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G Glaser

Publications and source records attributed to G Glaser.

At least 55 records · Page 3Linked to original sources
PubMed1986

Kindling induces a long-lasting change in the activity of a hippocampal membrane calmodulin-dependent protein kinase system.

Septal kindling has been shown to produce a long-lasting decrease in endogenous calcium/calmodulin-dependent phosphorylation of hippocampal synaptic plasma membrane proteins, including two major bands of approximately 50,000 and 60,000 Daltons. These two proteins differ from the B-50 protein and tubulin, as evidenced by differences in migration in SDS-PAGE gels and by lack of cross-immunoreactivity with specific antibodies. Identity of these two proteins with the rho and sigma subunits of purified calmodulin-dependent kinase (CaM Kinase II) is suggested by similar migration in SDS-PAGE and two-dimensional gels, by similar calmodulin binding in two-dimensional gels, and similar 125I-peptide mapping of the 50,000 Dalton protein. These results demonstrate that septal kindling is associated with changes in the activity of a major Ca2+/calmodulin-dependent kinase system in hippocampal synaptic plasma membrane. This long-lasting modulation of kinase activity may provide a molecular insight into some aspects of neuronal plasticity.

Animals↗
PubMed1986

Beta-thalassemia: analysis of mRNA precursors of a mutant human globin gene with defective splicing using peripheral blood nucleated red blood cells.

Studies on the effects of thalassemic mutations on gene function in vivo have clinical as well as scientific implications. Usually these studies have been performed on nucleated red blood cell (RBC) precursors normally present in bone marrow. Many patients with beta-thalassemia are splenectomized and may have high levels of nucleated RBC, orthochromatic normoblasts, in their peripheral blood (1-5% of total RBC). The possibility of exploiting these cells instead of bone marrow as a source for nuclear and cytoplasmic RNA for expression studies was investigated. A simple procedure was developed for enrichment for normoblasts in blood samples withdrawn from patients prior to transfusion. Globin transcripts were analyzed in RNA purified from 12 patients. Unspliced precursor beta-mRNA molecules were observed in a patient with beta o-thalassemia, homozygous for a mutation at the 5' IVS2 splice site of the beta-globin gene. Detailed analyses showed that his mature beta-mRNA was larger than normal, and that a cryptic 5' splice site, approximately 50 nucleotides downstream from the normal one, was utilized. We conclude that peripheral blood can be used as a reliable source of RNA for the analysis of the effects of beta-thalassemia mutations on gene expression and the relationship to the clinical condition. Moreover, this procedure facilitates the comparison of in vivo gene expression with the results obtained from DNA transfection experiments with cloned beta-thalassemia genes.

Adolescent↗
PubMed1985

Procaryotic and eucaryotic traits of DNA methylation in spiroplasmas (mycoplasmas).

Differences in the type of base methylated (cytosine or adenine) and in the extent of methylation were detected by high-pressure liquid chromatography in the DNAs of five spiroplasmas. Nearest neighbor analysis and digestion by restriction enzyme isoschizomers also revealed differences in methylation sequence specificity. Whereas in Spiroplasma floricola and Spiroplasma sp. strain PPS-1 5-methylcytosine was found on the 5' side of each of the four major bases, the cytosine in Spiroplasma apis DNA was methylated only when its 3' neighboring base was adenine or thymine. In Spiroplasma sp. strain MQ-1 over 95% of the methylated cytosine was in C-G sequences. Essentially all of the C-G sequences in the MQ-1 DNA were methylated. Partially purified extracts of S. apis and Spiroplasma sp. strain MQ-1 were used to study substrate and sequence specificity of the methylase activity. Methylation by the MQ-1 enzyme was exclusively at C-G sequences, resembling in this respect eucaryotic DNA methylases. However, the MQ-1 methylase differed from eucaryotic methylases by showing high activity on nonmethylated DNA duplexes, low activity with hemimethylated DNA duplexes, and no activity on single-stranded DNA.

Base Composition↗
PubMed1984

Physical mapping of the ribosomal RNA genes of Mycoplasma capricolum.

