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G Klotz

Publications and source records attributed to G Klotz.

At least 19 recordsLinked to original sources
PubMed1990

Terminal redundancy and circular permutation of mycoplasma virus L3 DNA.

This communication reports the physical map of mycoplasma virus L3 (MV-L3) DNA derived from restriction patterns obtained by digestion with seven different restriction endonucleases. The length of the restriction map is 36,200 bp in contrast to the contour length of native MV-L3 DNA molecules which is 39,400 bp as determined by electron microscopy. The difference in length of 3,200 bp (corresponding to 8.1% of the native viral DNA contour length) is explained by terminal redundancy. It was possible to clone all fragments from particular restriction patterns into Escherichia coli vector pAT153, an indication of circular permutation within a population of MV-L3 DNA. However clear evidence has been obtained from the molar ratios of fragments and from hybridization experiments. We suppose that viral DNA is packaged from a concatemeric precursor molecule starting at a specific site called pac.

Acholeplasma laidlawii↗
PubMed1989

Release of mycoplasmavirus L1 upon transfection of Acholeplasma laidlawii with homologous and heterologous viral DNA.

This communication reports on the release of Mycoplasmavirus L1 after infection of Acholeplasma laidlawii with purified L3 virus. Release also occurred after transfection with certain restriction fragments from MV-L3 and MV-L1 genomes. Since circular molecules are efficiently taken up in polyethylene glycol-mediated transfection, inducing fragments were applied cloned in E. coli plasmids. Release was also observed after electroporation of cells incubated with MV-L1 replicative intermediate DNA and linear MV-L3 DNA isolated from virus particles, respectively. Released MV-L1 viruses were identified after virus plaque formation on indicator lawns according to plaque morphology and hybridization with labeled viral DNA probes as well as by DNA restriction analysis. Uninfected and untransfected cells from six laboratory strains of A. laidlawii (including a MV-L1 resistant one) were examined for the presence of MV-L1 DNA. They all bear MV-L1 DNA integrated in their genomes.

Acholeplasma↗
PubMed1989

[Cervicofacial actinomycosis. Apropos of 2 atypical locations].

Cervico-facial actinomycosis is a chronic bacterial disease caused by actinomycetes. The diagnosis may be made on the specific anatomo-pathological appearance of the granulomas and be confirmed by anaerobic culture of the germs. The authors report two atypical cases: the first is a case of a thyroglossal pseudocyst, the second that of adenoidal vegetations in an adult. Treatment with Penicillin G or V for six weeks produced a favourable response. The various clinical forms of the condition described in the literature, should encourage the physician to include bacteriological testing for actinomycetes among his investigations.

Actinomycosis, Cervicofacial↗
PubMed1988

Increased amounts of small polydisperse circular DNA (spcDNA) in angiofibroma-derived cell cultures from patients with tuberous sclerosis (TS)

Much greater amounts of small polydisperse circular DNA (spcDNA) have been detected, in cell cultures derived from angiofibromas of six patients with tuberous sclerosis (TS) than in those from the skin of these patients or from the skin of 11 healthy donors. This observation could be confirmed by spreading the DNA of appropriate fractions from CsCl density gradients. The findings suggest the existence of a relationship between the chromosomal instability observed in angiofibroma cultures and the mobilization of spcDNA.

Adult↗
PubMed1988

Electroporation-mediated transfection of Acholeplasma laidlawii with mycoplasma virus L1 and L3 DNA.

In contrast to mycoplasma virus L1 and L2 circular DNA, mycoplasma virus L3 linear DNA is not biologically active in polyethylene glycol-mediated transfection. Electroporation of Acholeplasma laidlawii, however, leads to plaque formation after incubation with L3 DNA. The efficiency of electroporation-mediated transfection is 1/10 that of polyethylene glycol-mediated transfection as estimated with L1 DNA. Trypsin treatment of cells before DNA addition increases the efficiency of DNA uptake.

Acholeplasma laidlawii↗
PubMed1987

Recognition of covalent insulin-receptor complexes on viable adipocytes by anti-insulin antibodies.

