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Biomedical subjects

G Turner

Publications and source records attributed to G Turner.

At least 199 records · Page 11Linked to original sources
PubMed1990

Beta-lactam antibiotic biosynthetic genes have been conserved in clusters in prokaryotes and eukaryotes.

A cosmid clone containing closely linked beta-lactam antibiotic biosynthetic genes was isolated from a gene library of Flavobacterium sp. SC 12,154. The location within the cluster of the DNA thought to contain the gene for delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine synthetase (ACVS), the first step in the beta-lactam antibiotic biosynthetic pathway, was identified by a novel method. This DNA facilitated the isolation, by cross-hybridization, of the corresponding DNA from Streptomyces clavuligerus ATCC 27064, Penicillium chrysogenum Oli13 and Aspergillus nidulans R153. Evidence was obtained which confirmed that the cross-hybridizing sequences contained the ACVS gene. In each case the ACVS gene was found to be closely linked to other beta-lactam biosynthetic genes and constituted part of a gene cluster.

Anti-Bacterial Agents↗
PubMed1990

Spatial and biological characterisation of the complete quinic acid utilisation gene cluster in Aspergillus nidulans.

Heterologous probing of restriction digests of chromosomal DNA from Aspergillus nidulans with radioactively labelled probes encoding dehydroshikimate dehydratase (QA-4) and a repressor gene (QA1-S) from Neurospora crassa revealed a pattern of hybridisation inconsistent with an equivalent single copy of each gene in A. nidulans. Screening of size-selected and total genome A. nidulans DNA libraries allowed the isolation of four unique classes of sequence, two of which hybridised to the QA-4 probe, and two of which hybridised to the QA1-S probe. In each case, one of each pair of unique sequences was able to complement the equivalent mutations qutC (= QA-4) and qutR (= QA1-S) in A. nidulans, whereas the second of each pair was unable to complement the same mutation. The complementing sequences were physically mapped relative to the previously cloned A. nidulans QUT gene cluster, demonstrating that QUTR is distal and divergently transcribed from QUTA with approximately 3.6 kb between the ATG translational start codons, and that QUTC is transcribed in the same direction as QUTD on the other side of the cluster, approximately 1.65 kb downstream of the QUTD TAA translational stop signal. The physical and genetic maps of the QUT gene cluster correlate precisely. The non-complementing A. nidulans DNA sequences that hybridise to the N. crassa QA-4 (= QUTC) and QA1-S (= QUTR) fulfill many of the criteria characteristic of pseudogenes.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1990

Establishment of a karyotypically normal B-chronic lymphocytic leukemia cell line; evidence of leukemic origin by immunoglobulin gene rearrangement.

A new Epstein-Barr virus (EBV) transformed cell line was established from a patient with B-chronic lymphocytic leukemia (B-CLL). The karyotype of the cell line has remained normal for over 12 months in culture; however, identical heavy and light chain immunoglobulin (Ig) gene rearrangements in the patient's blood and the cell line provided evidence that the EBV transformed cells were derived from the neoplastic clone.

Aged↗
PubMed1990

Cloning and heterologous expression of the penicillin biosynthetic gene cluster from penicillum chrysogenum.

A cosmid clone containing the putative penicillin biosynthetic gene cluster from Penicillium chrysogenum was used to transform the related filamentous fungi Neurospora crassa and Aspergillus niger, which do not produce beta-lactam antibiotics. Both of the transformed hosts contained intact P. chrysogenum DNA derived from the cosmid clone and produced authentic penicillin V. Assays of penicillin biosynthetic enzyme activity additionally demonstrated that they possessed delta-(L-alpha-amino-adipyl)-L-cysteinyl-D-valine synthetase (ACVS), isopenicillin N synthetase (IPNS) and acyl coenzyme A:6-aminopenicillanic acid acyltransferase (ACT) activity. The data suggests that genes encoding all the enzymes necessary for the biosynthesis of penicillin from amino acid precursors are closely linked in P. chrysogenum and constitute a gene cluster.

Acyltransferases↗
PubMed1990

Small-bowel lipoma: an uncommon cause of obstruction.

Small-bowel tumours are an uncommon cause of small-bowel obstruction. The symptoms are unusually nonspecific and intermittent. Contrast studies of the small bowel are the best means of delineating the lesion. The authors present a case in which obstruction was treated with small-bowel resection, and they give a brief account of the occurrence of small-bowel tumours in a major teaching hospital.

Aged↗
PubMed1989

Börjeson-Forssman-Lehmann syndrome: clinical manifestations and gene localization to Xq26-27.

