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Biomedical subjects

A Morley

Publications and source records attributed to A Morley.

At least 37 records · Page 2Linked to original sources
PubMed1994

A comparison of Southern blot and polymerase chain reaction as techniques to identify loss of DNA heterozygosity in colorectal cancer.

Alterations in the tumour suppressor gene p53 have been found in a wide variety of tumours. The variable number tandem repeat present at the YNZ22 locus is a highly polymorphic marker closely linked to the p53 gene. Examination for loss of heterozygosity at the YNZ22 locus has been carried out by Southern blot or polymerase chain reaction (PCR). A comparison of these techniques shows a 100% concordance rate in normal tissue but a 90.9% rate in tumour tissue. Both false positive and false negative results were obtained. This must be considered in the interpretation of studies using PCR for this purpose.

Alleles↗
PubMed1994

The influence of age of template DNA derived from archival tissue on the outcome of the polymerase chain reaction.

The analysis of DNA from archival tumour tissue for molecular alterations has been facilitated by the use of the polymerase chain reaction (PCR). Degradation of tissue prior to fixation and the nature of the fixative used influence successful amplification from archival tissue. Age of the archival tissue may also be a factor. To determine if this was so, DNA was extracted from 30 archival specimens of spleen spanning a 15 year period. Polymerase chain reaction was performed on all specimens using primers for exon 2 (307 bp) and exon 9 (1278 bp) of the hypoxanthine phosphoribosyl transferase (HPRT) gene. It was not possible to show that the age of archival tissue had an influence on the capacity to amplify exon 2 of the HPRT gene. It was not possible to amplify exon 9 of the HPRT gene from archival tissue.

DNA, Neoplasm↗
PubMed1993

Classification of mutations at the HLA-A locus by use of the polymerase chain reaction.

We investigated whether the polymerase chain reaction (PCR) could be used to determine the mechanism of mutation in lymphocyte clones mutated at the HLA-A locus. Three polymorphisms, at Factor XIIIA, D6S109, and intron 3 of the HLA-A gene, were used to study a series of clones previously characterised by Southern blotting (SB) at multiple loci on chromosome 6. For detection of loss of heterozygosity, the results of PCR and SB were concordant in 140 of 141 clones when polymorphism in the Factor XIIIA region was studied and in 144 of 145 clones when polymorphism in the HLA-A gene was studied. For classification of the mechanism of mutation, PCR and SB gave the same result in 88 of 92 clones (96%) when a combination of the HLA-A and Factor XIIIA polymorphisms was used and in 46 of 47 clones (98%) when a combination of the HLA-A and D6S109 polymorphisms was used. The results indicate that PCR provides a simple and reliable method for categorising mutations at the HLA-A locus as arising from mitotic recombination, deletion, or from presumptive minor changes within the gene. Rare events such as gene conversion, nondisjunction, or large deletions extending to the telomere will be misclassified. However, such events are rare for mutations at this locus.

Base Sequence↗
PubMed1993

Using mitotic recombinant mutant clonal lymphocytes for physical mapping of polymorphic loci on the short arm of human chromosome 6.

Immunoselection has been used to identify human lymphocytes that have undergone spontaneous mutation resulting in the loss of expression of one of the codominant HLA-A alleles. Approximately 35% of such mutations are the consequence of mitotic recombination events. Mitotic recombination is the result of nonsister chromatid exchange that leaves the mutated cell homozygous for all loci distal to the crossover point. The location of the crossover has been regionalized for 99 independently derived mutant lymphocyte clones by identification of their loss or retention of heterozygosity at seven reference polymorphic loci on chromosome 6. If a polymorphic locus of unknown map position is studied in clones from this ordered set of mitotic recombinants, and clones that display loss of heterozygosity and retention of heterozygosity of the locus are observed, then the map position of the locus is between the appropriate reference loci of the ordered set. The newly mapped locus becomes a reference locus in turn. In this way the mitotic recombinant mutant clones can be used to generate an ordered set of crossover points with a theoretical resolution limited only by the number of mutants generated. In this paper such a set of mutants is used to refine or confirm the map position of eight polymorphic loci on chromosome 6.