Isolated rat adipocytes were photo-affinity-labelled with B2-(4-azido-2-nitrophenylacetyl)-des-PheB1-insulin or B29-(4-azido-2-nitrophenylacetyl)insulin. Four anti-insulin antibodies (3 monoclonal, 1 polyclonal) were tested for their ability to inhibit the persistent stimulation of lipogenesis caused by the covalently bound insulin [Brandenburg et al. (1980) Nature (London) 286, 821-822]. The polyclonal and 2 monoclonal antibodies, directed against the C-terminus of the B-chain, gave a significant depression, while one antibody, directed against the region A(8-10), was without effect. Under reversible conditions, without irradiation, all antibodies completely inhibited lipogenesis. For the polyclonal antibody this is shown in a dose-dependent way. It is concluded that the effective antibodies can recognize their epitope because it is accessible on the surface of the complex and does not represent part of the receptor-binding surface of insulin. This binding leads to interference with the generation and/or transmittance of the biological signal.

Adipose Tissue↗
PubMed1986

Structure of viroid replicative intermediates: physico-chemical studies on SP6 transcripts of cloned oligomeric potato spindle tuber viroid.

The structure and structural transitions of transcripts of cloned oligomeric viroid were studied in physico-chemical experiments and stability calculations. Transcripts of (+) and (-) polarity, from unit up to sixfold length, were synthesized from DNA clones of the potato spindle tuber viroid (PSTV) with the SP6 transcription system. Their structural properties were investigated by optical denaturation curves, high performance liquid chromatography (HPLC), electron microscopy, sedimentation-diffusion equilibrium and velocity sedimentation. Secondary structures of the RNAs and theoretical denaturation curves were calculated using an energy optimization program. The secondary structure of lowest free energy for unit length and oligomeric transcripts is a rod-like structure similar to that of the mature circular viroids. When this structure is used as a model for calculations, there is a large degree of agreement between the theoretical and the experimental denaturation curves. At high temperatures, however, (+) strand transcripts exhibited a transition which was more stable than expected from the calculations or than was known from curves of mature viroids. This transition arises from a rearrangement of the central conserved region of viroids to a helical region of 28 stable base pairs either intermolecularly leading to bimolecular complexes, or intramolecularly giving rise to a branched secondary structure. The rearrangement could be detected by electron microscopy, HPLC, and analytical ultracentrifugation. The helical region serves to divide up the oligomeric (+) strand into structural units which may be recognized by cleavage and ligation enzymes which process the oligomeric intermediates to circular mature viroids.

Microscopy, Electron↗
PubMed1984

Viroid replication: equilibrium association constant and comparative activity measurements for the viroid-polymerase interaction.

The binding and replication of purified potato spindle tuber viroid (PSTV) by DNA-dependent RNA polymerase II from wheat germ was studied in analytical ultracentrifugation experiments and in vitro transcription assays. The equilibrium association constant for the viroid-polymerase interaction is 1.9 X 10(7) M-1. Both ultraviolet and fluorescent monitoring during the sedimentation experiments showed two distinguishable viroid-polymerase complexes. These are interpreted as resulting from a 1:1 and 2:1 enzyme-to-viroid binding stoichiometry. A265/A280 ratios across the sedimenting boundaries, the sedimentation velocity of the complexes, as well as electron microscopic data support this interpretation. The role of viroid secondary structure in enzyme binding and polymerization is discussed in the light of these results and compared with binding and polymerization data for virusoid RNA, single- and double-stranded RNA, and double-stranded DNA.

Microscopy, Electron↗
PubMed1984

Biological potency of covalently linked insulin-receptor in rat adipocytes. Comparison with the potency of reversible complexes.

Irradiation of photoreactive insulin derivatives in the presence of isolated rat adipocytes produces a prolonged stimulation of lipogenesis in the cells even after exogenous and reversibly bound derivative has been removed by extensive washing. The quantitative nature of this response has now been studied using 125I-B2(2-nitro-4-azidophenylacetyl)des-PheB1-insulin. This derivative possesses nearly full biological potency and binding affinity prior to irradiation. After covalent linkage to adipocytes the efficacy of the derivative is reduced to 25 +/- 4% of the reversibly bound derivative, viz. 4-times as much needs to be covalently associated as reversibly bound to induce the same level of stimulation of lipogenesis. This reduced relative molar potency is due to a reduced ability of specific covalent insulin-receptor complexes to trigger a response.

Adipose Tissue↗
PubMed1984

Biological activity of covalently-linked insulin-receptor complexes in rat adipocytes. Effect of pH.

