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Biomedical subjects

B Frantz

Publications and source records attributed to B Frantz.

10 recordsLinked to original sources
PubMed1992

Guided tissue regeneration in interproximal defects in the monkey.

The potential for guided tissue regeneration was evaluated in one-walled interproximal sites in Macaca fascicularis. Histologic differences were evaluated at 1 and 3 months. Within the experimental (barrier) group, 100% of the root surfaces with potential for regeneration were covered with new cementum, whereas the control specimens had 20% or less new cementum. The amount of regeneration was determined by the position of the barrier membrane; the more coronal the barrier, the greater the regeneration. Observations indicated that the optimal time for barrier removal is between 1 and 3 months.

Animals↗
PubMed1990

DNA distortion accompanies transcriptional activation by the metal-responsive gene-regulatory protein MerR.

Transcriptional regulation of the bacterial mercuric ion resistance operon (mer) in response to nanomolar concentrations of mercuric ion is achieved by the allosterically modulated transcriptional activator protein MerR. We now show that mercuric ion modification of MerR activates transcription, facilitating the conversion of an RNA polymerase complex with the mer promoter from the closed conformation to the strand-separated, transcriptionally competent open complex. An Hg-MerR-induced structural alteration at the center of the promoter has been detected in the presence or absence of RNA polymerase by use of chemical nucleases sensitive to variations in DNA secondary structure. This hypersensitivity correlates directly with transcriptional activation, lending further support to a previous proposal that a protein-induced distortion in local DNA structure can be the key step in an allosterically modulated transcription activation mechanism.

Bacterial Proteins↗
PubMed1989

The MerR heavy metal receptor mediates positive activation in a topologically novel transcription complex.

Several physical and chemical signals from the extracellular environment are known to be transduced into changes in gene expression through multiple step pathways; however, mechanisms for triggering cellular responses to heavy metal stress have yet to be elucidated. We demonstrate here one such mechanism that employs a single heavy metal receptor protein, MerR, to directly activate transcription of the bacterial mercuric ion resistance operon. The mercuric ion-MerR complex and E. coli RNA polymerase holoenzyme synergistically bind to the metal responsive promoter in an unprecedented spatial relationship to form transcriptionally competent complexes. The activator binds adjacent to and overlaps with the polymerase molecule between the consensus -35 and -10 promoter regions. Our results support a model for transcriptional activation that includes both effector-induced protein-protein interactions and activator-induced alteration in DNA structure.

Allosteric Regulation↗
PubMed1989

Characterization and nucleotide sequence determination of a repeat element isolated from a 2,4,5-T degrading strain of Pseudomonas cepacia.

Pseudomonas cepacia strain AC1100, capable of growth on 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), was mutated to the 2,4,5-T- strain PT88 by a ColE1::Tn5 chromosomal insertion. Using cloned DNA from the region flanking the insertion, a 1477-bp sequence (designated RS1100) was identified which was repeated several times on the wild-type chromosome and was also present on AC1100 plasmid DNA. Various chromosomal fragments containing this sequence were cloned and their nucleotide sequence was determined. Examination of RS1100 revealed the presence of 38-39-bp terminal inverted repeats immediately flanked by 8-bp direct repeats. The translated sequence of the single large open reading frame of RS1100 showed structural similarity to the phage Mu transposase and other DNA-binding proteins. Thus the AC1100 repeated sequence has several structural features in common with insertion sequence elements. Three copies of RS1100 were mapped near 2,4,5-t genes encoding degradation of 5-chloro-1,2,4-trihydroxybenzene, an intermediate in 2,4,5-T degradation. Neither RS1100 nor the 2,4,5-t genes hybridized to DNA isolated from Pseudomonas strains, including P. cepacia, suggesting that both gene fragments may be of foreign origin recruited in strain AC1100. The origin of these two DNA segments as well as the role played by RS1100 in the recruitment of 2,4,5-t genes in AC1100 are presently under investigation.

2,4,5-Trichlorophenoxyacetic Acid↗
PubMed1988

Tissue interactions with dentin specimens after demineralization using tetracycline.

Greater cell attachment to demineralized dentin has been associated with subsequent development of a fiber attachment system. The purpose of this study was to evaluate tissue interactions to dentin demineralized with different concentrations of tetracycline solution. Dentin specimens were obtained from beneath root surfaces covered by periodontal ligament. Each rectangular specimen had a face of root surface dentin and an opposite surface of pulpal dentin. Experimental specimens were treated with a tetracycline solution of either 200 mg/cc or 100 mg/cc for five minutes. The remaining group of specimens served as untreated controls. Specimens were implanted transcutaneously into incisional wounds on the dorsal surface of rats with one end protruding through the skin. Four specimens in each group were available for examination one and ten days after implantation. Histologic and histometric analysis of both root and pulpal surface of implants included counts of adhering cells, assessment of implant length within the connective tissue, and evaluation of connective tissue fiber relationships. In each group, specimens became severely extruded between days one and ten, the number of attached cells decreased, and a fiber attachment system did not develop. Tetracycline-treated surfaces had greater numbers of attached cells at both time points compared to untreated controls. No differences were discernible relating to different tetracycline concentrations. It was concluded that tetracycline-demineralized dentin provided a substrate that increased cell attachment; however, this enhanced response did not result in a connective tissue attachment.