We have studied 7 males in one family with mild/moderate intellectual handicap, long thick ears, deep-set eyes, small testes, and post pubertal gynecomastia. The affected males and some of the heterozygous females also had tapering fingers and short, widely spaced flexed toes. The pedigree demonstrates X-linked recessive inheritance. The clinical manifestations are similar to those described in the Börjeson-Forssman-Lehmann (BFL) syndrome but differ in the degree of mental handicap and the absence of "dwarfism" and microcepaly. This milder manifestation may represent either phenotypic or genotypic variation. DNA marker studies demonstrated linkage to the DXS86, DXS51, and F9 cluster at Xq26-q27. The maximum lod score was 2.1 with DXS51, at theta = 0.0. Definite recombinants were observed between DXS10 (at Xq26 but proximal to DXS86), DXS105 (at Xq27 but distal to F9), and BFL. Thus, the regional localization for BFL is Xq26-q27 between DXS10 and DXS105.

Abnormalities, Multiple↗
PubMed1989

Prognostic significance of activation and differentiation antigen expression in B-cell non-Hodgkin's lymphoma.

Immunophenotyping shows heterogeneity of expression of activation and differentiation antigens in B-cell non-Hodgkin's lymphoma (NHL). To investigate whether antigen expression correlates with clinical behaviour we have studied the clinical presentation and follow-up of a series of 111 B-cell lymphomas previously phenotyped for a panel of antigens including CD groups 5, 9, 10, 21, 23, 25, 30, 38, 4F2 antigen, and transferrin receptor. CD antigens 5, 10, and 23 were expressed significantly more often by low grade lymphomas whereas CD38, 4F2 antigen, and transferrin receptor were more often expressed by high grade lymphomas. There was a significant correlation with survival and age, stage at presentation, histological grade, and expression of 4F2 antigen and transferrin receptor but not with the other antigens studied. 4F2 antigen and transferrin receptor may identify a poor prognostic group of cases in low grade lymphoma but we conclude that phenotyping B-cell NHL for many of the antigens expressed at various stages of B-cell differentiation and activation does not provide clinically useful information in addition to that obtained from standard histological classifications.

Antigens, CD↗
PubMed1989

Electroretinography and electro-oculography to localize abnormalities in early-stage inflammatory eye disease.

Electrophysiological investigations were performed in patients with inflammatory eye disease characterized by the presence of vitreous cells. The eyes were classified into four categories on the basis of fluorescein angiography: 1) no fluorescein leakage from retinal vessels, 2) fluorescein leakage from peripheral retinal vessels, 3) fluorescein leakage from the disc or macular vessels, and 4) fluorescein leakage from retinal vessels associated with pigment epithelial and choroidal changes. The electro-oculogram light rise was abnormally increased in the eyes in category 1, but it progressively declined for those in the other categories. The ratio of the b-wave (postreceptoral component) and a-wave (receptoral component) of the flash electroretinogram was unchanged in all categories, but the electroretinographic amplitudes progressively declined from a somewhat supernormal level in category 1 to subnormal in the other categories. Thus, in inflammatory eye disease, changes in the electrical potentials arising in the pigment epithelium and photoreceptors are the earliest detectable signs. Some biochemical changes in the choroid, pigment epithelium, and the photoreceptors appear to take place before any pathological changes in these structures or in the retinal vessels are detectable by ophthalmoscopy or fluorescein angiography.

Adult↗
PubMed1989

Amplification of the isopenicillin N synthetase gene in a strain of Penicillium chrysogenum producing high levels of penicillin.

The isopenicillin N synthetase (IPNS) gene has been isolated from wild-type Penicillium chrysogenum and used as a probe to detect the equivalent gene on Southern blots of genomic DNA from a mutant producing high levels of penicillin. The IPNS gene in this strain is contained within a region of DNA of wild-type restriction pattern that extends for at least 39 kb and is present at between 8 and 16 copies. The steady state level of IPNS mRNA in the mutant producing high levels of penicillin is between 32- and 64-fold of that of the wild type, suggesting that the rate of transcription of some or all of the copies has been increased. In addition we have also shown that both the IPNS mRNA and enzyme is present throughout the growth phase in both strains under the culture conditions used. IPNS enzyme activity is greatly increased in the strain with the high penicillin titre.

Cloning, Molecular↗
PubMed1989

Laser treatment of retinal angiomatosis.

We have treated 26 retinal angiomas of less than 4.5 mm in size in 15 eyes using repeated applications of contiguous argon blue green laser burns. All except one of the angiomas regressed without a massive exudative response of treatment. Haemorrhage occurred in two cases but only affected the visual outcome in one eye. Traction retinal detachment persisted in 50% of the large angiomas, despite regression of the tumour.

