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Biomedical subjects

L A Hawthorn

Publications and source records attributed to L A Hawthorn.

12 recordsLinked to original sources
PubMed1998

Construction of a bacterial artificial chromosome (BAC) contig across the minimally deleted region in 13q14.3 in B-cell chronic lymphocytic leukemia.

Loss of heterozygosity (LOH) analysis in B-cell chronic lymphocytic leukemia (BCLL) has indicated that a frequent genetic event is loss of alleles from an approximately 500 kb region in 13q14.3, distal to the retinoblastoma gene. We have used DNA markers from this region to isolate and characterize a series of bacterial artificial chromosomes (BACs) which span the region between markers D13S319 and D13S25, which represents the common region of LOH. This entire region appears to be contained within only two minimally overlapping BACs, representing a maximum distance of approximately 350 kb. This BAC contig has been used to position known STS, EST and gene markers within the region. We have also used a modified differential display/RNA fingerprinting procedure designed to isolated transcribed sequences from YACs to isolate two transcribed units from the region which have also been positioned within the contig. The construction of a BAC contig with minimal redundancy provides the ideal resources from which to begin to identify candidate genes related to BCLL.

Blotting, Southern↗
PubMed1996

Regional assignment of EST sequences on human chromosome 13.

We have used a panel of somatic cell hybrids carrying structural rearrangements of human chromosome 13 to regionally localise 10 expressed sequence tags (ESTs) from this chromosome. Three of these genes were not present in the somatic cell hybrid PGME, which contains chromosome 13 as its major human component. Using a panel of somatic cell hybrids, two of these genes were localised to chromosome 8 and one to chromosome 16. Using the PCR primers as published, it was impossible to map one EST; consequently, a YAC containing this gene was isolated, and fluorescence in situ hybridisation was used to map the gene to 13q14. The distribution of the remaining six chromosome 13-specific ESTs was nonrandom; one mapped to 13q14 and the remaining five to 13q12, with three mapping within the proximal portion and two mapping within the distal portion of this region.

Chromosome Mapping↗
PubMed1995

Regional localisation of tri- and tetranucleotide repeat sequence-containing cosmids on chromosome 13.

A human chromosome 13-specific cosmid library has been screened with oligonucleotides containing tri- and tetranucleotide repeats with motifs: GACA, GACT, CAC, TCC. 20 cosmid clones were identified and their physical location on chromosome 13 was determined using fluorescence in situ hybridisation. Over 80% of the cosmids were detected using tetranucleotide repeats of which 50% were GACT, but these were distributed along the length of the chromosome. Clones from the 13q12-->q14 and 13q32-->q34 regions were apparently overrepresented and 10% of cosmids were localised to the short arm of the chromosome. These simple tandem repeats will be an important addition to the genetic mapping strategy for human chromosome 13.

Chromosome Mapping↗
PubMed1994

A deletion hybrid breakpoint map of the chromosomal region 13q14-q21 orders 19 genetic markers in 10 intervals.

A deletion hybrid breakpoint map of the chromosomal region 13q14-q21 has been constructed using 19 DNA markers and 13 cell lines with breakpoints in this chromosomal region. The cell lines define 10 distinct intervals in this region, which spans approximately 20 Mb. The markers include 6 RFLP markers, 11 microsatellites that provisionally had been mapped to the region 13q14-21, and 2 new polymorphic CA-repeats that were developed from an EMBL3 library of cell line ICD, containing 13pter-q14.3. The following order of markers was established: CEN-D13S320-(D13S118, D13S153)-RB1-D13S319-D13S25-(D13S31, D13S59, D13S133, D13S137)-D13S163-D13S119-(D13S26, D13S55)-(D13S131, D13S134, D13S135, D13S144, D13S152)-TEL.

Base Sequence↗
PubMed1994

Frequent homozygous deletions of the D13S25 locus in chromosome region 13q14 defines the location of a gene critical in leukaemogenesis in chronic B-cell lymphocytic leukaemia.

Cytogenetic studies of B-cell chronic lymphocytic leukaemia show structural abnormalities involving the 13q14 chromosome region as the only karyotypic change in a significant proportion of tumours. This observation suggests the location of a gene important in leukaemogenesis. A series of 68 BCLL tumours have been analysed for allele loss using a series of probes from 13q14. Using intragenic polymorphic markers from the retinoblastoma predisposition gene LOH was observed in 25% of tumours including 3/6 showing cytogenetically obvious deletions of the 13q14 region and 3/6 showing translocations involving 13q14. However, three deletions with proximal breakpoints in 13q14 did not show allele loss, demonstrating that the breakpoint lay distal to RB1. Using the D13S25 locus, which lies 1.6 cM distal to RB1, allele loss was seen in 90% of tumours with structural rearrangements of 13q14 and 75% of tumours with an apparently normal karyotype. 50% of these tumours showed homozygous loss of D13S25, suggesting that a 'tumour suppressor gene' lies in this region. The more distal D13S31 locus, 1 cM distal to D13S25, was infrequently involved in allele loss demonstrating that the minimum region of overlap for homozygous deletions is approximately 1 Mbp around the D13S25 locus.

Alleles↗
PubMed1993

The consistent 13q14 translocation breakpoint seen in chronic B-cell leukaemia (BCLL) involves deletion of the D13S25 locus which lies distal to the retinoblastoma predisposition gene.

