Biomedical subjects
B Reiss
Publications and source records attributed to B Reiss.
Long-term clinical performance of CEREC restorations and the variables affecting treatment success.
Since the first patient was treated with a CEREC restoration in 1985, several system developments have expanded the indications for which this system can be applied. Concurrently, ongoing research in private practices has contributed to documentation supporting the placement of CEREC restorations based on their performance relative to specific criteria, including tooth vitality, papillary bleeding, quality of margins, quality of ceramic used, treatment required, and failures. This article summarizes the methodology and findings of the ongoing clinical evaluations of 1,010 ceramic restorations, including inlays and onlays, placed in 299 patients during a 39-month period, that were reexamined at 9 to 12 years postplacement.
RecA stimulates sister chromatid exchange and the fidelity of double-strand break repair, but not gene targeting, in plants transformed by Agrobacterium.
Expression of the bacterial RecA protein in plants stimulates homologous recombination in tobacco. Here we show that RecA plays a direct role in DNA strand exchange in vivo. The number of sister chromatid exchanges (SCEs) was increased 2.4-fold over wild type in transgenic tobacco plants expressing a nuclear-targeted RecA (nt-RecA) protein and could not be increased further by DNA damage, which caused a doubling of the baseline SCE frequency in wild-type plants. Although gene targeting requires homologous recombination, the number of targeted gene replacements was not increased markedly by the presence of nt-RecA by using Agrobacterium-mediated transformation. However, the number of double-strand breaks that were repaired at both sides by homologous recombination was increased 3.3-fold. Stimulation of SCE and fidelity of double-strand break repair by nt-RecA, but not by gene targeting, suggests that the stimulatory activity of RecA is linked to active DNA synthesis. Therefore, nascent replication-associated single strands may be a prerequisite for RecA action in plant cells.
Clinical long-term results and 10-year Kaplan-Meier analysis of Cerec restorations.
In a private practice, 299 patients were treated with 1010 full-ceramic restorations within a period of 39 months. The inlays and onlays were manufactured using the Cerec technique, and were seated in one single appointment. The clinical success was observed and documented continuously. Re-examination was conducted 9 to 12 years after the placement. According to the Kaplan-Meier method, the probability of survival decreased to 90% (s = 0.018) after 10 years and 84.9% after 11.8 years with no further loss by the final observation at 12 years. Size and outline form did not affect the success rate. Premolars rated better than molars. Vital teeth provided better results than non-vital teeth. The application of dentin adhesive increased the probability of success. Eighty-one failures were recorded during the observation period. The most frequent reason for failures were fractures of ceramic and tooth.
Cell type-specific gene expression in the cell cycle of the dimorphic ciliate Eufolliculina uhligi.
The life cycle of the unicellular eukaryote Eufolliculina uhligi includes two structurally and physiologically different cell types: a motile swarmer that is arrested in the cell cycle, and a sessile cell (trophont) that feeds and reproduces. These two cell types offer an exceptionally favourable system for the isolation of genes involved in cell cycle regulation and cellular morphogenesis. Differential screening of a trophont cDNA library using a swarmer-subtracted, trophont-specific probe yielded eleven clones that represent trophont-specific transcripts and one clone that represents a swarmer-specific transcript. Sequence analysis showed that seven clones, including the only swarmer-specific one, represent unknown genes, whereas five clones could be identified by sequence comparisons. Two of the clones appear to encode proteins that are involved in the regulation of growth and metabolism. The deduced sequences of three clones resemble potential cell cycle regulators. Data are presented on a putative member of the calcium/calmodulin-dependent protein kinase family and on a TIP120-like sequence, which is the first such sequence to be described since the discovery of the rat TIP120 protein. Furthermore, a unique new sequence is presented, whose features suggest that it represents a protein that is involved in the regulation of cell division. It includes domains characteristic of two different protein families, cyclin-dependent kinases (CDKs) and cyclins, both of which are known to be cell cycle regulators. Based on our results we propose a model for cell cycle regulation in ciliated protozoa.
Characterization of the activity of a plastid-targeted green fluorescent protein in Arabidopsis.
In Arabidopsis thaliana the PALE CRESS (PAC) gene product is required for both chloroplast and cell differentiation. Transgenic Arabidopsis plants expressing a translational fusion of the N-terminal part of the PAC protein harboring the complete plastid-targeting sequence and the green fluorescent protein (GFP) exhibit high GFP fluorescence. Detailed analyses based on confocal imaging of various tissues and cell types revealed that the PAC-GFP fusion protein accumulates in chloroplasts of mature stomatal guard cells. The GFP fluorescence within the guard cell chloroplasts is not evenly distributed and appears to be concentrated in suborganellar regions. GFP localization studies demonstrate that thin tubular projections emanating from chloroplasts and etioplasts often connect the organelles with each other. Furthermore, imaging of non-green and etiolated tissue further revealed that GFP fluorescence is present in proplastids, etioplasts, chromoplasts, and amyloplasts. Even photobleaching of carotenoid-free plastids does not affect PAC-GFP accumulation in the organelles of the guard cells indicating that the protein translocation machinery is functional in all types of plastids. The specific accumulation of GFP in guard cell chloroplasts, their tubular connections, the translocation of the precursor polypeptide into the different types of organelles, as well as the use of a plastid-targeted GFP protein as a versatile marker is discussed in the context of previously described observations.
