Effect of ligand interactions within modified granular activated carbon (GAC) on mixed perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) adsorption

A new adsorbent based on commercial granular activated carbon (GAC) and loaded with Cu(II) (GAC-Cu) was prepared to enhance the adsorption capacity of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). The surface area (SA) and pore volume of GAC-Cu decreased by ∼15% compared to those of pristine GAC. The scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) and leaching test results indicated that, compared with GAC, the Cu atomic ratio and Cu amount in GAC-Cu increased by 2.91 and 2.43 times, respectively. The point of zero charge (PZC) measured using a salt addition method obtained a pH of 6.0 (GAC) and 5.0 (GAC-Cu). According to the isotherm models obtaining highest coefficient of determination (R2), GAC-Cu exhibited a 20.4% and 35.2% increase for PFOA and PFOS in maximum uptake (qm), respectively, compared to those of GAC. In addition, the adsorption affinity (b) for GAC-Cu increased by 1045% and 175% for PFOA and PFOS, respectively. The pH effect on the adsorption capacity of GAC-Cu was investigated. The uptake of PFOA and PFOS decreased with an increase in pH for both GAC and GAC-Cu. GAC-Cu exhibited higher uptake than GAC at pH 6 and 7, but no enhanced uptake was observed at pH 4.0, 5.0, and 8.5. Therefore, ligand interaction was effective at weak acid or neutral pH.

Encapsulation of bacterial cells in cytoprotective ZIF-90 crystals as living composites

Exploiting metal-organic frameworks (MOFs) as selectively permeable shelters for encapsulating engineered cells to form hybrid living materials has attracted increasing attention in recent years. Optimizing the synthesis process to improve encapsulation efficiency (EE) is critical for further technological development and applications. Here, using ZIF-90 and genetically engineered Escherichia coli (E. coli) as a demo, we fabricated E. coli@ZIF-90 living composites in which E. coli cells were encapsulated in ZIF-90 crystals. We illustrated that ZIF-90 could serve as a protective porous cage for cells to shield against toxic bactericides including benzaldehyde, cinnamaldehyde, and kanamycin. Notably, the E. coli cells remained alive and could self-reproduce after removing the ZIF-90 crystal cages in ethylenediaminetetraacetic acid, suggesting a feasible route for protecting and prolonging the lifespan of bacterial cells. Moreover, an aqueous multiple-step deposition approach was developed to improve EE of the E. coli@ZIF-90 composites: the EE increased to 61.9 ± 5.2%, in contrast with the efficiency of the traditional method (21.3 ± 4.4%) prepared with PBS buffer. In short, we develop a simple yet viable strategy to manufacture MOF-based living hybrid materials that promise new applications across diverse fields.

Genome-wide association study reveals candidate genes associated with body measurement traits in Chinese Wagyu beef cattle

We performed a genome-wide association study to identify candidate genes for body measurement traits in 463 Wagyu beef cattle typed with the Illumina Bovine HD 770K SNP array. At the genome-wide level, we detected 18, five and one SNPs associated with hip height, body height and body length respectively. In total, these SNPs are within or near 11 genes, six of which (PENK, XKR4, IMPAD1, PLAG1, CCND2 and SNTG1) have been reported previously and five of which (CSMD3, LAP3, SYN3, FAM19A5 and TIMP3) are novel candidate genes that we found to be associated with body measurement traits. Further exploration of these candidate genes will facilitate genetic improvement in Chinese Wagyu beef cattle.

Removal of copper, nickel and chromium mixtures from metal plating wastewater by adsorption with modified carbon foam

In this study, the characterizations and adsorption efficiencies for chromium, copper and nickel were evaluated using manufacture-grade Fe2O3-carbon foam. SEM, XRD, XRF and BET analyses were performed to determine the characteristics of the material. Various pore sizes (12-420 μm) and iron contents (3.62%) were found on the surface of the Fe2O3-carbon foam. Fe2O3-carbon foam was found to have excellent adsorption efficiency compared to carbon foam for mixed solutions of cationic and anionic heavy metals. The adsorption capacities for chromium, copper and nickel were 6.7, 3.8 and 6.4 mg/g, respectively, which were obtained using a dual exponential adsorption model. In experiments with varying dosages of the Fe2O3 powder, no notable differences were observed in the removal efficiency. In a fixed-bed column test, Fe2O3-carbon foam achieved adsorption capacities for chromium, copper and nickel of 33.0, 12.0 and 9.5 mg/g, respectively, after 104 h. Based on these results, Fe2O3-carbon foam was observed to be a promising material for treatment of plating wastewater.

Effect of nitrogen doping on titanium carbonitride-derived adsorbents used for arsenic removal

Arsenic in water and wastewater is considered to be a critical contaminant as it poses harmful health risks. In this regard, to meet the stringent regulation of arsenic in aqueous solutions, nitrogen doped carbon-based materials (CN) were prepared as adsorbents and tested for the removal of arsenic ion from aqueous solutions. Nitrogen-doped carbon (CNs) synthesized by chlorination exhibited well-developed micro- and small meso-pores with uniform pore structures. The structure and characteristics of the adsorbents thus developed were confirmed by field-emission scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller analysis, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. Among the CNs developed, CN700 exhibited high adsorption capacity for arsenic (31.08 mg/g). The adsorption efficiency for arsenic ion was confirmed to be affected by pyrrolic nitrogen and micro-pores. These results suggest that CNs are useful adsorbents for the treatment of arsenic, and in particular, CN700 demonstrates potential for application as an adsorbent for the removal of anionic heavy metals from wastewater and sewage.