Adult↗
PubMed1988

Recurrence risks for relatives in families with an isolated case of the fragile X syndrome.

The proportion of sporadic cases among affected males with fragile X-related mental impairment was reinvestigated in a new sample of family data and compared to previous studies. It was found that the estimate has increased over time from 0 in the original study to 0.24 in the present study. This difference indicated that the correction used for the ascertainment of families in the original study may not have been adequate and that the suggestion that all mothers of affected males are obligate carriers may be wrong. Based on this new information, recurrence risks for relatives in a family with an isolated case of the fragile X or Martin-Bell syndrome were calculated under different assumptions in order to investigate the effect of 1) the knowledge of the phenotype of ancestors of the proband, 2) the dependence of expression of the mutation on the sex of the carrier parent, 3) the value of the penetrance of mental impairment (MI), and 4) the equality of mutation rates in egg and sperm. The assumptions made for modelling the mutational process had the greatest effect on the recurrence risk in sibs of an isolated case, whereas small differences in penetrance parameters and assumptions based on whether the ancestors were known to be normal or of unknown phenotype made little difference. Recurrence risks for the sibs and first cousins of an isolated case calculated under different assumptions are presented.

Female↗
PubMed1988

Transformation of Penicillium chrysogenum with a dominant selectable marker.

We have cloned a mutant oligomycin resistance allele of the mitochondrial ATP synthase subunit 9 gene from the filamentous fungus Penicillium chrysogenum. The gene was isolated using the equivalent gene from Aspergillus nidulans as a hybridisation probe. Using the cloned gene it is possible to select for oligomycin resistance in P. chrysogenum transformation experiments. This transformation system was used to introduce further copies of the P. chrysogenum isopenicillin N synthetase gene, which were stably maintained without selection. An assessment of the frequency with which homologous integration occurs was also made. With this system, it should prove possible to transform any strain of P. chrysogenum.

Chromosome Mapping↗
PubMed1988

The oliC3 gene of Aspergillus niger: isolation, sequence and use as a selectable marker for transformation.

The oliC3 gene of Aspergillus niger has been isolated and sequenced. This gene encodes an oligomycin-resistant variant of the mitochondrial ATP synthase subunit 9. In transformation experiments the gene can serve as a semi-dominant selectable marker for A. niger. It was possible to recognize transformants in which oliC3 had integrated at the homologous oliC locus, as opposed to elsewhere in the genome, by observation of phenotypes on medium containing oligomycin. DNA sequencing has allowed comparison of the deduced amino acid sequence with subunit 9 proteins from other species and comparison of 5' untranslated sequences with those from other fungi.

Amino Acid Sequence↗
PubMed1988

Behaviour of a replicating mitochondrial DNA sequence from Aspergillus amstelodami in Saccharomyces cerevisiae and Aspergillus nidulans.

An amplified sequence of mitochondrial DNA from a ragged (rgd) mutant of Aspergillus amstelodami has been shown to exist in multimeric circular form, suggesting that it is excised from the genome and can exist independently of it. This sequence has replicative (ARS) activity in Saccharomyces cerevisiae, and a subfragment responsible for this activity has been identified and sequenced. A homologous sequence from Aspergillus nidulans mtDNA also has ARS activity in S. cerevisiae. Both A. amstelodami and A. nidulans ARS elements have been incorporated into the integrative transformation vector pDJB1 and the derived vectors used to transform A. nidulans. Inclusion of the A. nidulans ARS element enhanced the transformation frequency 5-fold relative to pDJB1. No increase in transformation frequency was evident with the ARS element from A. amstelodami. The stability of transformants was variable but in comparison to pDJB1, ARS-containing plasmids were mitotically unstable in A. nidulans. Although plasmid DNAs could be rescued in Escherichia coli from undigested transformant DNA, no freely replicating plasmids were detected by Southern hybridisation.

Aspergillus↗
PubMed1988

Oculocerebral syndrome with hypopigmentation (Cross syndrome). Report of two siblings born to consanguineous parents.

In this report we describe two siblings, a 17-year-old male and his deceased sister, born to consanguineous parents, and presenting an oculocerebral syndrome with hypopigmentation as first delineated by Cross in 1967. In addition to the cutaneous hypopigmentation, both presented deep mental retardation and spastic tetraplegia with athetoid movements. A remarkable finding in this family is that a third sibling, an otherwise normal 23-year-old male, presents the same hypopigmentation with white-grey hair colour as his two severely affected siblings.

Adolescent↗