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P Fuchs

Publications and source records attributed to P Fuchs.

At least 37 records · Page 2Linked to original sources
PubMed1994

Restoration of the DNA damage resistance of Deinococcus radiodurans DNA polymerase mutants by Escherichia coli DNA polymerase I and Klenow fragment.

Deinococcus radiodurans and other species of this genus share extreme resistance to ionizing radiation and many other agents that damage DNA. D. radiodurans mutant strains defective in a deinococcal DNA polymerase that is homologous with E. coli DNA polymerase I are highly sensitive to DNA damage. In the current work we have inquired whether E. coli DNA Pol I can substitute for D. radiodurans Pol in partially or fully restoring to pol- D. radiodurans mutants the extreme DNA damage-resistance typical of this organism. The E. coli polA gene or a 5'-truncated polA gene that encodes the Klenow fragment were introduced and expressed in two different D. radiodurans pol- mutants: Strain 303, which is a chemically mutagenized derivative, and strain 6R1A, which is isogenic with wild-type D. radiodurans except for an insertional mutation within the pol gene. Expression of E. coli polA in both of these mutants fully restored wild-type resistance to ionizing- and UV254-radiation and mitomycin-C exposure. Expression of the Klenow fragment-encoding gene restored wild-type resistance to D. radiodurans strain 303, but only partial resistance to strain 6R1A. The observation that E. coli DNA Pol I is as effective as D. radiodurans Pol in restoring damage resistance, indicates that D. radiodurans DNA Pol per se does not have special properties that are essential or prerequisite for expression of the extreme resistance of D. radiodurans.

Bacterial Proteins↗
PubMed1994

In vivo damage and recA-dependent repair of plasmid and chromosomal DNA in the radiation-resistant bacterium Deinococcus radiodurans.

Deinococcus radiodurans R1 and other members of this genus share extraordinary resistance to the lethal and mutagenic effects of ionizing radiation. We have recently identified a RecA homolog in strain R1 and have shown that mutation of the corresponding gene causes marked radiosensitivity. We show here that following high-level exposure to gamma irradiation (1.75 megarads, the dose required to yield 37% of CFU for plateau-phase wild-type R1), the wild-type strain repairs > 150 double-strand breaks per chromosome, whereas a recA-defective mutant (rec30) repairs very few or none. A heterologous Escherichia coli-D. radiodurans shuttle plasmid (pMD68) was constructed and found to be retained in surviving D. radiodurans R1 and rec30 following any radiation exposure up to the highest dose tested, 3 megarads. Plasmid repair was monitored in vivo following irradiation with 1.75 megarads in both R1/pMD68 and rec30/pMD68. Immediately after irradiation, plasmids from both strains contained numerous breaks and failed to transform E. coli. While irradiation with 1.75 megarads was lethal to rec30 cultures, a small amount of supercoiled plasmid was regenerated, but it lacked the ability to transform E. coli. In contrast, wild-type cultures showed a cell division arrest of about 10 h, followed by exponential growth. Supercoiled plasmid was regenerated at normal levels, and it readily transformed E. coli. These studies show that D. radiodurans retains a heterologous plasmid following irradiation and repairs it with the same high efficiency as its chromosomal DNA, while the repair defect in rec30 prevents repair of the plasmid. Taken together, the results of this study suggest that plasmid DNA damaged in vivo in D. radiodurans is repaired by recA-dependent mechanisms similar to those employed in the repair of chromosomal DNA.

Chromosomes, Bacterial↗
PubMed1993

A family of vectors for surface display and production of antibodies.

Expression vectors for surface display and production of single-chain (Fv) antibodies (scAb) have been constructed based on the phagemid pSEX, which expresses DNA encoding a scAb fused to the gene III product of filamentous phage [Breitling et al., Gene 104 (1991) 147-153]. A smaller version of this phagemid, pSEX20, was made by removing an unnecessary cat. To produce a vector for the surface display of other proteins and peptides, the scAb of pSEX20 was substituted by a polycloning site (MCS) to give pSEX40. For the presentation of Ab on the surface of Escherichia coli, phagemid pAP10 was derived from pSEX20 by substituting gene III with a gene encoding the peptidoglycan-associated lipoprotein (PAL). Vectors for producing scAb that can be purified by antibody and metal affinity chromatography were constructed by substituting gene III in the vector pSEX20 with DNA encoding a peptide with a C-terminal epitope recognised by a monoclonal antibody (phagemid pOPE40) or with five C-terminal histidines (pOPE 90).

Amino Acid Sequence↗
PubMed1993

Relative efficacy of tazobactam, sulbactam and clavulanic acid in enhancing the potency of ampicillin against clinical isolates of Enterobacteriaceae.

Three beta-lactamase inhibitors were combined with ampicillin in a fixed 2:1 ratio. The activity of ampicillin was enhanced by tazobactam and by clavulanic acid, and to a lesser extent by sulbactam when tested against fresh clinical isolates of Enterobacteriaceae. At a concentration of 8 micrograms/ml, ampicillin alone inhibited 49.6% of 2,434 consecutive isolates of enteric bacilli compared to 81% inhibited by ampicillin combined with tazobactam or clavulanic acid and 69.3% inhibited by the sulbactam/ampicillin combination. A four-fold or greater reduction in ampicillin MICs was observed in comparable numbers of isolates with all three combinations, but the most marked effects were seen with strains that were highly resistant to ampicillin.

