[Pure titanium denture large-span frameworks additively manufactured with selective laser melting].

Objective: To investigate the accuracy of pure titanium and cobalt-chromium alloy frameworks fabricated using the additive manufacturing (AM) of selective laser melting technology (SLM) for the mandibular implant-supported fixed prostheses and the maxillary removable partial denture (RPD), and to provide a reference for clinical application of SLM pure titanium frameworks. Methods: One edentulous mandibular model with implants and screw fixed abutments at bilateral canines and the first molars was selected and used as the mandibular full arch implant-supported model. At the same time, a Kennedy class Ⅰ maxillary dentition defect model was selected. The digital models were obtained by scanning the dental models, and the metal frameworks of the mandibular full arch implant-supported denture and the maxillary RPD (design model) were designed using the 3 Shape software. Meanwhile, 12 mandibular frameworks in the cobalt-chromium alloy and the pure titanium (6 in each group were treated with heat treatment, while the other 6 were not treated), and 7 maxillary frameworks in the cobalt-chromium alloy and the pure titanium were respectively made by SLM with the improved dual-laser metal printer. The axial direction of the printing powder accumulation was taken as the Z-axis. During the design process, the software (3Shape Dental System 2018) automatically generated the X-axis and Y-axis, X axis was the sagittal axis of the dental model and Y axis was the coronal axis of the dental model. The deviation of the interface center of the abutment of the digital model of the mandibular frameworks from the design model in the X, Y and Z axes was analyzed. As for the trueness of the mandibular framework, the larger the deviation data was, the worse the trueness was. The deviation of the whole maxillary framework and 7 measuring points (palatal plate center point and bilateral occlusal rests, I bars, proximal plates) were analyzed. The fitness of the whole maxillary framework to the design model was expressed by root mean square (RMS) of the deviation data, and the fitness of measuring points was expressed by the mean±standard deviation of the data. The trueness differences of each group before and after heat treatment of the mandibular framework and the fitness of the maxillary framework were compared. Results: The cobalt-chromium alloy frameworks showed lower trueness on the X, Y, Z-axes [(96.3±12.1), (86.3±11.4), (61.2±13.2) µm] than did the pure Ti frameworks [(82.3±11.2), (72.2±10.2), (51.2±11.6) µm] by SLM, and the heat treatment could reduce the discrepancy between the SLM frameworks and STL models, for pure titanium frameworks [(62.4±11.3), (55.2±13.2), (41.3±10.8) µm] and for cobalt-chromium alloy [(84.5±10.5), (72.3±11.2), (54.2±11.6) µm]. For the thin RPD major frameworks, pure titanium had better fitness [(121.3±17.0) µm] than cobalt-chromium alloy [(174.0±18.3) µm] by SLM, and the difference was statistically significant (P<0.05). Conclusions: Pure titanium frameworks fabricated by SLM additive manufacturing technology exhibited better fitness and trueness than did the Co-Cr frameworks after heat treatment respectively, and this satisfied the requirements of implant-supported fixed prostheses and RPD major metal frameworks.

Fading and showing mechanisms of ancient color relics based on light scattering induced by particles.

Fading and showing mechanisms of ancient color paintings based on light scattering induced by particles were proposed. To confirm the mechanisms, simulated and application experiments were carried out to restore an ancient blurred color painting. Loading TiO2 particles (500-1000 nm) onto a piece of colored paper could result in blurring of the color of the paper, which is attributed to light scattering caused by air voids between the particles. Filling air voids with ionic liquid (a non-volatile solution with a high refractive index) could highlight the color by reducing scattering. These results were experimentally testified by the combination of a fluorescence probe and multi-angle reflectance spectra, in which scattering decreased the incident optical path in the painting layer while the incident optical path was increased by filling the air voids with ionic liquid. As a practical example, the proposed method was applied to highlight an ancient Chinese painting with blurred color. This investigation is very useful to restore faded color paintings.

Correlation between presence of primary iris- and cilliary body cysts and intraocular pressure.

