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Biomedical subjects

G Christiansen

Publications and source records attributed to G Christiansen.

At least 109 records · Page 6Linked to original sources
PubMed1986

Ultrastructural changes in mollicutes induced by the peptide antibiotic herbicolin A.

Electron microscopy of negatively stained mycoplasma, ureaplasma, and acholeplasma cells showed ultrastructural changes after 10 min of treatment of the organisms with the peptide antibiotic herbicolin A in concentrations ranging from 10 micrograms/ml for Mycoplasma capricolum to 600 micrograms/ml for Ureaplasma urealyticum. The morphological changes were shown to be reversible at low concentrations of the antibiotic but irreversible at high concentrations.

Acholeplasma↗
PubMed1985

The structure of two distinct pancreatic amylase genes in mouse strain YBR.

The amylase complex on mouse chromosome 3 encodes both salivary and pancreatic amylase. It appears that one active gene is present for salivary amylase, whereas pancreatic amylase in some strains is coded by at least 4, and perhaps by more than 10, genes. Strain YBR is different from other strains in that it produces twice as much salivary amylase. Pancreatic amylase in YBR is present as two different protein forms, A beta and B beta, the sum of which amounts to only one-third of that in, for instance, strain A/J. YBR chromosomal DNA was cloned in phage gamma, followed by restriction and heteroduplex analysis of recombinant phages carrying amylase genes. Among 32 phage isolates, 5 carried parts of the salivary amylase sequence. The remaining phage isolates contained pancreatic amylase-like sequences and represented three nonoverlapping genomic regions, i.e., one of 34 kb containing a complete gene, PAN-II beta; another of 41 kb with a complete but different gene, PAN-I beta, plus a truncated gene, PAN-psi 1; and finally, one of 23 kb with another truncated gene, PAN-psi 2. Parts of the amino acid sequence of A beta and B beta have previously been determined, and we report here the sequencing of a 4-kb DNA fragment from Pan-II beta which establishes that this gene codes for B beta.

Amino Acid Sequence↗
PubMed1984

Electrophoretic analysis of proteins from Mycoplasma capricolum and related serotypes using extracts from intact cells and from minicells containing cloned mycoplasma DNA.

The acidic proteins of six different mycoplasma serotypes causing bovine or caprine pleuropneumonia were compared by two-dimensional gel electrophoresis of extracts of 35S-labelled cells. The organisms investigated were Mycoplasma mycoides subsp. mycoides (PG1), M. mycoides subsp. mycoides (Y-goat), M. mycoides subsp. capri (PG3), M. capricolum (California kid), the unclassified bovine serogroup 7 of Leach (PG50) and the F38-like group (F38). The results suggested a close relationship between M. capricolum and F38 and a similarly close relationship between the different M. mycoides subspecies, whereas the two M. mycoides subspecies appeared to be quite distant from M. capricolum and F38. The representative strain of the bovine serogroup 7 of Leach was equally distant from F38, M. capricolum and the three strains of M. mycoides. Strikingly, all six mycoplasma strains apparently shared six proteins in the two-dimensional gels. In Escherichia coli minicells, DNA from strain PG50 cloned in the vector pBR325 gave rise to incorporation of radioactive label into proteins which were identified as mycoplasma proteins by two-dimensional electrophoresis and immunoprecipitation.

Autoradiography↗
PubMed1984

Comparison of gel filtration and ammonium sulphate precipitation in the purification of diphtheria toxin and toxoid.

Crude diphtheria toxin and toxoid were subjected to purification by gel filtration and stepwise ammonium sulphate precipitation. The various fractions obtained by the purification procedures were studied by immunological methods. A high molecular weight fraction of glycoprotein nature was present in all of the crude preparations studied. The fraction was antigenically non-identical with the real toxin or toxoid and did not have its origin in the culture medium. It showed a long flocculation time when tested against equine diphtheria toxoid antiserum. The fraction could be removed from the crude preparations by gel filtration or by precipitation with 21% (w/v) ammonium sulphate. When comparing toxoids purified by each of these methods, the method of gel filtration resulted in a somewhat higher degree of purity, suggesting that this method would be more suitable than the AS precipitation method for the purification of diphtheria toxoid.