Physical mapping of the rRNA genes of Mycoplasma capricolum was done by digestion of the mycoplasmal DNA with EcoRI, PstI and BglII and hybridization with nick-translated probes consisting of defined portions of the rrnB ribosomal RNA operon of Escherichia coli. The results indicate that the rRNA genes in the chromosome of M. capricolum are arranged in two clusters, each organized in the order 5'-16S-23S-5S-3', resembling the order of the genes in the rrnB operon, with no large spacer regions separating the genes in each cluster.

Base Sequence↗
PubMed1984

Detection of mycoplasmas infecting cell cultures by DNA hybridization.

Infection of cell cultures by mycoplasmas can be detected and the mycoplasma identified by Southern blot hybridization of the Eco RI-digested DNA of the suspected cell cultures with a nick-translated probe consisting of cloned ribosomal RNA genes of Mycoplasma capricolum. The probe does not hybridize with eukaryotic DNA. The hybridization pattern with mycoplasmal DNA is species specific, enabling the identification of the four most prevalent mycoplasma contaminants, Mycoplasma orale, Mycoplasma hyorhinis, Mycoplasma arginini, and Acholeplasma laidlawii. The test is also very sensitive and can detect as little as 1 ng of mycoplasmal DNA, roughly equivalent to the DNA content of 10(5) mycoplasmas.

Animals↗
PubMed1984

Developmental aspects of focal epilepsies of childhood treated by neurosurgery.

Data on 50 patients treated surgically for intractable focal epilepsy were analysed. There were 10 hemispherectomies, 32 temporal lobectomies and eight operations to other areas of the brain. The median age at operation was 14 years. 29 patients were found to have mesial temporal sclerosis or sclerotic hemispheres and 17 had alien tissue and one sclerosis with heterotopia. No lesion was found in three cases. The nature of the first seizure was found to relate significantly to pathology. 30 patients had suffered an early convulsion. Between the convulsive insult and the onset of focal epilepsy there was a silent interval, the duration of which was biased by sex and side of lesion. The remaining 20 patients, of whom a highly significant number had alien tissue, had not had an early convulsion before the onset of focal epilepsy. The importance of accurate clinical histories is stressed. Clinical considerations alone predicted the pathology and laterality of the lesion in more than half the series. Regular EEG recordings and repeat scanning were found to be important investigations. Major disorders of behaviour had occurred in 44 patients. As adults, the series were free of severe psychiatric symptoms, but many required years of careful rehabilitation. 31 children had been excluded from normal schools before operation. Postoperatively, many patients continued their education in normal schools. Some required basic remedial teaching, others successfully undertook higher education and training. 49 patients benefited over-all from neurosurgical treatment. 34 had no more habitual epilepsy at all. Full global gains often took at least five years to achieve.

Adolescent↗
PubMed1984

Mycoplasmas (Mollicutes) have a low number of rRNA genes.

DNA from Mycoplasma, Ureaplasma, Acholeplasma, and Spiroplasma species digested by restriction endonucleases was hybridized with probes consisting of portions of the rrnB rRNA operon of Escherichia coli and the rRNA operon of Mycoplasma capricolum. The results indicate the presence of only one or two sets of rRNA genes in the genome of Mollicutes linked in the procaryotic fashion, 16S-23S-5S.

Acholeplasma↗
PubMed1984

Mycoplasmal ribosomal RNA genes and their use as probes for detection and identification of Mollicutes.