Computerized dentistry?
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Picrotoxin blockade of invertebrate glutamate-gated chloride channels: subunit dependence and evidence for binding within the pore.
Glutamate-gated chloride channels have been described in nematodes, insects, crustaceans, and mollusks. Subunits from the nematode and insect channels have been cloned and are phylogenetically related to the GABA and glycine ligand-gated chloride channels. Ligand-gated chloride channels are blocked with variable potency by the nonselective blocker picrotoxin. The first two subunits of the glutamate-gated chloride channel family, GluClalpha and GluClbeta, were cloned from the free living nematode Caenorhabditis elegans. In this study, we analyze the blockade of these novel channels by picrotoxin. In vitro synthesized GluClalpha and GluClbeta RNAs were injected individually or coinjected into Xenopus oocytes. The EC50 values for picrotoxin block of homomeric GluClalpha and GluClbeta were 59 microM and 77 nM, respectively. Picrotoxin block of homomeric GluClbeta channels was promoted during activation of membrane current with glutamate. In addition, recovery from picrotoxin block was faster during current activation by glutamate. A chimeric channel between the N-terminal extracellular domain of GluClalpha and the C-terminal membrane-spanning domain of GluClbeta localized the higher affinity picrotoxin binding site to the membrane-spanning domains of GluClbeta. A point mutation within the M2 membrane-spanning domain of GluClbeta reduced picrotoxin sensitivity >10,000-fold. We conclude that picrotoxin blocks GluCl channels by binding to a site accessible when the channel is open.
The PAC protein affects the maturation of specific chloroplast mRNAs in Arabidopsis thaliana.
The pale cress (pac) mutation arrests chloroplast development at an early stage in Arabidopsis thaliana and leads to a white phenotype. Chlorophyll fluorescence measurements demonstrated that the photosynthetic apparatus was impaired. The mutation did not reduce transcription of nuclear genes with photosynthetic function. However, distinct chloroplast-encoded transcripts were affected. The mutation mainly changed the maturation pattern, but the abundance of specific transcripts was also reduced. The defects observed imply a specific role for PAC in chloroplast mRNA maturation. PAC is encoded by a nuclear gene and is transported into the chloroplast. Therefore PAC may be one of the nucleus-encoded factors that function in plastid mRNA maturation and accumulation.
Percutaneous sonographic gastrostomy: method, indications, and problems.
OBJECTIVES: This study evaluated the application of ultrasound (US) guidance in the percutaneous placement of gastric feeding tubes in patients in whom endoscopic placement of a nutrition tube is not possible. METHODS: Thirty-eight patients with upper gastrointestinal obstruction were entered in a prospective study with US-guided nutrition tube application. Feasibility of placement, side effects, and nutritional states were monitored for a mean follow-up of 4 months. RESULTS: Ultrasound allowed rapid puncture after filling of the stomach with water through a nasal tube in 34/38 cases. In four cases a total upper gastrointestinal obstruction required an initial stomach insufflation through a direct puncture. Puncture-related major complications were not observed. Minor complications during the observation time were one late dislocation, five cases with broken material after about 6 months (four could be changed by using the Seldinger technique), and two minor local infections. The nutrition through feeding tubes stabilized body weight and body composition parameters. CONCLUSION: The percutaneous sonographic gastrostomy (PSG) is a safe and minimally invasive procedure for enteral nutrition in all cases with upper gastrointestinal obstruction when endoscopic placement of a feeding tube is not possible. Percutaneous sonographic gastrostomy may help to stabilize the nutritional parameters and general condition in patients with malignant diseases.
Computer applications in dental diagnosis.
Formerly, computer applications in the dental office were restricted mainly to administration and organization. The revolutionary potential of digital applications does not halt at other fields, however. Besides applications in dental therapy, computerized methods have entered all levels of classic dental diagnosis: acquisition of findings, evaluation, and categorization. All three components have a new quality, worthy of being reevaluated if not redefined. New systems are described and evaluated in relation to relevant practice requirements, from both the practitioner's and the scientific clinician's points of view.
Targeting of a functional Escherichia coli RecA protein to the nucleus of plant cells.
