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Biomedical subjects

R Williamson

Publications and source records attributed to R Williamson.

At least 451 records · Page 25Linked to original sources
PubMed1980

Model for antenatal diagnosis of beta-thalassaemia and other monogenic disorders by molecular analysis of linked DNA polymorphisms.

Polymorphisms of DNA restriction sites within the human fetal globin genes have been used to identify chromosomes that carry beta-thalassaemia genes in individuals heterozygous for this disease. This has allowed an antenatal diagnosis for beta-thalassaemia to be carried out by observation of the pattern of the inherited polymorphism of a linked DNA sequence not involved in the genetic pathogenesis of the disease. In the populations we have investigated there is no constant pattern of polymorphism that segregates with the beta-thalassaemia gene. The use of linked polymorphisms should, therefore, be applicable to antenatal diagnosis both of beta-thalassaemia and of any other single-gene defect for which there is a DNA probe specific for a sequence linked to the affected locus.

DNA↗
PubMed1980

Cloning of carp preproinsulin cDNA in the bacterial plasmid pBR322.

The successful cloning of recombinants between cDNA from fractionated poly(A)+-RNA of Brockmann bodies of the carp and the plasmid pBR322 in Escherichia coli chi 1776 is reported. One of the recombinant clones has been identified as a preproinsulin-cDNA recombinant by the hybrid-arrest translation assay. Recombination was at the PstI site of pBR322; reconstitution of this site was by 3'-tailing of the vector with dGn. The transformants were screened by in situ hybridization with kinase-labeled poly(A)+-RNA sedimenting at 9S from Brockmann bodies. Restriction analysis was performed on 26 of the strongly hybridizing clones to estimate the size of the inserted cDNA. Six of the recombinants studied contain inserts of a size approximating to full length 9S preproinsulin mRNA. The hybrid-arrest translation assay on selected clones identified one as a recombinant containing the preproinsulin cDNA sequence.

Animals↗
PubMed1980

The structure of the human gamma-globin gene locus and its relation to the delta/beta-globin gene locus.

Previous maps of the human gamma-globin gene locus and the human delta/beta-globin gene locus have been linked to one another by the identification of a DNA fragment, generated by BamHI, that contains portions of the A gamma- and delta-globin genes. The intergene distances are: between G gamma and A gamma, 3500 base pairs; between A gamma and delta, 13,500 base pairs; between delta and beta, 5500 base pairs. All genes contained introns between the EcoRI and BamHI intragenic sites. All genes were transcribed from the same strand.

Base Sequence↗
PubMed1980

In vivo interaction of beta-lactam antibiotics with the penicillin-binding proteins of Streptococcus pneumoniae.

The interactions of several beta-lactam antibiotics with the penicillin-binding proteins (PBPs) of Streptococcus pneumoniae have been studied using whole organisms treated with such antibiotics and subsequently with [3H]benzylpenicillin. Differences in chemical structure were shown to cause major and selective changes in the affinities of the beta-lactams for the PBPs Only 4 of the 28 compounds tested induced a specific morphological effect (enlargement of the equatorial region) under the particular conditions tested. In 12 of the 18 beta-lactams studied, a close correlation was found between the minimal inhibitory concentrations and the concentrations required to half-saturate PBP2b. However, such a correlation was no longer apparent when the bacteria were treated with the antibiotics at their minimal inhibitory concentrations. These findings are discussed in the context of various approaches that have been used to identify the growth-inhibitory targets of beta-lactam antibiotics in bacteria.

Aminoacyltransferases↗
PubMed1980

Antibiotic-tolerant mutants of Streptococcus pneumoniae that are not deficient in autolytic activity.

Several mutants of Streptococcus pneumoniae were isolated that appeared tolerant, to varying extents, to the lytic and bactericidal effects of some antibiotics that inhibit peptidoglycan synthesis, but were not deficient in autolytic activity. The method used to select the mutants was based on the survival of tolerant mutants during treatment with either bacitracin, benzylpenicillin, D-cycloserine plus beta-chloro-D-alanine, or vancomycin. Most (60 to 80%) of the surviving isolates were found to be deficient in autolytic activity, and these were rejected. The smaller proportion that had wild-type sensitivity to deoxycholate-induced lysis was studied further with respect to tolerance to the other antibiotics used in the selection procedures. Two of these mutants (selected by treatment with benzylpenicillin) were tolerant to either benzylpenicillin or D-cycloserine plus beta-chloro-D-alanine, but were supersusceptible, in terms of initiation of lysis, to either bacitracin or vancomycin. The minimal inhibitory concentration values of several antibiotics for these two mutants were identical to those for the wild-type strain. Moreover, the interaction of radioactive benzylpenicillin with the penicillin-binding proteins, examined in whole organisms, also appeared the same as previously found for either wild-type or autolytic-deficient strains of S. pneumoniae.

