Crystallization, microstructure and properties of selected glasses and glass-ceramics in the SiO2-Li2O-ZnO-K2O-P2O5 system

The crystallization behavior of selected glasses in the multicomponent SiO2-Li2O-ZnO-K2O-P2O5 system was investigated using high-temperature X-ray diffraction and differential scanning calorimetry. Proceeding from a dental model glass with the molar composition 63.2 SiO2, 29.1 Li2O, 3.3 ZnO, 2.9 K2O and 1.5 P2O5, 20 glasses were melted, varying the concentrations of the single components systematically. Glass compositions mainly influenced the formations and dissolutions of metastable and stable phases in the temperature range of 480 to 1100 °C. In the majority of the glasses hthium disilicate (Li2Si2O5) precipitated as the main crystal phase during heating, while lithium metasilicate, lithium orthophosphate, cristobalite and quartz crystallized as secondary phases. After a one-step heat treatment microstructures of glass-ceramics and morphologies of Li2Si2O5 crystals were characterized by scanning electron microscopy. With few exceptions glass-ceramics showed a finegrained microstructure with interlocking, rodshaped Li2Si2O5 crystals with 0.5 to 10 µm in length. The corresponding glass-ceramics were processed by a hot-pressing technique to test samples for mechanical and optical measurements. Concentration variations of the base glasses caused bending strengths between 224 and 675 MPa. Within a comparison of translucency according to dental standard BS 5612 contrast ratios between 0.3 and 0.8 were determined

Evaluating Toxicity of Chemicals using a Zebrafish Vibration Startle Response Screening System

We developed a simple screening system for the evaluation of neuromuscular and general toxicity in zebrafish embryos. The modular system consists of electrodynamic transducers above which tissue culture dishes with embryos can be placed. Multiple such loudspeaker-tissue culture dish pairs can be combined. Vibrational stimuli generated by the electrodynamic transducers induce a characteristic startle and escape response in the embryos. A belt-driven linear drive sequentially positions a camera above each loudspeaker to record the movement of the embryos. In this way, alterations to the startle response due to lethality or neuromuscular toxicity of chemical compounds can be visualized and quantified. We present an example of the workflow for chemical compound screening using this system, including the preparation of embryos and treatment solutions, operation of the recording system, and data analysis to calculate benchmark concentration values of compounds active in the assay. The modular assembly based on commercially available simple components makes this system both economical and flexibly adaptable to the needs of particular laboratory setups and screening purposes

Identification of an Imidazopyridine-based Compound as an Oral Selective Estrogen Receptor Degrader for Breast Cancer Therapy.

UNLABELLED: The pro-oncogenic activities of estrogen receptor alpha (ERα) drive breast cancer pathogenesis. Endocrine therapies that impair the production of estrogen or the action of the ERα are therefore used to prevent primary disease metastasis. Although recent successes with ERα degraders have been reported, there is still the need to develop further ERα antagonists with additional properties for breast cancer therapy. We have previously described a benzothiazole compound A4B17 that inhibits the proliferation of androgen receptor-positive prostate cancer cells by disrupting the interaction of the cochaperone BAG1 with the AR. A4B17 was also found to inhibit the proliferation of estrogen receptor-positive (ER+) breast cancer cells. Using a scaffold hopping approach, we report here a group of small molecules with imidazopyridine scaffolds that are more potent and efficacious than A4B17. The prototype molecule X15695 efficiently degraded ERα and attenuated estrogen-mediated target gene expression as well as transactivation by the AR. X15695 also disrupted key cellular protein-protein interactions such as BAG1-mortalin (GRP75) interaction as well as wild-type p53-mortalin or mutant p53-BAG2 interactions. These activities together reactivated p53 and resulted in cell-cycle block and the induction of apoptosis. When administered orally to in vivo tumor xenograft models, X15695 potently inhibited the growth of breast tumor cells but less efficiently the growth of prostate tumor cells. We therefore identify X15695 as an oral selective ER degrader and propose further development of this compound for therapy of ER+ breast cancers. SIGNIFICANCE: An imidazopyridine that selectively degrades ERα and is orally bioavailable has been identified for the development of ER+ breast cancer therapeutics. This compound also activates wild-type p53 and disrupts the gain-of-function tumorigenic activity of mutant p53, resulting in cell-cycle arrest and the induction of apoptosis

