Improving the tensile properties of additively manufactured β-containing tial alloys via microstructure control focusing on cellular precipitation reaction

The effect of a two-step heat treatment on the microstructure and high-temperature tensile properties of β-containing Ti-44Al-4Cr (at%) alloys fabricated by electron beam powder bed fusion were examined by focusing on the morphology of α2/γ lamellar grains and β/γ cells precipitated at the lamellar grain boundaries by a cellular precipitation reaction. The alloys subjected to the first heat treatment step at 1573 K in the α + β two-phase region exhibit a non-equilibrium microstructure consisting of the α2/γ lamellar grains with a fine lamellar spacing and a β/γ duplex structure located at the grain boundaries. In the second step of heat treatment, i.e., aging at 1273 K in the β + γ two-phase region, the β/γ cells are discontinuously precipitated from the lamellar grain boundaries due to excess Cr supersaturation in the lamellae. The volume fraction of the cells and lamellar spacing increase with increasing aging time and affect the tensile properties of the alloys. The aged alloys exhibit higher strength and comparable elongation at 1023 K when compared to the as-built alloys. The strength of these alloys is strongly dependent on the volume fraction and lamellar spacing of the α2/γ lamellae. In addition, the morphology of the β/γ cells is also an important factor controlling the fracture mode and ductility of these alloys.Cho K., Odo H., Okamoto K., et al. Improving the tensile properties of additively manufactured β-containing tial alloys via microstructure control focusing on cellular precipitation reaction. Crystals, 11, 7, 809. https://doi.org/10.3390/cryst11070809

Peculiar microstructural evolution and tensile properties of β-containing γ-TiAl alloys fabricated by electron beam melting

The microstructure and tensile properties of β-containing Ti–44Al–4Cr alloy rods additively manufactured by electron beam melting (EBM) process were examined as a function of input energy density determined by the processing parameters. To the best of our knowledge, this is the first report to demonstrate that two types of fine microstructures have been obtained in the β-containing γ-TiAl alloys by varying the energy density during the EBM process. A uniform α2/β/γ mixed structure containing an α2/γ lamellar region and a β/γ dual-phase region is formed at high energy density conditions. On the other hand, a lower energy density leads to the formation of a peculiar layered microstructure perpendicular to the building direction, consisting of a ultrafine α2/γ lamellar grain layer and a α2/β/γ mixed structure layer. The difference in the microstructures originates from the difference in the solidification microstructure and the temperature distribution from the melt pool, which are dependent on the energy density. Furthermore, it was found that the strength of the alloys is closely related to the volume fractions of the β phase and the ultrafine α2/γ lamellar grains which originates from the massive α grains formed by rapid cooling under low energy density conditions. The alloys with high amounts of these peculiar microstructures exhibit high strength comparable to and higher than the conventional β-containing γ-TiAl at room temperature and 1023 K, respectively.Cho K., Kawabata H., Hayashi T., et al. Peculiar microstructural evolution and tensile properties of β-containing γ-TiAl alloys fabricated by electron beam melting. Additive Manufacturing, 46, 102091. https://doi.org/10.1016/j.addma.2021.102091

Inhibition of Rho-associated coiled-coil containing protein kinase enhances the activation of epidermal growth factor receptor in pancreatic cancer cells

<p>Abstract</p> <p>Background</p> <p>Rho-associated coiled-coil containing protein kinase (Rho-kinase/ROCK) is involved in various cellular functions including cell proliferation, and is generally considered to be oncogenic, while some studies show that ROCK functions as a negative regulator of cancer progression. As a result, the precise role of ROCK remains controversial. We have previously reported that Rho-kinase/ROCK negatively regulates epidermal growth factor (EGF)-induced cell proliferation in SW480 colon cancer cells. In the present study, we investigated the role of ROCK in EGF receptor (EGFR) signaling in the pancreatic cancer cell lines, Panc1, KP3 and AsPc1.</p> <p>Results</p> <p>In these cells, Y27632, a specific ROCK inhibitor, enhanced EGF-induced BrdU incorporation. The blockade of EGF stimulation utilizing anti-EGFR-neutralizing antibodies suppressed Panc1 cell proliferation. EGF induced RhoA activity, as well as the phosphorylation of cofilin and myosin light chain (MLC), both targets of ROCK signaling, and Y27632 suppressed both of these processes, indicating that the phosphorylation of cofilin and MLC by EGF occurs through ROCK in Panc1 cells. EGF-induced phosphorylation of EGFR at tyrosine residues was augmented when the cells were pretreated with Y27632 or were subjected to gene silencing using ROCK-siRNA. We also obtained similar results using transforming growth factor-α. In addition, EGF-induced phosphorylation of p44/p42 mitogen-activated protein kinase and Akt were also enhanced by Y27632 or ROCK-siRNA. Moreover, an immunofluorescence microscope study revealed that pretreatment with Y27632 delayed EGF-induced internalization of EGFR. Taken together, these data indicate that ROCK functions to switch off EGFR signaling by promoting the internalization of the EGFR.</p> <p>Conclusions</p> <p>While EGF first stimulates the activation of the EGFR and subsequently increases cancer cell proliferation, EGF concurrently induces the activation of ROCK, which then turns off the activated EGFR pathway via a negative feedback system.</p

