In vitro stability and compatibility of tenecteplase in central venous access devices

Central venous access devices (CVADs) aid in the delivery of nutritional support, infusion therapy, and hemodialysis. Maintaining continuous flow through these devices is challenging, because they are susceptible to complications such as thrombi occlusion. Therefore, CVADs may require treatment with anticoagulant or thrombolytic agents. Using these agents as locking solutions has been widely investigated; however, few publications have described the compatibility of the therapeutic with the CVAD itself. The objective of this investigation was to evaluate the in vitro stability and compatibility of a thrombolytic biologic agent, tenecteplase, with various CVAD materials. Tenecteplase was reconstituted to 1 mg/mL with either sterile water for injection or bacteriostatic water for injection (0.9% benzyl alcohol) then incubated in glass vials, polysulfone/silicone vascular access ports, and polyurethane or silicone catheters for up to 96 hours. Biochemical assays including protein monomer, protein one-chain, and in vitro bioactivity were used to assess tenecteplase's compatibility with the investigated diluents and materials every 24 hours. Antimicrobial testing was also performed for up to 28 days on bacteriostatic water for injection-reconstituted samples only. Our results showed tenecteplase to be compatible with both types of diluents (in glass vials) and catheters for up to 72 hours. Furthermore, tenecteplase was compatible with the polysulfone/silicone vascular access ports for up to 24 hours. Finally, bacteriostatic water for injection-reconstituted tenecteplase effectively met USP criteria for the inhibition of growth of micro-organisms. This study serves as an example of a best practice to evaluate the in vitro stability and compatibility of a biologic agent with CVAD materials.     

Purification and characterization of a second aminopeptidase (pepC-like) from Lactobacillus delbrueckii subsp. bulgaricus B14

A second aminopeptidase was purified from cell-free extracts of Lactobacillus delbrueckii subsp. bulgaricus B14 by ammonium sulphate precipitation and two steps of anion-exchange chromatography. After SDS polyacrylamide-gel electrophoresis in the presence of β-mercaptoethanol, one protein band was detected at 54 kDa. The same molecular mass was estimated by gel filtration. SDS polyacrylamide-gel electrophoresis in the absence of β-mercaptoethanol resulted in a single band at 220 kDa, indicating that the enzyme forms complexes of four molecules under non-reducing conditions. Activity was markedly increased by reducing and metal-chelating agents. Thiol-group inhibitors, such as iodoacetic acid, inhibited the enzyme strongly. In contrast to Mg²⁺ and Ca²⁺, which had slightly activating effects, other divalent cations reduced enzyme activity at a concentration of 1 mM. The aminopeptidase showed highest activity at 50°C and pH 6·5–7 and hydrolyzed a wide range of di- and tripeptides. The most suitable substrates were Leu-Gly, Leu-Gly-Gly, Ala-Ala-Ala, and Met-Gly-Gly. For Leu-Gly and Leu-Gly-Gly, K_m-values of 1·81 mM and 2·17 mM and turnover numbers of 870 s⁻¹ were calculated, with a maximal rate of hydrolysis (V_max) of 4600 and 2780 μmol/min per mg of protein, respectively. The aminopeptidase did not cleave Lys-pNA, a substrate hydrolyzed by all type-‘N’ aminopeptidases from lactic acid bacteria with high velocities. It compared well, however, with pepC found in Lactococcus.     

Structure-function studies of an engineered scaffold protein derived from Stefin A. II: Development and applications of the SQT variant

Constrained binding peptides (peptide aptamers) may serve as tools to explore protein conformations and disrupt protein-protein interactions. The quality of the protein scaffold, by which the binding peptide is constrained and presented, is of crucial importance. SQT (Stefin A Quadruple Mutant-Tracy) is our most recent development in the Stefin A-derived scaffold series. Stefin A naturally uses three surfaces to interact with its targets. SQT tolerates peptide insertions at all three positions. Peptide aptamers in the SQT scaffold can be expressed in bacterial, yeast and human cells, and displayed as a fusion to truncated pIII on phage. Peptides that bind to CDK2 can show improved binding in protein microarrays when presented by the SQT scaffold. Yeast two-hybrid libraries have been screened for binders to the POZ domain of BCL-6 and to a peptide derived from PBP2', specific to methicillin-resistant Staphylococcus aureus. Presentation of the Noxa BH3 helix by SQT allows specific interaction with Mcl-1 in human cells. Together, our results show that Stefin A-derived scaffolds, including SQT, can be used for a variety of applications in cellular and molecular biology. We will henceforth refer to Stefin A-derived engineered proteins as Scannins.     

