Role of reactor type on Cr(VI) removal by zero-valent iron in the presence of pyrite: Batch versus sequential batch reactors.

This study was conducted to understand the role of application sequence of pyrite and zero-valent iron (Fe0) (simultaneous vs. sequential) on chromium (VI) removal by Fe0. In batch experiments, pyrite and Fe0 were homogeneously mixed in batch reactors maintained at a constant total solids loading of 2 g L-1. In sequential batch experiments, however, the first reactor containing variable doses of pyrite was operated for 20 min, and the liquid fraction from the first reactor was then subsequently loaded into the second reactor containing a fixed Fe0 dose of 1.2 g L-1. The batch reactors achieved much higher Cr(VI) removal efficiency than sequential batch reactors under similar operating conditions due to discrepancies in Fe redox cycling activities between these two systems. In batch reactors, the Fe0 particles deposited on pyrite surface due to electrostatic attraction between negatively charged pyrite and positively charged Fe0, thus, rendering the overall solids surface charge neutral at optimum pyrite and Fe0 doses. As a result, the whole system behaved like a composite material, with pyrite functioning as a support material for Fe0. This stimulated Fe redox cycling more effectively to generate new Fe(II) sites on Fe0 for enhanced Cr(VI) removal relative to Fe0 only system. In sequential batch reactors, however, the Fe redox cycling activity was limited, but significantly increased with increasing pyrite dose in the first reactor. Overall, our results indicate that the stimulatory effect of pyrite on Cr(VI) removal by Fe0 may be much higher if the reactors are operated in batch mode.

Ligand enhanced pharmaceutical wastewater treatment with Fenton process using pyrite as the catalyst: Column experiments.

Advanced oxidation processes offer practical and cost effective solutions for the treatment of poorly biodegradable industrial wastewaters. Here, column experiments were performed to understand the role of a complexing agent, citrate, on Fenton-treatment of an actual pharmaceutical wastewater with pyrite as the catalyst under dynamic flow conditions. Our results suggest that the pharmaceutical wastewater treatment with Fenton reaction using pyrite as the catalyst was mainly regulated by the extent of Fe dissolution from pyrite, which, in turn, resulted in formation of hydroxyl radicals in solution. The Fenton treatment efficiency was much lower in the absence of citrate compared to citric acid containing systems due to clogging of column pores with oxidized Fe species. On the other hand, the addition of citrate to wastewater significantly improved Fenton process efficacy, and prolonged the lifecycle of pyrite-packed columns depending on solution pH. Low pH values were favorable for better Fenton efficiency in systems containing citrate due to combined effect of proton and ligand promoted dissolution and mobilization of oxidized Fe species.

Role of complexing agents on oxidative degradation of chlorophenolic compounds by pyrite-Fenton process: Batch and column experiments.

This study involves batch reactor and fixed-bed continuous flow experiments to determine the effects of complexing agents (e.g., tartrate and citrate) on the treatment of chlorophenolic (CP) compounds using heterogeneous Fenton system with pyrite mineral as the iron source. While the addition of organic ligands to the batch systems adversely affected CP removal, organic ligands had a beneficial effect on CP removal in column systems. Although the ligands extended the life span of pyrite-packed columns by removing surface oxidation products through the formation of soluble Fe-ligand complexes, the ligands competed against CPs for hydroxyl radicals (HO*). The competitive effect was much higher in batch systems since pyrite loading was very low in order to generate sufficient hydroxyl radicals. On the other hand, at much higher pyrite loading of column experiments, the HO* radicals generated during Fenton process were sufficient to overcome the competitive effect exerted by organic ligands. In spite of much higher Fe solubility in the presence of citrate, citrate was less effective in enhancing CP removal in column systems compared to tartrate since the competitive effect caused by citrate for HO* radicals was more than that exerted by tartrate.

Diclofenac removal by pyrite-Fenton process: Performance in batch and fixed-bed continuous flow systems.