Anti-Bacterial Agents↗
PubMed1980

The detection and use of hemoglobin mutants in the direct analysis of human globin genes.

Many human globin-chain mutants contain amino acid replacements that result from single base changes in the corresponding globin gene. Using recombinants, the coding sequences of each of the alpha-, beta-, Ggamma-, and Agamma-globin genes have now been determined. Those sequences of DNA that are cleaved by a number of specific restriction endonucleases have been identified and accurately positioned. Mutations at these sequences abolish the restriction site, and therefore, the pattern of DNA fragments containing hybridizing globin-gene sequences is altered compared to DNA from normal persons. This allows the identification of one of a pair of cross-hybridizing human globin-gene sequences, as is shown here for the two alpha-globin, the two gamma-globin, and the delta- and beta-globin genes.

Amino Acid Sequence↗
PubMed1980

A comparison of plasma phenytoin level determinations by EMIT and gas-liquid chromatography in patients with renal insufficiency.

Monitoring the blood levels of antiepileptic drugs (AED) has proven to be of value in the clinical management of epileptic patients. We have compared the plasma concentrations of AED determined by enzyme multiplied immunoassays (EMIT) and gas-liquid chromatography (GLC) assays and identified a group of patients (n = 22) in whom the EMIT values for phenytoin were up to three times higher than those obtained by GLC. All these patients were oliguric with various degrees of azotemia, most of them undergoing weekly hemodialysis. The ratio of EMIT over GLC was 2.0 in 14 patients, 2.5 in 5 patients, and near 3.0 in 3 patients. These ratios remained relatively constant during repeated determinations over several months. The magnitude of difference between EMIT and GLC values (microgram/ml) was not related to the degree of azotemia. The discrepancy remained unchanged when various modifications of EMIT and GLC techniques were used. When phenytoin was added in vitro to plasma from nonepileptic oliguric azotemic patients, the measured phenytoin values were close to and not higher than the target values by either methodology. We feel that, when monitoring phenytoin blood levels in epileptic patients with renal insufficiency, one should be aware of a discrepancy between phenytoin values assayed by GLC and EMIT.

Chromatography, Gas↗
PubMed1980

Mapping the alpha-globin genes in an Algerian HbH patient and his family.

The organization of alpha-globin genes in normal white European, normal Algerian, and alpha-thalassemic Algerian DNA was examined by restriction endonuclease mapping using HindIII, HpaI, Bamhi, EcoRI, BgIII, and PstI. The results for normal DNA confirm and add to the findings of Surrey et al. and Orkin; the two alpha-genes are approximately 3.0 kb apart. The restriction enzymes BgIII and HpaL cut between the two alpha-genes. Four PstL sites are located: two surrounding each alpha-gene. The physical maps for a number of Algerian controls (normal alpha- and beta-globin biosynthesis profiles) are identical to that of the European controls. The Algerian alpha-thalassemic presenting with HbH disease was found to be homozygous for a 3.5-3.7 kb deletion at the alpha-gene locus, leaving one alpha-gene per chromosome. The patient's mother and father are both found to be heterozygous for this deletion. An unaffected sibling carries both normal chromosomes. The deletion could be the result of a Lepore-like crossover fusion event between the two alpha-globin genes, or of a 3.7 kb deletion of either the entire 5' alpha-gene or the entire 3' alpha-gene. The Algerian case of HbH disease studied differs from Asian cases in both the mode of inheritance and the molecular pathology of the alpha-thalassemia mutation. If this type of deletion is the major cause of Algerian alpha-thalassemia, it would explain the apparent absence of Hydrops fetalis in this geographical area.

Algeria↗
PubMed1979

A nuclear precursor to human gamma-globin messenger RNA.

RNA isolated from human foetal liver at an erythroid stage of development was transferred from methyl mercury hydroxide agarose gels to diazobenzyloxymethyl paper. A 16S RNA species containing gamma-globin mRNA sequences was identified by hybridisation to 32P-labelled human gamma-globin cDNA recombinant plasmid pHgamma GI. This RNA is found only in the cell nucleus and is polyadenylated. Human globin gene transcription is thus analagous to that in mouse: interventing sequences are transcribed and processed from the pre-mRNA in the nucleus after polyadenylation.