A chemical probe for BAG1 targets androgen receptor-positive prostate cancer through oxidative stress signaling pathway

BAG1 is a family of polypeptides with a conserved C-terminal BAG domain that functions as a nucleotide exchange factor for the molecular chaperone HSP70. BAG1 proteins also control several signaling processes including proteostasis, apoptosis and transcription. The largest isoform, BAG1L, controls the activity of the androgen receptor (AR) and is upregulated in prostate cancer. Here, we show that BAG1L regulates AR dynamics in the nucleus and its ablation attenuates AR target gene expression especially those involved in oxidative stress and metabolism. We show that a small molecule, A4B17 that targets the BAG domain downregulates AR target genes similar to a complete BAG1L knockout and upregulates the expression of oxidative stress-induced genes involved in cell death. Furthermore, A4B17 outperformed the clinically approved antagonist enzalutamide in inhibiting cell proliferation and prostate tumor development in a mouse xenograft model. BAG1 inhibitors therefore offer unique opportunities for antagonizing AR action and prostate cancer growth

Cathepsin D from human leukocytes. Purification by affinity chromatography and properties of the enzyme

von Clausbruch UC, Tschesche H. Cathepsin D from human leukocytes. Purification by affinity chromatography and properties of the enzyme. Biol Chem Hoppe Seyler. 1988;369(8):683-691.Cathepsin D of human leukocytes was isolated and characterized. Purified leukocytes were lysed under nitrogen pressure and the proteinase activity precipitated by centrifugation at 48,000 x g. The precipitate was extracted by various buffers. The yield of cathepsin D was almost pH-independent but could be increased by Triton X-100. Employing gel chromatography the activity was found at a molecular mass close to 42,000 Da. Purification of the enzyme was performed by a two-step procedure using pepstatin-Sepharose chromatography and ion exchange chromatography. Three multiple forms of the enzyme were separated by ion exchange chromatography. The isoelectric points of the three forms of the enzyme were close to pH 5.0. The enzyme showed the typical characteristics of the acid proteinase cathepsin D. Enzyme activity was influenced by heavy metals such as Hg2 and Fe3 as well as by typical inhibitors for carboxyl-proteinases such as diazoacetyl-DL-norleucine methyl ester, 1,2-epoxy-3-(4-nitrophenoxy)propane and 4-bromo-phenacylbromide. An immunological comparison with cathepsin D from human liver by immunodiffusion and immunoelectrophoresis indicates identity of the two enzymes

Effect of ZnO on the crystallization, microstructure, and properties of glass-ceramics in the SiO2-Li2O-ZnO-K2O-P2O5 system

Six glasses in the SiO2-Li2O-ZnO-K2O-P2O5 system were prepared. Starting from a dental glass-ceramic model composition the ZnO content was varied from 0.0 to 8.3 mol% with the molar ratios of the other components being invariant. Crystallization processes of these glasses were investigated using high-temperature X-ray diffraction and differential scanning calorimetry. Crystal phases occurred in the temperature range of 500 to 1050 °C, while the main precipitated phase was lithium disilicate (Li2Si2O5). Lithium metasilicate, lithium orthophosphate, and cristobalite were secondary phases. Morphology and microstructure of the glass-ceramics were studied using scanning electron microscopy. Li2Si2O5 crystals in glass-ceramics had elongated shapes along the c-axis, crystal lengths ranging from 1 to 5 µm and aspect rados between 2 and 5. The lath-shaped Li2Si2O5 crystals were randomly oriented in the volume of the glass-ceramics and were responsible for the good mechanical properties. With increasing ZnO content a decrease of flexural strengths from 520 to 450 MPa was observed. It was concluded that the ZnO variation mainly influenced the translucency of the glass-ceramics. Relating to dental standard contrast ratios between 0.23 and 0.74, method limits of 0 and 1 provided, were determined