This study provides experimental results from batch and column studies to investigate diclofenac degradation by pyrite-Fenton process under variable chemical conditions (e.g., pyrite loading). Batch experiments show that diclofenac removal increased with increasing hydrogen peroxide and pyrite concentration. On the other hand, the addition of organic chelating agents such as citrate had an adverse effect on diclofenac removal by pyrite-Fenton process in batch systems due to scavenging effect of these agents for hydroxyl radicals. Batch results showed a direct correlation between the rate of diclofenac degradation and the rate of iron dissolution from pyrite, suggesting that diclofenac removal by pyrite-Fenton process was mainly controlled by solution phase hydroxyl radical attack on aromatic structure. Column experiments show that the effluent diclofenac concentration initially reached a peak value, and then sharply decreased to zero at higher pore volumes. The initial diclofenac breakthrough coincided well with the highest Fe(II) concentration observed in the breakthrough curve, implying that the generation of excess Fe(II) had a detrimental effect on removal efficiency due to scavenging effect of excess Fe(II) for hydroxyl radicals. The column system continued to function with 100% diclofenac removal efficiency when the effluent Fe(II) concentration decreased to a level at which the scavenging effect was minimized.

Oxidative degradation of chlorophenolic compounds with pyrite-Fenton process.

Batch experiments, in conjunction with chromatographic and spectroscopic measurements, were performed to comparatively investigate the degradation of various chlorophenolic (CP) compounds (e.g., 2-CP, 4-CP, 2,3-DCP, 2,4-DCP, 2,4,6-TCP, 2,3,4,6-TeCP) by a modified Fenton process using pyrite as the catalyst. The batch results show that the CP removal by pyrite-Fenton process was highly dependent on chemical conditions (e.g., pH, CP and pyrite concentration), CP type, number and location of chlorine atoms on the aromatic ring. With the exception of 2,3,4,6-TeCP and 2,3-DCP, the CP removal decreased with increasing the number of chlorine constituents. While the main mechanism responsible for monochlorophenol removal (e.g., 2-CP and 4-CP) was the hydroxyl radical attack on aromatic rings, the CP removal for multichlorophenolic compounds (e.g., 2,3,4,6-TeCP) was driven by both: (1) hydroxyl radical attack on aromatic rings by both solution and surface-bound hydroxyl radicals and (2) adsorption onto pyrite surface sites. The adsorption affinity increased with increasing the number of Cl atoms on the aromatic ring due to enhanced hydrophobic effect. The TOC removal was not 100% complete for all CPs investigated due to formation of chemically less degradable chlorinated intermediate organic compounds as well as low molecular weight organic acids such as formic and acetic acid. Spectroscopic measurements with SEM-EDS, zeta potential and XPS provided evidence for the partial oxidation of pyrite surface Fe(II) and disulfide groups under acidic conditions.

Synthesis, characterization, and biological properties of composites of hydroxyapatite and hexagonal boron nitride.

Hydroxyapatite (HA), obtained from bovine bones, was successfully reinforced with hexagonal boron nitrite (h-BN). h-BN/HA composites, with BN content up to 1.5 wt %, were sintered at various temperatures between 1000 and 1300°C, in air. Well-sintered samples were obtained after sintering at 1200 and 1300°C. The presence of h-BN contributed to dense, fine, and well-crystallized microstructure. The results of X-ray diffraction analysis and FT-IR spectroscopy showed that the produced composites comprised biphasic ß-TCP/HCA (HCA: carbonate partially substituted HA). High values of mechanical properties were achieved, namely compression strength 155 MPa for the sample 0.5% h-BN/HA and Vickers microhardness of 716 HV for the samples 1.5% h-BN/HA, both sintered at 1300°C. U2OS human bone osteosarcoma proliferation and cell viability showed no adverse effect in the presence of h-BN/HA, suggesting the potential use of the produced materials as safe biomaterials in bone tissue engineering. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2384-2392, 2018.

Involvement of autophagy in T cell biology.

Autophagy is an essential cellular pathway that sequesters various cytoplasmic components, including accumulated proteins, damaged organelles or invading microorganisms and delivers them to lysosomes for degradation. The function of autophagy has been reported in various tissues and systems, including its role in the regulation of cellular immunity. Autophagy plays a fundamental role at various stages of T cell maturation. It regulates the thymocyte selection and the generation of T cell repertoire by presenting intracellular antigens to MHC class molecules. Autophagy is crucial for metabolic regulation of T cells, and therefore supports cell survival and homeostasis, particularly in activated mature T cells. Furthermore, deletion of specific autophagy-related genes induces several immunological alterations including differentiation of activated T cells into regulatory, memory or natural killer T cells. In this review, we emphasize the impact of autophagy on T cell development, activation and differentiation, which is pivotal for the adaptive immune system.

IBMPFD Disease-Causing Mutant VCP/p97 Proteins Are Targets of Autophagic-Lysosomal Degradation.