The number and organization of ribosomal RNA (rRNA) genes in the genome of Mycoplasma, Ureaplasma, Acholeplasma and Spiroplasma species were studied by the Southern hybridization technique. Restriction endonuclease-digested DNAs of the organisms were hybridized with nick-translated probes consisting of defined portions of the rrnB rRNA operon of Escherichia coli and with a recombinant plasmid pMC5 constructed of pBR325 and an insert containing M. capricolum genes for 23S, 5S and most of the 16S rRNA gene. The hybridization data indicate the presence of only one or two sets of rRNA genes in the mollicutes tested, a number lower than in eubacteria. The rRNA genes in mollicutes appear to be organized as clusters (acting apparently as operons) in the typical prokaryotic fashion, 5'-16S-23S-5S-3'. Despite the marked sequence homology shared by the rRNA operons of the different mollicutes and of E. coli, the operons are not identical. Thus, there is an EcoRI restriction site in the 16S rRNA genes in only 8 of the 13 species tested. The recombinant plasmid pMC5 has provided a sensitive probe for detection and identification of mollicutes in contaminated cell cultures. The purified DNA of the tested cell culture, or its supernatant fluid, was digested by EcoRI, and Southern blot hybridization of the products was performed with nick-translated pMC5. The probe did not hybridize with eukaryotic DNA. Each of the mollicutes species examinated exhibited a species-specific hybridization pattern. The hybridization tests enabled the identification of the four most prevalent mycoplasma contaminants of cell cultures, M. orale, M. hyorhinis, M. arginini and A. laidlawii. The test is capable of detecting 1 ng of mycoplasmal DNA, roughly equivalent to the DNA content of 10(5) mycoplasmas. The possibility of using this approach for detection and identification of noncultivable mycoplasmas in plant and insect tissues is under investigation.

Animals↗
PubMed1983

Functional interrelationship between two tandem E. coli ribosomal RNA promoters.

The Escherichia coli chromosome carries seven cistrons encoding ribosomal RNA sequences. In all cases studied, in vitro and in vivo, it has been established that transcription is initiated from two tandem promoters. The expression of the rRNA cistrons is regulated in response to growth rate as well as to aminoacyl tRNA availability. In the present study, a plasmid (pPS1) carrying the promoter region of the rrnA cistron fused to the terminator region of rrnB has been used for in vitro transcription experiments. The presence of the terminators (T1 and T2) together with the fact that supercoiled DNA is found to be a highly efficient template, provide an ideal in vitro system in which to study the functional interrelationship between the two tandem promoters of E. coli rRNA cistrons. The results suggest that the rate of rRNA synthesis in E. coli cells growing in various conditions, as reflected by the availability of RNA polymerase, is primarily dependent on the properties of the two tandem rRNA promoters.

Escherichia coli↗
PubMed1982

[Gene therapy].

Explore the source record for details and available documents.

DNA, Recombinant↗
PubMed1982

Ribosomal RNA genes in Mycoplasma.

Using Southern blotting analysis with labelled mycoplasmal ribosomal RNA as probe, two fragments (1 Kb and 5 Kb) were detected in an EcoR I digest of Mycoplasma capricolum DNA. This analysis revealed that the 5 Kb fragment carries both 16S rRNA sequences and the entire 23S rRNA gene of this mycoplasma. The 1 Kb fragment contains 16S rRNA sequences only. The 5 Kb EcoR I fragment has been cloned and used to characterize the structure of rRNA cistrons in various Mycoplasma strains. These experiments clearly demonstrate a substantial homology of Mycoplasma capricolum rRNA sequences with the E. coli rRNA cistron on one hand, and with Mycoplasma mycoides subsp. capri and Acholeplasma laidlawii on the other hand. This analysis also reveals two rRNA cistrons in Mycoplasma mycoides subsp. capri and Acholeplasma laidlawii whereas one rRNA cistron is present in Mycoplasma capricolum.

Acholeplasma laidlawii↗
PubMed1982

The chemistry of favism-inducing compounds. The properties of isouramil and divicine and their reaction with glutathione.

Isouramil and divicine are pyrimidine aglycones of two glucosides found in broad beans. They have been shown to be strong reducing agents. Their reaction with oxygen in a (gas) saturated solution, 26 degrees C, is characterized by tau 1/2 = 1 min and 3 min respectively. Hydrogen peroxide is formed in this reaction stoichiometrically (1:1). The pyrimidines lose two hydrogen and form an intermediate that is structurally analogues to alloxan. This intermediate is not stable, and in the absence of reducing agents it decomposes, possibly by ring-cleavage. In the presence of reduced glutathione the intermediate is reduced and can now react with oxygen once again. Thus, the pyrimidines cycle between the two states and the net reaction is the catalytic oxidation of glutathione by molecular oxygen; in each cycle 4 molecules of glutathione are dissipated. The possible involvement of these pyrimidines in the pathogenesis of favism may be in a similar mechanism. Red blood cells deficient in glucose-6-phosphate dehydrogenase cannot cope with such an oxidative challenge exerted by the pyrimidines. Consequently an irreversible cellular damage can take place leading to the enhanced sequestration of these red blood cells by the reticuloendothelial system.