We have characterised a RecA protein fused to the simian virus 40 large T nuclear-localisation signal. The fusion protein was targeted to the nucleus in transgenic tobacco plants with high efficiency. By contrast, authentic RecA was not enriched in the nuclei of plant cells expressing comparable amounts of protein. For detailed characterisation of the strand-exchange activity of the nuclear-targeted RecA protein, a nearly identical protein was expressed in Escherichia coli and purified to homogeneity. This protein was found to bind to single-stranded DNA with the same stoichiometry and to promote the exchange of homologous DNA strands with the same kinetics as authentic RecA. It was concluded that the amino-terminal modification did not alter any of the essential properties of RecA and that the fusion protein is a fully functional strand-exchange protein. However, the ATPase activity of this protein was 20 times greater than that of RecA in the absence of single-stranded DNA. As with RecA, this activity was further stimulated by the addition of single-stranded DNA. Since ATPase activity is correlated with the ability of RecA to assume its high affinity state for DNA, the nuclear-targeted RecA protein might be regarded as a constitutively stimulated RecA variant, fully functional in promoting homologous recombination.
Characterisation of a new allele of pale cress and its role in greening in Arabidopsis thaliana.
A recessive mutant with white leaves was identified in a screen of a population of T-DNA-tagged Arabidopsis thaliana plants. The mutation is lethal, but plants develop almost to maturity under sterile conditions. The white areas in leaves are devoid of developed chloroplasts, but the plants frequently develop green sectors which contain green chloroplasts. Molecular characterisation of the affected gene revealed that the mutant is allelic to pale cress (pac), a recently described mutation, and was therefore named pac-2. Sequencing of cDNAs and the genomic region revealed several noteworthy features of this genetic locus. In pac-2 the T-DNA had inserted in the region of the promoter and abolished transcription of the PAC gene completely. Cytokinin induced greening in mature, white homozygous pac-2 plants, and therefore is likely to be responsible for the greening observed in callus and shoots induced on roots from such plants. However, the PAC transcript was found to be absent in both white leaves and green callus. Thus, since cytokinin induced greening in the absence of PAC RNA this plant hormone appears to be able to bypass PAC function.
Enhanced green fluorescence by the expression of an Aequorea victoria green fluorescent protein mutant in mono- and dicotyledonous plant cells.
The expression of the jellyfish green fluorescent protein (GFP) in plants was analyzed by transient expression in protoplasts from Nicotiana tabacum, Arabidopsis thaliana, Hordeum vulgare, and Zea mays. Expression of GFP was only observed with a mutated cDNA, from which a recently described cryptic splice site had been removed. However, detectable levels of green fluorescence were only emitted from a small number of protoplasts. Therefore, other mutations in the GFP cDNA leading to single-amino acid exchanges in the chromophore region, which had been previously studied in Escherichia coli, were tested in order to improve the sensitivity of this marker protein. Of the mutations tested so far, the exchange of GFP amino acid tyrosine 66 to histidine (Y66H) led to detection of blue fluorescence in plant protoplasts, while the exchange of amino acid serine 65 to cysteine (S65C) and threonine (S65T) increased the intensity of green fluorescence drastically, thereby significantly raising the detection level for GFP. For GFP S65C, the detectable number of green fluorescing tobacco (BY-2) protoplasts was raised up to 19-fold, while the fluorimetricly determined fluorescence was raised by at least 2 orders of magnitude.
RecA protein stimulates homologous recombination in plants.
A number of RecA-like proteins have been found in eukaryotic organisms. We demonstrate that the prokaryotic recombination protein RecA itself is capable of interacting with genomic homologous DNA in somatic plant cells. Resistance to the DNA crosslinking agent mitomycin C requires homologous recombination as well as excision repair activity. Tobacco protoplasts expressing a nucleus-targeted RecA protein were at least three times as efficient as wild-type cells in repairing mitomycin C-induced damage. Moreover, homologous recombination at a defined locus carrying an endogenous nuclear marker gene was stimulated at least 10-fold in transgenic plant cells expressing nucleus-targeted RecA. The increase in resistance to mitomycin C and the stimulation of intrachromosomal recombination demonstrate that Escherichia coli RecA protein is functional in genomic homologous recombination in plants, especially when targeted to the plant nucleus.
T-DNA integrations in a new family of repetitive elements of Nicotiana tabacum.
A number of T-DNA insertions in the genome of Nicotiana tabacum were characterized. One class of integrations was found to have occurred in a new family of highly repetitive sequences. Three genomic regions (ecoA, ecoB, and ecoC) were isolated, all of which contain basic units of 180 bp, organized in direct tandem repeats. Several of the 180-bp elements contain an EcoRI recognition site within the repeating unit and are therefore named "eco repeats." All members of this family are weakly homologous in sequence to a previously described class of repeat elements which contained a BamHI site (HRS60 repeat family), which suggests that both groups of sequences are of common evolutionary origin. The allotetraploid genome of N. tabacum is presumed to originate from the hybridization of two diploid genomes. The HRS60 elements previously described have been found exclusively in the genome of one of the ancestors, N. sylvestris, and in N. tabacum itself. Our DNA hybridization data suggest that the eco elements originate from the genome of the other ancestor, N. tomentosiformis. Whereas the HRS60 elements are transcriptionally silent, at least some eco elements appear to be transcribed.
Reporter genes.
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A functional assay for Taq DNA polymerase in PCR.
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