Ampicillin↗
PubMed1993

Ampicillin-sulbactam susceptibility testing criteria.

In vitro studies in five different medical centers documented the susceptibility of 2,440 consecutive isolates of the Enterobacteriaceae against ampicillin-sulbactam disks of different potencies. For determination of MICs, both 2:1 or 1:1 ratios were used as long as the concentrations of sulbactam at the breakpoints remained the same, i.e. MIC < or = 16/8.0 micrograms/ml or < or = 8.0/8.0 micrograms/ml for the susceptible category. Disks containing 10 micrograms of ampicillin and 10 micrograms of sulbactam are still to be preferred with interpretive criteria of > or = 15 mm for susceptible and < or = 11 mm for resistant (MIC > or = 64/32 micrograms/ml or > or = 32/32 micrograms/ml). The reliability of the disk test actually diminished when the amount of sulbactam in the disk was increased.

Ampicillin↗
PubMed1993

Habenula lesions attenuate lateral hypothalamic analgesia in the formalin test.

The purpose of the experiment was to determine the role of the habenula complex (Hb) in lateral hypothalamic (LH) analgesia for tonic pain. The results demonstrate that lesions of the Hb attenuated LH analgesia in the formalin test. The result of Hb lesions cannot be attributed to non-specific brain damage since bilateral caudate nucleus lesions of similar extent to the Hb complex damage failed to modify the analgesic effect of LH stimulation. The critical damage was probably to the lateral habenula nucleus since it receives a major input from the LH. In addition to the primary finding, we observed that lesions of the Hb had no effect on the baseline response to formalin.

Analgesia↗
PubMed1993

Identification, sequencing, and targeted mutagenesis of a DNA polymerase gene required for the extreme radioresistance of Deinococcus radiodurans.

Deinococcus radiodurans and other species of the same genus share extreme resistance to ionizing radiation and many other agents that damage DNA. Two different DNA damage-sensitive strains generated by chemical mutagenesis were found to be defective in a gene that has extended DNA and protein sequence homology with polA of Escherichia coli. Both mutant strains lacked DNA polymerase, as measured in activity gels. Transformation of this gene from wild-type D. radiodurans restored to the mutants both polymerase activity and DNA damage resistance. A technique for targeted insertional mutagenesis in D. radiodurans is presented. This technique was employed to construct a pol mutant isogenic with the wild type (the first example of targeted mutagenesis in this eubacterial family). This insertional mutant lacked DNA polymerase activity and was even more sensitive to DNA damage than the mutants derived by chemical mutagenesis. In the case of ionizing radiation, the survival of the wild type after receiving 1 Mrad was 100% while survival of the insertional mutant extrapolated to 10(-24). These results demonstrate that the gene described here encodes a DNA polymerase and that defects in this pol gene cause a dramatic loss of resistance of D. radiodurans to DNA damage.

Amino Acid Sequence↗
PubMed1993

The visibility of symbolic highway signs can be increased among drivers of all ages.

Visibility and comprehension of standard text, standard symbolic, and improved symbolic highway signs were compared among young, middle-aged, and elderly observers. The average distance at which standard symbolic signs could be identified was about two times that of text signs for all three age groups. The visibility distances of the improved symbolic signs, which were designed using an optical blur (i.e., low-pass) approach in order to avoid higher spatial frequencies, exceeded those of both text and standard symbolic signs. Visibility distance was decreased significantly among older drivers on some signs but not others. There were no significant age differences in the comprehension of symbolic signs. Acuity, a good predictor of visibility distance of both text and standard symbolic signs, was only weakly related to the visibility distance of the improved symbolic signs. These findings demonstrate that low-pass symbolic signs have significant advantages in visibility over their test counterparts for all drivers.

Adult↗
PubMed1992

Prognostic importance of human papillomavirus type 16 DNA in cervical cancer.

Human papillomavirus (HPV) type 16 DNA is frequent in invasive cervical cancers. Among 43 patients with invasive cervical cancer, HPV-16-positive tumors spread to the parametrial and pelvic lymph nodes significantly more often than did HPV-16-negative tumors (P less than 0.05). Demonstration of HPV-16 DNA in invasive cervical cancers may be an additional prognostic factor for this disease.

Adult↗
PubMed1992

Structure of the human TNF receptor 1 (p60) gene (TNFR1) and localization to chromosome 12p13 [corrected].

Clones encoding the entire coding and 3' untranslated region of the human type I tumor necrosis factor receptor (p60) gene (TNFR1) were isolated by hybridization using probes derived from TNFR-1 cDNA. The gene was characterized by restriction mapping. DNA blot analysis and sequence analysis. The coding region and the 3' untranslated region are distributed over 10 exons. Each of the four repeats, comprising the extracellular ligand binding domain and characterizing a receptor superfamily, is interrupted by an intron. However, the intron-exon structure is not conserved in the nerve growth factor receptor gene, another member of this superfamily. By PCR analysis of human-mouse somatic cell hybrids and in situ hybridization using biotinylated genomic TNFR1 DNA, we localized the gene to human chromosomal band 12p13. This corresponds to the homologous murine gene localized at the distal region of mouse chromosome 6.

