Search PubMed⌕ Search

Biomedical subjects

M De Wilde

Publications and source records attributed to M De Wilde.

33 records · Page 2Linked to original sources
PubMed1979

Interactions and DNA transfer between Agrobacterium tumefaciens, the Ti-plasmid and the plant host.

Agrobacterium tumefaciens is a gram-negative bacterium with the unique capacity to induce neoplasmic transformations in dicotyledonous plants. Recently, both the mechanism and the biological significance of this transformation have been elucidated. Agrobacterium tumefaciens strains contain a large extrachromosomal DNA plasmid (the Ti-plasmid). This Ti-plasmid is responsible for the oncogenic properties of Agrobacterium strains. A particular segment of the Ti-plasmid, containing information determining the tumorous growth pattern and the synthesis of so-called 'opines', e.g. octopine (N-alpha-(D-1-carboxyethyl)-L-arginine) and nopaline (N-alpha-(1,3-dicarboxypropyl)-L-argine), is transferred and stably maintained and expressed in the transformed plant cells. This phenomenon can be understood as a 'genetic colonization' of the plant cells by bacterial plasmid DNA so that the transformed plant cells will produce and secrete into the medium amino acid derivatives (the opines) that Ti-plasmid carrying agrobacteria can selectively use as carbon and nitrogen sources.

DNA Restriction Enzymes↗
PubMed1978

Low molecular weight RNA species encoded by a multiple drug resistance plasmid.

Multiple drug resistance plasmid NR1 is shown to code for at least 10 low molecular weight RNAs. These species, ranging in size from 60 to 120 nucleotides, have been purified from minicells by two-dimensional gel electrophoresis and characterized by RNase T1 fingerprinting. Hybridization of purified RNAs to restriction endonuclease digests of NR1 DNA indicates that most are derived from the resistance transfer factor region of the plasmid genome. One RNA was found to be coded by the transposable tetracycline resistance element Tn10, and several are associated with DNA fragments that contain origins of replication.

Escherichia coli↗
PubMed1977

Translational fidelity in Escherichia coli: contrasting role of neaA and ramA gene products in the ribosome functioning.

Strains carrying both the ramA1 and the neaA301 mutations do not exhibit the restriction of informational suppressors normally associated with resistance to neamine. Furthermore, ribosomes from such strains exhibit increased misreading in vitro with respect to particles from the neaA strain. These properties suggest that translational fidelity may be cooperatively controlled by ribosomal proteins S4 and S17, coded by ramA (rpsd) and neaA (rpsq) genes respectively.

Drug Resistance, Microbial↗
PubMed1976

Cooperative control of translational fidelity by ribosomal proteins in Escherichia coli. III. A ram mutation in the structural gene for protein S5 (rpx E).

The effect on translational fidelity of a particular mutation in the gene coding for protein S5(rpxE) has been investigated. This mutation has the opposite effect of a restrictive strA mutation; in vivo, it relieves the restriction imposed by strA on the suppression of T4 nonsense mutants and results in hypersensitivity to streptomycin; in vitro, the presence of the altered S5 protein in 30S ribosomes results in increased intrinsic misreading. It is concluded that this mutation, ramC319, acts as a ribosomal ambiguity mutation similar to certain mutations of protein S4 (ramA).

Bacterial Proteins↗
PubMed1975

Cooperative control of translation fidelity by ribosomal proteins in Escherichia coli. I. Properties of ribosomal mutants whose resistance to neamine is the cumulative effect of two distinct mutations.

Two spontaneous mutants of Escherichia coli strain KMBL-146 selected for resistance to the aminoglycoside antibiotic neamine show severe restriction of amber suppressors in vivo. Purified ribosomes from the mutant strains exhibit low neamine-induced misreading in vitro and a decreased affinity for the related antibiotic streptomycin. Biochemical analysis shows that the mutants each have two modified 30S ribosmal proteins, S12 and S5. In agreement with these results, genetic analysis shows that two mutations are present, neither of which confers resistance to neamine by itself; the mutation located in gene rpxL (the structural gene for protein S12) confers streptomycin dependence but this dependence is suppressed in the presence of the second mutation, located in gene rpxE (the structural gene for protein S5).