A Practical Anodic and Cathodic Curve Intersection Model to Understand Multiple Corrosion Potentials of Fe-Based Glassy Alloys in OH- Contained Solutions

A practical anodic and cathodic curve intersection model, which consisted of an apparent anodic curve and an imaginary cathodic line, was proposed to explain multiple corrosion potentials occurred in potentiodynamic polarization curves of Fe-based glassy alloys in alkaline solution. The apparent anodic curve was selected from the measured anodic curves. The imaginary cathodic line was obtained by linearly fitting the differences of anodic curves and can be moved evenly or rotated to predict the number and value of corrosion potentials.

Multiplex Quantitative PCR Assays for the Detection and Quantification of the Six Major Non-O157 Escherichia coli Serogroups in Cattle Feces

Shiga toxin-producing Escherichia coli (STEC) serogroups O26, O45, O103, O111, O121, and O145, called non-O157 STEC, are important foodborne pathogens. Cattle, a major reservoir, harbor the organisms in the hindgut and shed them in the feces. Although limited data exist on fecal shedding, concentrations of non-O157 STEC in feces have not been reported. The objectives of our study were (i) to develop and validate two multiplex quantitative PCR (mqPCR) assays, targeting O-antigen genes of O26, O103, and O111 (mqPCR-1) and O45, O121, and O145 (mqPCR-2); (ii) to utilize the two assays, together with a previously developed four-plex qPCR assay (mqPCR-3) targeting the O157 antigen and three virulence genes (stx1, stx2, and eae), to quantify seven serogroups and three virulence genes in cattle feces; and (iii) to compare the three mqPCR assays to a 10-plex conventional PCR (cPCR) targeting seven serogroups and three virulence genes and culture methods to detect seven E. coli serogroups in cattle feces. The two mqPCR assays (1 and 2) were shown to be specific to the target genes, and the detection limits were 4 and 2 log CFU/g of pure culture-spiked fecal samples, before and after enrichment, respectively. A total of 576 fecal samples collected from a feedlot were enriched in E. coli broth and were subjected to quantification (before enrichment) and detection (after enrichment). Of the 576 fecal samples subjected, before enrichment, to three mqPCR assays for quantification, 175 (30.4%) were quantifiable (≥4 log CFU/g) for at least one of the seven serogroups, with O157 being the most common serogroup. The three mqPCR assays detected higher proportions of postenriched fecal samples (P > 0.01) as positive for one or more serogroups compared with cPCR and culture methods. This is the first study to assess the applicability of qPCR assays to detect and quantify six non-O157 serogroups in cattle feces and to generate data on fecal concentration of the six serogroups.

Determining the selectivity of divalent metal cations for the carboxyl group of alginate hydrogel beads during competitive sorption

To investigate the competitive sorption of divalent metal ions such as Ca(2+), Cu(2+), Ni(2+), and Pb(2+) on alginate hydrogel beads, batch and column tests were conducted. The concentration of carboxyl group was found to be limited in the preparation of spherical hydrogel beads. From kinetic test results, 80% of sorption was observed within 4h, and equilibrium was attained in 48 h. According to the comparison of the total uptake and release, divalent metal ions were found to stoichiometrically interact with the carboxyl group in the alginate polymer chain. From the Langmuir equation, the maximum capacities of Pb(2+), Cu(2+), and Ni(2+) were calculated to be 1.1, 0.48, and 0.13 mmol/g, respectively. The separation factor (α) values for αPb/Cu, αPb/Ni, and αCu/Ni were 14.0, 98.9, and 7.1, respectively. The sorption capacity of Pb(2+) was not affected by the solution pH; however, the sorption capacities of Cu(2+) and Ni(2+) decreased with increasing solution pH, caused by competition with hydrogen. According to the result from the fixed column test, Pb(2+) exhibited the highest affinity, followed by Cu(2+) and Ni(2+), which is in exact agreement with those of kinetic and isotherm tests. The sorbent could be regenerated using 4% HCl, and the regenerated sorbent exhibited 90% capacity upto 9 cycles.

Preparation and characterization of an organic/inorganic hybrid sorbent (PLE) to enhance selectivity for As(V)

For the selective removal of arsenate (As(V)) a hybrid sorbent was prepared using a non-toxic natural organic material, chitosan, by loading a transition metal, nickel. The immobilization of nickel was achieved by coordination with a deprotonated amino group (NH2) in the chitosan polymer chain. The amount of nickel was directly correlated to the presence of the amino group and was calculated to be 62 mg/g. FTIR spectra showed a peak shift from 1656 to 1637 cm(-1) after Ni(2+) loading, indicating the complexation between the amino group and nickel, and a peak of As(V) was observed at 834 cm(-1). An increase of sulfate concentration from 100 mg/L to 200 mg/L did not significantly affect As(V) sorption, and an increase in the concentration of bicarbonate reduced the As(V) uptake by 33%. The optimal pH of the solution was determined at pH 10, which is in accordance with the fraction of HAsO4(2-) and AsO4(-3). According to a fixed column test, a break through behavior of As(V) revealed that selectivity for As(V) was over sulfate. Regeneration using 5% NaCl extended the use of sorbent to up to uses without big loss of sorption capacity.

