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81.
Yoshiba N Yoshiba K Stoetzel C Perrin-Schmitt F Cam Y Ruch JV Hosoya A Ozawa H Lesot H 《Cell and tissue research》2006,324(1):97-104
Tissue inhibitors of metalloproteinases (TIMPs) possess multiple functions, in addition to their matrix metalloproteinase
(MMP) inhibitory activity. The continuously growing incisor of mouse possesses a stem cell compartment at the apical end of
the epithelium (the apical loop) and thus provides an excellent tool to analyze the mechanisms of organogenesis and cytodifferentiation.
To understand the functions of TIMPs in tooth development, we have analyzed the gene expression and protein localization
of TIMP-1, -2, and -3 during mouse incisor development, from embryonic day 13 (E13) to postnatal day 3 (P3). TIMP-1 was present
on the basement membrane during early developmental stages. At P2, TIMP-1 was strongly detected along the apical loop, transiently
disappeared from the basement membrane in the cytodifferentiation zone, and later reappeared at the distal end of functional
ameloblasts. Expression of TIMP-2 protein was restricted to the outer part of the apical loop throughout the examined stages.
At P2, TIMP-2 was present on the basement membrane at the outer part of the apical loop. The dental follicle also expressed
Timp-2, and the corresponding protein was abundant within the extracellular matrix. Timp-3 mRNA was highly expressed in the mesenchyme surrounding the apical loop. During matrix formation, Timp-3 was expressed by subodontoblasts, and the protein was detected in this layer and between odontoblasts. Distinct temporal
and spatial expression patterns of TIMPs suggest divergent functions of these factors in incisor organogenesis.
This work was supported by INSERM, CNRS, ARC, French Ministry of Research (ACI), Japanese Ministry of Education, Culture,
Sports, Science, and Technology, and Niigata University Research Projects. 相似文献
82.
OBJECTIVE: To test the association between a shift in vaginal flora (SVF) and chorioamnionitis in a population with a high prevalence of both conditions. STUDY DESIGN: Subjects were women with Pap smears and placentas examined at the Medical Center of Louisiana, New Orleans. The presence of subchorionitis, chorionitis, chorioamnionitis and necrotizing chorioamnionitis was evaluated blindly on placental tissue sections. The presence of SVF was evaluated on matching cervical Pap smears obtained during gestation. RESULTS: Three hundred twenty-two placentas and the corresponding Pap smears were examined. Chorioamnionitis was identified in 112 placentas. It was not significantly associated with maternal age or ethnicity, but its prevalence was inversely related to gestational age. SVF was observed in 114 Pap smears. It was more common among African Americans than other ethnic groups but was not significantly associated with maternal age or gestational age at delivery. SVF was more often observed in Pap smears collected in early pregnancies than in those collected later. There was no significant association between chorioamnionitis and SVF before and after accounting for ethnicity, maternal age, gestational age at Pap smear collection, and interval between Pap smear collection and delivery. CONCLUSION: SVF had no significant predictive value for chorioamnionitis in our study population. 相似文献
83.
Nishida Y Yokota T Takahashi T Uchihara T Jishage K Mizusawa H 《Biochemical and biophysical research communications》2006,350(3):530-536
Increased oxidative damage is a prominent and early feature in Alzheimer disease (AD). However, whether it is a primary cause or merely a downstream consequence in AD pathology is still unknown. We previously generated alpha-tocopherol transfer protein knockout (Ttpa-/-) mice, in which lipid peroxidation in the brain was significantly increased by complete depletion of alpha-tocopherol (alpha-Toc). Here we crossed AD transgenic (APPsw) model mice (Tg2576) with Ttpa-/- mice. The resulting double-mutant (Ttpa-/- APPsw) mice showed earlier and more severe cognitive dysfunction in the Morris water maze, novel-object recognition, and contextual fear conditioning tests. They also showed increased amyloid beta-peptide (Abeta) deposits in the brain by immunohistochemical analysis, which was ameliorated with alpha-Toc supplementation. In this report we provide clear evidence indicating that chronic lipid peroxidation due to alpha-Toc depletion enhances AD phenotype in a mouse model. 相似文献
84.
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86.