Adult↗
PubMed1979

The structure of the human beta-globin gene in beta-thalassaemia.

Twenty-one cases of beta 0 and beta +-thalassaemia have been analysed by restriction endonuclease mapping. In most cases no deletion in the regions surrounding the beta- and delta-globin genes could be detected. However, in a single Asian case of beta 0-thalassaemia, homozygous clinically, one of the homologous chromosomes contained a beta-globin gene with a deletion of 600 base pairs of DNA and comprising most or all of the 3' end of the structural gene including the EcoRI restriction site within the beta-globin coding sequence.

DNA↗
PubMed1979

Structure of the human fetal globin gene locus.

We have derived a 'map' of restriction enzyme sites in and around the human gamma-globin genes. This has enabled us to show that there are two gamma-globin genes per haploid set, that the genes contain 'introns' within the same regions of DNA as the human beta and delta-globin genes, and that the genes are 3,500 base pairs apart. We conclude that the correct gene organisation of the human beta-like globin locus is GgammaAgammadeltabeta.

Chromosome Mapping↗
PubMed1979

Structure of the human G gamma-A gamma-delta-beta-globin gene locus.

We have constructed a physical map of the human G gamma-, A gamma-, delta-, and beta-globin genes. The previously described maps of the fetal and adult beta-like globin genes have been linked to one another by identification of a DNA fragment, generated by BamHI, that contains part of each of the A gamma- and delta-globin genes. The map obtained, which spans more than 40 kilobases, shows the following intergene distances: between G gamma and A gamma, 3500 base pairs; between A gamma and delta, 13,500 base pairs; and between delta and beta, 5500 base pairs. All genes are transcribed from the same DNA strand.

Adult↗
PubMed1979

The Friend virus genome: partial characterization of a complete DNA copy.

A complementary DNA probe has been prepared from the Friend murine erythroleukaemia virus complex released by Friend cells (FV cDNAD-) and Friend cells induced to differentiate (FV cDNAD+). Molecular hybridization analysis shows that: (a) FV cDNAD+ is close to being a complete copy of the virus genome and the distribution of sequences is uniform with respect to their distribution in the Friend virus genome. (b) Hybridization of 70S RNA from the cloned helper virus to the total FVc DNAD+ probe demonstrates that a large proportion of the cDNA is specific to the transforming spleen focus forming virus. (c) Hybridization of the probe to normal and transformed cell DNA shows that there are about seven Friend virus related genes in normal DNA and almost twice this amount in transformed cell DNA. A significant minor proportion (20%) of the cDNA probe anneals only to virus related sequences in the transformed cell DNA. (d) An analysis of the kinetics of annealing of the cDNA to an excess template RNA shows that the minimum base sequence complexity of the Friend virus complex is 4 x 10(6). (e) An analysis of the cross hybridization between FV cDNAD+ and 60 to 70S RNA isolated from virus released by uninduced and induced cells shows that the genome of the induced and uninduced Friend virus is almost identical.

Animals↗
PubMed1979

Characterization of the autolytic enzymes of Clostridium perfringens.

Clostridium perfringens and isolated walls of this organism autolysed rapidly when incubated in buffer at pH 7.0 with the release of free-reducing groups but no N-terminal amino acids. The predominant autolytic enzyme was an endo-beta-N-acetylglucosaminidase, and an endo-beta-N-acetylmuramidase was also present. The autolytic enzymes could be solubilized by extraction of the organisms with 5 M-LiCl and would then subsequently bind to and rapidly lyse walls of Micrococcus luteus and, more slowly, formamide-extracted walls of C. perfringens and walls of Bacillus subtilis. Lysis of C. perfringens walls by these extracted enzymes could not be demonstrated.

Acetylglucosaminidase↗
PubMed1979

Use of chromosomal translocations with in situ DNA hybridisation to confirm localisation of human 5S ribosomal RNA genes.

Two cases of chromosomal translocations involving the long arm of chromosome 1 were investigated for 5S ribosomal gene localisation using in situ hybridisation. In the first family, there was an interstitial translocation of 1q25-32 to chromosome 5; the 5S genes remained on chromosome 1. In the second family, there was a translocation of 1q42-44 to chromosome 21q12; the 5S gene locus in this case was translocated. This shows that the 5S ribosomal genes are at position 1q42-44, confirming a previous assignment based on adenovirus-induced uncoiling and on a partial trisomy (Steffensen et al., 1977).

Chromosome Banding↗