutagenesis in stable MEL transfectants. We have identified two independent elements within the DNase I hypersensitive sites 2 and 3, containing fragments which direct strong transcriptional inducibility of a beta-globin gene. Whilst the remaining two hypersensitive sites do not direct significant transcriptional induction, our data suggest that all four sites may be necessary for the fully regulated expression conferred by the DCR. We have also tested a number of beta-globin minigene constructs under the control of the DCR to assess if any of the local sequences from the gene may be removed without loss of expression. We find that the 3' enhancer may be removed without affecting expression, but there is an absolute requirement for the presence of the second intron, not related to the enhancer present in that intron.

Animals↗
PubMed1989

A dominant control region from the human beta-globin locus conferring integration site-independent gene expression.

The regulatory elements that determine the expression pattern of a number of eukaryotic genes expressed specifically in certain tissues have been defined and studied in detail. In general, however, the expression conferred by these elements on genes reintroduced into the genomes of cell lines and transgenic animals has turned out to be at a low level relative to that of endogenous genes, and influenced by the chromosomal site of insertion of the exogenous construct. We have previously shown that if regions flanking the human beta-globin locus are introduced into the mouse genome along with the human beta-globin gene, a level of expression comparable to that of endogenous genes can be achieved that is also independent of integration site. We have now defined a dominant control region with these properties consisting of 6.5 kilobases of DNA encompassing erythroid cell-specific DNase I hypersensitive sites. The identification of such dominant control regions could have important applications in somatic gene therapy.

Animals↗
PubMed1988

In situ hybridisation and S1 mapping show that the presence of infiltrating plasma cells is associated with poor prognosis in breast cancer.

In order to identify potential markers of prognosis in breast cancer, representative cDNA libraries were constructed using RNA isolated from primary breast tumour tissue associated with good and poor prognosis. Cross-screening of these libraries repeatedly identified cloned mRNA species associated with the immune system, in particular B-cells, in libraries derived from tumours of poor prognosis. We have used one of these a kappa IV light chain cDNA probe, in two complementary studies to investigate the relationship between immunoglobin gene expression and prognosis. The results obtained using a combination of S1 mapping, RNA blotting and in situ hybridisation demonstrate that the presence of plasma cells, as defined by infiltrating cells which express high levels of immunoglobulin kappa-chain mRNA, is associated with a poor prognosis.

Adult↗
PubMed1988

Adeno-associated virus general transduction vectors: analysis of proviral structures.

We used two kinds of adeno-associated virus (AAV) vectors to transduce the neomycin resistance gene into human cells. The first of these (dl52-91) retains the AAV rep genes; the second (dl3-94) retains only the AAV terminal repeats and the AAV polyadenylation signal (428 base pairs). Both vectors could be packaged into AAV virions and produced proviral structures that were essentially the same. Thus, the AAV sequences that are required in cis for packaging (pac), integration (int), rescue (res), and replication (ori) of viral DNA are located within a 284-base-pair sequence that includes the terminal repeat. Most of the G418r cell lines (73%) contained proviruses which could be rescued (Res+) when the cells were superinfected with the appropriate helper viruses. Some produced high yields of viral DNA; other rescued at a 50-fold lower level. Most of the lines that were Res+ (79%) contained a tandem repeat of the AAV genome (2 to 20 copies) which was integrated randomly with respect to cellular DNA. Junctions between two consecutive AAV copies in a tandem array contained either one or two copies of the AAV terminal palindrome. Junctions between AAV and cellular sequences occurred predominantly at or within the AAV terminal repeat, but in some cases at internal AAV sequences. Two lines were seen that contained free episomal copies of AAV DNA. Res+ clones contained deleted proviruses or tandem repeats of a deleted genome. Occasionally, flanking cellular DNA was also amplified. There was no superinfection inhibition of AAV DNA integration. Our results suggest that AAV sequences are amplified by DNA replication either before or after integration and that the mechanism of replication is different from the one used during AAV lytic infections. In addition, we have described a new AAV general transduction vector, dl3-94, which provides the maximum amount of room for insertion of foreign DNA and integrates at a high frequency (80%).

Cell Line↗
PubMed1986

The prevalence of locomotor disability and handicap in the Cape Peninsula. Part I. The coloured population of Bishop Lavis.

