Environmental Stress Cracking of High-Density Polyethylene Applying Linear Elastic Fracture Mechanics.

The crack propagation rate of environmental stress cracking was studied on high-density polyethylene compact tension specimens under static loading. Selected environmental liquids are distilled water, 2 wt% aqueous Arkopal N100 solution, and two model liquid mixtures, one based on solvents and one on detergents, representing stress cracking test liquids for commercial crop protection products. The different surface tensions and solubilities, which affect the energetic facilitation of void nucleation and craze development, are studied. Crack growth in surface-active media is strongly accelerated as the solvents induce plasticization, followed by strong blunting significantly retarding both crack initiation and crack propagation. The crack propagation rate for static load as a function of the stress intensity factor within all environments is found to follow the Paris-Erdogan law. Scanning electron micrographs of the fracture surface highlight more pronounced structures with both extensive degrees of plasticization and reduced crack propagation rate, addressing the distinct creep behavior of fibrils. Additionally, the limitations of linear elastic fracture mechanisms for visco-elastic polymers exposed to environmental liquids are discussed.

Determination of CD43 and CD200 surface expression improves accuracy of B-cell lymphoma immunophenotyping.

BACKGROUND: The Matutes score (MS) was proposed to differentiate chronic lymphocytic leukemia (CLL) from other B-cell non-Hodgkin lymphomas (B-NHLs). However, ambiguous immunophenotypes are common and remain a diagnostic challenge. Therefore, we evaluated the diagnostic benefit of measuring CD200 and CD43 expression together with the standard MS antigens. METHODS: 138 lymphoma patient samples and a validation cohort of 138 additive samples were classified according to the standard MS and further assigned with one or two additional points, for high CD200 and/or CD43 expression levels. The "classical" MS and the "Matutes score-extended" (MS-e) were categorized as high (4-5/6-7), intermediate (2-3/4-5), and low (0-1/0-3). Samples were reclassified into the MS-e with focus on ambiguous cases with an intermediate "classical" MS. RESULTS: A total of 35 of 138 (25.4%) patient samples were assigned to the intermediate MS group and confirmed by histopathological reports as CLL (14/40.0%) and B-NHLs other than CLL (21/60%). MS-e analysis identified 13 of 14 (92.9%) of CLL cases (MS-e 4-5) and 18/21 (85.7%) non-CLL cases (MS-e ≤ 3) correctly. Overall, the sensitivity of the CLL diagnosis was significantly increased by application of MS-e compared to the "classical" MS (98.8% vs. 82.7%; p = 0.0009), while specificity of both methods was almost equal (94.7% vs. 98.3%; p = 0.4795). Of note, sole measurement of CD43 and CD200 on B-cells sufficiently differentiated CLL from non-CLL with a test accuracy superior to the "classical" MS (F1 score 96.2 vs. 93.6). CONCLUSION: CD200 and CD43 have a high informative value in diagnostic immunophenotyping and facilitate the separation of CLL from other B-NHLs particularly in ambiguous cases.

Interleukin-4 and interleukin-13 stimulate the osteoclast inhibitor osteoprotegerin by human endothelial cells through the STAT6 pathway.

INTRODUCTION: Endothelial cells of the bone vasculature modulate development, remodeling, and repair of bone by secreting osteotropic cytokines and hormones, which can act on osteoblastic and osteoclastic lineage cells. RANKL is the essential factor for differentiation, activation, and survival of osteoclasts, whereas osteoprotegerin (OPG) is a soluble decoy receptor and inhibitor for RANKL. MATERIALS AND METHODS: In this study, we analyzed the regulation of OPG by T helper 2 (Th2) cytokines interleukin (IL)-4 and the closely related IL-13 in human umbilical vein endothelial cells (HUVECs), the underlying signaling pathway, and its functional relevance on osteoclastic resorption. RESULTS: IL-4 and IL-13 induced OPG mRNA levels and protein secretion in HUVEC by up to 4-fold in a dose- and time-dependent fashion (maximum effect after 48 h and at 10 ng/ml). Activation of the transcription factor STAT6 preceded IL-4-induced OPG expression, and blockade of IL-4-induced STAT6 activation by the phospholipase C-specific inhibitor D609 decreased OPG expression. Soluble IL-4 receptor (sIL-4R) dose-dependently abolished both IL-4-induced STAT6 phosphorylation and OPG expression. RANKL stimulated the activity of osteoclasts, which was antagonized by HUVEC-derived supernatant containing OPG. The inhibitory effect on osteoclastogenesis was completely and specifically abrogated by a neutralizing OPG antibody in unstimulated HUVEC supernatant and partially in IL-4-stimulated HUVEC supernatant. CONCLUSIONS: In summary, IL-4 and IL-13 induced OPG expression through activation of STAT6 in endothelial cells, and HUVEC-derived OPG is an IL-4/IL-13-induced inhibitor of osteoclastic resorption. These data underline the impact of Th2 cytokines on bone resorption through modulation of endothelial cell-derived cytokines.

17beta-Estradiol inhibits osteoprotegerin production by the estrogen receptor-alpha-positive human breast cancer cell line MCF-7.

Estrogen regulates various cytokines and growth factors in estrogen receptor (ER)-positive human breast cancer. Receptor activator of NF-kappaB ligand (RANKL) is an essential cytokine for osteoclasts, whereas osteoprotegerin (OPG) is a soluble inhibitor for RANKL. We analyzed the regulation of the RANKL/OPG system by estrogens and androgens in the ER-positive breast cancer cell line MCF-7 and the ER-negative breast cancer cell line MDA-MB-231. In MCF-7 cells, which predominantly express ER-alpha, 17beta-estradiol and testosterone dose-dependently decreased OPG mRNA levels and protein secretion by 70 and 65%, respectively (p<0.0001 by ANOVA). The inhibition of OPG production by 17beta-estradiol and testosterone was specifically prevented by the pure anti-estrogen ICI 182,780, and the testosterone effect was prevented by an aromatase inhibitor. In conclusion, 17beta-estradiol suppressed OPG production by human breast cancer cell lines in a dose-dependent and specific manner, indicating that the RANKL/OPG cytokine system is an estrogen-responsive target in breast cancer.

Interleukin-4 differentially regulates osteoprotegerin expression and induces calcification in vascular smooth muscle cells.

Vascular calcification is characterized by cellular transdifferentiation and expression of bone-related matrix proteins that result in the presence of bone-like structures in the vascular wall. Interleukin (IL)-4, a pleiotropic cytokine, and osteoprotegerin (OPG), an essential regulator of osteoclast biology, have both been linked to vascular disease. Here, we assessed the role of IL-4 and OPG in vascular calcification in vitro. IL-4 induced OPG mRNA levels and protein secretion by 5-fold in a dose- and time-dependent fashion in human coronary artery smooth muscle cells (CASMC). Activation of the transcription factor STAT6 preceded IL-4-induced OPG expression, and blockade of IL-4-induced STAT6 activation by the phospholipase C inhibitor D609 decreased OPG expression. Long-term exposure of IL-4 for 4 weeks resulted in transformation of CASMC towards an osteoblastic phenotype, based on the expression of the transcription factor Cbfa1 and increased mineral deposition. Notably, calcification of CASMC was inhibited by gene silencing of Cbfa1. During osteogenic transformation, IL-4 down-regulated OPG production in CASMC. IL-4 has differential effects in CASMC: While short-term exposure enhances OPG production through a STAT6-dependent mechanism, long-term exposure causes Cbfa1-dependent osteogenic transformation and a decreased production of OPG, an inhibitor of bone resorption.