PubMed Health⌕ Search

Biomedical subjects

Jin Jiang

Publications and source records attributed to Jin Jiang.

33 records · Page 2Linked to original sources
PubMed2004

Direct contact between enamel matrix derivative (EMD) and osteoblasts is not required for EMD-induced cell proliferation.

OBJECTIVE: The purpose of this study was to determine whether the effect of enamel matrix derivative (EMD) on osteoblast proliferation is dependent on direct contact between EMD and the cells. STUDY DESIGN: MC3T3-E1 cells were seeded onto 6-well culture plates at an initial density of 5000/cm(2) in Dulbecco's modified eagle medium (DMEM) with 10% fetal bovine serum (FBS). Serum was removed from the culture medium after 24 hours with or without the addition of EMD. Four groups were evaluated: group 1, DMEM only; group 2, DMEM with 100 microg/mL EMD directly added to the culture medium; group 3, DMEM with a culture plate insert (30-mm diameter; 0.4-microm pore size) only; group 4, DMEM with 100 microg/mL EMD added onto a culture plate insert. The porous membrane of the insert prevented direct contact between EMD and the cells. After 3-day incubation, cell morphology was examined and the total cell number per well was counted and analyzed using 1-way ANOVA. RESULTS: EMD formed precipitated aggregates on the membrane of the culture insert with the same appearance as when it was added directly to the medium. The culture plate insert alone did not cause any changes in cell morphology or proliferation. The addition of EMD significantly increased cell number regardless the presence of the culture plate insert. CONCLUSION: This study suggests that direct contact between EMD and osteoblasts is not required to induce cell proliferation. Soluble peptides released from EMD may contribute to the stimulating effects of EMD on cell proliferation.

3T3 Cells↗
PubMed2004

[Relationship between ephemeral plants distribution and soil moisture on longitudinal dune surface in Gurbantonggut desert].

Ephemeral plant is a particular group of desert flora only distributed in northern Xinjiang, China. In this study, field surveys of vegetation and soil moisture were conducted in the southern area of the Gurbantonggut desert from March to August 2002. The species number, coverage and growth of ephemerals and soil moisture were measured in 7 quadrats at different geomorphic positions on the longitudinal dune surface. The results showed that soil moisture in a depth of 0-30 cm affected ephemeral plants distribution significantly. In early spring, the soil moisture was 4.62% on the intredune, 3.98% on the plinth, and 2.01% on the crest. Consequently, the average coverage of ephemeral plants reached 51.8%, 38.2% and 4.4%, respectively. The existence of ephemeral plants distribution influenced soil moisture as well. In later May, there was an increase of surface soil moisture from the interdune to the crest. The soil moisture was 1.00% on the intredune, 1.90% on the plinth, and 2.45% on the crest.

China↗
PubMed2003

Actin-related protein 2/3 complex is required for actin ring formation.

UNLABELLED: Actin rings are vital for osteoclastic bone resorption, and actin-related protein 2/3 complex is a pivotal regulator of actin polymerization. Actin-related protein 2/3 complex was found in the podosomes of actin rings. A short interfering RNA knocked down expression of actin-related protein 2 in osteoclasts and disrupted actin rings, suggesting that the complex is crucial to actin ring formation. INTRODUCTION: To resorb bone, osteoclasts form an extracellular acidic compartment segregated by a sealing zone. This is dependent on an actin ring that is composed of filamentous actin organized into dynamic structures called podosomes. The actin-related protein 2/3 (Arp2/3) complex is a vital regulator of actin polymerization. We tested whether the Arp2/3 complex is a component of actin rings and is important for actin ring formation. MATERIALS AND METHODS: Western blot analysis was used to determine levels of Arp2 and Arp3, two components of the Arp2/3 complex in osteoclast-like cells. Confocal microscopy studies using antibodies for immunocytochemistry demonstrated localization of Arp2/3 complex in osteoclasts. Short interfering RNA oligonucleotides (siRNAs) were made against Arp2 and used to knock down its expression. RESULTS: A 3-fold increase in Arp2 and Arp3 was detected during RANKL-induced differentiation of RAW 264.7 cells into osteoclast-like cells. Arp2/3 complex was concentrated in actin rings and enriched near the sealing zone. Arp2/3 complex co-localized with cortactin, a component of podosomes, but not vinculin, which surrounds podosomes. siRNA against Arp2, transfected into RAW 264.7 cells 5 days after stimulation with RANKL, reduced Arp2 protein levels 70% compared with cells transfected with ineffective siRNAs. Cytochemical characterization of RAW 264.7 osteoclast-like cells and marrow osteoclasts in which Arp2 was knocked down revealed fewer podosomes and no actin rings, although many cells remained well spread. CONCLUSIONS: These data show that Arp2/3 complex is a component of actin rings and that the presence of Arp2/3 complex is vital to the formation of actin rings. In addition, the results show the use of siRNAs for the study of RAW 264.7 osteoclast-like cells.

