Removable dental prostheses and cardiovascular survival: a 15-year follow-up study.

OBJECTIVES: In previous studies, increasing number of teeth predicted better survival and the acute needs for dental treatment predicted mortality. We sought to investigate whether restored dentitions by various removable dental prostheses impact cardiovascular (CVD) longevity. METHODS: Kuopio Oral Health and Heart study was initiated as a cross-sectional investigation with 256 subjects with diagnosed coronary artery disease [CAD] and 250 age- and sex-matched controls without CAD in 1995-1996. The mean age of both groups was 61, 30% were females. We appended mortality follow-up records to the baseline data and formulated this 15-year follow-up study. We examined the relationship between various types of dental prostheses and cardiovascular mortality by proportional hazard regression analyses. We also explored their correlation to oral and systemic inflammatory markers such as asymptotic dental score and C-reactive protein. RESULTS: In a model adjusted for age, sex and smoking, groups having only natural teeth (NT), removable partial denture(s) [PD] and NT, a PD and a full denture [FD], and FD/FD or FD/NT demonstrated the following hazard ratios for mortality (95% confidence interval). NT both arches: 1.00 [reference]; PD and NT: 0.75 [0.22-2.56]; PD and FD: 1.99 [1.05-3.81]; and FD opposed by FD or NT: 1.71 [0.93-3.13], respectively [p for trend=0.05]. Although statistically not significant, those with PD and NT with mean a number of teeth [Nteeth] of 15.4 had better survival compared with those who had all NT [Nteeth=22.5]; while those who had FD and PD [Nteeth=6.5] had shorter longevity than those with FD/FD or FD/NT [Nteeth=3.5]. CONCLUSIONS: Although not all subgroups of dental prostheses reached significant relationship with CVD mortality, our study suggests that not only the number [quantity] of remaining teeth but their maintenance [quality] removing potential inflammatory foci, such as pericoronitis or retained root tips, may positively impact on cardiovascular survival.

Isolation and characterization of a new transposable element in Chlamydomonas reinhardtii.

A new transposable element, Tcr3, was identified in the unicellular green alga Chlamydomonas reinhardtii. The Tcr3 element contained imperfect terminal inverted repeat sequences of 56 bp and created a 2 bp target site duplication upon insertion. Insertion of Tcr3 into the 3'-untranslated region of the NIT8 gene, which is essential for nitrate assimilation, prevented expression of the gene. Excision of the Tcr3 element correlated with reversion of the mutant phenotype and left behind a 3 bp footprint. Tcr3 was found in all Chlamydomonas isolates tested and should prove to be useful for transposon-tagging experiments in Chlamydomonas.

Five nitrate assimilation-related loci are clustered in Chlamydomonas reinhardtii.

Three overlapping clones covering a Chlamydomonas reinhardtii genomic region of about 32 kb appear to contain five genes potentially involved in nitrate assimilation in addition to the nitrate reductase structural locus nit-1. These new loci produced transcripts of 2.8, 2.2, 1.8 and 1.7 kb in nitrate-induced wild-type cells that, like the 3.4 kb transcript of nit-1, were undetectable in cells grown in ammonium. In addition, in a mutant defective at the regulatory locus, nit-2 for nitrate assimilation, which does not express the nit-1 gene transcript, accumulation of the four other transcripts was also blocked. They have been named nar (nitrate assimilation related) genes. The nar-1 and nar-2 loci are transcribed in the same orientation as nit-1. The nar-3 and nar-4 loci are transcribed divergently from nit-1. DNA and RNA sequences from both nar-3 and nar-4 cross-hybridized with each other indicating that they share similar sequences. Four nitrate assimilation-deficient mutants (C2, D2, F6 and G1) were characterized. These mutants lack nar transcripts and have major deletions and/or rearrangements in the nar gene cluster. In contrast to other nitrate reductase-deficient mutants and to wild type, deletion mutants and the regulatory mutant nit-2 were incapable of accumulating intracellular nitrate. Two of the mutants in which expression of all the nar loci did not occur, C2 and D2, grew in nitrite medium and showed wild-type levels of both nitrite uptake and nitrite reductase activities.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation of the Chlamydomonas regulatory gene NIT2 by transposon tagging.

Genetic evidence suggests that the NIT2 gene of Chlamydomonas reinhardtii encodes a positive regulator of the nitrate-assimilation pathway. To learn more about the function of the NIT2 gene product, we isolated the gene using a transposon-tagging strategy. A nit2 mutation caused by the insertion of a transposon was identified by testing spontaneous nit2 mutants for the presence of new copies of Gulliver or TOC1, transposable elements that have been identified in Chlamydomonas. In 2 of the 14 different mutants that were analyzed, a Gulliver element was found to be genetically and phenotypically associated with the nit2 mutation. Using the Gulliver element as a probe, one of the transposon-induced nit2 alleles was isolated, and a sequence adjoining the transposon was used to isolate the corresponding wild-type locus. The NIT2 gene was delimited by mapping DNA rearrangements associated with nit2 mutations and mutant rescue by genetic transformation. The NIT2 gene encodes a 6-kb transcript that was not detected in cells grown in the presence of ammonium. Likewise, NIT2-dependent genes are repressed in ammonium-grown cells. These results suggest that repression of the NIT2 gene may mediate metabolite repression of the nitrate assimilation pathway in Chlamydomonas.

Stable nuclear transformation of Chlamydomonas using the Chlamydomonas gene for nitrate reductase.

We have developed a nuclear transformation system for Chlamydomonas reinhardtii, using micro-projectile bombardment to introduce the gene encoding nitrate reductase into a nit1 mutant strain which lacks nitrate reductase activity. By using either supercoiled or linear plasmid DNA, transformants were recovered consistently at a low efficiency, on the order of 15 transformants per microgram of plasmid DNA. In all cases the transforming DNA was integrated into the nuclear genome, usually in multiple copies. Most of the introduced copies were genetically linked to each other, and they were unlinked to the original nit1 locus. The transforming DNA and nit+ phenotype were stable through mitosis and meiosis, even in the absence of selection. nit1 transcripts of various sizes were expressed at levels equal to or greater than those in wild-type nit+ strains. In most transformants, nitrate reductase enzyme activity was expressed at approximately wild-type levels. In all transformants, nit1 mRNA and nitrate reductase enzyme activity were repressed in cells grown on ammonium medium, showing that expression of the integrated nit1 genes was regulated normally. When a second plasmid with a nonselectable gene was bombarded into the cells along with the nit1 gene, transformants carrying DNA from both plasmids were recovered. In some cases, expression of the unselected gene could be detected. With the advent of nuclear transformation in Chlamydomonas, it becomes the first photosynthetic organism in which both the nuclear and chloroplast compartments can be transformed.