Ammonium Sulfate↗
PubMed1984

Analysis of the mycoplasma genome by recombinant DNA technology.

A library of DNA fragments from Mycoplasma sp. strain PG50 has been made in the vector pBR325. Analysis in Escherichia coli minicells of randomly picked clones from this library demonstrated that many plasmids can promote synthesis of mycoplasma protein in the E. coli genetic background. Screening with labeled rRNA identified plasmids with sequences from the beginning of the rRNA cistron to about two-thirds within the gene for 23S rRNA. Use of these plasmids as probes allowed an accurate determination of the number of RNA cistrons as two, and demonstrated that the cistrons are more than 20 kbp apart. The DNA sequence of 16S rRNA and the surrounding control regions has been determined.

Bacterial Proteins↗
PubMed1984

Subdivision of vaginal isolates of anaerobic curved bacteria based on genetic, morphologic, biochemical and gas-chromatographic/mass-spectrometric studies.

By DNA-DNA hybridization we could recognize two distinct groups of anaerobic curved rods (CR) that had been isolated from the vaginal content of women with bacterial vaginosis. On the basis of morphological studies these two groups correlated with one group of short, Gram-variable, curved rods (SCR) and another consisting of similar but somewhat longer rods (LCR). The SCR had up to four flagella per cell and the LCR up to eight. Among 79 biochemical tests, only tests for ONPG and arginine dehydrolase differentiated the two groups, SCR being positive and LCR negative. The gas chromatographic analysis of spent culture medium revealed that LCR, but not SCR, produced oxalacetic and oxalic acids. The groups were also differentiated by gas-chromatographic/mass-spectrometric patterns of certain cellular fatty aldehydes. Cell wall structure and presence of cytoplasmic inclusions did not distinguish SCR from LCR. On the basis of DNA-DNA hybridization values the SCR formed a more heterogeneous group than did LCR. Of all biochemical tests performed, only the production of alpha-galactosidase separated two strains of SCR that showed a low percentage of hybridization along with the rest of the SCR strains. Our study does not support a subdivision of SCR.

Aldehydes↗
PubMed1984

Genetic relationships of short and long anaerobic curved rods isolated from the vagina.

DNA from anaerobic curved rods (CR) isolated from the human vagina were analysed regarding sequence homology and guanine + cytosine content. Of the strains of CR tested, ten belonged to the short (SCR) (approximately 1 micron) and eight to the long (LCR) (approximately 2-4 micron) CR type. A low level of homology (5-10%) was found between SCR and LCR. The LCR were a fairly homogeneous group of bacteria, with homologies ranging from 70 to 100%. The SCR fell into three DNA homology groups: one with 85%, and another with approximately 60% homology, while two strains belonging to the latter group hybridized with only 33%.

Bacteria, Anaerobic↗
PubMed1983

Heterology of mitochondrial DNA from mammals detected by electron microscopic heteroduplex analyses.

Heteroduplex analysis of mitochondrial DNA (mtDNA) from evolutionary closely related mammals (rat vs. mouse, man vs. monkey) are analyzed and compared to heteroduplex analysis of mt-DNA from more distantly related mammals (rat vs. man, rat vs. monkey, mouse vs. man, mouse vs. monkey and man vs. cow). Each analysis is transformed into a heteroduplex map and all maps are aligned to restriction enzyme maps and to genetic maps and where possible compared with the known sequence. We show that early evolutionary changes are seen mainly in URF2, URFA6L, URF6 and the D-loop region. The regions of rRNA, URF1, COI and COIII are generally very conserved regions but areas with some evolutionary activity can be localized. Heteroduplex analysis between distantly related species show much more heterology than do closely related species and the heteroduplex maps between all the distantly related species show a common pattern of heterology. Comparisons between the DNA sequence of mtDNA from man, cow and mouse and the equivalent heteroduplex maps show that base pair homologies higher than 73% are displayed as homologous regions. In the heteroduplex analysis of mtDNA's from more closely related species very few heterologies are displayed at 50% formamide but an increase in formamide concentration to 65-70% demonstrate also in these instances general heterologous regions.