Actin Cytoskeleton↗
PubMed2003

Vacuolar H+-ATPase binding to microfilaments: regulation in response to phosphatidylinositol 3-kinase activity and detailed characterization of the actin-binding site in subunit B.

Vacuolar H(+)-ATPase (V-ATPase) binds microfilaments, and that interaction may be mediated by an actin binding domain in subunit B of the enzyme. To test for possible physiologic functions of the actin binding activity of V-ATPase, early responses of resorbing osteoclasts to inhibition of phosphatidylinositol 3-kinase activity by wortmannin and LY294002 were examined. Rapid co-localization between V-ATPase and F-actin was demonstrated by immunocytochemistry, and corresponding association between V-ATPase and F-actin in immunoprecipitations and pelleting assays was detected. This response was reversed as osteoclasts recovered resorptive activity after inhibitors were removed. By expressing and characterizing fusion proteins containing segments of the actin-binding amino-terminal regions of the B subunits of V-ATPase, we mapped the actin-binding site to a 44-amino acid domain. An 11-amino acid segment with a sequence similar to the actin-binding site of human profilin I was detected within this region. 13-Mers containing these profilin-like segments bound actin in fluorescent anisotropy studies and competed with profilin for binding to actin. Using site-directed mutagenesis, the 11-amino acid profilin-like actin-binding motifs (amino acids 49-59 of B1 and 55-65 of B2) were replaced with an 11-amino acid spacer with a sequence based on the homologous sequence from subunit B of Pyrococcus horikoshii, an organism that lacks an actin cytoskeleton. These substitutions eliminated the actin-binding activity of the B subunit fusion proteins. In summary, binding between V-ATPase and F-actin in osteoclasts occurs in response to blocking phosphatidylinositol 3-kinase activity. This response was fully reversible. The actin binding activities of the B subunits of V-ATPase required 11-amino acid actin-binding motifs that are similar in sequence to the actin-binding site of mammalian profilin I.

Actin Cytoskeleton↗
PubMed2003

Smoothened transduces Hedgehog signal by physically interacting with Costal2/Fused complex through its C-terminal tail.

The Hedgehog (Hh) family of secreted proteins controls many aspects of growth and patterning in animal development. The seven-transmembrane protein Smoothened (Smo) transduces the Hh signal in both vertebrates and invertebrates; however, the mechanism of its action remains unknown. We found that Smo lacking its C-terminal tail (C-tail) is inactive, whereas membrane-tethered Smo C-tail has constitutive albeit low levels of Hh signaling activity. Smo physically interacts with Costal2 (Cos2) and Fused (Fu) through its C-tail. Deletion of the Cos2/Fu-binding domain from Smo abolishes its signaling activity. Moreover, overexpressing Cos2 mutants that fail to bind Fu and Ci but retain Smo-binding activity blocks Hh signaling. Taken together, our results suggest that Smo transduces the Hh signal by physically interacting with the Cos2/Fu protein complex.

Animals↗
PubMed2003

The Drosophila Ste20 family kinase dMST functions as a tumor suppressor by restricting cell proliferation and promoting apoptosis.

In a genetic screen for mutations that restrict cell growth and organ size, we identified a new tumor suppressor gene, dMST, which encodes the Drosophila homolog of the mammalian Ste20 kinase family members MST1 and MST2. Loss-of-function mutations in dMST result in overgrown tissues containing more cells of normal size. dMST mutant cells exhibit elevated levels of Cyclin E and DIAP1, increased cell growth and proliferation, and impaired apoptosis. dMST forms a complex with Sav and Wts, two tumor suppressors also implicated in regulating both cell proliferation and apoptosis, suggesting that they act in common pathways.

Amino Acid Sequence↗
PubMed2003

Molecular genetic analysis of the glycosyltransferase Fringe in Drosophila.

Fringe proteins are beta1,3-N-acetylglucosaminyltransferases that modulate signaling through Notch receptors by modifying O-linked fucose on epidermal growth factor domains. Fringe is highly conserved, and comparison among 18 different Fringe proteins from 11 different species identifies a core set of 84 amino acids that are identical among all Fringes. Fringe is only distantly related to other glycosyltransferases, but analysis of the predicted Drosophila proteome identifies a set of four sequence motifs shared among Fringe and other putative beta1,3-glycosyltransferases. To gain functional insight into these conserved sequences, we genetically and molecularly characterized 14 point mutations in Drosophila fringe. Most nonsense mutations act as recessive antimorphs, raising the possibility that Fringe may function as a dimer. Missense mutations identify two distinct motifs that are conserved among beta1,3-glycosyltransferases, and that can be modeled onto key motifs in the crystallographic structures of bovine beta1,4-galactosyltransferase 1 and human glucuronyltransferase I. Other missense mutations map to amino acids that are conserved among Fringe proteins, but not among other glycosyltransferases, and thus may identify structural motifs that are required for unique aspects of Fringe activity.