Transcription factor LSF (TFCP2) inhibits melanoma growth.

Late SV40 factor 3 (LSF), a transcription factor, contributes to human hepatocellular carcinoma (HCC). However, decreased expression level of LSF in skin melanoma compared to that in benign melanocytic tumors and nevi in mice and humans was found in this study. Anchorage-dependent and -independent growth of melanoma cells was suppressed by LSF overexpression through an increased percentage of G1 phase cells and an increased p21CIP1 expression level in vitro and in vivo. Anchorage-dependent growth in LSF-overexpressed melanoma cells was promoted by depletion of LSF in the LSF-overexpressed cells. Integrated results of our EMSA and chromatin immunoprecipitation assays showed binding of LSF within a 150-bp upstream region of the transcription start site of p21CIP1 in melanoma cells. Taken together, our results suggest potential roles of LSF as a growth regulator through control of the transcription of p21CIP1 in melanocytes and melanoma cells as well as a biomarker for nevus

Ultrasound-mediated gene transfer (sonoporation) in fibrin-based matrices: potential for use in tissue regeneration

It has been suggested that gene transfer into donor cells is an efficient and practical means of locally supplying requisite growth factors for applications in tissue regeneration. Here we describe, for the first time, an ultrasound-mediated system that can non-invasively facilitate gene transfer into cells entrapped within fibrin-based matrices. Since ultrasound-mediated gene transfer is enhanced using microbubbles, we compared the efficacy of neutral and cationic forms of these reagents on the ultrasound-stimulated gene transfer process in gel matrices. In doing so we demonstrated the beneficial effects associated with the use of cationic microbubble preparations that interact directly with cells and nucleic acid within matrices. In some cases, gene expression was increased two-fold in gel matrices when cationic microbubbles were compared with neutral microbubbles. In addition, incorporating collagen into fibrin gels yielded a 25-fold increase in gene expression after application of ultrasound to microbubble-containing matrices. We suggest that this novel system may facilitate non-invasive temporal and spatial control of gene transfer in gel-based matrices for the purposes of tissue regeneration. Copyright © 2013 John Wiley & Sons, Ltd

Intraoral versus extraoral cementation of implant-supported single crowns: clinical, biomarker, and microbiological comparisons

Objectives: Implant supported single metal-ceramic crowns cemented either extraorally or intraorally were comparatively evaluated by clinical, radiologic, biomarker, and microbiological parameters. Materials and Methods: Twelve patients with bilateral single tooth gap in the maxillary posterior region received two locking-taper implants; 4.5 mm width, 8 mm length. Selection of intraoral (IOC) or extraoral cementation (EOC) using screwless titanium abutments was done randomly. Peri-implant crevicular fluid (PICF), gingival crevicular fluid (GCF) samples were collected from the implants, adjacent teeth, and bleeding on probing, soft tissue thickness, keratinized tissue width were recorded before starting the prosthetic procedures (baseline) and 3, 6 months after implant loading. Crestal bone loss was measured on radiographs taken immediately and 6 months after cementation. Cytokine levels, amounts of bacteria were determined in PICF/GCF samples. Data were tested by appropriate statistical analyses. Results: Clinical findings were similar in the crowns cemented extraorally or intraorally at all times (P &#60; .05). PICF and GCF data were similar. At 3 month, interleukin-17E and osteoprotegerin levels were lower in the intraorally cemented crowns. Conclusion: Extraorally and intraorally cemented crowns exhibited similar crestal bone loss after loading. Higher amount of osteoprotegerin at 3 month at the EOC than the IOC sites might bode well for good osseointegration