Chromosome Mapping↗
PubMed1992

Improved PCR method for detecting monoclonal immunoglobulin heavy chain rearrangement in B cell neoplasms.

AIMS: To develop a simple, optimised, polymerase chain reaction (PCR) based method for detecting the rearranged immunoglobulin heavy chain (IgH). METHODS: Using as primers oligonucleotides (Fr2A, Fr2B) homologous to the conserved sequences to the framework II region and the joining (JH) region, 25 patients with B cell lymphoproliferative disorders, previously characterised by Southern blotting, and three patients with light chain myeloma were studied. RESULTS: The PCR product from a polyclonal B cell population showed a broad band when analysed on a 3% agarose gel; DNA from B cell lines and B lymphoproliferative disorders showed a discrete band. Specificity of the amplification was confirmed by cloning and sequencing the amplified product as well as by Southern blotting with an internal probe homologous to the framework 3 region. Primers Fr2A and Fr2B detected monoclonality in three patients with light chain myeloma, while primers directed against the FrIII region showed a polyclonal response. CONCLUSIONS: Deletions and extensive somatic mutations within the FrIII region may give false negative results with primers homologous to the region. A PCR using the method described, with a repertoire of primers homologous to the FrII and FrIII regions, will therefore increase the frequency of detection of monoclonality.

Aged↗
PubMed1990

Micronuclei in cytokinesis-blocked lymphocytes of cancer patients following fractionated partial-body radiotherapy.

We applied the cytokinesis-block micronucleus assay to measure chromosome damage in lymphocytes of 11 cancer patients undergoing fractionated partial-body irradiation. Measurements performed before, during and after cessation of radiotherapy showed a dose-related increase in micronucleus frequency in each of the patients studied. When the results for micronucleus frequency (Y) were plotted against the estimated equivalent whole-body dose (X) the dose-response relationship obtained was Y = 75.8X + 49.5 (r = 0.783, P less than 0.0001). A general decline in MN frequency was observed during the post-treatment period down to 57 per cent (+/- 10) after 12 months but there was considerable variation between individuals. The advantages and disadvantages of the application of the cytokinesis-block micronucleus assay as a biological dosimeter for lymphocytes irradiated in vivo are discussed.

Adult↗
PubMed1986

RCH-ACV: a lymphoblastic leukemia cell line with chromosome translocation 1;19 and trisomy 8.

A cell line (RCH-ACV) was established from a bone marrow sample of a child with acute lymphoblastic leukemia (ALL). The cell line lacked Epstein-Barr virus nuclear antigen and exhibited a recently described nonrandom chromosome translocation, 1;19, thought to be associated with pre-B-ALL and poor prognosis. Banding studies confirm that the breakpoint of chromosome #19 occurs at p13.3. Cell surface marker analysis using a panel of monoclonal antibodies revealed markers consistent with common ALL phenotype. Although the cells did not show cytoplasmic immunoglobulin, studies of the immunoglobulin gene rearrangement confirmed the pre-B phenotype. This cell line could be of great value to studies of the role of the specific translocation 1;19 in the etiology of pre-B-ALL.

Cell Line↗
PubMed1986

Preservation of islet function and morphology after transplantation into high dose streptozotocin-diabetic rats.

Rats made diabetic with 0.15 g/kg streptozotocin showed a complete absence of islet B cells in their pancreases, even after 3-6 months of normoglycaemia. Glucagon- and somatostatin-containing cells were preserved. In these animals transplantation of 5,000 cultured fetal islets was required to restore normal blood glucose and intermediary metabolite profiles after a meal challenge, while 2,000 islets resulted in a marked metabolic disturbance. The larger number of islets produced comparable effects whether transplanted under the kidney capsule or into the splenic pulp. In either site, however, considerable proliferation of adipose tissue was found by 3-6 months. Transplanted islets were then demonstrated to retain the normal morphology with a central mass of insulin-containing cells surrounded by a ring of A cells in which a few D cells were embedded.

