The gene encoding glucosyltransferase responsible for water-insoluble glucan synthesis (GTF-I) of Streptococcus sobrinus (formerly Streptococcus mutans 6715) was cloned, expressed, and sequenced. A gene bank from S. sobrinus 6715 DNA was constructed in vector pUC18 and screened with anti-GTF-I antibody to detect clones producing GTF-I peptide. Five immunopositive clones were isolated, all of which produced peptides that bound oa-1,6 glucan. GTF-I activity was found in only two large peptides: one stretching over the full length of the GTF-I peptide and composed of about 1,600 amino acid residues (AB1 clone) and the other lacking about 80 N-terminal residues and about 260 C-terminal residues (AB2 clone). A deletion study of the AB2 clone indicated that specific glucan binding, which is essential for water-insoluble glucan synthesis, was lost prior to sucrase activity with an increase in deletion from the 3' end of the GTF-I gene. These results suggest that the GTF-I peptide consists of three segments: that for sucrose splitting (-1,100 residues), that for glucan binding (-240 residues), and that of unknown function (-260 residues), in order from the N terminus. The primary structure of the GTF-I peptide, deduced by DNA sequencing of the AB1 clone, was found to be very similar to that of the homologous protein from another strain of S. sobrinus.Mutans streptococci produce several extracellular glucosyltransferases (GTFs) which synthesize water-soluble glucans and water-insoluble glucans (ISGs) containing co-1,6-and a-1,3-glucosyl linkages [ISG(1,6) and ISG(1,3), respectively]. The ISGs adhere to smooth tooth surfaces and facilitate aggregation of oral bacteria, so that GTFs are believed to play a key role in the formation of dental plaque (12,20).In view of this etiological importance, a number of studies of the properties of GTFs to understand the mechanism of ISG synthesis have been conducted over the past two decades (2,5,8,9,11,23,24,30,33). From the culture fluids of a strain of Streptococcus sobrinus (previously named Streptococcus mutans 6715), we purified an enzyme responsible for ISG synthesis (GTF-I) from sucrose in the presence of a-1,6 soluble glucan such as dextran T10 as a primer (9). In this reaction, sucrose is split into fructose and an enzymebound glucosyl moiety (26); the latter is transferred to the C-3 position of the glucose residue of the glucan, resulting in the formation of a-1,3-glucosyl polymer (GTF-I activity) (9). In the absence of the primer glucans, however, the glucosyl moiety is transferred to water (hydrolysis of sucrose or sucrase activity). Further studies have not been made because of a limited supply of purified GTF-I.In the meantime, the structure and function of GTFs have been studied by biochemical and recombinant DNA techniques. Glucan-binding fragments were isolated by tryptic digestion of GTF proteins from S. sobrinus, but none of them showed glucan-synthesizing activity (18,22). Of several molecular cloning studies of GTF genes from mutans streptococci (1,7,10,13,14,25...

Three colonial variants of Actinobacillus actinomycetemcomitans, which formed transparent rough (TR)-, transparent smooth (TS)-, and opaque smooth (OS)-surfaced colonies, were described in relation to their fimbriation. TR- and TS-cells were adhesive to agar and glass surfaces but not the OS-cells. The examination by electron microscopy revealed that TR-cells were highly fimbriated but not TS- and OS-cells. Thus, TS-cells seemed to be an intermediate type. The fimbriae were isolated from TR-cells by suspending in 0.15 M ethanolamine-HCl buffer (pH 10.5) and purified by dissolving non-fimbrial components in 0.5% deoxycholate and 0.7% n-octyl-beta-D-glucopyranoside. The relative molecular mass of the fimbrial subunit protein was 54,000.