Modified composites based on mesostructured iron oxyhydroxide and synthetic minerals: a potential material for the treatment of various toxic heavy metals and its toxicity

The composites of mesostructured iron oxyhydroxide and/or commercial synthetic zeolite were investigated for use in the removal of toxic heavy metals, such as cadmium, copper, lead and arsenic, from aqueous solution. Four types of adsorbents, dried alginate beads (DABs), synthetic-zeolite impregnated beads (SZIBs), meso-iron-oxyhydroxide impregnated beads (MIOIBs) and synthetic-zeolite/meso-iron-oxyhydroxide composite beads (SZMIOIBs), were prepared for heavy metal adsorption tests. Laboratory experiments were conducted to investigate the removal efficiencies of cations and anions of heavy metals and the possibility of regenerating the adsorbents. Among these adsorbents, the MIOIBs can simultaneously remove cations and anions of heavy metals; they have high adsorption capacities for lead (60.1mgg(-1)) and arsenic (71.9mgg(-1)) compared with other adsorbents, such as DABs (158.1 and 0.0mgg(-1)), SZIB (42.9 and 0.0mgg(-1)) and SZMIOIB (54.0 and 5.9mgg(-1)) for lead and arsenic, respectively. Additionally, the removal efficiency was consistent at approximately 90%, notwithstanding repetitive regeneration. The characteristics of meso-iron-oxyhydroxide powder were confirmed by X-ray diffraction, Brunauer-Emmett-Teller and transmission electron microscopy. We also performed a comparative toxicity study that indicated that much lower concentrations of the powdered form of mesostructured iron oxyhydroxide had stronger cytotoxicity than the granular form. These results suggest that the granular form of meso iron oxyhydroxide is a more useful and safer adsorbent for heavy metal treatment than the powdered form. This research provides promising results for the application of MIOIBs as an adsorbent for various heavy metals from wastewater and sewage.

Characterization of natural organic matter treated by iron oxide nanoparticle incorporated ceramic membrane-ozonation process

In this study, changes in the physical and structural properties of natural organic matter (NOM) were observed during hybrid ceramic membrane processes that combined ozonation with ultrafiltration ceramic membrane (CM) or with a reactive ceramic membrane (RM), namely, an iron oxide nanoparticles (IONs) incorporated-CM. NOM from feed water and NOM from permeate treated with hybrid ceramic membrane processes were analyzed by employing several NOM characterization techniques. Specific ultraviolet absorbance (SUVA), high-performance size exclusion chromatography (HPSEC) and fractionation analyses showed that the hybrid ceramic membrane process effectively removed and transformed relatively high contents of aromatic, high molecular weight and hydrophobic NOM fractions. Fourier transform infrared spectroscopy (FTIR) and 3-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy revealed that this process caused a significant decrease of the aromaticity of humic-like structures and an increase in electron withdrawing groups. The highest removal efficiency (46%) of hydroxyl radical probe compound (i.e., para-Chlorobenzoic acid (pCBA)) in RM-ozonation process compared with that in CM without ozonation process (8%) revealed the hydroxyl radical formation by the surface-catalyzed reaction between ozone and IONs on the surface of RM. In addition, experimental results on flux decline showed that fouling of RM-ozonation process (15%) was reduced compared with that of CM without ozonation process (30%). These results indicated that the RM-ozonation process enhanced the destruction of NOM and reduced the fouling by generating hydroxyl radicals from the catalytic ozonation in the RM-ozonation process.

Involvement of RB kinases and phosphatases in life and death decisions

Previously we found that retinoblastoma protein (RB) became dephosphorylated in an early stage of DNA damage-induced, p53-independent apoptosis. Here, we report that both RB dephosphorylation and apoptosis are regulated by relative levels of RB kinases (cyclin-dependent kinases, or cdks) and phosphatases. Treatment of human Jurkat T cells with roscovitine, a potent and selective synthetic inhibitor of several cdks, rapidly induced RB dephosphorylation, which was followed by induction of apoptosis-associated internucleosomal DNA fragmentation. The roscovitine treatment did not increase levels of the endogenous cdk inhibitor proteins p16(Ink4a), p27(kip1) and p21(Waf1), supporting the idea that the observed RB dephosphorylation was due to a direct inhibition of cdk activities by roscovitine. Treatment with a protein kinase C inhibitor (sphingosine or staurosporine), which leads to suppression of several cdk kinase activities, also induced cellular RB dephosphorylation and apoptosis. Finally, roscovitine- or sphingosine-induced RB dephosphorylation was blocked by a specific inhibitor of protein-serine/threonine phosphatases (calyculin A or okadaic acid). Therefore, RB phosphorylation status and cellular fate are regulated by the ratio of RB kinases to RB phosphatases.

Immobilization of As(III) in soil and groundwater using a new class of polysaccharide stabilized Fe-Mn oxide nanoparticles

A new class of stabilized Fe-Mn binary oxide nanoparticles was prepared with a water-soluble starch or carboxymethyl cellulose (CMC) as a stabilizer. The nanoparticles were characterized and tested with respect to sorption of As(III) and As(V) from water and for immobilization of As(III) in soil. While arsenic sorption capacities were comparable for bare, or stabilized Fe-Mn nanoparticles, particle stabilization enabled the nanoparticles to be delivered into soil for in situ immobilization of arsenite. High As(III) sorption capacity was observed over a broad pH range of 5-9. Column breakthrough tests demonstrated soil mobility of CMC-stabilized nanoparticles. Once delivered, the nanoparticles remain virtually immobile in soil under typical groundwater conditions, serving as a fixed sink for arsenic. When an As(III)-laden soil was treated with CMC-stabilized Fe-Mn at an Fe-to-As molar ratio of 6.5-39, the water leachable arsenic was reduced by 91-96%, and the TCLP leachability was reduced by 94-98%. Column elution tests of an As(III)-laden soil indicated that application of CMC-stabilized Fe-Mn transferred nearly all water-soluble As(III) to the nanoparticle phase. Consequently, As(III) is immobilized as the nanoparticles are immobilized in the soil. The nanoparticle amendment was able to reduce the TCLP leachability of As(III) remaining in the soil bed by 78%.