Animals↗
PubMed1985

The human leucocyte P30 antigen: properties and assessment of value as a clonal marker.

FMC3 and FMC29 are monoclonal antibodies which react with a 30,000 Dalton molecule expressed on the lymphocyte surface membrane. The molecule is a protein which does not appear to be N-glycosylated. The antigen, which is also expressed intracellularly, does not appear to be a marker of differentiation or maturation. Polyclonal cell populations, such as peripheral blood lymphocytes, show a bimodal distribution of surface antigen density, whilst monoclonal cell populations analysed quantitatively showed unimodal antigen density distributions. This suggests the antigen may be a clonal marker.

Antibodies, Monoclonal↗
PubMed1985

Solutions to the kinetic problem in the micronucleus assay.

The standard micronucleus assay as applied to lymphocyte cultures does not discriminate between non-dividing cells and cells that have divided. Micronuclei can only be expressed after nuclear division and because the proportion of dividing cells may vary from one culture to another the standard micronucleus assay can be very imprecise. To overcome this problem we have developed four new methods for scoring micronuclei only in lymphocytes that have divided once only. In the stathmokinetic method the proportion of dividing cells was measured by blocking them at metaphase with colchicine and the number of micronuclei was determined in a parallel culture. The ratio of micronucleus index and metaphase index gave the number of micronuclei per metaphase. With the flow cytometric method, the cells in S phase were allowed to incorporate bromodeoxyuridine and then allowed to divide. By virtue of their reduced fluorescence after staining with Hoechst 33342 it was possible to sort these cells out with a fluorescence activated cell sorter. The autoradiographic method employed incorporation of tritiated thymidine in cells in S phase so that after division these cells could be recognised by their labelled nuclei. In the cytokinesis-block method, dividing cells were inhibited from performing cytokinesis by exposing them to 3.0 micrograms/ml cytochalasin-B. Dividing cells were easily recognised by their binucleate appearance. Results from the four methods for micronuclei induced by X-rays were in close agreement, but the simplest and most precise of the methods was the cytokinesis-block method.

Adult↗
PubMed1982

The need for unity.

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Psychiatric Nursing↗
PubMed1979

Cyclic hemopoiesis and feedback control.

Hemopoiesis exhibits a variety of oscillatory phenomena. Since hemopoiesis is controlled by many feedback loops and since feedback loops are potentially oscillatory, it is possible that the observed oscillatory phenomena are the result of movement of hemopoiesis into an area of operation which favors stable oscillation. Although this hypothesis explains many of the observed phenomena and has had some predictive value, its important predictions have not yet been satisfactorily tested.

Agranulocytosis↗
PubMed1978

Is aplastic anaemia due to abnormality of D.N.A.?

Lymphocytes from eleven patients with aplastic anaemia were cultured with various agents which interact with D.N.A., and the proliferative responses to phytohaemagglutinin were measured. Lymphocytes from seven of the eleven patients were unduly sensitive to bleomycin, an agent causing strand breaks in D.N.A. The findings suggest that D.N.A. in these seven patients was abnormal, possibly as a result of an abnormality of D.N.A. repair. It is suggested that in aplastic anaemia D.N.A. damage in stem cells may lead to a failure of proliferation.

Adolescent↗
PubMed1976

Residual marrow damage: possible explanation for idiosyncrasy to chloramphenicol.

The effect of oral administration of chloramphenicol was studied in normal mice and mice having residual marrow damage. In the concentration used the drug had no detectable effect on the marrow of normal mice but caused a progressive fall in the numbers of pluripotential stem cells and granulocytic progenitor cells in mice bearing residual marrow damage. However, cells taken from such mice were no more sensitive than normal cells to the in vitro action of chloramphenicol. The results suggest that unrecognized residual marrow damage can be an aetiological factor in marrow failure due to drug idiosyncrasy.

Anemia, Aplastic↗