Hormone interactions during lateral root formation 总被引:2,自引:0,他引:2
Lateral root (LR) formation, the production of new roots from parent roots, is a hormone- and environmentally-regulated developmental
process in higher plants. Physiological and genetic studies using Arabidopsis
thaliana and other plant species have revealed the roles of several plant hormones in LR formation, particularly the role of auxin
in LR initiation and primordium development, resulting in much progress toward understanding the mechanisms of auxin-mediated
LR formation. However, hormone interactions during LR formation have been relatively underexamined. Recent studies have shown
that the plant hormones, cytokinin and abscisic acid negatively regulate LR formation whereas brassinosteroids positively
regulate LR formation. On the other hand, ethylene has positive and negative roles during LR formation. This review summarizes
recent findings on hormone-regulated LR formation in higher plants, focusing on auxin as a trigger and on the other hormones
in LR formation, and discusses the possible interactions among plant hormones in this developmental process. 相似文献
87.
Hidehiro Takahashi Naohiro Ohtaki Masae Maeda-Sato Michiko Tanaka Keiko Tanaka Hirofumi Sawa Toyokazu Ishikawa Akihisa Takamizawa Tomohiko Takasaki Hideki Hasegawa Tetsutaro Sata William W. Hall Takeshi Kurata Asato Kojima 《Microbes and infection / Institut Pasteur》2009,11(13):1019-1028
Expression of genes for precursor M (prM) and envelope (E) proteins of West Nile virus (WNV) leads to the production of small, capsidless, and non-infectious virus-like particles (VLPs) possessing the E antigen which is responsible for viral entry and immune protection. It has been reported that processing of the secretion signal affects viral release. We examined the secretion efficiency of VLPs into the culture medium from RK13 or 293 T cells transfected with expression vectors for prM and E proteins of WNV which were constructed to comprise different lengths of signal peptides upstream of the prM-E domain. The number of amino acid residues present in the segment markedly affected the production, processing, and secretion of VLPs. Secreted VLPs possessed both the processed M protein and the glycosylated E protein. In addition, immunization with VLPs induced neutralizing antibodies in C3H/HeN mice. These results indicate that the number of amino acid residues comprising the N-terminus of the signal segment controls the efficiency of assembly, maturation, and release of VLPs in the absence of viral protease, which in turn indicates the potential of VLPs as a candidate for an effective WNV subunit vaccine. 相似文献
88.
Hajime Masukawa Kazuhito Inoue Hidehiro Sakurai C. Peter Wolk Robert P. Hausinger 《Applied and environmental microbiology》2010,76(20):6741-6750
Cyanobacteria use sunlight and water to produce hydrogen gas (H2), which is potentially useful as a clean and renewable biofuel. Photobiological H2 arises primarily as an inevitable by-product of N2 fixation by nitrogenase, an oxygen-labile enzyme typically containing an iron-molybdenum cofactor (FeMo-co) active site. In Anabaena sp. strain 7120, the enzyme is localized to the microaerobic environment of heterocysts, a highly differentiated subset of the filamentous cells. In an effort to increase H2 production by this strain, six nitrogenase amino acid residues predicted to reside within 5 Å of the FeMo-co were mutated in an attempt to direct electron flow selectively toward proton reduction in the presence of N2. Most of the 49 variants examined were deficient in N2-fixing growth and exhibited decreases in their in vivo rates of acetylene reduction. Of greater interest, several variants examined under an N2 atmosphere significantly increased their in vivo rates of H2 production, approximating rates equivalent to those under an Ar atmosphere, and accumulated high levels of H2 compared to the reference strains. These results demonstrate the feasibility of engineering cyanobacterial strains for enhanced photobiological production of H2 in an aerobic, nitrogen-containing environment.Photobiologically produced hydrogen gas (H2) is a clean energy source with the potential to greatly supplement our use of fossil fuels (39). Whereas coal and oil are limited, cyanobacteria and eukaryotic microalgae can use