Removal of arsenic(V) from spent ion exchange brine using a new class of starch-bridged magnetite nanoparticles

Ion exchange (IX) is considered by US EPA as one of the best available technologies for removing arsenic from drinking water. However, typical IX processes will generate large volumes of arsenic-laden regenerant brine that requires costly further handling and disposal. This study aimed to develop an engineered strategy to minimize the production and arsenic leachability of the process waste residual. We prepared and tested a new class of starch-bridged magnetite nanoparticles for removal of arsenate from spent IX brine. A low-cost, "green" starch at 0.049% (w/w) was used as a stabilizer to prevent the nanoparticles from agglomerating and as a bridging agent allowing the nanoparticles to flocculate and precipitate while maintaining their high arsenic sorption capacity. When applied to a simulated spent IX brine containing 300 mg/L As and 6% (w/w) NaCl, nearly 100% removal of arsenic was achieved within 1 h using the starch-bridged nanoparticles at an Fe-to-As molar ratio of 7.6, compared to only 20% removal when bare magnetite particles were used. Increasing NaCl in the brine from 0 to 10% (w/w) had little effect on the arsenic sorption capacity. Maximum uptake was observed within a pH range of 4-6. The Langmuir capacity coefficient was determined to be 248 mg/g at pH 5.0. The final treatment sludge was able to pass the TCLP (Toxicity Characteristic Leaching Procedure) based leachability of 5 mg/L as As.

Selective removal of arsenate from drinking water using a polymeric ligand exchanger

The new maximum contaminant level (MCL) of 10 microg/L for arsenic in the US drinking water will take effect on January 22, 2006. The compliance cost is estimated to be approximately dollar 600 million per year using current treatment technologies. This research aims to develop an innovative ion exchange process that may help water utilities comply with the new MCL in a more cost-effective manner. A polymeric ligand exchanger (PLE) was prepared by loading Cu2+ to a commercially available chelating ion exchange resin. Results from batch and column experiments indicated that the PLE offered unusually high selectivity for arsenate over other ubiquitous anions such as sulfate, bicarbonate and chloride. The average binary arsenate/sulfate separation factor for the PLE was determined to be 12, which were over two orders of magnitude greater than that (0.1-0.2) for commercial strong-base anion (SBA) exchangers. Because of the enhanced arsenate selectivity, the PLE was able to treat approximately 10 times more bed volumes (BVs) of water than commonly used SBA resins. The PLE can operate optimally in the neutral pH range (6.0-8.0). The exhausted PLE can be regenerated highly efficiently. More than 95% arsenate capacity can be recovered using approximately 22 BVs of 4% (w/w) NaCl at pH 9.1, and the regenerated PLE can be reused without any capacity drop. Upon treatment using FeCl3, the spent brine was recovered and reused for regeneration, which may cut down the regenerant need and reduces the volume of process waste residuals. The PLE can be used as a highly selective and reusable sorbent for removal of arsenate from drinking water.

Effects of liraglutide (NN2211), a long-acting GLP-1 analogue, on glycaemic control and bodyweight in subjects with Type 2 diabetes

AIMS

Liraglutide (NN2211) is a long-acting GLP-1 analogue, with a pharmacokinetic profile suitable for once-daily administration. This multicentre, double-blind, parallel-group, double-dummy study explored the dose-response relationship of liraglutide effects on bodyweight and glycaemic control in subjects with Type 2 diabetes.

METHODS

Subjects (BMI 27-42 kg/m(2)) with Type 2 diabetes who were previously treated with an OAD (oral anti-diabetic drug) monotherapy (69% with metformin), and had HbA(1c) < or = 10% were enrolled. After a 4-week metformin run-in period, 210 subjects (27-73 years, 60% female) were randomised to receive liraglutide (0.045-0.75 mg) once daily or continued on metformin 1000 mg b.d. for 12 weeks.

RESULTS

Mean baseline values for the six treatment groups ranged from 6.8 to 7.5% for HbA(1c), and 8.06-9.44 mmol/l (145-170 mg/dl) for fasting plasma glucose. After 12-week treatment, a weight change of -0.05 to -1.9% was observed for the six treatment groups. Mean HbA(1c) changes from baseline for 0.045, 0.225, 0.45, 0.6, 0.75 mg liraglutide and metformin were +1.28%, +0.86%, +0.22%, +0.16%, +0.30% and +0.09%, respectively. No significant differences in HbA(1c) were observed between liraglutide and metformin groups at the three highest liraglutide dose levels (0.45, 0.6 and 0.75 mg). The lowest two liraglutide doses (0.045 mg and 0.225 mg) were not sufficient to maintain the fasting plasma glucose values achieved by metformin. No major hypoglycaemic episodes were reported. Episodes of nausea and/or vomiting were reported by 11 patients (6.3%) receiving liraglutide and three (8.8%) receiving metformin.