Fimbriae preparation from Actinobacillus actinomycetemcomitans was found to contain an abundant low-molecular-weight protein (termed Flp) with an apparent molecular mass of approximately 6.5 kDa, in addition to a small amount of 54-kDa protein. Immunogold electron microscopy localized the Flp protein at the bacterial fimbriae but not at the cell surface. The DNA fragment including the flp gene was cloned from A. actinomycetemcomitans 304-a and its nucleotide sequence was determined. An open reading frame of the flp gene was composed of 225 by encoding a protein of 75 amino acids. Comparison of the translated amino acid sequence with the sequence of native Flp determined by Edman degradation indicated that the N-terminal part of 26 amino acids is leader peptide. The N-terminal sequence of mature Flp exhibited some similarity to type-IV pilin. Furthermore, the processing site of premature Flp is also similar to that of type-IV prepilin, and a gene encoding a protein homologous to type-IN prepilin-like protein leader peptidase was found downstream of theflp gene. These findings indicate that Flp is the major component protein of A. actinomycetemcomitans fimbriae.

The purpose of this study was to assess the serum antibody levels to periodontal bacteria in patients with periodontal disease, and to explore the diagnostic uses of the serum antibody assessment and its potential as a therapeutic guide. One hundred twenty-nine patients were clinically examined for the type and extent of periodontal destruction and serum IgG antibody levels to Actinobacillus actinomycetemcomitans (Aa), Actinomyces israelii (Ai), A. viscosus (Av), Bacteroides asaccharolyticus (Ba), B. corporis (Bc), B. denticola (Bd), B. gingivalis (Bg), B. intermedius (Bi), B. loescheii (BI), Capnocytophaga gingivalis (Cg), C. ochracea (Co), and Fusobacterium nucleatum (Fn). Clinical and serological data were subjected to correlation analyses. A small group of patients was monitored during the progress of periodontal treatments. The IgG antibody levels were assessed with an enzyme-linked immunosorbent assay (ELISA). Significantly elevated IgG antibody levels were manifested to Aa, Ai, Bg, and Fn in all forms of periodontal disease, additionally to Cg and Co in juvenile periodontitis, and to Bi in adult periodontitis. There were some correlations between a few clinical parameters and the antibody levels. Successful periodontal treatment significantly decreased the antibody levels to all of the micro-organisms; however, during periodontal treatment, there were no marked differences between pre- and post-treatment levels. The antibody reactivities to the periodontopathic micro-organisms may be of diagnostic and predictive value in patients.

Amyloid-β (Aβ) deposition is known to starts decades before the onset of clinical symptoms of Alzheimer’s disease (AD), however, the detailed pathophysiological processes underlying this preclinical period are not well understood. This study aimed to investigate functional network alterations in cognitively intact elderly individuals at risk for AD, and assessed the association between these network alterations and changes in Aβ deposition, glucose metabolism, and brain structure. Forty-five cognitively normal elderly subjects, who were classified into Aβ-positive (CN+) and Aβ-negative (CN−) groups using 11C-Pittsburgh compound B PET, underwent resting state magnetoencephalography measurements, 18F-fluorodeoxyglucose PET (FDG-PET) and structural MRI. Results demonstrated that in the CN+ group, functional connectivity (FC) within the precuneus was significantly decreased, whereas it was significantly enhanced between the precuneus and the bilateral inferior parietal lobules in the low-frequency bands (theta and delta). These changes were suggested to be associated with local cerebral Aβ deposition. Most of Aβ+ individuals in this study did not show any metabolic or anatomical changes, and there were no significant correlations between FC values and FDG-PET or MRI volumetry data. These results demonstrate that functional network alterations, which occur in association with Aβ deposition, are detectable using magnetoencephalography before metabolic and anatomical changes are seen.

