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Biomedical subjects

J K Cowell

Publications and source records attributed to J K Cowell.

At least 127 records · Page 7Linked to original sources
PubMed1988

Molecular evidence that the esterase-D gene lies proximal to the retinoblastoma susceptibility locus in chromosome region 13q14.

Somatic cell hybrids have been created between transformed mouse 3T3 cells and fibroblasts from a retinoblastoma patient with normal red-cell esterase-D (ESD) levels and a constitutional deletion of chromosome region 13q14-q31. In one subclone, which has retained the deletion chromosome but not the homologous normal copy, we have demonstrated the presence of the human ESD gene sequence. The breakpoint in this patient therefore must have occurred between the ESD gene and the retinoblastoma (Rb) predisposition locus. We have also been able to demonstrate that the ESD gene lies proximally to be the Rb gene in region 13q14. The recently isolated 4.7R cDNA gene sequence was absent from the deletion-containing hybrid, a finding consistent with the hypothesis that this sequence represents the Rb gene itself.

Animals↗
PubMed1988

Deletion of chromosome region 13q14 is transmissible and does not always predispose to retinoblastoma.

During routine screening of retinoblastoma patients for esterase D activity in red blood cell lysates a patient was identified with only 50% of normal enzyme activity. Chromosome analysis showed that this patient had a small deletion within chromosome region 13q14. Parental studies showed that, whereas the father had normal enzyme levels, the mother had esterase D levels which were also 50% of normal and a similar small 13q14 deletion. Ophthalmological examination failed to demonstrate any retinal abnormality in either parent. Thus we present the first case not only of the direct transmission of a 13q14 deletion within a family but also of an individual in whom the deletion has not predisposed to tumour formation.

Cell Line↗
PubMed1988

Cytogenetic changes in Wilms' tumors.

Cytogenetic analysis of 20 Wilms' tumors using short-term culture techniques were undertaken. Chromosome abnormalities were detected in all tumors. In 19 of 20 cases only minor karyotypic changes were observed within cells with near-diploid chromosome numbers; only one tumor was predominantly hyperdiploid. Rearrangements involving chromosome 1 were the most frequently observed abnormality (in 25%) and often resulted in partial or complete trisomy for the long arm. In 20% of the tumors, abnormalities involving chromosomes 11 and 16 were present. The only other chromosomes frequently involved in structural or numerical changes were #12, and #18. Two discrete tumor foci within the same kidney differed cytogenetically, suggesting an independent origin for each focus. No correlation could be made between specific chromosome abnormalities and tumor stage or histologic subtype. Although constitutional deletion of chromosome region 11p13 has frequently been reported to predispose to Wilms' tumor formation, only two tumors with deletions involving this region were observed. Chromosomes from tumors treated with chemotherapy prior to surgical removal and culture yielded findings similar to those in untreated tumor cells.

Child↗
PubMed1988

The T-ALL specific t(11;14)(p13;q11) translocation breakpoint cluster region is located near to the Wilms' tumour predisposition locus.

A breakpoint cluster region (T-ALLbcr) has been previously described on 11p13 for T-ALL carrying t(11;14)(p13;q11). One further T-ALL breakpoint is described bringing to 5 out of 6 such translocations which are found to break within a maximum of 6.7 kb on chromosome 11p13. Studies of somatic cell hybrids derived from t(11;14)(p13;q11) T-ALL placed the T-ALLbcr between the genes for catalase (CAT) and the beta-subunit of follicle stimulating hormone (FSHB). This suggested a link between the T-ALLbcr and the Wilms' tumour predisposition locus (WT) since constitutional 11p13 deletions predispose to Wilms' tumour. Utilising somatic cell hybrids from patients with Wilms' tumours and aniridia, we show that while the T-ALLbcr maps distal to the catalase gene at 11p13, it maps outside the shortest region of overlap of a series of 11p13 deletions associated with Wilms'-Aniridia. The data suggest the order of genes at 11p13 to be: centromere-CAT-T-ALLbcr-WT-aniridia-FSHB-telomere. Therefore, the T-ALLbcr must lie very close to but may be distinct from the Wilms' predisposition locus at 11p13.

Aniridia↗
PubMed1987

A chromosomal breakpoint that separates the esterase D and retinoblastoma predisposition loci in a patient with del(13)(q14q31).

A patient with severe mental retardation and other congenital abnormalities who developed retinoblastoma was shown to have a deletion on the long arm of chromosome #13 with breakpoints in regions q14 and q31. Quantitation of enzyme activity of the esterase-D gene which, together with the retinoblastoma locus, is located in region 13q14 showed levels that were equal to those of normal controls. The 13q14 breakpoint, therefore, appears to have occurred between the two loci, which places the esterase D gene in a more proximal position in this band than the retinoblastoma locus.

Carboxylesterase↗
PubMed1987

An assessment of the usefulness of electrophoretic variants of esterase-D in the antenatal diagnosis of retinoblastoma in the United Kingdom.

