Analysis of malachite green and metabolites in fish using liquid chromatography atmospheric pressure chemical ionization mass spectrometry

Malachite green (MG), a traditional agent used in aquaculture, is structurally related to other carcinogenic triphenylmethane dyes. Although MG is not approved for use in aquaculture, its low cost and high efficacy make illicit use likely. We developed sensitive and specific methods for determination of MG and its principal metabolite, leucoMG (LMG), in edible fish tissues using isotope dilution liquid chromatography atmosphere pressure chemical ionization mass spectrometry. MG and LMG concentrations were measured in filets from catfish treated with MG under putative use conditions (ca. 250 and 1000 ppb, respectively) and from commercial trout samples (0-3 and 0-96 ppb, respectively). Concentrations of LMG in edible fish tissues always exceeded those of MG. A rapid cone voltage switching acquisition procedure was used to simultaneously produce molecular ions for quantification and diagnostic fragment ions for confirmation of MG and metabolites. The accurate and precise agreement between diagnostic ion intensity ratios produced by LMG in authentic standards and incurred fish samples was used to unambiguously confirm the presence of LMG in edible fish tissue. This suggested the validity of using LMG as a marker residue for regulatory determination of MG misuse. Additional metabolites derived from oxidative metabolism of MG or LMG (demethylation and N-oxygenation) were identified in catfish and trout filets, including a primary arylamine which is structurally related to known carcinogens. The ability to simultaneously quantify residues of MG and LMG, and to confirm the chemical structure of a marker residue by using LC/MS, suggests that this procedure may be useful in monitoring the food supply for the unauthorized use of MG in aquaculture.     

Optimization of Ethylene Production via Catalytic Partial Oxidation of Ethane on Pt–LaMnO3 Catalyst

A novel catalyst formulation (Pt–LaMnO₃) was recently developed and disclosed for ethylene production via the catalytic partial oxidation of ethane at short contact time. In this paper we report results of the extensive experimental campaign performed on the Pt–LaMnO₃ system for the tuning and optimization of process parameters, which, in turn, shed light on the effect of the main variables controlling overall performance. The novel catalytic system under optimized operating conditions was capable of performances better than state-of-the art systems, with ethylene yields exceeding 65% while preserving selectivities above 80% under self-sustained operation, by adding H₂ as a sacrificial fuel in a simple reactor configuration, thus suggesting to reconsider the economical viability of ethylene production by ethane CPO at short contact time.     

Characterization of the binding sites for plasminogen and tissue-type plasminogen activator in cytokeratin 8 and cytokeratin 18

Cytokeratin 8 (CK8) is an intermediate filament protein that penetrates to the external surfaces of breast cancer cells and is released from cells in the form of soluble heteropolymers. CK8 binds plasminogen and tissue-type plasminogen activator (t-PA) and accelerates plasminogen activation on cancer cell surfaces. The plasminogen-binding site is located at the C-terminus of CK8. In this study, we prepared GST-fusion proteins which contained either 174 amino acids from the C-terminus of CK8 (CK8f) or 134 amino acids from the C-terminus of CK18 (CK18f). A third GST-CK fusion protein was identical to CK8fexcept that the C-terminal lysine was mutated to glutamine (CK8fK483Q). CK8f bound plasminogen; the K(D) was 0.5 microM. Binding was completely inhibited by epsilonACA. CK8fK483Q also bound plasminogen, albeit with decreased affinity (K(D) approximately 1.5 microM). CK18f did not bind plasminogen at all. All three fusion proteins bound t-PA equivalently, providing the first evidence that CK18 may function as a t-PA receptor, t-PA and plasminogen cross-competed for binding to CK8f. Thus, t-PA and plasminogen cannot bind to the same CK8f monomer simultaneously. Nevertheless, CK8f still promoted plasminogen activation, probably reflecting the fact that CK8f was purified in dimeric or tetrameric form. These studies demonstrate that CK8 may promote plasminogen activation by t-PA only when present in an oligomerized state. CK18 may participate in the oligomer, together with CK8, based on its ability to bind t-PA.     

Pilot evaluation of venlafaxine hydrochloride for the therapy of hot flashes in cancer survivors

PURPOSE: Hot flashes can be a prominent clinical problem for breast cancer survivors and men who undergo androgen-deprivation therapy. Anecdotal information suggested a low dose of a relatively new antidepressant, venlafaxine, could abrogate this clinical problem. MATERIALS AND METHODS: This study included 28 consecutive assessable patients entered onto a phase II clinical trial. Hot flash data were collected by daily diary questionnaires during a 1-week baseline period and then for 4 weeks, during which time patients received venlafaxine 12.5 mg orally twice daily. RESULTS: Fifty-eight percent of patients who completed the study had a greater than 50% reduction in hot flash scores (frequency times severity) during the fourth treatment week as compared with the baseline week. Median weekly hot flash scores were reduced by 55% from baseline during the fourth week of venlafaxine therapy. Therapy was generally well tolerated and appeared to alleviate fatigue, sweating, and trouble sleeping. CONCLUSION: Venlafoxine appears to represent an efficacious new method to alleviate hot flashes. Further evaluation of this compound for alleviating hot flashes is indicated.     

A 1.3-A resolution crystal structure of the HIV-1 trans-activation response region RNA stem reveals a metal ion-dependent bulge conformation

The crystal structure of an HIV-1 trans-activation response region (TAR) RNA fragment containing the binding site for the trans-activation protein Tat has been determined to 1.3-A resolution. In this crystal structure, the characteristic UCU bulge of TAR adopts a conformation that is stabilized by three divalent calcium ions and differs from those determined previously by solution NMR. One metal ion, crucial to the loop conformation, binds directly to three phosphates in the loop region. The structure emphasizes the influence of metal ion binding on RNA structure and, given the abundance of divalent metal ion in the cell, raises the question of whether metal ions play a role in the conformation of TAR RNA and the interaction of TAR with Tat and cyclin T in vivo.     

The Esperanto Broker: a communication platform for nomadic computing systems

There is an increasing demand for middleware for nomadic computing applications. Owing to the inherent characteristics of such environments, these platforms have to address two fundamental issues: (i) device disconnections and the limitations of wireless networks may force users to experience short periods of service unavailability; and (ii) the complexity to design and develop next‐generation mobile computing applications. This paper proposes the Esperanto Broker (EB), a communication platform that addresses mobility issues via an integrated approach, i.e. at data‐link, network, and middleware levels. Decoupling interactions are achieved via a tuple‐space underlying infrastructure. To support developers with advanced services, the EB enhances the distributed objects computing model providing the abstraction for the communication paradigms standardized by the W3C. Esperanto applications can be modeled as sets of objects that are distributed over mobile devices, which communicate via remote method invocations (RMIs). RMIs natively implement pull and push models, in both one‐to‐one and one‐to‐many multiplicity. The paper focuses on the EB design issues, essential aspects of the implementation, and performance evaluations of the implemented prototype. Copyright © 2006 John Wiley & Sons, Ltd.     

水热／溶剂热法制备Mn3O4纳米材料的研究进展

Mn3O4广泛应用于催化、电化学、软磁材料、空气净化等领域。近年来，采用多种新技术研制Mn3O4新材料，如电子级Mn3O4、Mn3O4超细粉体、Mn3O4纳米带、纳米棒、纳米纤维、纳米空心球等。重点评述了近几年水热／溶剂热法制备纳米级Mn3O4新材料的研究进展，并展望了Mn3O4新材料制备技术的发展方向。