Animals↗
PubMed1988

Associations between bleeding and visual signs of interdental gingival inflammation.

Interdental gingival tissues are designated inflamed on the basis of their color and bleeding after stimulation. Gingival bleeding was previously shown in histological studies to indicate the presence of inflammatory lesions. The present study was undertaken to determine associations between bleeding and visual signs of interdental gingival inflammation. Each interdental site in 82 males, aged 18 to 30, was evaluated for the presence or absence of visual signs of inflammation. The interdental sites on one side of the mouth were evaluated for bleeding tendency using the Papilla Bleeding Index (PBI), while the other half was evaluated using the Eastman Interdental Bleeding Index (EIBI). The percentage of inflamed areas detected with the EIBI and visual method was similar and significantly higher than with the PBI. When the visually noninflamed sites were examined, 38.5% of these areas bled, indicating that interdental inflammatory lesions existed in the absence of visual signs of inflammation. Of the sites that bled but were visually noninflamed, 33.1% were detected using the PBI, while 66.9% were detected using the EIBI. The Eastman Interdental Bleeding Index was a more reliable clinical indicator for detecting interdental inflammatory lesions than the Papilla Bleeding Index.

Adolescent↗
PubMed1987

Cloning and complete nucleotide sequence determination of the catB gene encoding cis,cis-muconate lactonizing enzyme.

The enzyme, cis,cis-muconate lactonizing enzyme I (MLEI; EC 5.5.1.1), has been proposed to play a key role in the beta-ketoadipate pathway of benzoate degradation. A 10.2-kb EcoRI fragment isolated from a Pseudomonas putida genomic library complemented a mutant deficient in this enzyme. The MLEI coding gene, catB, was localized to a 1.6-kb fragment which was sequenced by the dideoxy chain termination method. MLEI was purified 25-fold from crude extracts of benzoate-grown P. putida PRS2015 harboring the cloned catB gene. Purified MLEI was greater than 95% homogeneous as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The subunit Mr was 40,000 which was in close agreement with the nucleotide sequence data. N-terminal sequence analysis of purified MLEI protein agreed with the N terminus predicted by the nucleotide sequence. Comparison of the nucleotide and amino acid sequences for catB with the corresponding sequences of the clcB gene (K.L. Ngai, B.F., D.K. Chatterjee, L.N. Ornston, and A.M.C., unpublished), whose gene product catalyzes the analogous reaction in 3-chlorobenzoate degradation, showed significant homology. These results suggest that catB and clcB have diverged from a common ancestral gene.

Amino Acid Sequence↗
PubMed1987

Organization and nucleotide sequence determination of a gene cluster involved in 3-chlorocatechol degradation.

Three critical enzymes catechol oxygenase II (chlorocatechol dioxygenase), muconate cycloisomerase II, and dienelactone hydrolase, are involved in the degradation of chlorocatechols, which are obligatory intermediates in the catabolism of chlorinated aromatic compounds. The organization and complete nucleotide sequence of the genes for these enzymes have been determined on a 4.2-kilobase-pair (kbp) Bgl II fragment cloned from the plasmid pAC27, based on the agreement of open reading frame lengths with apparent mobilities of polypeptides expressed in Escherichia coli maxicells, predicted N-terminal amino acid sequences with those of the purified proteins, and predicted total amino acid compositions with those of the purified proteins. The 4.2-kbp fragment contains the three genes and ribosome binding sites for those genes but no promoter. When placed downstream of the tac promoter in the broad-host-range plasmid pMMB22, this fragment directs the synthesis of all three enzymes in both E. coli and Pseudomonas putida only on induction with isopropyl beta-D-thiogalactopyranoside, suggesting that the gene cluster is regulated as a single unit under the control of a single promoter. Endogenous transcription initiation of the gene cluster on pAC27, however, occurs from a site present within a 386-bp Bgl II fragment upstream of the 4.2-kbp fragment, and sequences 5' to that site are similar to the sequences of other positively controlled Pseudomonas promoters occurring on the TOL and NAH plasmids.

Amino Acid Sequence↗
PubMed1986

Nucleotide sequence analysis of the phosphomannose isomerase gene (pmi) of Pseudomonas aeruginosa and comparison with the corresponding Escherichia coli gene manA.

Phosphomannose isomerase (PMI) has been proposed to catalyze the first step of the alginic acid biosynthetic pathway in Pseudomonas aeruginosa. The nucleotide sequence of the P. aeruginosa pmi gene contained on a 2.0-kb BamHI-SstI DNA fragment has been determined. The gene was defined by the start and stop codons and by in vitro disruption of an open reading frame of 1440 bp corresponding to a polypeptide product with a predicted Mr of 52 860. This polypeptide displayed an apparent Mr of approx. 56 000 upon electrophoresis of a maxicell extract on sodium dodecyl sulfate-polyacrylamide gels. The codon utilization of the pmi gene was distinct in the wobble base preference and influenced by the high G + C content (66 mol%) of the P. aeruginosa DNA. Computer assisted matching analysis failed to demonstrate any significant homology at the nucleotide level between the P. aeruginosa pmi and Escherichia coli manA (pmi) genes. However, sequences homologous to the P. aeruginosa pmi gene were found in other Pseudomonas species, such as P. putida and P. mendocina, and in Azotobacter vinelandii, all capable of producing alginic acid.

Amino Acid Sequence↗