inexhaustible sunlight as the energy source and water as the electron donor to produce H2 (42). This gas is generated either by hydrogenases (52) or as an inevitable by-product of N2 fixation by nitrogenases (49). In contrast to the reaction of hydrogenases which is reversible, nitrogenases catalyze the unidirectional production of H2, although with substantial energy input in the form of ATP (47). Under optimal N2-fixing conditions: N2 + 8 e− + 8 H+ + 16 ATP → H2 + 2 NH3 + 16 (ADP + Pi), whereas, in the absence of N2 (e.g., under Ar), all electrons are allocated to proton reduction: 2 e− + 2 H+ + 4 ATP → H2 + 4 (ADP + Pi). Thus, one expects to be able to increase the H2 production activity of nitrogenase by decreasing the electron allocation to N2 fixation.Nitrogenases are sensitive to inactivation by O2; however, N2-fixing cyanobacteria have developed mechanisms to protect these enzymes from photosynthetically generated oxygen (5). Of particular interest, Anabaena (also known as Nostoc) sp. strain PCC 7120 and some other filamentous cyanobacteria respond to combined-nitrogen deprivation by undergoing differentiation in which a subset of cells become heterocysts that provide a microaerobic environment, allowing nitrogenase to function in aerobic culture conditions. The nitrogenase-related (nif) genes are specifically expressed in heterocysts which lack O2-evolving photosystem II activity and are surrounded by a thick cell envelope composed of glycolipids and polysaccharides that impede the entry of O2 (56). Vegetative cells perform oxygenic photosynthesis and fix CO2. Heterocysts obtain carbohydrates from those cells and, in turn, provide them with fixed nitrogen.The molybdenum-containing nitrogenase of Anabaena sp. strain PCC 7120 consists of the Fe protein (encoded by nifH) and the MoFe protein (encoded by nifD and nifK). As in other organisms, the Fe protein is a homodimer containing a single [4Fe-4S] cluster and functions as an ATP-dependent electron donor to the MoFe protein. The latter is an α2β2 heterotetramer with each nifD-encoded α subunit coordinating the FeMo cofactor (FeMo-co; MoFe7S9X-homocitrate) that binds and reduces substrate, while α plus the nifK-encoded β subunits coordinate the [8Fe-7S] P-cluster (14). Additional nif genes are required for the biosynthesis of the metal clusters and maturation of the enzyme (40). The major nif gene cluster of Anabaena sp. strain PCC 7120 undergoes two rearrangements in the heterocyst to yield nifB-fdxN-nifSUHDK-(1 ORF)-nifENX-(2 ORFs)-nifW-hesAB-fdxH (19).One approach to increase H2 production by nitrogenase is to enhance the electron flux to proton reduction and away from N2 reduction. Although replacement of N2 by Ar is effective for increasing H2 production, this approach increases the operational cost for large-scale generation of H2. Mutagenesis offers an alternative mechanism to overcome N2 competition. The amino acid sequences of the MoFe α subunit are highly conserved among different phyla (18). The V75I substitution in the suspected gas channel of NifD2 of Anabaena variabilis (equivalent to V70 in A. vinelandii) resulted in greatly diminished N2 fixation, while allowing for H2 production rates (under N2) that were similar to those of wild-type cells under Ar (55). Significantly, however, the nonheterocyst nitrogenase of this strain, which is expressed mainly in vegetative cells under anaerobic conditions, is incompatible with O2-evolving photosynthesis and thus requires continuous anaerobic conditions along with a supply of exogenous reducing sugars for H2 production. Substitutions of selected amino acids in the vicinity of the FeMo-co active site within Azotobacter vinelandii nitrogenase were shown to eliminate or greatly diminish N2 fixation while, in some cases, allowing for effective proton reduction (2, 10, 17, 27, 36, 44, 45, 48). Therefore, certain amino acid exchanges near FeMo-co might produce variant MoFe proteins in heterocyst-forming Anabaena that redirect the electron flux through the enzyme preferentially to proton reduction so as to synthesize more H2 in the presence of N2 in an aerobic environment.To examine whether Anabaena sp. strain PCC 7120 nitrogenase can be modified to increase photobiological H2 production by effecting such a redirection, we evaluated in vivo H2 production and acetylene reduction rates of a series of cyanobacterial nifD site-directed mutants. We mutated six NifD residues (Fig. (Fig.1)1) predicted to lie within 5 Å of FeMo-co to create 49 variants using an Anabaena ΔNifΔHup (previously denoted ΔhupL) parental strain that lacks both an intact nifD and an uptake hydrogenase (34). In an atmosphere containing N2 and O2, several mutants exhibited significantly enhanced rates of in vivo H2 production and accumulated high levels of H2 compared to the reference strains.Open in a separate windowFIG. 