Amino Acid Sequence↗
PubMed2003

The synergistic effect of peptidoglycan and lipopolysaccaride on osteoclast formation.

PURPOSE: The purpose of this study was to investigate the mechanisms leading to periapical tissue destruction by the Gram-positive bacterial cell component, peptidoglycan (PGN) and Gram-negative bacterial cell component lipopolysaccaride (LPS). STUDY DESIGN: Osteoclast precursor RAW 264.7 cells were cultured with 50 ng/ml receptor activator of NF-kappaB ligand (RANKL) for 72 hours. RANKL was then removed and the cells were treated with various concentrations of PGN in the presence or absence of various concentration of LPS for an additional 48 hours. RT-PCR analysis was performed to examine the presence of receptors on osteoclasts known to be involved in mediating cellular activation in response to PGN (TLR2) and LPS (TLR 4). RESULTS: PGN dose dependently and reproducibly stimulated TRAP-positive multinucleated osteoclast-like (OCL) cell formation. PGN and LPS had synergistic effects on the induction of OCL cell formation. Both unstimulated and RANKL-stimulated RAW 264.7 cells expressed TLR2 and TLR4 mRNA. CONCLUSION: The results underscore the importance of considering both Gram-positive and Gram-negative bacteria when interpreting findings associated with primary and secondary periapical lesions.

Acid Phosphatase↗
PubMed2003

Calcium hydroxide reduces lipopolysaccharide-stimulated osteoclast formation.

OBJECTIVE: The purpose of this study was to determine the direct effects of lipopolysaccharide (LPS) on osteoclastogenesis and to assess the ability of calcium hydroxide-Ca(OH)(2)-to inhibit the osteoclast formation stimulated by LPS. STUDY DESIGN: RAW 264.7 cells were cultured with 50 ng/mL recombinant receptor activator of NF-kappaB ligand (RANKL) for 72 hours. RANKL was then removed, and the cells were treated with 0, 1, 10, or 100 ng/mL of LPS, Ca(OH)(2)-treated LPS, or 50 ng/mL of RANKL as a positive control for an additional 48 hours. Cells were fixed and stained with fluorescein isothiocyanate-conjugated phalloidin to detect actin ring formation, and histochemistry was performed to detect multinucleated cells expressing tartrate-resistant acid phosphatase activity. RESULTS: LPS induced osteoclast-like cell (OCL) formation in a dose-dependent manner when osteoclast precursor RAW 264.7 cells were pretreated for 72 hours with RANKL. Ca(OH)(2) significantly inhibited the ability of LPS to stimulate OCL formation. CONCLUSION: This study shows that LPS directly stimulates OCL formation. The detoxification of LPS by treatment with Ca(OH)(2) significantly reduced its ability to trigger the differentiation of OCLs.

Acid Phosphatase↗
PubMed2003

[Clinical characters and CT findings of steatohepatitis in highland area].

OBJECTIVE: To explore the relationship between the CT findings of steatohepatitis and the special environmental factors in highland area, such as anoxia and life styles. METHODS: CT scan was performed for 64 patients, who were 44 males and 20 females in Tibet with a 3500-meter elevation. RESULTS: Hypodensity in liver parenchyma and the invertion of liver density and spleen density were found in all the 64 patients. According to the degree and scope in their pathological changes, these patients were divided into three groups: severe 14, moderate 26, and mild 24.And diffused 43, sectional 14, regional 7 by CT findings. Among the 44 drinkers, 34 with more than 10 years were diffused by CT scan, the other 10 drinkers under 10 years, diffused 8, and sectional 2. In addition, the 27 steatohepatitis patients were all diffused by CT who were obese and had drinked more than 10 years. CONCLUSION: anoxia and drinking excessively in highland area are relevant to fatty degeneration in liver.

Adult↗
PubMed2002

Role for Slimb in the degradation of Drosophila Period protein phosphorylated by Doubletime.