OBJECTIVE: The objective of this study was to examine the correlation between the presence of primary iris-ciliary cysts and the intraocular pressure. PATIENTS AND METHODS: Sixty patients with short-sightedness undergoing routine examination for laser vision correction in our hospital in 2003 were enrolled. Patients with known high intraocular pressure and risk of glaucoma were excluded from the study. A total of 119 eyes were examined by the Ultrasound Biomicroscope (UBM), and the presence of the primary iris-ciliary cysts was confirmed. Intraocular pressure was measured by using a blowing tonometer for each eye in triplicate. Through Pentacam correction of intraocular pressure using the Ehlers formula, the influence of the thickness of central cornea on intraocular pressure was excluded. RESULTS: Among all participants, 62 eyes (52.1%) were with high myopia, 57 eyes (47.9%) with low and moderate myopia, 27 eyes (22.7%) with single cyst, 20 eyes (16.8%) with multiple cysts, and 72 eyes (60.5%) were free from cysts. Moreover, the intraocular pressure was found within the normal range in 72 eyes (60.5%), and abnormally high in 47 eyes (39.5%). CONCLUSIONS: Our results showed that the presence of primary iris-ciliary cysts and the intraocular pressure were positively correlated, with a correlation coefficient of 0.235 (p = 0.01). These findings may prove useful for prediction and screening of high intraocular pressure.

MiR-577 inhibits papillary thyroid carcinoma cell proliferation, migration and invasion by targeting SphK2.

OBJECTIVE: MiRNAs are small, noncoding RNA molecules that serve as important regulators of cancer-related processes. Abnormal expression of miR-577 has been found in several tumors. However, the expression pattern and biological function of miR-577 in progression of papillary thyroid cancer (PTC) remain unknown. This study is aimed to determine its expression pattern and explore the function underlying the mechanism of miR-577 in PTC. PATIENTS AND METHODS: Using quantitative RT-PCR, we detected miR-577 expression in PTC cell lines and primary tumor tissues. MTT assay and colony formation were performed to measure the viabilities of tumor cells. Transwell invasion and migration assays were used to test the invasion and migration of PTC cells transfected with miR-577 mimic. TargetScan, miRanda and PicTar were used to analyze whether sphingosine kinase 2 (SphK2) was a potential target gene. Next, the direct target gene of miR-577 was also identified by luciferase reporter assays and Western blot analysis. RESULTS: The results showed that miR-577 was significantly downregulated in PTC tissues and cell lines. The up-regulation of miR-577 inhibited the proliferation, migration and invasion of PTC cells in vitro. Furthermore, bioinformatics analysis indicated that SphK2 was a putative target of miR-577. A luciferase reporter assay further confirmed that SphK2 was a direct target of miR-577. The results of Western blot indicated that the expression level of miR-577 was negatively correlated with the expression level of SphK2 in PTC tissues. In addition, knockdown of SphK2 significantly suppressed PTC cells proliferation, migration and invasion. CONCLUSIONS: Our findings indicate that miR-577 is a potential tumor suppressor in PTC by targeting SphK2, and may be a potential therapeutic target in PTC.

[Progress in neoadjuvant and transformation therapy of pancreatic cancer].

Pancreatic adenocarcinoma is a malignant disease with considerable metastatic potential.While surgical resection can be potentially curative, tumor recurrence remains an important cause of treatment failure.Neoadjuvant chemotherapy can increase rate of resectability by decreasing tumor burden and decrease recurrence rate by clearing microscopic disease in lymph nodes and vessels.Currently, neoadjuvant therapy is recommended for patients with resectable who has signs of high risks or borderline resectable pancreatic adenocarcinoma.However, no consensus exists in current literature on the evaluation of treatment response or operative timing.FOLFIRINOX has recently emerged as an effective chemotherapy regimen in several large clinical trials.

A laccase with antiproliferative activity against tumor cells from an edible mushroom, white common Agrocybe cylindracea.

A laccase, with HIV-1 reverse transcriptase inhibitory activity (IC(50)=12.7 µM) and antiproliferative activity against HepG2 cells (IC(50)=5.6 µM) and MCF7 cells (IC(50)=6.5 µM), was purified from fresh fruiting bodies of the edible white common Agrocybe cylindracea mushroom. The laccase, which had a novel N-terminal sequence, displayed a molecular mass of 58 kDa within the range reported for most other mushroom laccases. The purification protocol entailed ion exchange chromatography on DEAE-cellulose, SP-Sepharose, and Q-Sepharose and gel filtration on Superdex 75. The laccase was adsorbed on DEAE-cellulose and Q-Sepharose, but unadsorbed on SP-Sepharose. Its optimum pH was pH 3-4 and its optimum temperature was 50°C. The activity of the isolated laccase differed from one substrate to another. The ranking was ABTS>N,N-dimethyl-1,4-phenylenediamine>hydroquinone>catechol>2-methylcatechol>pyrogallol.