Animals↗
PubMed1981

Stable RNA synthesis and its control in Mycoplasma capricolum.

The synthesis of stable RNA in Mycoplasma capricolum was studied by [32P] labeling of cellular RNA of cells grown in a partially-defined medium in the presence or absence of an amino acid mixture supplement. The results indicate that M. capricolum employs the same stringent control mechanism used by E. coli cells, as judged by a decreased synthesis of stable RNA and accumulation of 5'-triphosphoguanosine-3'-diphosphate (pppGpp) and 5'-diphosphoguanosine-3'-diphosphate (ppGpp) in response to amino acid starvation. In addition, the results suggest that precursors of stable RNA accumulate and an intracellular pool of the precursors exists at all times under the growth conditions used by us. These findings may be interpreted to reflect a slow rate of RNA processing in M. capricolum.

Amino Acids↗
PubMed1980

On the mechanism of the glucose-induced ATP catabolism in ascites tumour cells and its reversal by pyruvate.

Addition of glucose to Ehrlich-Landschütz ascites tumour cells preincubated for 30-60 min in phosphate-buffered Krebs-Ringer salt solution ("starved cells") resulted within 1-2 min in an approx. 90% decline of their ATP content and a massive accumulation of fructose 1,6-bisphosphate. These alterations, which took place under both aerobic and anaerobic conditions, were followed by a gradual spontaneous recovery with restoration of normal ATP and fructose 1,6-bisphosphate values. The transient derangement of the energy metabolism after glucose addition to starved ascites tumour cells by preventable by simultaneous addition of pyruvate or 2-oxobutyrate, or by preincubating the cells in the presence of glucose. The protective effect of pyruvate was duplicated by addition of phenazine methosulphate or NAD+ to the incubation medium. The data seem to warrant the conclusion that the glucose-induced ATP depletion is determined by a blockade of glycolysis at the stage of glyceraldehyde phosphate dehydrogenase caused by the failure of the cells to oxidize the NADH produced in the same reaction. The continued unrestrained action of 6-phosphofructokinase results in accumulation of fructose 1,6-bisphosphate, which constitutes a trap for the high-energy phosphate bonds of ATP. The primary metabolic disturbance appears to consist of a transient inhibition of pyruvate kinase with the resultant inability of the cells to maintain an unimpaired supply of pyruvate, as required for the lactate dehydrogenase-mediated oxidation of NADH. The regulatory mechanism underlying this phenomenon is discussed.

Adenosine Triphosphate↗
PubMed1980

Fusion of the promoter region of rRNA operon rrnB to lac Z gene.

A Lambda phage was constructed in which the structural gene for beta galactosidase is fused to a DNA segment carrying the ribosomal promoter rrnB of E. coli. In this hybrid operon beta galactosidase synthesis in vitro is repressed by ppGpp. Repression of beta galactosidase synthesis by cAMP is reported.

Bacteriophage lambda↗
PubMed1980

Studies on the biological role of dna methylation; IV. Mode of methylation of DNA in E. coli cells.

Two pairs of restriction enzyme isoschizomers were used to study in vivo methylation of E. coli and extrachromosomal DNA. By use of the restriction enzymes MboI (which cleaves only the unmethylated GATC sequence) and its isoschizomer Sau3A (indifferent to methylated adenine at this sequence), we found that all the GATC sites in E. coli and in extrachromosomal DNAs are symmetrically methylated on both strands. The calculated number of GATC sites in E. coli DNA can account for all its m6Ade residues. Foreign DNA, like mouse mtDNA, which is not methylated at GATC sites became fully methylated at these sequences when introduced by transfection into E. coli cells. This experiment provides the first evidence for the operation of a de novo methylation mechanism for E. coli methylases not involved in restriction modification. When the two restriction enzyme isoschizomers, EcoRII and ApyI, were used to analyze the methylation pattern of CCTAGG sequences in E. coli C and phi X174 DNA, it was found that all these sites are methylated. The number of CCTAGG sites in E. coli C DNA does not account for all m5Cyt residues.

Base Sequence↗