PubMed Health⌕ Search

Biomedical subjects

M Meijer

Publications and source records attributed to M Meijer.

14 recordsLinked to original sources
PubMed1992

[The course of a clinically treated depression in the elderly].

A study was performed of the course of major depressions (DSM-III) of elderly people who had been admitted to a psychogeriatric ward of a general psychiatric hospital. Patients were selected by searching the files. Patients with another diagnosis on axis I or a serious physical illness were excluded. The selected patients were traced and asked to participate in a follow-up investigation. From the files 38 patients were selected, of whom three had died in hospital. The remaining 35 patients included 28 women and seven men, with an average age of 78 years. After discharge seven of them died a natural death and six patients refused to participate. The remaining 22 patients were visited. From the files it appeared that 54% had completely recovered at discharge. Patients with a delusional depression had been hospitalised significantly longer, had been treated with more medicines and had less often been completely recovered at discharge. At the time of the follow up 64% had completely recovered but 32% had had a relapse. Patients with a delusional depression less often recovered completely. A remarkably low percentage of the population studied were able to live on their own. The results of this study are compared with foreign studies.

Aftercare↗
PubMed1992

MPI1, an essential gene encoding a mitochondrial membrane protein, is possibly involved in protein import into yeast mitochondria.

To identify components of the mitochondrial protein import pathway in yeast, we have adopted a positive selection procedure for isolating mutants disturbed in protein import. We have cloned and sequenced a gene, termed MPI1, that can rescue the genetic defect of one group of these mutants. MPI1 encodes a hydrophilic 48.8 kDa protein that is essential for cell viability. Mpi1p is a low abundance and constitutively expressed mitochondrial protein. Mpi1p is synthesized with a characteristic mitochondrial targeting sequence at its amino-terminus, which is most probably proteolytically removed during import. It is a membrane protein, oriented with its carboxy-terminus facing the intermembrane space. In cells depleted of Mpi1p activity, import of the precursor proteins that we tested thus far, is arrested. We speculate that the Mpi1 protein is a component of a proteinaceous import channel for translocation of precursor proteins across the mitochondrial inner membrane.

Amino Acid Sequence↗
PubMed1991

Borderline and schizotypal disorders in children and adolescents.

Until recently, research on borderline disorder in children has sought the common denominator of the symptoms. In recent years there have been attempts to circumscribe the definition with the help of DSM-III criteria and the DIB. This approach appears fruitful. The scanty data on schizotypal children suggest that the validity of this diagnosis in childhood should be investigated. In adolescence it is possible to discern those with borderline and schizotypal disorders whose symptoms meet both DIB and DSM-III-R criteria respectively. No data exist, however, concerning the predictive validity of such disorders in adolescents. Classification on an empirical basis is advocated in order to refine the diagnosis of these and related disorders in children and adolescents.

Adolescent↗
PubMed1988

Mitochondrial biogenesis: recent developments and insights.

Biosynthesis of a functional mitochondrion requires the coordinate expression of genes in both mitochondrial and nuclear DNAs. In yeast, three mitochondrial genes are split and RNA splicing plays a pivotal role in their expression. The recent finding that some introns are capable of self-splicing activity in vitro has permitted analysis of the mechanisms involved in RNA catalysis and may eventually shed light on the evolution of splicing mechanisms in general. Most mitochondrial proteins are encoded by nuclear genes, synthesized in the cytoplasm and imported by the organelle. The availability of cloned genes coding for several constituent subunits of the ubiquinol-cytochrome c reductase, which are imported by mitochondria, has allowed study of selected steps in the addressing of proteins to mitochondria and their intercompartmental sorting within the organelle. Recent developments are discussed.

DNA, Mitochondrial↗
PubMed1987

Evidence for the involvement of the 16kD gene promoter in initiation of chromosomal replication of Escherichia coli strains carrying a B/r-derived replication origin.

Initiation of chromosomal DNA replication of several Escherichia coli dnaA (Ts) strains is diminished in cell harbouring pBR322 hybrid plasmids carrying both oriC and the adjacent 16kD gene promoter of E. coli K12. This perturbance, resulting in very slow growth, is caused both by the dnaA allele and the E. coli B/r-derived region of the replication origin of these strains. Cloning and DNA sequence analysis of the E. coli B/r replication origin revealed several base differences as compared to the E. coli K12 sequence. The replication origin of temperature sensitive fast growing mutants, originating from a homologous exchange between chromosomal and plasmid DNA sequences were also cloned. Sequence data showed that a single base change within the promoter of the 16kD gene of these dnaA (Ts) strains is able to suppress the inhibition of chromosomal DNA replication by the mentioned pBR322 hybrid plasmids. Our results strongly indicate a role of the 16kD gene promoter in control of initiation of chromosomal DNA replication.