A number of homeodomain transcription factors, which play significant roles in retinal development, have been identified in vertebrates (1-4). Rax is a homeodomain transcription factor that is essential for various processes in vertebrate retinal development (5). The Rax gene was first identified as a paired-type homeobox gene expressed in the optic vesicle and the presumptive diencephalon area in the early mouse embryo (6, 7). Rax is evolutionarily well conserved from Drosophila melanogaster to humans. Rax is highly expressed in retinal progenitor cells (RPCs), and its expression in the retina gradually decreases as RPCs become postmitotic and begin to differentiate. Rax-null mutant mice exhibit a reduction of brain size and an absence of the optic vesicle (5, 7). Mutations in human RAX are associated with anophthalmia and microphthalmia (8, 9). Rax overexpression promotes the proliferation of RPCs in frogs and zebra fish (7,(10)(11)(12)(13). In addition to the function in RPCs, Rax plays significant roles in the development of photoreceptor cells and Müller glial cells (14)(15)(16)(17)(18)(19).Rax paralog genes have been identified in various vertebrate species (20)(21)(22). In Xenopus laevis, two Rax genes (xRx and xRx-L/xRx2) have been identified (7, 21), and in zebra fish, three Rax genes (zRx1 to zRx3) have been isolated (7). Interestingly, the expression pattern of zebra fish Rx3 showed more similarity to that of frog and mouse Rax genes than to that of the zebra fish Rx1 and Rx2 genes (23). In chicks, two Rax genes (cRax and cRaxL/ cRax2) have been identified (20). The chick Rax2 gene is expressed in both retinal progenitor cells and early-developing photoreceptors, while chick Rax is predominantly expressed in retinal progenitor cells. It was also reported that chick Rax2 is implicated in cone photoreceptor differentiation and that the expression of a putative dominant negative allele of a chick Rax2 gene caused a significant reduction in the level of expression of cone photoreceptor genes (20). Human RAX2/QRX, which is expressed in the outer nuclear layer (ONL) and inner nuclear layer (INL) of the adult human retina, was identified to be a PCE-1-binding protein by acting synergistically with CRX and NRL to modulate the expression of photoreceptor genes. Monkey, cow, and dog genomes also contain two Rax genes. On the other hand, the Rax2 gene is absent from mouse and rat genomes (22). This raises the question of whether mouse Rax plays an essential role in photoreceptor development during postnatal stages like human Rax2 does.In the current study, we investigated a functional role for Rax in postnatal mouse retinas, which contain a single Rax gene. We report that mouse Rax modulates the expression of photoreceptor genes in the postnatal retina by interacting with Crx. Conditional ablation of Rax in postnatal photoreceptors led to a significant decrease in the level of expression of rod and cone genes and to cone photoreceptor cell death, suggesting that Rax is essential for the maturation of rods and co...

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The dnaA gene is essential for initiation of chromosomal replication in Escherichia coli. A gene homologous with the E. coli dnaA was found in the replication origin region of the Bacillus subtilis chromosome. We have now isolated a temperature sensitive mutant of the B. subtilis dnaA by in vitro mutagenesis of the cloned gene. At a nonpermissive temperature, 49 degrees C, DNA replication stops completely after 60% increase in a rich medium, while cell mass continues to increase exponentially at 2.5 times the rate at 30 degrees C. A ratio of gene frequency between purA (origin marker) and metB (terminus marker) changes gradually from 2.7 at 30 degrees C to 1.0 in 45 min at 49 degrees C, indicating completion of the ongoing replication cycle. Upon the temperature shift down to 30 degrees C after the incubation at 49 degrees C for 60 min, DNA replication resumes without delay, and the purA/metB ratio increases rapidly to 6, i.e. consecutive initiation of more than two rounds of replication. Addition of chloramphenicol at the time of the temperature shift down did not inhibit the increase in the purA/metB ratio, while rifampicin inhibited the re‐initiation completely. The mutation is a single base change from C to T in the dnaA gene resulting in an amino acid substitution from Ser to Phe in the DnaA protein. The mutation was responsible for both temperature sensitive growth and the defect in initiation of chromosomal replication. We observed a remarkable correlation between the amount of DnaA protein and the amount of initiation potential accumulated during incubation at the non‐permissive temperature.