CONCLUSIONS

Once-daily liraglutide improved glycaemic control and weight, in a comparable degree to metformin. Liraglutide appeared to be safe and generally well tolerated. Higher doses of liraglutide merit study in future clinical trials.

Cell surface expression and turnover of the alpha-subunit of the epithelial sodium channel

The renal epithelial cell line A6, derived from Xenopus laevis, expresses epithelial Na(+) channels (ENaCs) and serves as a model system to study hormonal regulation and turnover of ENaCs. Our previous studies suggest that the alpha-subunit of Xenopus ENaC (alpha-xENaC) is detectable as 150- and 180-kDa polypeptides, putative immature and mature alpha-subunit heterodimers. The 150- and 180-kDa alpha-xENaC were present in distinct fractions after sedimentation of A6 cell lysate through a sucrose density gradient. Two anti-alpha-xENaC antibodies directed against distinct domains demonstrated that only 180-kDa alpha-xENaC was expressed at the apical cell surface. The half-life of cell surface-expressed alpha-xENaC was 24-30 h, suggesting that once ENaC matures and is expressed at the plasma membrane, its turnover is similar to that reported for mature cystic fibrosis transmembrane conductance regulator. No significant changes in apical surface expression of alpha-xENaC were observed after treatment of A6 cells with aldosterone for 24 h, despite a 5.3-fold increase in short-circuit current. This lack of change in surface expression is consistent with previous observations in A6 cells and suggests that aldosterone regulates ENaC gating and increases channel open probability.

[The numerical simulation of the dynamic stress field from impacting head]

In order to study the mechanism of impact injury to the head, we have simulated the development of the stress field by using the numerical simulation method. The process of the head having been impacted vertically by an impactor can be described as a 2D problem, and the reactions of the head subjected to impacted force can be simulated and analyzed by the method based on the finite difference method (FDM). The model is subjected to applied force by an impactor with the initial velocity of 25 m/s (90 km/h). The pre-processing for the model is done on the microcomputer software. Once imported to the software, the nodes and elements are generated and material characteristics are assigned. The results demonstrate that the high resolution computer graphics can provide the dynamic distribution of the stress field, which can clearly show how the stress is developed, and how many its value is. The results are helpful to understanding the mechanism of impact injury to head.

Modification of the amino terminus of a class II epitope confers resistance to degradation by CD13 on dendritic cells and enhances presentation to T cells

Dendritic cells and human B cell lines were compared for ability to present synthetic peptides corresponding to residues 145-159 and 188-203 of human Ig kappa-chains to peptide-specific mouse T cell hybridomas restricted by HLA-DR4Dw4. B cell lines presented both peptides, but dendritic cells could only efficiently present the latter epitope. In this paper, we show that dendritic cells degrade the 145-159 peptide, removing four residues from the amino terminus. Binding of the peptide to the class II restriction element is not required for this process. The degradation product is resistant to further cleavage, accumulates in the culture supernatant, and does not bind to HLA-DR4Dw4 or stimulate T cell reactivity. Cleavage can be blocked with bestatin, but not with other protease inhibitors tested, or by a mAb directed against aminopeptidase N (CD13). Addition of an acetyl group to the amino terminus of peptide 145-159 also blocks degradation, and allows dendritic cells to present the peptide to specific T cells with greatly increased efficiency. These results demonstrate that CD13 on dendritic cells is able to selectively and efficiently degrade exogenously provided peptide Ags, in a process that can be blocked by addition of an acetyl group to the amino terminus of the peptide. Modification of the amino terminus of peptide epitopes susceptible to degradation may prove to be useful as a general strategy for enhancing their immunogenicity.

Proteasome inhibition leads to significant reduction of Bcr-Abl expression and subsequent induction of apoptosis in K562 human chronic myelogenous leukemia cells

The chimeric oncogene bcr-abl is detected in virtually every case of chronic myelogenous leukemia. It has been shown that cells (such as K562) expressing Bcr-Abl/p210, a protein tyrosine kinase, not only undergo cellular transformation but also demonstrate multiple drug resistance. Recent studies also demonstrate that the proteasome is involved in the survival signaling pathway(s). In the current study, we tested the hypothesis that the proteasome might play a role in regulating Bcr-Abl function. We have demonstrated by using a variety of inhibitors that inhibition of the proteasome, but not of the cysteine protease, activity is able to activate the apoptotic cell death program in K562 cells. Proteasome inhibition-induced apoptosis is demonstrated by condensation and fragmentation of nuclei, appearance of an apoptotic population with sub-G1 DNA content, the internucleosomal fragmentation of DNA, and cleavage of poly(ADP-ribose) polymerase, and can be blocked by a specific caspase-3-like tetrapeptide inhibitor. Western blot analysis with specific antibodies to c-Abl and Bcr proteins show that treatment of K562 cells with a proteasome inhibitor results in significant reduction of Bcr-Abl protein expression, which occurs several hours before the onset of apoptotic execution. Levels of c-Abl/p145 and Bcr/p160 proteins, however, remain essentially unaltered at that time. Furthermore, reduced Bcr-Abl expression is reflected in significantly attenuated Bcr-Abl-mediated protein tyrosine phosphorylation. Taken together, these results indicate that proteasome inhibition is sufficient to inactivate Bcr-Abl function and subsequently activate the apoptotic death program in cells that are resistant to apoptosis induced by chemotherapy.