The ubiquitin-proteasome system (UPS) degrades soluble proteins and small aggregates, whereas macroautophagy (autophagy herein) eliminates larger protein aggregates, tangles and even whole organelles in a lysosome-dependent manner. VCP/p97 was implicated in both pathways. VCP/p97 mutations cause a rare multisystem disease called IBMPFD (Inclusion Body Myopathy with Paget's Disease and Frontotemporal Dementia). Here, we studied the role IBMPFD-related mutants of VCP/p97 in autophagy. In contrast with the wild-type VCP/p97 protein or R155C or R191Q mutants, the P137L mutant was aggregate-prone. We showed that, unlike commonly studied R155C or R191Q mutants, the P137L mutant protein stimulated both autophagosome and autolysosome formation. Moreover, P137L mutant protein itself was a substrate of autophagy. Starvation- and mTOR inhibition-induced autophagy led to the degradation of the P137L mutant protein, while preserving the wild-type and functional VCP/p97. Strikingly, similar to the P137L mutant, other IBMPFD-related VCP/p97 mutants, namely R93C and G157R mutants induced autophagosome and autolysosome formation; and G157R mutant formed aggregates that could be cleared by autophagy. Therefore, cellular phenotypes caused by P137L mutant expression were not isolated observations, and some other IBMPFD disease-related VCP/p97 mutations could lead to similar outcomes. Our results indicate that cellular mechanisms leading to IBMPFD disease may be various, and underline the importance of studying different disease-associated mutations in order to better understand human pathologies and tailor mutation-specific treatment strategies.

Review on Lithotripsy and Cavitation in Urinary Stone Therapy.

Cavitation is the sudden formation of vapor bubbles or voids in liquid media and occurs after rapid changes in pressure as a consequence of mechanical forces. It is mostly an undesirable phenomenon. Although the elimination of cavitation is a major topic in the study of fluid dynamics, its destructive nature could be exploited for therapeutic applications. Ultrasonic and hydrodynamic sources are two main origins for generating cavitation. The purpose of this review is to give the reader a general idea about the formation of cavitation phenomenon and existing biomedical applications of ultrasonic and hydrodynamic cavitation. Because of the high number of the studies on ultrasound cavitation in the literature, the main focus of this review is placed on the lithotripsy techniques, which have been widely used for the treatment of urinary stones. Accordingly, cavitation phenomenon and its basic concepts are presented in Section II. The significance of the ultrasound cavitation in the urinary stone treatment is discussed in Section III in detail and hydrodynamic cavitation as an important alternative for the ultrasound cavitation is included in Section IV. Finally, side effects of using both ultrasound and hydrodynamic cavitation in biomedical applications are presented in Section V.

RACK1 Is an Interaction Partner of ATG5 and a Novel Regulator of Autophagy.

Autophagy is biological mechanism allowing recycling of long-lived proteins, abnormal protein aggregates, and damaged organelles under cellular stress conditions. Following sequestration in double- or multimembrane autophagic vesicles, the cargo is delivered to lysosomes for degradation. ATG5 is a key component of an E3-like ATG12-ATG5-ATG16 protein complex that catalyzes conjugation of the MAP1LC3 protein to lipids, thus controlling autophagic vesicle formation and expansion. Accumulating data indicate that ATG5 is a convergence point for autophagy regulation. Here, we describe the scaffold protein RACK1 (receptor activated C-kinase 1, GNB2L1) as a novel ATG5 interactor and an autophagy protein. Using several independent techniques, we showed that RACK1 interacted with ATG5. Importantly, classical autophagy inducers (starvation or mammalian target of rapamycin blockage) stimulated RACK1-ATG5 interaction. Knockdown of RACK1 or prevention of its binding to ATG5 using mutagenesis blocked autophagy activation. Therefore, the scaffold protein RACK1 is a new ATG5-interacting protein and an important and novel component of the autophagy pathways.

Physiological and pathological significance of the molecular cross-talk between autophagy and apoptosis.

Autophagy and apoptosis are two important molecular mechanisms that maintain cellular homeostasis under stress conditions. Autophagy represents an intracellular mechanism responsible for turnover of organelles and long-lived proteins through a lysosome-dependent degradation pathway. Cell death signals or sustained stress might trigger programmed cell death pathways, and among them, apoptosis is the most extensively studied one. Recent studies indicate the presence of a complex interplay between autophagy and apoptosis. Physiological relevance of autophagy-apoptosis crosstalk was mainly shown in vitro. However, in vivo consequences possibly exist both during health and disease. In this review, we will summarize the current knowledge about molecular mechanisms connecting autophagy and apoptosis, and about the significance of this crosstalk for human health.