Structural rearrangements involving chromosome 13 are frequently seen in B-cell chronic lymphocytic leukaemia. The presence of reciprocal translocations involving 13q14 in 10-15% of cases pinpoints the location of a gene important in leukaemogenesis. In order to characterise the exact location of the 13q14 breakpoint, somatic cell hybrids were constructed between mouse 3T3 cells and leukaemic cells from 5 patients with translocations involving chromosome 13. Hybrid pairs were isolated which carried either of the two derivative chromosomes carrying subsections of 13 and the position of the breakpoint investigated using a series of probes along the length of the chromosome. In all cases breakpoint region associated with rhabdomyosarcoma tumours and proximal to the D13S31 locus which lies in 13q14.3. In three translocations the RB1 gene was deleted as a result of the translocation but in at least one other case the BCLL breakpoint did not involve the RB1 gene, which consistently cosegregated in hybrids carrying other proximal markers. The D13S25 probe, which lies between RB1 and D13S31, however, was deleted in the translocation retaining RB1. It appears therefore that deletion of a gene(s) in this 2Mbp region is a critical event in some cases of BCLL tumorigenesis.

Animals↗
PubMed1991

Ability of uropathogens to bind to Tamm Horsfall protein-coated renal tubular cells.

Epithelial cells were isolated from a healthy human kidney and found to be of normal, renal tubular origin. The cells were maintained in tissue culture and found to secrete Tamm Horsfall protein (THP). Three strains of uropathogenic Escherichia coli, and one each of Proteus mirabilis and Pseudomonas aeruginosa were found to adhere to the THP-coated tubular cells. Extraneous THP bound to all the organisms except P fimbriated E. coli, and caused a reduction in the adhesion of type 1 fimbriated E. coli and P. mirabilis to the renal cells. However, irrespective of reduced adhesion in three of five strains tested, there was adequate evidence to indicate that THP does not competitively exclude all uropathogenic adhesion. On the contrary, its presence on renal cells may act to mediate bacterial colonization.

Bacterial Adhesion↗
PubMed1990

Exclusion of uropathogen adhesion to polymer surfaces by Lactobacillus acidophilus.

The ability of bacteria to adhere to surfaces is a major cause of concern in the use of biomaterial substrates. The adhesion of Staphylococcus epidermidis strain 1938 was examined using image analysis and was found not to correlate with polymer surface tension, unlike that of Lactobacillus acidophilus, which adhered to more hydrophobic polymers. A fimbriated uropathogenic E. coli strain showed very low levels of adherence to the biomaterials. Precoating the polymers with lactobacilli significantly reduced the staphylococcal and E. coli adhesion, a result which could have clinical significance. An additional finding was that the interaction of staphylococci and E. coli with lactobacilli coated polymers altered the adhesion profile of the latter. Lactobacilli appeared to detach from polymers of low surface tension and reattach to polymers with high surface tensions. This resulted in the highest levels of exclusion of uropathogens being found for lactobacilli-coated glass and sulfonated polystyrene, both of which are hydrophilic (with high surface tensions). These results demonstrate that lactobacilli can be used to coat biomaterial surfaces leading to a reduced adhesion of uropathogens.

Bacterial Adhesion↗
PubMed1988

Kinetics of cell adhesion to polymer surfaces.

Results of the kinetics of adhesion of granulocytes as well as fresh and glutaraldehyde-fixed erythrocytes, suspended in Hanks Balanced Salt Solution (HBSS; pH 7.2, ionic strength of 0.15) to various polymeric substrates are presented. Cell adhesion increases rapidly initially and reaches a plateau value after approximately 30 minutes. There is no evidence for a lag-time in the onset of cell adhesion, suggesting that electrostatic double-layer forces are negligible under these experimental conditions. For the experiments in which the cells are suspended in HBSS, which has a surface tension larger than that of the cells, the level of cell adhesion increases with decreasing surface tension of the polymeric substrates. An additional experiment with fresh human granulocytes suspended in HBSS containing 10% dimethyl sulfoxide was also performed. The surface tension of the resulting liquid medium is below that of the cells and the pattern of adhesion is reversed, in agreement with the predictions of a thermodynamic model for cell adhesion. The slightly different behavior of siliconized glass as a substrate is discussed in terms of "screening."

Biocompatible Materials↗
PubMed1988

Endothelialization of polymer surfaces.

The role that substrate surface properties play in influencing the extent of endothelialization of polymer surfaces has been investigated. For a wide range of polymer surfaces, the degree of endothelialization for both porcine and bovine endothelial cells is directly related to polymer surface tension: increased endothelialization occurring with increasing substrate surface tension. As a result of adsorption of the proteins in the culture media, the surface properties of the polymers are altered considerably. The protein-coated polymers were characterized by means of liquid-liquid contact angle measurements under non-denaturing conditions. A striking correlation is observed between the degree of endothelialization and the measured dextran contact angle. The degree of endothelial cell spreading is not related to polymer surface tension. Cell morphology and extracellular matrix production, however, are influenced by substrate surface properties.

Adsorption↗
PubMed1984

Organotypic development of neonate rabbit hippocampus in roller tube culture.

Maintenance of organotypic cultures of hippocampus derived from neonate rabbit has not been previously reported. The study described here was undertaken to define the conditions most suitable for organotypic development, in vitro, of this structure. Slices of hippocampus, on flying cover-slips, were maintained on plasma clots in roller tubes, for periods of up to 6 weeks. The results showed that the explanted, immature hippocampus developed in a manner which parallels the in vivo development, previously described. Specifically, pronounced neuronal differentiation was noted as the cultures matured. There is evidence that the hippocampus of rabbit, in vivo, at 3 weeks of age has assumed the mature pattern of neuronal and synaptic differentiation. Such differentiation similarly occurred in the cultured hippocampus described in this study. This system would serve as an ideal tool in applications in experimental neuropathology, where the use of a model of a phylogenetically advanced central nervous system is preferred.

Animals↗