Alleles↗
PubMed1986

Efficient isolation of the linear DNA killer plasmid of Kluyveromyces lactis: evidence for location and expression in the cytoplasm and characterization of their terminally bound proteins.

Differential centrifugation of an osmotic lysate of K. lactis protoplasts showed that the linear DNA killer plasmids of K. lactis, pGKL1 and pGKL2, are almost exclusively present in the cytoplasmic fraction. This fractionation procedure allows the rapid isolation of large amounts of plasmid DNA without contamination by chromosomal and mitochondrial DNA. With these DNA preparations the size of the terminally bound proteins was estimated to be 28 and 36 kDal for pGKL1 and pGKL2, respectively. The entire pGKL1 sequence (except for 21 base pairs at the right terminus) was cloned in a shuttle vector that permits autonomous replication in the nucleus of K. lactis. However, killer gene expression could not be established in transformants. In connection with the observed cytoplasmic localization, this result suggests that gene expression of the killer DNA plasmids is entirely cytoplasmic.

Cloning, Molecular↗
PubMed1986

Dissection of promoter sequences involved in transcriptional activation of the Escherichia coli replication origin.

The replication frequency of oriC plasmids in vivo is positively affected by specific transcripts running into oriC. These transcripts that activate oriC are initiated at a promoter of a gene coding for a 16kD protein. Genetic evidence is presented for binding of the initiation factor dnaA to a specific sequence (dnaA box) upstream of this promoter. Binding of the dnaA protein to this dnaA box regulates transcription initiation negatively. It was also demonstrated that binding of dnaA protein to the 16kD promoter region is essential to accomplish the actual activation event within the origin. Replication and incompatibility experiments suggest that dnaA protein is present within the activating transcription complex. The function of dnaA in this replication control mechanism is discussed.

Bacterial Proteins↗
PubMed1985

Site-directed mutagenesis of the Escherichia coli chromosome near oriC: identification and characterization of asnC, a regulatory element in E. coli asparagine metabolism.

We developed a new method for the specific mutagenization of the E. coli chromosome. This method takes advantage of the fact that a pBR322 plasmid containing chromosomal sequences is mobilizable during an Hfr-mediated conjugational transfer, due to an homologous recombination between the E. coli Hfr chromosome and the pBR322 derivative. Transconjugants are screened with a simple selection procedure for integration of mutant sequences in the chromosome and loss of pBR322 sequences. Using this method we specifically inactivated several genes near the E. coli replication origin oriC. We found that a gene coding for asparagine synthetase A. This regulatory mechanism was investigated in detail by determining in vivo regulation of asnA promoter activity by the 17kD protein under different growth conditions. Results obtained also suggest a general regulatory role of the 17kD protein in E. coli asparagine metabolism. Therefore the 17kD gene is proposed to be renamed asnC.

Asparaginase↗
PubMed1979

Nucleotide sequence of the origin of replication of the Escherichia coli K-12 chromosome.

The origin of replication, oriC, of the Escherichia coli chromosome was mapped within a DNA segment of 422 base pairs. The nucleotide sequence of this segment was determined. The source of DNA for the sequence analysis was a minichromosome constructed in vivo, consisting exclusively of chromosomal DNA and a minichromosome constructed by cloning in vitro. The nucleotide sequence of the replication origin is characterized by a high degree of repetitiveness due to both inverted and direct repeats. Sequence homologies were found between portions of the replication origins of E. coli and phages lambda and G4. This suggests similarities in some steps in the initiation of replication of the different replicons.

Base Sequence↗
PubMed1978

Mini-chromosomes: plasmids which carry the E. coli replication origin.

We have isolated plasmids by linking the 5.9 MD EcoRI fragment of E. coli that carries the origin of replication to an EcoRI fragment that carries an amplicillin resistance determinant, but lacks an origin of replication. 3 plasmids of this type, pOC1, pOC2, and pOC3, are described in detail in this report. Although the plasmids have some adverse effect on the growth properties of the host strain, their existence shows that two functioning chromosomal origins can coexist in one cell. Deletions generated from this type of plasmids allow an allocation of the origin of replication of E. coli within a DNA segment less than 0.4 MD in size.

Ampicillin↗