Effect of Varying Magnetic Fields on Targeted Gene Delivery of Nucleic Acid-Based Molecules.

Several physical methods have been developed to introduce nucleic acid expression vectors into mammalian cells. Magnetic transfection (magnetofection) is one such transfection method, and it involves binding of nucleic acids such as DNA, RNA or siRNA to magnetic nanoparticles followed by subsequent exposure to external magnetic fields. However, the challenge between high efficiency of nucleic acid uptake by cells and toxicity was not totally resolved. Delivery of nucleic acids and their transport to the target cells require carefully designed and controlled systems. In this study, we introduced a novel magnetic system design providing varying magnet turn speeds and magnetic field directions. The system was tested in the magnetofection of human breast (MCF-7), prostate (DU-145, PC-3) and bladder (RT-4) cancer cell lines using green fluorescent protein DNA as a reporter. Polyethylenimine coated superparamagnetic iron oxide nanoparticles (SPIONs) were used as nucleic acid carriers. Adsorption of PEI on SPION improved the cytocompatibility dramatically. Application of external magnetic field increased intracellular uptake of nanoparticles and transfection efficiency without any additional cytotoxicity. We introduce our novel magnetism-based method as a promising tool for enhanced nucleic acid delivery into mammalian cells.

Hydrodynamic cavitation kills prostate cells and ablates benign prostatic hyperplasia tissue.

Hydrodynamic cavitation is a physical phenomenon characterized by vaporization and bubble formation in liquids under low local pressures, and their implosion following their release to a higher pressure environment. Collapse of the bubbles releases high energy and may cause damage to exposed surfaces. We recently designed a set-up to exploit the destructive nature of hydrodynamic cavitation for biomedical purposes. We have previously shown that hydrodynamic cavitation could kill leukemia cells and erode kidney stones. In this study, we analyzed the effects of cavitation on prostate cells and benign prostatic hyperplasia (BPH) tissue. We showed that hydrodynamic cavitation could kill prostate cells in a pressure- and time-dependent manner. Cavitation did not lead to programmed cell death, i.e. classical apoptosis or autophagy activation. Following the application of cavitation, we observed no prominent DNA damage and cells did not arrest in the cell cycle. Hence, we concluded that cavitation forces directly damaged the cells, leading to their pulverization. Upon application to BPH tissues from patients, cavitation could lead to a significant level of tissue destruction. Therefore similar to ultrasonic cavitation, we propose that hydrodynamic cavitation has the potential to be exploited and developed as an approach for the ablation of aberrant pathological tissues, including BPH.

Cleavage of Atg3 protein by caspase-8 regulates autophagy during receptor-activated cell death.

Autophagy is an evolutionarily conserved mechanism contributing to cell survival under stress conditions including nutrient and growth factor deprivation. Connections and cross-talk between cell death mechanisms and autophagy is under investigation. Here, we describe Atg3, an essential regulatory component of autophagosome biogenesis, as a new substrate of caspase-8 during receptor-mediated cell death. Both, tumor necrosis factor α and tumor necrosis factor-related apoptosis inducing ligand induced cell death was accompanied by Atg3 cleavage and this event was inhibited by a pan-caspase inhibitor (zVAD) or a caspase-8-specific inhibitor (zIETD). Indeed, caspase-8 overexpression led to Atg3 degradation and this event depended on caspase-8 enzymatic activity. Mutation of the caspase-8 cleavage site on Atg3 abolished its cleavage both in vitro and in vivo, demonstrating that Atg3 was a direct target of caspase-8. Autophagy was inactive during apoptosis and blockage of caspases or overexpression of a non-cleavable Atg3 protein reestablished autophagic activity upon death receptor stimulation. In this system, autophagy was important for cell survival since inhibition of autophagy increased cell death. Therefore, Atg3 provides a novel link between apoptosis and autophagy during receptor-activated cell death.

Bubbly cavitating flow generation and investigation of its erosional nature for biomedical applications.