Protein phosphorylation has a key role in modulating the stabilities of circadian clock proteins in a manner specific to the time of day. A conserved feature of animal clocks is that Period (Per) proteins undergo daily rhythms in phosphorylation and levels, events that are crucial for normal clock progression. Casein kinase Iepsilon (CKIepsilon) has a prominent role in regulating the phosphorylation and abundance of Per proteins in animals. This was first shown in Drosophila with the characterization of Doubletime (Dbt), a homologue of vertebrate casein kinase Iepsilon. However, it is not clear how Dbt regulates the levels of Per. Here we show, using a cell culture system, that Dbt promotes the progressive phosphorylation of Per, leading to the rapid degradation of hyperphosphorylated isoforms by the ubiquitin-proteasome pathway. Slimb, an F-box/WD40-repeat protein functioning in the ubiquitin-proteasome pathway interacts preferentially with phosphorylated Per and stimulates its degradation. Overexpression of slimb or expression in clock cells of a dominant-negative version of slimb disrupts normal rhythmic activity in flies. Our findings suggest that hyperphosphorylated Per is targeted to the proteasome by interactions with Slimb.

Animals↗
PubMed2002

Shaggy/GSK3 antagonizes Hedgehog signalling by regulating Cubitus interruptus.

The Drosophila protein Shaggy (Sgg, also known as Zeste-white3, Zw3) and its vertebrate orthologue glycogen synthase kinase 3 (GSK3) are inhibitory components of the Wingless (Wg) and Wnt pathways. Here we show that Sgg is also a negative regulator in the Hedgehog (Hh) pathway. In Drosophila, Hh acts both by blocking the proteolytic processing of full-length Cubitus interruptus, Ci (Ci155), to generate a truncated repressor form (Ci75), and by stimulating the activity of accumulated Ci155 (refs 2-6). Loss of sgg gene function results in a cell-autonomous accumulation of high levels of Ci155 and the ectopic expression of Hh-responsive genes including decapentaplegic (dpp) and wg. Simultaneous removal of sgg and Suppressor of fused, Su(fu), results in wing duplications similar to those caused by ectopic Hh signalling. Ci is phosphorylated by GSK3 after a primed phosphorylation by protein kinase A (PKA), and mutating GSK3-phosphorylation sites in Ci blocks its processing and prevents the production of the repressor form. We propose that Sgg/GSK3 acts in conjunction with PKA to cause hyperphosphorylation of Ci, which targets it for proteolytic processing, and that Hh opposes Ci proteolysis by promoting its dephosphorylation.

Amino Acid Sequence↗
PubMed2002

Expression of adenosine triphosphate P2X3 receptors in rat molar pulp and trigeminal ganglia.

OBJECTIVE: The objective of this study was to investigate the expression of adenosine triphosphate P2X3 receptor subunits in rat molar pulp and trigeminal ganglia and their relationship to substance P. STUDY DESIGN: Rat molar pulp and trigeminal ganglia were fixed and sectioned. Double immunostaining with anti-P2X3 and anti-substance P were used to localize P2X3 and substance P expression simultaneously with different stains. RESULTS: P2X3 immunoreactivity (IR) fibers were present in root and coronal pulp. P2X3-IR fibers formed subodontoblastic plexus and advanced into the predentin and dentin. P2X3-IR neurons were localized in small and medium-sized cells in trigeminal ganglia. Colocalization of P2X3 and substance P was not found in either molar pulp or trigeminal ganglia. CONCLUSION: The results of this study indicated that adenosine triphosphate in pulp tissues may stimulate a subpopulation of non-substance P trigeminal afferent fibers through activation of P2X3 receptors.

Adenosine Triphosphate↗
PubMed2002

Measurement of the distance between the minor foramen and the anatomic apex by digital and conventional radiography.

The purpose of this study was to determine the distance between the minor foramen and the anatomic apex from digital and conventional radiographs. Thirty permanent single-canal teeth with mature root apex were used. After access preparation, a K-file was inserted into the canal until the tip of the file was just seen at the minor foramen under a x40 stereomicroscope. The file was fixed in the canal by filling the access with composite resin. The teeth with files in the canals were radiographed using a Schick CDR digital system and conventional radiography with E-speed film. For digital radiographs, the distance between the file tip and the center of radiographic apex was directly measured from the computer screen by using Schick CDR measurement software. For conventional radiographs, the distance was measured under a stereomicroscope at a magnification of x10 with a calibrated millimeter ruler. The mean distance was 0.494 mm measured from conventional radiographs and 0.594 mm from digital radiographs. These results agree with the current conception that endodontic working length should terminate 1 mm from the radiographic apex. There was a significant difference between the measurements on digital radiographs and those on conventional radiographs (p < 0.05, paired t test). However, the 0.1-mm difference has no clinical significance, because clinically, the working length is generally measured to the nearest 0.5 mm.

Dental Pulp Cavity↗