Chromosome Mapping↗
PubMed1975

Cooperative control of translational fidelity by ribosomal proteins in Escherichia coli. II. Localization of amino acid replacements in proteins S5 and S12 altered in double mutants resistant to neamine.

Protein S5 and S12 were isolated from 30S ribosomal subunits of two E. coli mutants highly resistant to the antibiotic neamine, and of the parental strain. Proteinchemical analyses on these proteins led to the following results: a) In protein S5 the arginine residue in peptide T2 of the parental strain is replaced by glycine in one (nea 314) or serine in the other (nea 319) of the two mutants. b) In protein S12 The proline residue in peptide T15 of the parental strain is replaced by leucine in mutant nea 314 and by glutamine in mutant nea 319. Comparison of these results with those obtained in earlier studies on other mutants with altered ribosomal proteins revealed that the amino acid replacements in neamine resistant mutants and in "revertants" from streptomycin dependence occur at the same amino acid positions of proteins S5 and S12. Therefore it is likely that both types of mutants belong to the same class.

Amino Acid Sequence↗
PubMed1975

Expression of ribosomal protein genes in Escherichia coli.

Streptomycin or spectinomycin treatment of an E. coli strain, carrying the strR and spcR alleles on the chromosome and the wild-type (sensitive) alleles on the episome, selects for inactivation of the relevant sensitive allele. After Mu induced mutagenesis, in the absence of selection against extended deletions upon the episome, a large proportion of stro mutants are also spco, and vice versa. However, when markers flanking the strA and spcA gene cluster are simultaneously selected, effectively eliminating long deletions, the majority of stro mutants continue to express the spcs allele, and vice versa. Insofar as inactivation after Mu treatment is due to prophage insertion within or proximal to the genes in question, this result indicates that the genes strA and spcA are not parts of a single operon. In virtue of the high frequency of extended deletions observed in the absence of suitable counter-selection, we must place a word of caution upon the use of phage Mu-1 as a means of isolating polar mutations and defining transcriptional units.

Bacterial Proteins↗
PubMedDate not supplied

Factors predicting success in picture naming in Alzheimer's disease and primary progressive aphasia.

The aim of the present study was to determine the predictive value of all important variables in the picture naming performance of 8 patients with probable Alzheimer's disease (AD) and 8 patients with primary progressive aphasia (PPA). The experimental investigation controlled for (i) visual complexity, (ii) name agreement on dominant response, (iii) age of acquisition, (iv) frequency, (v) word length, (vi) concept familiarity, and (vii) category membership. The results of the multiple regression analyses showed that age of acquisition and name agreement were significant for 10/16 subjects. Visual complexity, frequency, familiarity, and category were also significant for four patients respectively. Word length had no effect. These results are at variance with those of series of patients with AD (Gaillard et al., 1998) and with PPA (Lambon Ralph et al., 1998) where concept familiarity was found to be one of the most predictive factors of naming success.

Aged↗
PubMedDate not supplied

Age of acquisition and name agreement as predictors of mean response latencies in picture naming of French adults.

We studied the influence of five variables on picture naming latencies in French adult subjects: frequency, age of acquisition and length of words, name agreement in oral naming, and visual complexity of pictures. 140 pictures were presented to 56 subjects with control of individual factors (age, educational level, gender). Naming latency was measured as the time from picture onset until keystroke corresponding to the begin of verbal production. The results of simple and multiple regression analyses show that only two variables make independent contributions to mean response latency: age of acquisition and name agreement. Such state of affairs confirms similar findings obtained with English speaking subjects.

Adult↗