Fifty retinoblastoma families have been studied. In 41 it has been possible to determine the esterase-D phenotypes in all family members. Seven families were informative for the enzyme polymorphism and in all cases cosegregation of the retinoblastoma gene and esterase-D alleles was demonstrated, giving a lod score of 2.61. When combined with other published reports the cumulative lod score is 13.69 with no recombination in 45 meioses. In 10-15% of retinoblastoma families therefore, it is possible to offer prenatal diagnosis using the ESD protein polymorphism. The application of this test to the retinoblastoma population in the UK is limited by the low frequency of the rarer allele (0.116) and, as a result of genetic counseling, the smaller families generally associated with retinoblastoma.

Carboxylesterase↗
PubMed1987

The need to screen all retinoblastoma patients for esterase D activity: detection of submicroscopic chromosome deletions.

Roughly 5% of all patients with retinoblastoma carry a constitutional chromosome deletion on the long arm of chromosome 13, which confers a prezygotic predisposition to tumour development. As offspring of deletion carriers have a 50% risk of inheriting the predisposition locus it is important to identify deletion carriers. The site of the esterase D gene to the often deleted region offers an objective means of deletion identification. The chromosomes of a patient with unilateral retinoblastoma, previously supposed to have a normal karyotype, were reexamined after the discovery that his red blood cells contained reduced activities of esterase D. A small sub-band deletion was found in chromosome region 13q14. These findings emphasise the importance of measurements of esterase D in all patients with retinoblastoma, even those with an apparently normal karyotype.

Carboxylesterase↗
PubMed1986

Effect of the esterase-D phenotype on its in vitro enzyme activity.

Esterase-D phenotypes and in vitro activity have been measured in red blood cells from 258 retinoblastoma patients and 73 unaffected relatives. Individuals with the 1-1 and 2-1 phenotypes showed distributions of enzyme activity which were not significantly different from each other. Individuals with the 2-2 phenotype, however, consistently showed a 25-30% lower level of enzyme activity. These results demonstrate the importance of determining the esterase-D phenotype in individuals with low ESD activity who might otherwise be assumed to carry a chromosome deletion at the esterase-D locus. We have also shown that, in vitro, the ESD enzyme is unstable over relatively short periods of time which, if uncontrolled, can give rise to a large variation in measured enzyme levels. The addition of b-mercaptoethanol to the assay buffer, which stabilises the enzyme, results in more consistent values being obtained within the same ESD phenotype. This feature could account in part for much of the variability in enzyme activity observed between different individuals in other studies.

Alleles↗
PubMed1986

Deletions of the esterase D locus from a survey of 200 retinoblastoma patients.

Esterase D levels from 200 retinoblastoma patients have been measured in an attempt to identify individuals carrying deletions of chromosome region 13q14. In this series 75% had bilateral tumours and 23% were familial. Of nine patients identified as having low esterase D levels, five had not previously been diagnosed as deletion carriers. These observations demonstrate the benefit of screening retinoblastoma populations for esterase D deficiency.

Adult↗
PubMed1984

The ability of normal mouse cells to reduce the malignant potential of transformed mouse bladder epithelial cells depends on their somatic origin.

Somatic cell hybrids have been made between a transformed mouse bladder carcinoma cell line and normal mouse bladder epithelium and mesenchyme. In the epithelial tumour/mesenchyme hybrids the malignant phenotype was expressed dominantly whereas in the carcinoma/normal epithelium hybrids the malignant potential was greatly reduced. In both cases the dominant in vitro and in vivo phenotype was that of the normal parental cells. All hybrid tumours were first palpable after 4-7 days, demonstrating that the tumours had not arisen as a result of in vivo selection of a sub-population of tumorigenic cells. Chromosome analysis showed that the carcinoma/normal epithelium hybrids were all in the hypertetraploid range but the large variation in the karyotypic profile of each hybrid made it impossible to implicate any specific chromosomes in the control of expression of the malignant phenotype. During normal development in bladder epithelium, terminal differentiation is associated with tetraploid formation by cell fusion. The reduction in malignancy of the carcinoma/normal epithelium hybrids may perhaps be due to the expression of genes associated with normal terminal differentiation after cell fusion and tetraploid formation. This is also supported by the more differentiated phenotype of the hybrid tumours. Of the 10 mesenchyme/epithelium hybrids analysed cytogenetically , four were in the hypertetraploid range from which little meaningful data could be obtained about specific chromosome losses. Chromosome analysis of the cells from the near-tetraploid hybrids showed only minor differences from what might have been expected from the input of the two parents; these differences appeared to be due to random chromosome loss. The maximum number of chromosomes lost from any of the hybrids was five, although one, two or three was more usual. The only consistent chromosome loss was of a single copy of chromosome 4, which in two of the hybrids represented the only chromosome change. The possibility that this loss might facilitate re-expression of the malignant phenotype is discussed.