A novel ribonuclease with antiproliferative activity from fresh fruiting bodies of the edible mushroom Lyophyllum shimeiji.

A 14.5-kDa ribonuclease, with an optimum pH of 6 and a temperature optimum at 70 degrees C, was isolated from fresh fruiting bodies of the edible mushroom Lyophyllum shimeiji. It was purified by ion exchange chromatography on DEAE cellulose, Q Sepharose, and SP Sepharose, followed by FPLC gel filtration on Superdex 75, and was adsorbed on all three ion exchangers. It showed the highest ribonucleolytic potency toward poly (U), 25% as much activity toward poly (C), and undetectable activity toward poly (A) and poly (G). Its ribonucleolytic activity at 100 degrees C was similar to that at 20 degrees C. It suppressed proliferation of hepatoma HepG2 cells and breast cancer MCF7 cells with an IC(50) of 10 and 6.2 microM, respectively. It inhibited the activity of HIV-1 reverse transcriptase with an IC(50) of 7.2 microM.

Probing chemical and conformational differences in the resting and active conformers of platelet integrin alpha(IIb)beta(3).

Integrin alpha(IIb)beta(3) is the fibrinogen receptor that mediates platelet adhesion and aggregation. The ligand binding function of alpha(IIb)beta(3) is "activated" on the platelet surface by physiologic stimuli. Two forms of alpha(IIb)beta(3) can be purified from platelet lysates. These forms are facsimiles of the resting (Activation State-1 or AS-1) and the active (Activation State-2 or AS-2) conformations of the integrin found on the platelet surface. Here, the differences between purified AS-1 and AS-2 were examined to gain insight into the mechanism of activation. Four major findings are put forth. 1) The association rate (k(1)) between fibrinogen and the integrin is a key difference between AS-1 and AS-2. 2) Although the divalent ion Mn(2+) enhances the ligand binding function of AS-1, this ion is unable to convert AS-1 to AS-2. Therefore, its effect on integrin is unrelated to activation. 3) Peptide mass fingerprints indicate that the chemical structure of AS-1 and AS-2 are virtually identical, calling into question the idea that post-translational modifications are necessary for activation. 4) The two forms of alpha(IIb)beta(3) have significant conformational differences at three positions. These include the junction of the heavy and light chain of alpha(IIb), the divalent ion binding sites on alpha(IIb), and at a disulfide-bonded knot linking the amino terminus of beta(3) to the cysteine-rich domain. These observations indicate that integrin is activated by a series of specific conformational rearrangements in the ectodomain that increase the rate of ligand association.

A new model of dual interacting ligand binding sites on integrin alphaIIbbeta3.

The platelet integrin alphaIIbbeta3 mediates platelet aggregation and platelet adhesion. This integrin is the key to hemostasis and also to pathologic vascular occlusion. A key domain on alphaIIbbeta3 is the ligand binding site, which can bind to plasma fibrinogen and to a number of Arg-Gly-Asp (RGD)-type ligands. However, the nature and function of the ligand binding pocket on alphaIIbbeta3 remains controversial. Some studies suggest the presence of two ligand binding pockets, whereas other reports indicate a single binding pocket. Here we use surface plasmon resonance to show that alphaIIbbeta3 contains two distinct ligand binding pockets. One site binds to fibrinogen, and a separate site binds to RGD-type ligands. More importantly, however, the two ligand binding pockets are interactive. RGD-type ligands are capable of binding to alphaIIbbeta3 even when it is already occupied by fibrinogen. Once bound, RGD-type ligands induce the dissociation of fibrinogen from alphaIIbbeta3. This allosteric cross-talk has important implications for anti-platelet therapy because it suggests a novel approach for the dissolution of existing platelet thrombi.

An allosteric Ca2+ binding site on the beta3-integrins that regulates the dissociation rate for RGD ligands.

Here we use a model RGD-containing ligand to study how Ca2+ and Mg2+ regulate ligand binding to beta3-integrins. Fab-9, an antibody that contains an optimized RGD loop in its antigen binding site (Barbas, C. F., Languino, L., and Smith, J. W. (1993) Proc. Natl. Acad. Sci. U. S. A. 90, 10003-10007), was used as the model ligand. Across a physiologic range of Mg2+, Fab-9 bound to both alphavbeta3 and alphaIIbbeta3 with a monophasic binding isotherm. Across the same range of Ca2+, the binding of Fab-9 to the beta3-integrins was biphasic. Low concentrations of Ca2+ (microM) promoted the binding of Fab-9. Higher concentrations of Ca2+ (m) blocked Fab-9 binding. These data suggest that Ca2+ binds to two distinct classes of sites on the beta3-integrins, with the low affinity Ca2+ binding site(s) being an inhibitory site. We designate this inhibitory site(s) as the I site. Further biochemical characterization showed that the I site has the following characteristics: 1) it is specific for Ca2+; 2) it is allosteric to the ligand binding site; 3) its occupation increases the dissociation rate between integrin and RGD ligand; and 4) occupation of the I site can induce cellular deadhesion.