This paper presents a study that investigates the destructive energy output resulting from hydrodynamic bubbly cavitation in microchannels and its potential use in biomedical applications. The research performed in this study includes results from bubbly cavitation experiments and findings showing the destructive effects of bubbly cavitating flow on selected solid specimens and live cells. The bubbles generated by hydrodynamic cavitation are highly destructive at the surfaces of the target medium on which they are carefully focused. The resulting destructive energy output could be effectively used for biomedical treatments, such as destroying kidney stones (renal calculi) or killing cancer cells. Motivated by this potential, the cavitation damage to cancerous cells and material removal from chalk pieces (which possess similar material properties as some kidney stones) was investigated. Our results showed that cavitation could induce damage both on chalk pieces and leukemia/lymphoma cells. We discovered that hydrodynamic cavitation exposure had early and delayed effects on cancer cell survival. Hence, the potential of hydrodynamic bubbly cavitation generated at the microscale for biomedical treatments was revealed using the microchannel configuration as a microorifice (with an inner diameter of 147 µm and a length of 1.52 cm), which acts as the source of bubbly cavitating flows.

The roles of pericystic cells and Sertoli cells in spermatogonial proliferation stimulated by some growth factors in organ culture of newt (Cynops pyrrhogaster) testis.

We have previously shown FSH promotes spermatogonial proliferation and their differentiation into primary spermatocytes in organ culture of newt testicular fragments. Several growth factors identified in newt testis, such as stem cell factor (SCF), insulin-like growth factor (IGF)-I, and neuregulin (NRG)1, also stimulate spermatogonial proliferation in the organ culture. However, any growth factor added in vitro might not work on spermatogonia directly, but act on somatic cells such as Sertoli cells or pericystic cells, because size-selective barrier exists around a cyst which is enclosed by Sertoli cells. In order to determine the target somatic cells of the growth factors as well as the role of pericystic cells in spermatogonial proliferation and differentiation, we searched for agents that kill pericystic cells selectively. We found that treatment of the testicular fragments with trypan blue (TB) caused cell death of only pericystic cells and significant abolishment of the activity of SCF to stimulate spermatogonial proliferation, while the activities of neither IGF-I nor NRG1 were affected. In addition, the potency of neither IGF-I nor FSH to stimulate the differentiation of spermatogonia into primary spermatocytes was abolished by TB treatment. Consistent with these results, only the mRNA expression of c-kit was reduced by TB treatment, whereas those of FSH receptor, SCF, IGF-I, IGF-I receptor, Immunoglobulin-like domain-containing NRG1, ErbB2, and ErbB4 were unaffected. These results indicate that SCF stimulates pericystic cells, while IGF-I and NRG1, as well as FSH, activate Sertoli cells, resulting in stimulation of spermatogonial proliferation in organ culture of testicular fragments.

Promotion of spermatogonial proliferation by neuregulin 1 in newt (Cynops pyrrhogaster) testis.

We have previously shown that mammalian follicle-stimulating hormone (FSH) promotes the proliferation of spermatogonia and their differentiation into primary spermatocytes in organ culture of newt testis. In the current study, we performed microarray analysis to isolate local factors secreted from somatic cells upon FSH treatment and acting on the germ cells. We identified neuregulin 1 (NRG1) as a novel FSH-upregulated clone homologous to mouse NRG1 known to control cell proliferation, differentiation and survival in various tissues. We further isolated cDNAs encoding two different clones. Amino acid sequences of the two clones were 75% and 94% identical to Xenopus leavis immunoglobulin (Ig)-type and cysteine-rich domain (CRD)-type NRG1, respectively, which had distinct sequences in their N-terminal region but identical in their epidermal growth factor (EGF)-like domain. Semi-quantitative and quantitative PCR analyses indicated that both clones were highly expressed at spermatogonial stage than at spermatocyte stage. In vitro FSH treatment increased newt Ig-NRG1 (nIg-NRG1) mRNA expression markedly in somatic cells, whereas newt CRD-NRG1 (nCRD-NRG1) mRNA was only slightly increased by FSH. To elucidate the function of newt NRG1 (nNRG1) in spermatogenesis, recombinant EGF domain of nNRG1 (nNRG1-EGF) was added to organ and reaggregated cultures with or without somatic cells: it promoted spermatogonial proliferation in all cases. Treatment of the cultures with the antibody against nNRG1-EGF caused remarkable suppression of spermatogonial proliferation activated by FSH. These results indicated that nNRG1 plays a pivotal role in promoting spermatogonial proliferation by both direct effect on spermatogonia and indirect effect via somatic cells in newt testes.