Animals↗
PubMed1984

A photographic representation of the variability in the G-banded structure of the chromosomes in the mouse karyotype. A guide to the identification of the individual chromosomes.

Analysis of the mouse chromosomes is becoming increasingly important in many fields of genetic research. It is generally considered that the mouse chromosomes are more difficult to analyse than, for example, human chromosomes which has often led to their misidentification. This article presents a guide to the correct identification of trypsin-Giemsa banded chromosomes from the mouse. The variability in the G-banded structure of each chromosome is presented pictorially together with some suggestions for their unequivocal identification. Since many of the mouse chromosomes have similar banding patterns, those chromosomes which are more frequently misidentified have been compared and contrasted. Finally a summary of the main features for the identification of each chromosome is presented.

Animals↗
PubMed1984

Presence of two cytogenetic forms of amplified DNA: evidence for a role in tumor growth in an intraspecific mouse hybrid cell line.

An intraspecific mouse hybrid epithelial cell line, F5/B, is described in which the homogeneously staining region (HSR)-containing marker chromosome from one parent is absent in about half of the cells. It is replaced in these cells by double minutes (DM), an alternative form of amplified DNA, which is liable to loss because of its instability at mitosis. DM probably arise from the breakdown of the HSR during clonal growth of F5/B. Subclones were derived possessing one or another cytogenetic feature, and their cloning efficiency in vitro and tumorigenicity in syngeneic animals were compared. There were no differences in in vitro tumorigenicity, but in vivo DM-containing subclones were significantly less tumorigenic than HSR-containing subclones or the F5/B parent hybrid. In tumors that developed after long latent periods, cells had increased numbers of DM compared with the inoculated population, demonstrating a selective advantage in vivo for cells with a high DM content. These results indicate a role for the amplified DNA in tumor growth.

Animals↗
PubMed1983

Occurrence and evolution of homogeneously staining regions may be due to breakage-fusion-bridge cycles following telomere loss.

Chromosomes with homogeneously staining regions (HSR) were analysed in a subclone of the H4 rat hepatoma cell line, where they represent amplification of the ribosomal RNA (rRNA) genes. Detailed G-band analysis of the subclone revealed that an HSR on the short arm of chromosome 3 became unstable and changed its position within the chromosome. The evolution of this marker chromosome was associated with the terminal deletion of the normal long arm of the HSR-bearing chromosome 3 and may have involved ring formation as a result of fusion between the HSR on the short arm and the broken end of the long arm. Evidence was obtained for breakage at different sites within the ring, producing chromosomes with HSRs located terminally on either the long arms or both arms. The terminally located HSR underwent elongation in some cells presumably as a result of a breakage-fusion-bridge cycle characteristic of instability due to telomeric loss. It is suggested that terminally located HSRs may generally occur this way.

Animals↗
PubMed1983

Chromosome analysis of human neuroblastoma cell line TR14 showing double minutes and an aberration involving chromosome 1.

The chromosomal analysis of a human neuroblastoma cell line derived from a pediatric patient is presented. The cell line has a modal chromosome number of 64 and contains large numbers of double minutes (DMs). The DMs are stable over many passages in vitro. A consistent feature of the karyotype is an abnormality involving the short arm of chromosome 1, which is consistent with previous reports from human neuroblastomas. The region distal to band 1p31 has homogeneously staining characteristics and as such this cell line represents a rare example where DMs and HSRs are constitutive features of the same cells. The possibility that such regions could arise from chromosome rearrangements is discussed.

Cell Line↗
PubMed1982

Chromosome changes associated with the progression of cell lines from preneoplastic to tumorigenic phenotype during transformation of mouse salivary gland epithelium in vitro.

Two mouse salivary gland epithelial cell lines, CSG 211 and CSG 205/2B1, isolated during carcinogen-induced neoplastic transformation in vitro, were analyzed cytogenetically before and after they acquired the ability to produce carcinomas in syngeneic animals. With the use of Giemsa banding techniques, chromosome changes were identified that were associated with the transition from a preneoplastic to a fully transformed (tumorigenic) phenotype during serial passage in vitro. Results were compared with those from a third cell line of similar origin, CSG 225, which was tumorigenic at the earliest passage tested. These cell lines were found to be subtetraploid, which confirms previous data, and the tumorigenic lines showed consistent losses of copies of chromosomes 1, 4, 7, 9, and 14. Compared with their preneoplastic counterparts, the loss of no single chromosome seems to be sufficient to generate the tumorigenic phenotype, but the loss of a combination of some or all of these chromosomes appears to be important in the phenotypic transition. In CSG 211 the loss of chromosome 7 is probably more important in this respect than loss of the other chromosomes listed. The karyotype of this cell line undergoes major structural rearrangement, which suggests that loss of specific regions of chromosomes 1 and 9 is also important.

Animals↗