A biochemical characterization of the binding of osteopontin to integrins alpha v beta 1 and alpha v beta 5.

Osteopontin (OPN) is an extracellular matrix protein that binds to integrin alpha v beta 3. Here we demonstrate that two other integrins, alpha v beta 1 and alpha v beta 5, are also receptors for OPN. Human embryonic kidney 293 cells adhere to human recombinant osteopontin (glutathione S-transferase-osteopontin; GST-OPN) using integrin alpha v beta 1. When the 293 cells are transfected with the beta 5 subunit, they can also adhere to GST-OPN using integrin alpha v beta 5. Divalent cations regulate the binding of GST-OPN to both alpha v beta 1 and alpha v beta 5. Mg2+ and Mn2+ support the binding of GST-OPN to these integrins but Ca2+ does not. The highest affinity is observed in Mn2+. In the presence of this ion, the affinity of GST-OPN for alpha v beta 1 is 18 nM and the affinity for alpha v beta 5 is 48 nM. The antibody 8A2, which is an agonist for beta 1, promotes the adhesion of 293 cells to GST-OPN even when Ca2+ is present. This observation suggests that cellular events could modulate the affinity of alpha v beta 1 for OPN. Collectively, these findings prove that integrins alpha v beta 1, alpha v beta 3, and alpha v beta 5 have similar affinity for OPN. Therefore, all three integrins must be considered when evaluating the biological affects of OPN.

Ca2+ suppresses cell adhesion to osteopontin by attenuating binding affinity for integrin alpha v beta 3.

Osteopontin (OPN) is an extracellular matrix protein that supports osteoclast adhesion to the bone by binding to integrin alpha v beta 3. We measured the binding between OPN and integrin alpha v beta 3 with recombinant human OPN and the urinary form of human OPN, uropontin. Recombinant OPN was expressed in Escherichia coli as a fusion protein with glutathione S-transferase and cleaved from glutathione S-transferase with Factor Xa. The mass of this form of OPN (rOP27) is 27,046 Da. rOP27 is truncated at arginine residue 228, 69 amino acids short of the native carboxyl terminus. Uropontin and rOP27 support RGD-dependent cell adhesion and to bind purified integrin alpha v beta 3 with similar affinities. Further study showed that OPN is the only known naturally occurring RGD-containing protein with a much greater affinity for alpha v beta 3 than for the platelet integrin alpha IIb beta 3. Most importantly, we find that physiologic levels of Ca2+ block cell adhesion to OPN. Measurement of binding constants between rOPN and purified integrin alpha v beta 3 with surface plasmon resonance showed that the affinity between rOPN and alpha v beta 3 is 26-fold lower in Ca2+ (Kd = 1.1 x 10(-8) M) than in Mn2+ (Kd = 4.3 x 10(-10) M) and 9-fold lower than in Mg2+ (Kd = 1.3 x 10(-9) M). In bone, the resorbing osteoclast generates elevated levels of extracellular Ca2+, therefore the findings presented here suggest a previously unappreciated mechanism for the modulation of bone resorption by extracellular Ca2+.

Thermodynamic studies of the interaction of trp aporepressor with tryptophan analogs.

The association of L-tryptophan and some of its analogs, including three conformationally restricted analogs, with trp aporepressor (apo trpR) was studied by isothermal titration microcalorimetry. Contributions of the functional groups of a ligand to the free energy change, delta G degrees', and enthalpy change, delta H degree', of the interaction were evaluated on a molecular basis. Analogs without the alpha-amino group (i.e. desamino analogs) bind with a slightly higher affinity to the protein. On the other hand, descarboxy analogs show weaker binding to the apo trpR. In addition, it is found that there exists enthalpy-entropy compensation for the association of the congener series of ligands with the protein. The entropy change, delta S degree', appears to play a more important role in the binding of the conformationally restricted analogs than in the binding of L-tryptophan and the unlocked ligands.