Animals↗
PubMed1983

Complex forms of mitochondrial DNA in human B cells transformed by Epstein-Barr virus (EBV).

Human lymphocytes and lymphoid cell lines were analyzed for the presence of complex forms of mitochondrial DNA (mtDNA) by electron microscopy. A high frequency (9%-14.5%) of catenated dimers, circular dimers, or oligomers were found in samples from Epstein-Barr-virus-(EBV) transformed lymphoblastoid cell lines. These complex forms of mtDNA were present in much lower frequencies in lymphocytes isolated from donor blood (1.3%-4.6%). Similar low frequencies were found with primary fibroblasts (1.1%) or freshly isolated monkey liver cells (2.1%). Samples from cultures of Burkitt lymphoma (BL) cell lines of EBV-positive or -negative origin contained intermediate (5%-7%) frequencies of complex forms of mtDNA.

Animals↗
PubMed1983

Fc-mediated immune precipitation. III. Visualization by electron microscopy.

Fc-mediated interactions between immune complexes are of major importance for the precipitin reaction. In the present study these interactions were investigated by means of electron microscopy. Keyhole limpet haemocyanin (KLH) was adsorbed to a thin glow charged carbon supporting film and reacted with either rabbit anti-KLH IgG or anti-KLH F(ab')2 fragments. The Fc-Fc interactions were investigated by reacting these surface-adsorbed antibody-rich KLH immune complexes with soluble, antigen-rich ferritin-anti-ferritin complexes using either rabbit anti-ferritin IgG or the corresponding isomolar F(ab')2 fragments as antibody. Fc-Fc interactions were indicated by the formation of clusters or ring structures of ferritin molecules, which were only seen when using KLH anti-KLH IgG and ferritin-anti-ferritin IgG complexes. When F(ab')2 fragments were used as antibody, no reaction between KLH anti-KLH complexes and ferritin-anti-ferritin complexes could be demonstrated.

Animals↗
PubMed1979

Quantification of tetanus antitoxin in human sera. II. Comparison of counter-immunoelectrophoresis and passive haemagglutination with toxin neutralization in mice.

We described recently an improved counter-immunoelectrophoretic method for quantification of tetanus antitoxin. The toxin neutralization test in mice is considered to correlate well with protection in humans. In the present study, the correlation coefficient between the two methods was 0.89. Sera containing more than 7.0 I.U./ml could be quantified directly by counter-immunoelectrophoresis, while sera containing less tetanus antitoxin had to be concentrated prior to quantification. The passive haemagglutination test was also compared with the toxin neutralization test in mice. The correlation coefficient between the two methods was 0.76.

Antibodies, Bacterial↗
PubMed1978

Electron microscope visualization of chromatin and other DNA-protein complexes.

In this review we have tried to cover the direct mounting techniques currently in use and, through micrographs kindly supplied by our colleagues, to illustrate uses of the different methods. For the novice, it is important to select one technique, taking time to become acquainted with its use in visualizing simple test samples before applying it to examine more complex structures. We have tried to emphasize the importance of controlling the fixation for two reasons. First, confidence in the fixation step allows one to correlate structures observed by EM with structures present in solution. Second, fixation of otherwise labile samples allows one to apply powerful purification techniques.

Chromatin↗
PubMed1977

Salt and divalent cations affect the flexible nature of the natural beaded chromatin structure.

A natural chromatin containing simian virus 40 (SV40) DNA and histone has been used to examine changes in chromatin structure caused by various physical and chemical treatments. We find that histone H1 depleted chromatin is more compact in solutions of 0.15M NaCl or 2 mM MgCl2 than in 0.01 M NaCl or 0.6M NaCL, and is compact in 0.01 M NaCl solutions if histone H 1 is present. Even high concentrations of urea did not alter the fundamental beaded structure, consisting of 110A beads of 200 base pair content, each joined by thin DNA bridges of 50 base pairs. The physical bead observed by EM therefore contains more DNA than the 140 base pair "core particle". The natural variation in the bridge length is consistent with the broad bands observed after nuclease digestion of chromatin. Chromatin prepared for EM without fixation containing long 20A to 30A fibers possibly complexed with protein.

Cations, Divalent↗