1.Side-on (left) and Mo end-on (right) views of the predicted active site for nitrogenase of Anabaena sp. strain PCC 7120. The FeMo-co cluster, a [7Fe-8S-Mo-X-homocitrate] complex, where X is a central unidentified light atom (N, C, or O), and its two coordinating residues (C282 and H449) are shown in a ball-and-stick representation. Water molecules near the FeMo-co are indicated by isolated spheres in red. The side chains of the residues targeted for mutagenesis—Q193, H197, Y236, R284, S285, and F388—are shown in stick representation. Residues V362 through P367 are represented by lines. The Anabaena residues were mapped onto the corresponding residues from the crystal structure of the A. vinelandii enzyme (PDB file 1M1N). The figure was generated by using PyMOL (www.pymol.org/), with the following color scheme: Fe, orange; S, yellow; C, gray; N and central atom X, blue; O, red; and Mo, pink. 相似文献
89.
Yoshinao Azuma Hideki Hirakawa Atsushi Yamashita Yan Cai Mohd Akhlakur Rahman Harumi Suzuki Shigeki Mitaku Hidehiro Toh Susumu Goto Tomoyuki Murakami Kazuro Sugi Hideo Hayashi Hideto Fukushi Masahira Hattori Satoru Kuhara Mutsunori Shirai 《DNA research》2006,13(1):15-23
Chlamydophila felis (Chlamydia psittaci feline pneumonitis agent) is a worldwide spread pathogen for pneumonia and conjunctivitis in cats. Herein, we determined the entire genomic DNA sequence of the Japanese C. felis strain Fe/C-56 to understand the mechanism of diseases caused by this pathogen. The C. felis genome is composed of a circular 1,166,239 bp chromosome encoding 1005 protein-coding genes and a 7552 bp circular plasmid. Comparison of C. felis gene contents with other Chlamydia species shows that 795 genes are common in the family Chlamydiaceae species and 47 genes are specific to C. felis. Phylogenetic analysis of the common genes reveals that most of the orthologue sets exhibit a similar divergent pattern but 14 C. felis genes accumulate more mutations, implicating that these genes may be involved in the evolutional adaptation to the C. felis-specific niche. Gene distribution and orthologue analyses reveal that two distinctive regions, i.e. the plasticity zone and frequently gene-translocated regions (FGRs), may play important but different roles for chlamydial genome evolution. The genomic DNA sequence of C. felis provides information for comprehension of diseases and elucidation of the chlamydial evolution. 相似文献
90.
Wakida K Amizuka N Murakami C Satoda T Fukae M Simmer JP Ozawa H Uchida T 《Histochemistry and cell biology》1999,111(4):297-303
Amelogenins are the most abundant constituent in the enamel matrix of developing teeth. Recent investigations of rodent incisors
and molar tooth germs revealed that amelogenins are expressed not only in secretory ameloblasts but also in maturation ameloblasts,
although in relatively low levels. In this study, we investigated expression of amelogenin in the maturation stage of porcine
tooth germs by in situ hybridization and immunocytochemistry. Amelogenin mRNA was intensely expressed in ameloblasts from
the differentiation to the transition stages, but was not detected in maturation stage ameloblasts. C-terminal specific anti-amelogenin
antiserum, which only reacts with nascent amelogenin molecules, stained ameloblasts from the differentiation to the transition
stages. This antiserum also stained the surface layer of immature enamel at the same stages. At the maturation stage, no immunoreactivity
was found within the ameloblasts or the immature enamel. These results indicate that, in porcine tooth germs, maturation ameloblasts
do not express amelogenins, suggesting that newly secreted enamel matrix proteins from the maturation ameloblast are not essential
to enamel maturation occurring at the maturation stage.
Accepted: 14 January 1999 相似文献