Novel dipeptidyl proteasome inhibitors overcome Bcl-2 protective function and selectively accumulate the cyclin-dependent kinase inhibitor p27 and induce apoptosis in transformed, but not normal, human fibroblasts

It has been suggested that overexpression of the Bcl-2 oncoprotein in human cancer cells contributes to their resistance to apoptosis induced by chemotherapy. We report here that a novel dipeptidyl proteasome inhibitor, CEP1612, at low concentrations rapidly induces apoptosis in human Jurkat T cells overexpressing Bcl-2 and also in all human prostate, breast, tongue and brain tumor cell lines we have tested to date, without exception. In contrast, etoposide, a standard anticancer drug, fails to kill these cells when employed under the same conditions. The apoptosis-inducing abilities of CEP1612 and its analogous compounds match precisely their order for inhibition of the proteasome chymotrypsin-like activity. CEP1612-induced apoptosis is p53-independent, inhibitable by a tetrapeptide caspase inhibitor, and associated with accumulation of the cyclin-dependent kinase inhibitors p21 and p27. Furthermore, CEP1612 selectively accumulates p27 and induces apoptosis in simian virus 40-transformed, but not the parental normal, human fibroblasts. Proteasome inhibitors such as those investigated herein might therefore have potential use as novel anticancer drugs.

[Studies of antitumor and chemopreventive agents against neoplasm: synthesis of coumarin 3-glyoxal derivatives and relationship between structure and antimutagenic activity]

It has been shown that alpha-glyoxal and its derivatives possess antivirus and antitumor activities. Eighteen new coumarin 3-glyoxal derivatives were synthesized in our laboratory. The fragmentation pattern of MS and the characteristic signals of 1HNMR of these compounds have also been studied. In pharmacological test in vitro most of these analogues showed antimutagenic activities, among them, compound 9 exhibited very strong antimutagenic activity and eight compounds showed strong effects. The struture-activity relationship and the possible active substructure responsible for the activity of these compounds were discussed. As expected, coumarin 3-glyoxals showed higher antimutagenic activities than their 3-acetyl coumarin counterparts. We also found that alkylation or esterification of 7-hydroxy were favorable to their activities.

p53-independent dephosphorylation and cleavage of retinoblastoma protein during tamoxifen-induced apoptosis in human breast carcinoma cells

We have investigated several molecular events that occur during the process of tamoxifen-induced apoptosis in human breast carcinoma cells. We show that the treatment of either MCF-7 (containing wild-type p53) or MDA-MB-231 cells (containing mutant p53) with tamoxifen resulted in apoptotic nuclear changes and an increase in the pre-G1 apoptotic population. This was accompanied by activation of the caspase enzymes, as evidenced by specific cleavage of poly(ADP-ribose) polymerase and retinoblastoma (RB) protein. The RB protein was cleaved at both an interior and carboxyl terminus cleavage site. In addition, dephosphorylation of RB was found at an early stage of tamoxifen-induced apoptosis in both cell lines. However, neither induction of p53 in MCF-7 cells nor induction of p21 in either cell line was detected, suggesting that tamoxifen-induced RB dephosphorylation and apoptosis are independent of the p53/p21 pathway. We also observed an increase in levels of the pro-apoptotic Bax protein, the inhibitory cytokine TGF-beta1 and the transcription factor c-Myc in tamoxifen-treated MDA-MB-231 cells, suggesting the possible involvement of these proteins during apoptosis in this system.

RB and apoptotic cell death

Homeostasis of cell numbers is achieved by balancing the proliferative and death states of cells. Proper regulation in a cell requires an accurate coordination between these two processes. Indeed, dysregulation of cell cycle progression is essential for the initiation of apoptosis. Retinoblastoma protein (RB) is an important tumor suppressor and a cell cycle regulator. Most recent studies suggest that RB also plays a regulatory role in the process of apoptosis. During the onset of apoptosis, the hyperphosphorylated form of RB (p120/hyper) is converted to a hypophosphorylated form (p115/hypo), which is mediated by a specific protein-serine/ threonine phosphatase activity. Accompanied by the internucleosomal fragmentation of DNA, the newly formed p115/hypo/RB is immediately cleaved by a protease that has properties of the caspase family. During apoptosis, RB is also cleaved in its carboxyl terminus by a caspase-3-like activity. By contrast, the unphosphorylated form of RB (p110/unphos) remains uncleaved during apoptosis. Further studies suggest that p110/unphos/RB functions as an inhibitor of apoptosis. Therefore, regulation of the RB proteolytic activities and consequent RB levels is important for the determination of cellular fate.

Bcl-2- and CrmA-inhibitable dephosphorylation and cleavage of retinoblastoma protein during etoposide-induced apoptosis

Cell numbers are regulated by a balance between proliferation and apoptosis (programmed cell death). Recent evidence suggests that proteins regulating cell proliferation also mediate apoptosis. Therefore, cellular fate might be determined by cross talk between regulators of cell cycle progression and apoptosis. Previously, we had found that during DNA damage-induced apoptosis, retinoblastoma protein (RB), an important G1/S regulator and tumor suppressor, became dephosphorylated and then immediately cleaved into p48 and p68 fragments. Here, we report that expression of the Bcl-2 oncoprotein, an inhibitor of caspases (interleukin 1 -converting enzyme-like proteases), blocked RB dephosphorylation, RB cleavage and apoptosis in etoposide-treated human Jurkat T cells. In addition, expression of the cowpox virus CrmA protein, a direct inhibitor of caspases, also inhibited both RB changes and apoptosis. Taken together, our findings demonstrate important roles for caspases in the processes of etoposide-induced RB dephosphorylation, RB proteolysis and apoptosis.