The relative molar potencies of covalently and reversibly-bound insulin-receptor complexes were studied as a function of pH. The insulin derivatives used were 125I-B2 (2-nitro-4-azidophenylacetyl)des-PheB1-insulin and 125I-B29(2-nitro-4-azidophenylacetyl)des-PheB1-insulin. The potencies of both types of reversible complexes were effectively identical and constant between pH 7 and 8. The relative potency of the covalent B2-complex increased from 25 to 75%, and of the covalent B29 complex from 30 to nearly 100%. This indicates that the covalently linked partners in the complex are able to flex about the cross-linkages. Variations in the potency are due to variations in the number of correctly associated, reversibly or covalently bound insulin-receptor complexes. The form of the pH dependance suggests that an ionizable group, possibly an amino group, must be deprotonated to allow effective interaction.

Adipose Tissue↗
PubMed1984

The biological potency of covalent insulin-receptor complexes. Dependence on site of cross-linkage.

A radioactive photosensitive insulin analogue, 125I-N epsilon B29-(4-azido-2-nitrophenyl-acetyl)insulin, was covalently bound to the receptors of isolated rat adipocytes by irradiation with UV light. This caused a stimulation of lipogenesis. The relative potency of the covalent complexes to that of normal reversible complexes was calculated by comparing the amounts of radioactivity required to be covalently or reversibly bound by adipocytes to cause the same levels of stimulation. For several different occupancies , this relative potency was constant at 50 +/- 3%. Previous studies had shown that the relative potency of covalently bound 125I-N alpha B2-(4-azido-2- nitrophenylacetyl )des- PheB1 -insulin was only 25 +/- 4% under identical conditions. This demonstrates that the sites of crosslinking have a marked effect on the potency of the covalent hormone-receptor complex. It appears that attachment through the C-terminus of the B-chain leads to a better stabilization of the biologically active form than linking through the more flexible N-terminus.

Adipose Tissue↗
PubMed1981

An unusual symmetric recombinant between adenovirus type 12 DNA and human cell DNA.

On purification of human adenovirus type 12 (Ad12) by equilibrium sedimentation in CsCl density gradients, two bands of particles, Ad12-3 and Ad12-3a, are observed. The particles from band Ad12-3a contain a recombinant of human host cell DNA and of Ad12 DNA. The human cell DNA sequences contain repetitive DNA recurring 200 to 500 times in cellular DNA. Ad12 DNA and the recombinant genomes exhibit the same or similar lengths. This finding suggests that a constant amount of DNA is packaged into complete Ad12 particles. On cleavage of KB cellular DNA with EcoRI, BamHI, HinfI, Msp I, Mbo I Pst I, or Bgl II, the (32)P-labeled cellular DNA from Ad12-3a particles hybridizes on Southern blots to distinct bands of KB DNA. There is also less-specific background hybridization that is not observed in the control. The cellular DNA from Ad12-3a particles is not methylated, whereas the same cellular sequences in KB cell DNA appear to be extensively methylated. On denaturation and renaturation, the recombinant DNA molecules are converted to molecules half as long as Ad12 DNA, as determined by gel electrophoresis and electron microscopy. The recombinant DNA molecules were terminally labeled by exonuclease III treatment and subsequent refilling of the depleted segments with [(32)P]dNTPs by using DNA polymerase I (Klenow fragment). When these molecules were cleaved with EcoRI, BamHI, Msp I, or Pst I, only one terminal DNA fragment was found to be labeled. The results of partial digestion experiments using Msp I, HinfI, or Mbo I are consistent with a model in which 700-1150 base pairs from the left terminus of Ad12 DNA are linked to host cell DNA containing repetitious sequences, and this structure is symmetrically duplicated as a large inverted repeat of the type ABCDD'C'B'A'. The Ad12 DNA sequences are flanking the entire molecule, which consists mainly of human KB cell DNA. The recombinants appear to be stable on serial passage of the virus preparation for many years, although variations in the sequence of the recombinants occur. These symmetric recombinant (SYREC) molecules suggest a way to use adenovirus DNA as a eukaryotic vector. Their occurrence provides further evidence for the generation of virus-host DNA recombinants and may help elucidate the role this interaction may have in adenovirus replication and oncogenesis.

Adenoviruses, Human↗
PubMed1981

Viroid structure.

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Base Composition↗