Probing Cell‐Type‐Specific Intracellular Nanoscale Barriers Using Size‐Tuned Quantum Dots

The compartmentalization of size‐tuned luminescent semiconductor nanocrystal quantum dots (QDs) in four distinctive cell lines, which would be representative of the most likely environmental exposure routes to nanoparticles in humans, is studied. The cells are fixed and permeabilized prior to the addition of the QDs, thus eliminating any cell‐membrane‐associated effects due to active QD uptake mechanisms or to specificity of signaling routes in different cell types, but leaving intact the putative physical subcellular barriers. All quantitative assays are performed using a high content analysis (HCA) platform, thereby obtaining robust data on large cell populations. While smaller QDs 2.1 nm in diameter enter the nuclei and localize to the nucleoli in all cell types, the rate and dynamics of their passage vary depending on the cell origin. As the QD size is increased to 4.4 nm, penetration into the cell is reduced but each cell line displays its own cutoff size thresholds reflecting cell‐type‐determined cytoplasmic and nuclear pore penetration specificity. These results give rise to important considerations regarding the differential compartmentalization and susceptibility of organs, tissues, and cells to nanoparticles, and may be of prime importance for biomedical imaging and drug‐delivery research employing nanoparticle‐based probes and systems.     

Rebuttal re: "Confirmatory bias and the persistent influence of discredited data in interpreting the stress-cancer link: Commentary on Michael et al. (2009)".

[Correction Notice: An erratum for this article was reported in Vol 30(4) of Health Psychology (see record 2011-13978-001). The letter was missing the doi. The correct doi is 10.1037/a0022737. The online version of this article has been corrected.] Responds to the comments by J. C. Coyne and C. Johansen (see record 2011-09497-016) on the current author's original article, "Influence of stressors on breast cancer incidence in the Women's Health Initiative" (see record 2009-03297-001). Coyne and Johansen (2011) took issue with the study conducted by the current authors' group (Michael et al., 2009), which analyzed the interaction between stressful life events and social support on breast cancer risk among 83,334 postmenopausal women enrolled in the Women’s Health Initiative (WHI). While the current authors agree with the Coyne and Johansen that too often null results are difficult to publish due to confirmatory bias that privileges results that support an alternative hypothesis, they strongly disagree with the assertion that their group selectively reported findings, inaccurately reported findings, or provided selective and uncritical reference to the existing literature. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The Need for Greater Transparency When Assessing the Performance and Prospects of Melbourne’s Rail Franchise Contracts

Among policymakers and researchers at an international level, there is great interest in the performance of the Melbourne rail franchise model. This review attempts to examine the Melbourne model in an international context and assess the performance of the system under current contracts. Potential flaws are highlighted including lack of information, concerns over performance and contestability, and the treatment of the potential long-term maintenance backlog under short-term contracts. The authors conclude with an overall stance of there needing to be far greater public information transparency to allow proper scrutiny of the effectiveness of these contracts for the public good.     

The Ensemble Effect in Bifunctional Catalysis: Influence of Zinc as Promoter for Pd-H-ZSM-5 Catalysts during the Dehydroalkylation of Toluene with Ethane

The ensemble effect, i.e., the fact that the reaction requiring the largest ensemble of surface metal atoms will be most sensitive to promoting with a second metal, has rarely been studied in bifunctional catalysis. In this contribution, it is shown that, during the dehydroalkylation of toluene with ethane on Pd-H-ZSM-5 catalysts with zinc as promoter, the ensemble effect has only an influence on the side reactions on the metal such as hydrogenolysis, but not on the desired acid-catalyzed alkylation reaction.     

Multi-stage production planning on the IBM PC — an application

Job shop scheduling is one of the most intriguing and potentially useful problems in Operations Research. It is also a very difficult problem to solve. In this article, we discuss a hybrid approach we have developed which automates the scheduling functions in a plant materials management department. The system performs multi-stage time phased materials planning calculations, while performing capacity checks and job sequencing. The scheduling algorithm performs a heuristic reduction of the n/m/Smin problem to a set of n/l/Smin problems which are solved optimally. The heuristic reduction and optimization algorithms are described. Design criteria which made implementation possible in a plant setting are also discussed.     

A statistical evaluation of aggregate monthly industrial demand for natural gas in the U.S.A.

We examine the temporal pattern and effect of heating degree days, price of natural gas, price of residual fuel oil, and industrial activity on industrial demand for natural gas between January 1980 and March 1984. Time plots are used to display these patterns. Regression analysis is used to estimate these effects. The results of the regression analysis are then evaluated, including an examination of the effect of measurement error on estimated coefficients. The evaluation indicates that the estimated coefficients are reliable.