Characterization of interior cleavage of retinoblastoma protein in apoptosis

Previously we reported that at the onset of apoptotic execution, retinoblastoma protein (RB) was cleaved in its interior region, resulting in production of two major fragments, p48 and p68, and that the RB interior cleavage was mediated by a caspase-like activity. Here, we further characterized the RB interior cleavage process in human leukemia cells treated with the anticancer agent etoposide. We found that the RB interior cleavage activity was much more sensitive to two specific tetrapeptide caspase inhibitors, YVAD-CMK and DEVD-FMK, than the poly(ADP-ribose) polymerase cleavage activity, suggesting that two distinct caspases are involved in these processes. Several Asp residues are located in amino acids 341-421 of RB protein, and cleavage of any one of these sites by a caspase would generate a p48, which contains the amino terminus, and a p68 fragment, which contains the A/B pocket and the carboxyl terminus. This hypothesis was supported by the fact that the p48 and p68 fragments had selective binding affinity to different RB antibodies and that the p48 was found only in the low-salt-extracted cytoplasmic fraction, while the p68 was only in the nuclear fraction, of the apoptotic cells. However, the nuclear binding partner of the p68 RB fragment is not the transcription factor E2F-1 since a specific E2F-1 antibody coimmunoprecipitated only the unphosphorylated form of RB, but not the p68 fragment. Lastly, we confirmed that RB also underwent dephosphorylation and carboxyl terminal cleavage during apoptosis, as we and others reported previously.

A prospective evaluation of alcohol-assisted versus mechanical epithelial removal before photorefractive keratectomy

OBJECTIVE

The purpose of the study is to compare alcohol-assisted versus mechanical debridement of the corneal epithelium before photorefractive keratectomy (PRK) for low-to-moderate myopia.

DESIGN

A prospective study was performed on a group of consecutive patients operated on at the Massachusetts Eye and Ear Infirmary from February to April 1996 and followed for 6 months.

PARTICIPANTS

Eighty patients (eyes) were divided in 2 groups: 40 alcohol and 40 mechanical.

INTERVENTION

The patients underwent PRK for myopia (-1.5 to -7.5 diopters) with a Summit Apex excimer laser. The corneal epithelium was removed either with 20% ethanol or with a scalpel blade.

MAIN OUTCOME MEASURES

The two groups were compared for epithelial removal time, epithelial defect size at the end of surgery, and rate of re-epithelialization. Uncorrected visual acuity (UCVA), refractive outcome, best-corrected visual acuity (BCVA), and subjective haze were measured at 4 days and at 1, 3, and 6 months. In an additional short-term study, 40 patients (20 alcohol, 20 mechanical) had intraoperative pachymetry performed.

RESULTS

Alcohol-assisted de-epithelialization was faster than mechanical debridement (107 [+/-20.6 standard deviation] versus 141 [+/-30.5] seconds [P < 0.0001]) and led to a more circumscribed and reproducible epithelial defect at the end of surgery (87,739 [+/-11,852] versus 103,518 [+/-33,942] square pixels [t test, P = 0.04; f test, P = 0.001]). At 4 days, 95% of the alcohol-treated patients had healed compared with 78% of the mechanically scraped patients (Fisher's exact test, P = 0.04). The alcohol group had a better UCVA at 4 days (logarithm of the minimum angle of resolution UCVA 0.36 [+/-0.22] versus 0.51 [+/-0.26]) and at 1 month (0.14 [+/-0.17] versus 0.22 [+/-0.16] [Mann-Whitney U test, P = 0.02 and P = 0.03]) but equalized at 3 months (0.10 [+/-0.14] versus 0.13 [+/-0.16]) and at 6 months (0.11 [+/-0.15] versus 0.14 [+/-0.13] [Mann-Whitney U test, P = 0.23 and P = 0.34]). There was a trend toward less subjective haze in the alcohol-treated patients over the course of the study (area under the curve, 71.9 [+/-35.3] versus 87.9 [+/-33.8] [Mann-Whitney U test, P = 0.07]). The difference from target was equivalent in both groups at 6 months (-0.22 [+/-0.58] diopter in the alcohol group and -0.43 [+/-0.52] diopter in the mechanical group [t test, P = 0.14; f test, P = 0.57]). There were no differences in intraoperative pachymetry, corneal uniformity index as calculated from the corneal topography, and loss of BCVA between the two groups.

CONCLUSIONS

Twenty percent ethanol is a simple, safe, and effective alternative to mechanical scraping before PRK and appears to be associated with a quicker visual rehabilitation.

Fas stimulation induces RB dephosphorylation and proteolysis that is blocked by inhibitors of the ICE protease family

Fas antigen is a member of the tumor necrosis factor/nerve growth factor receptor family. Stimulation of Fas by Fas ligand or agonistic antibodies results in the activation of interleukin-1 beta converting enzyme-like (ICE-like) proteases, and proteolytic cleavage of poly(ADP-ribose) polymerase (PARP). Ultimately, Fas activation leads to apoptotic cell death. The importance of PARP cleavage to the death process remains unclear. We have hypothesized that the cleavage of other cellular substrates may be important for Fas-mediated apoptosis. Here we show that stimulation of Fas results in significant alterations of retinoblastoma protein (RB). Treatment of Jurkat cells, a human leukemic T cell line, with anti-Fas induces dephosphorylation of RB, followed by proteolytic cleavage. These events precede internucleosomal DNA fragmentation. Dephosphorylation and cleavage of RB are inhibited by a specific tetrapeptide inhibitor of ICE-like proteases or by expression of cowpox virus CrmA protein or the Bcl-2 oncoprotein. Inhibition of these RB changes correlates with inhibition of apoptosis. We propose that cleavage of RB may represent an important step in the pathway of Fas-mediated apoptotic cell death.