A door-to-door survey to identify the locomotor disabled was carried out on 33.35% of the so-called coloured population in a low socio-economic area of the Cape Peninsula (9112 people). The prevalence rate of locomotor disability was 11.2/1000. The main causes of disability were illness (44.1%) and trauma (41.2%); the former resulted mostly from cerebrovascular accidents (15.7%) and poliomyelitis (15.7%). Of the disabled persons 11.8% were 15 years of age or less, 57.8% between the ages of 16 and 59 years and 30.4% were more than 60 years. Of those in the working-age group 15% were employed. Few of the unemployed had hobbies or interests or had any contact with health or social services.

Activities of Daily Living↗
PubMed1986

The prevalence of locomotor disability and handicap in the Cape Peninsula. Part II. The black population of Nyanga.

A door-to-door survey to identify the locomotor-disabled was carried out on 8.5% of the population of a black residential area of the Cape Peninsula (2072 people). The prevalence rate of locomotor disability was 18.3/1000; causes of disability related to illness (36.8%), trauma (31.6%) and congenital factors (23.7%). The main illnesses described were cerebrovascular accidents (26.1%) and poliomyelitis (21.7%). Persons aged 15 years or less constituted 18,4% of the disabled, while 42.1% were aged 16-59 years and 39.5% 60 years or more. Although many of the disabled individuals identified could move about independently, the proportion bedridden was high (15.8%). At the time of the survey 13.3% of adults were working and 51.1% of children over 6 years old attended school. Eighty per cent had no contact with health services.

Activities of Daily Living↗
PubMed1986

The prevalence of locomotor disability and handicap in the Cape Peninsula. Part III. The white population of Fish Hoek.

A door-to-door survey to identify the locomotor-disabled was carried out on 24.2% of the population living in a white middle-class residential area of the Cape Peninsula (2391 people). This coastal resort is a popular place for retirement and has a large elderly population (23.3%). The prevalence rate of locomotor disability was 13/1000. Illness caused 74.2% of the disability, and in 34.5% of cases this was identified as arthritis. Most of the disabled were aged 60 years or more (77.4%), while 22.6% were 16-59 years old. Fifty per cent of those in the working-age group were employed; one-third competed in the open labour market and the rest were in sheltered employment. Few people were in contact with health, geriatric or social services.

Activities of Daily Living↗
PubMed1983

Characterization of am404, an amber mutation in the simian virus 40 T antigen gene.

We analyzed the biological activity of an amber mutation, am404, at map position 0.27 in the T antigen gene of simian virus 40. Immunoprecipitation of extracts from am404-infected cells demonstrated the presence of an amber protein fragment (am T antigen) of the expected molecular weight (67,000). Differential immunoprecipitation with monoclonal antibody demonstrated that am T antigen was missing the carboxy-terminal antigenic determinants. The amber mutant was shown to be defective for most of the functions associated with wild-type T antigen. The mutant did not replicate autonomously, but this defect could be complemented by a helper virus (D. R. Rawlins and N. Muzyczka, J. Virol. 36:611-616, 1980). The mutant failed to transform nonpermissive rodent cells and did not relieve the host range restriction of adenovirus 2 in monkey cells. However, stimulation of host cell DNA, whose functional region domain has been mapped within that portion of the protein synthesized by the mutant, could be demonstrated in am404-infected cells. A number of unexpected observations were made. First, the am T antigen was produced in unusually large amounts in a simian virus 40-transformed monkey cell line (COS-1), but overproduction was not seen in nontransformed monkey cells regardless of whether or not a helper virus was present. This feature of the mutant was presumably the result of the inability of am T antigen to autoregulate, the level of wild-type T antigen in COS-1 cells, and the unusually short half-life of am T antigen in vivo. Pulse-chase experiments indicated that am T antigen had an intracellular half-life of approximately 10 min. In addition, although the am T antigen retained the major phosphorylation site found in simian virus 40 T antigen, it was not phosphorylated. Thus, phosphorylation of simian virus 40 T antigen is not required for the stimulation of host cell DNA synthesis. Finally, fusion of am404-infected monkey cells with Escherichia coli protoplasts containing appropriate procaryotic suppressor tRNAs showed that am404 is a suppressible nonsense mutation.

Animals↗