Amino Acid Sequence↗
PubMed1992

Neuronal cell cultures as a model for assessing neurotoxicity induced by encephalitic viruses.

Primary dispersed and organotypic cultures were prepared from selected brain areas and spinal cords of rat (Sprague-Dawley) and mouse (SJL/OLA(F) Ness-Ziona) fetuses and neonates. Following fiber regeneration, synapse formation and myelination, cultures were infected with one of the following viruses: Rabies CVS-21 strain, Sindbis Alphavirus, West-Nile Flavivirus and Theiler Murine Encephalomyelitis virus. Light and electron microscopical studies showed clear differences in the target cells for virus infection; time of viral replication and in the intensity and specificity of the cytopathic effects induced by these viruses. Thus, Sindbis and Theiler viruses induced severe cytotoxicity and demyelination due to rapid viral replication in both neurons and all glial cell types. Rabies and West-Nile viruses, on the other hand, replicated mainly in neurons and at a much slower rate, causing only mild damage to the cells and the myelin sheath. A very specific alignment of West-Nile virions was observed along the interperiod lines of the myelin sheath in several myelinated axons. This peculiar arrangement of the virions, entrapped between the myelin lamellae may lead to a novel concept in the understanding of viral infection.

Animals↗
PubMed1991

Eccentric and posteccentric contractile behaviour of skeletal muscle: a comparative study in frog single fibres and in humans.

Eccentric and posteccentric force behaviour in human skeletal muscle and in isolated frog muscle fibres was studied by imposing stretch-and-hold loading conditions during contractions with maximal voluntary effort or under tetanic stimulation in the isolated preparations. The investigations on human muscle were made on the forearm flexors of a group of kayak racers (n = 16; age: 17-22 years) and of schoolgirls (n = 15; age: 17-18 years) with both groups participating in a strength-training programme over 4 (kayak racers) or 3 (girls) months. Half of the training regime consisted of eccentric elements. In the isolated muscle fibres, it could be shown that in the posteccentric hold phase the enhanced force decayed exponentially to the original isometric value with a mean time-constant of 0.35 s (10 degrees C) and of 0.23 (20 degrees C). In the forearm flexor of human subjects similar results were obtained not only qualitatively but even quantitatively (time constant of posteccentric force decay: 0.25-0.37 s). Strength training in both groups did not lead to an enhancement in maximal isometric force alone [mean increase in force 17 (SD 10)%], a well-known and generally accepted fact, but also to a parallel shift in eccentric [21 (SD 10)%] and posteccentric force level. The close similarity between the findings in isolated muscle fibres and in human muscle in situ suggests that the eccentric and posteccentric behaviour must be primarily ascribed to the contractile properties of the muscle fibres themselves. A three-element muscle model with variable visco-elastic properties would appear to be most suitable for simulating the experimental findings.

Adolescent↗
PubMed1991

Targeting recombinant antibodies to the surface of Escherichia coli: fusion to a peptidoglycan associated lipoprotein.

To target recombinant antibodies to the surface of Escherichia coli, we have fused single-chain variable domains to its peptidoglycan associated lipoprotein (PAL). The fusion protein was able to bind antigen and was tightly bound to the murein layer of the cell envelope. Antibody-PAL had little effect on cell growth and viability. In contrast, the expression of single chain antibody alone eventually resulted in cell lysis. Immunofluorescence studies on unfixed cells showed that functional antibodies were accessible at the surface of intact bacteria. This could provide a means of isolating single cells producing specific antibodies from libraries in E. coli by fluorescence assisted cell sorting (FACS). Pal fusions may also be of general interest for the presentation of proteins at the surface of E. coli as, for example, in the production of live vaccines.

Amino Acid Sequence↗
PubMed1990

[Logic and myth of tooth morphology].

Measuring 32 selected maxillary dental casts in all dimensions with the aid of a laser scanner, we obtained 3-dimensional coordinates in a standardized coordinate system. Vertical-sagittal cuts were simulated to extract data of the protrusive curvatures. In this way, the original measuring data were available for analysis. It was the purpose of this study to verify two statements of Kubein-Meesenburg's theory. One is that all protrusive curvatures of one individual are identical, the other that there is an individual-specific parameter a which, when inserted in the equation of the katenate, yields a description of these identical protrusive curvatures. Two different methods of approximation were designed, one optical/graphic method, the other according to strict mathematical criteria of analysis. Both provided different results. In interpreting this discrepancy of results, we found that the reason is associated with the way of handling the so-called third dimension, a sum of mathematical criteria that is necessarily involved in approximating the curvatures. Based on strictly mathematical modes of analysis we feel compelled to deny the identity of the protrusive curvatures in any one individual and the existence of the proposed individual-specific parameter a.

Dental Arch↗