Failure to activate interleukin 1beta-converting enzyme-like proteases and to cleave retinoblastoma protein in drug-resistant cells

We previously found that retinoblastoma (RB) is cleaved at the initiation of apoptotic execution. Here we report that when an HL-60 cell line resistant to cytosine arabinoside (Ara-C) was exposed to this anticancer drug, neither RB cleavage nor apoptosis was detected. Consistent with that, processing of interleukin 1beta-converting enzyme (ICE) and CPP32 (an ICE-like protease) was also prevented in these cells. In contrast, treatment of the HL-60-Ara-C-resistant cells with etoposide induced all of these apoptotic events. Furthermore, the etoposide-induced RB cleavage was inhibited by a specific tetrapeptide ICE-like inhibitor. Our results demonstrate that activation of the RB cleavage enzyme, an ICE-like protease, is required for overcoming drug resistance.

Cleavage of retinoblastoma protein during apoptosis: an interleukin 1 beta-converting enzyme-like protease as candidate

We had found that in an early stage of DNA damage-induced, p53-independent apoptosis, retinoblastoma (RB) protein is hypophosphorylated to a p115 form by an activated serine/threonine phosphatase. Here, we report that accompanying the internucleosomal fragmentation of DNA, the newly formed p115/hypo/RB was immediately cleaved into at least two fragments, p68 and p48. The RB cleavage activity possessed properties of interleukin 1 beta-converting enzyme family. Addition of a specific tetrapeptide interleukin 1 beta-converting enzyme inhibitor prevented cleavage of p115/hypo/RB and early apoptotic cells from undergoing further apoptosis. We suggest that activation of the RB phosphatase and protease may be involved in mediating the two physiological stages of apoptosis, commitment and execution, respectively.

[Studies of chemopreventive agents against neoplasma: synthesis of 3-acetyl coumarin derivatives and relationship between antimutagenic activity and structure]

Twenty-five 3-acetylcoumarin derivatives were synthesized among which twenty-two were not reported before. Antimutagenic activity screen in vitro has shown that some of these compounds have various activities. The structure and activity relationship for 5-, 7-, 8-substituents has been studied. Pharmacological data showed that: the substituent on position 8 has important effect on its activity. When there is only a hydroxy group on position 7, its activity is the highest among those with other substituents, but when a methyl is on position 8, the order of the activity is reversed. Other trends have also been found which provided some clues for further structural modification.

Induction of a retinoblastoma phosphatase activity by anticancer drugs accompanies p53-independent G1 arrest and apoptosis

DNA-damaging agents induce accumulation of the tumor suppressor and G1 checkpoint protein p53, leading cells to either growth arrest in G1 or apoptosis (programmed cell death). The p53-dependent G1 arrest involves induction of p21 (also called WAF1/CIP1/SDI1), which prevents cyclin kinase-mediated phosphorylation of retinoblastoma protein (RB). Recent studies suggest a p53-independent G1 checkpoint as well; however, little is known about its molecular mechanisms. We report that induction of a protein-serine/threonine phosphatase activity by DNA damage signals is at least one of the mechanisms responsible for p53-independent, RB-mediated G1 arrest and consequent apoptosis. When two p53-null human leukemic cell lines (HL-60 and U-937) were treated with a variety of anticancer agents, RB became hypophosphorylated, accompanied with G1 arrest. This was followed immediately (in less than 30 min) by apoptosis, as determined by the accumulation of pre-G1 apoptotic cells and the internucleosomal fragmentation of DNA. Addition of calyculin A or okadaic acid (specific serine/threonine phosphatase inhibitors) or zinc chloride (apoptosis inhibitor) prevented the G1 arrest- and apoptosis-specific RB dephosphorylation. The levels of cyclin E- and cyclin A-associated kinase activities remained high during RB dephosphorylation, supporting the involvement of a chemotherapy-induced serine/threonine phosphatase(s) rather than p21. Furthermore, the induced phosphatase activity coimmunoprecipitated with the hyperphosphorylated RB and was active in a cell-free system that reproduced the growth arrest- and apoptosis-specific RB dephosphorylation, which was inhibitable by calyculin A but not zinc. We propose that the RB phosphatase(s) might be one of the p53-independent G1 checkpoint regulators.

Activation of cyclin E-dependent kinase by DNA-damage signals during apoptosis

Preexposure of HL-60 cells to a DNA-damaging agent, cytosine arabinoside (Ara-C), dramatically induced the levels of H1 kinase activities associated with cyclin E (CycE-H1K) but not cyclin A. This induction was cell cycle-independent and accompanied by loss of cell viability, a late event in apoptosis. When an Ara-C-resistant variant of HL-60 cells were treated with Ara-C at a low concentration, neither CycE-H1K nor apoptosis were observed. Both events were induced in the resistant cells but only after treatment with Ara-C at a much higher concentration for a longer period. The DNA-damage-induced CycE-H1K is proposed to be involved in a late apoptosis checkpoint.