Cellular mechanisms for developmental toxicity of chlorpyrifos: targeting the adenylyl cyclase signaling cascade

Developmental neurotoxicity caused by chlorpyrifos exposure is generally thought to target cholinesterase but chlorpyrifos may also act on cellular intermediates, such as adenylyl cyclase, that serve global functions in the coordination of cell development. In the current study, neonatal rats were exposed to apparently subtoxic doses of chlorpyrifos (no weight loss, no mortality) either on Postnatal Days 1-4 or on Postnatal Days 11-14, and the effects on components of the adenylyl cyclase cascade were evaluated in brain regions that are enriched (forebrain) or sparse (cerebellum) in cholinergic innervation, as well as in a nonneural tissue (heart). In all three, chlorpyrifos evoked deficits in multiple components of the adenylyl cyclase cascade: expression and activity of adenylyl cyclase itself, functioning of G-proteins that link neurotransmitter and hormone receptors to cyclase activity, and expression of neurotransmitter receptors that act through this cascade. Disruption of signaling function was not restricted to transduction of cholinergic signals but rather extended to adrenergic signals as well. In most cases, the adverse effects were not evident during the immediate period of chlorpyrifos administration, but appeared after a delay of several days. These results suggest that chlorpyrifos can affect cell development by altering the activity and reactivity of the adenylyl cyclase signaling cascade, a major control point for trophic regulation of cell differentiation. The effects are not restricted to cholinergic targets, nor even to the central nervous system. Hence, disruption of cell development by chlorpyrifos is likely to be more widespread than previously thought.     

Managing your process hazards as a means of conforming to ohsa requirements

There is considerable evidence that improper changes have directly caused or through the “domino sequence” led to many of the major accidents that have occurred in the chemical process industry and related industries that use hazardous chemicals and technology. Central Government has recognised the importance of careful management of change(MOC) for ensuring the safety of chemical operations and the quality of manufactured goods by the proposed adding of the Major Hazardous Installation Regulation to the OHSA (Act 85 of 1993).

The concept and the need to properly manage change are not new; many companies have adopted MOC procedures. It is common practice nowadays to perform detailed risk assessments on any new or intended project to ensure safety and reliability of the project. Yet, incidents and near misses attributable to inadequate management of changes on existing systems and processes continue to occur. To improve the performance of MOC systems throughout industry, managers need advice on how to better institutionalise MOC systems within their companies and plants.

The purpose of this paper is to define the important features of MOC systems and to assist in the implementation and management of process hazards. MOC systems help ensure that changes to design and operation of company facilities will not adversely affect employees, the public, or the environment. This document outlines a process that can be used for designing, developing, installing, operating, and maintaining MOC systems at individual company sites.

This paper is intended for an audience ranging from plant and corporate managers of process safety to workers who have differing levels of knowledge about the principles of safely managing change. It is primarily designed to equip people responsible for MOC systems with new ideas for implementing and improving MOC systems. It was indeed a privilege to have met the personnel of JBF Associates, Inc. and Process Safety Institute in Knoxville, Tennessee, USA, without whose lectures and study material (including the book “Managing process changes”) this paper would never have seen the light. They have succeeded in putting me firmly on the “process safety road”.     

Leaching of sulfidized chalcopyrite with H<Subscript>2</Subscript>SO<Subscript>4</Subscript>-NaCl-O<Subscript>2</Subscript>

The recovery of copper from chalcopyrite by leaching is complex not only due to the slow dissolution kinetics of this mineral in most aqueous media but also due to the production of solutions that are heavily contaminated with iron. On the contrary, the leaching of sulfidized chalcopyrite is very attractive because of a faster and more selective dissolution of copper compared to the leaching of the untreated chalcopyrite. In this work, the results of leaching in H₂SO₄-NaCl-O₂ solutions of sulfidized chalcopyrite concentrate are discussed. Experiments were carried out with chalcopyrite concentrates previously reacted with elemental sulfur at 375 °C for 60 minutes. The results showed that the concentration of chloride ions below 0.5 M, temperature, and leaching time are important variables for the extraction of Cu. On the other hand, Fe extraction was little affected by the same variables, remaining below 6 pct for all the experimental conditions tested. Microscopic observations of the leached particles showed that the elemental sulfur produced by the reaction does not form a coherent layer surrounding the particle, but rather concentrates in certain locations as large clusters. The leaching kinetics can be accurately described by a nonreactive core-shrinking rim topochemical expression for spherical particles 1 − (1 − 0.45X)^1/3=kt. The activation energy found was 76 kJ/mol for the range 85 °C to 100 °C.     

Evaluation of Serum Volume Losses During Long-Term Storage

Aliquots of serum collected in a large case-control study of cervical cancer were stored at −70°C for up to 4 years during implementation of the study. When 500 μL serum aliquots were thawed in preparation for carotenoid and vitamin A assays, volumes were noticeably variable and fell below 500 μL in the majority of the samples. We were concerned about evaporation/sublimation during storage of the samples because loss of water would concentrate the analytes of interest. We evaluated the use of density and sodium ion concentration measurements to confirm its occurrence. We found that serum density was an unreliable indicator of extent of volume loss since the anticipated increases in density due to evaporation were of the same magnitude as inter-individual variation in serum density. In contrast, Na⁺ concentration is tightly regulated and would rise if water had been lost from the samples. In a representative sample of serum aliquots from the case-control study, 24 of 25 vials contained less than 500 μL of serum. The mean sodium ion concentration (138.1 ± 3.6 mmol/L) was within the normal range for human serum of 136–145 mmol/L, and no correlation was observed between serum volume and Na⁺ concentration. These results strongly suggest that the observed low volumes were not due to evaporative losses. Instead, the variably low volumes of serum aliquots were probably due to pipetting errors in the initial aliquotting resulting from the use of air-displacement pipettes.     

The effect of nanoclays on the nucleation,crystallization, and melting mechanisms of isotactic polypropylene

The influence of organomodified nanoclay (montmorillonite) on the crystallization and melting mechanisms of isotactic polypropylene (iPP) was studied. Films of both neat polymer and clay nanocomposites were prepared after molecular weight optimization through melt extrusion. Products exhibited the tactoidlike morphology since no compatibilizers were used. The effect of introduction of nanoclay within the polymer was studied through isothermal crystallization and linear heating. The results indicated that low nanoclay concentrations induce the formation of the β‐crystalline structure, its formation being inhibited with high nanoclay contents. Dynamic nonisothermal bulk crystallization experiments indicated that nanoclays act as nucleating agents of iPP. Isothermal, bulk crystallization studies indicated that the crystallization process (induction time and crystallization kinetics) is proportionally accelerated by the nanoclay presence. There was also an accelerated formation of secondary crystallization when nanoclays were present in high concentrations. POLYM. ENG. SCI., 47:1889–1897, 2007. © 2007 Society of Plastics Engineers     

Functional properties of a protein product from Caryodendron orinocense (Barinas nut)

The functional properties of Caryodendron orinocense protein product were investigated and compared with those of soybean (Glycina maxima). The product protein content was 24.47 g/100 g (Nx6.25). Solubility increased at both sides of the isoelectric point (pH 4.0) and with increased NaCl concentration up to 0.5M. Compared with soybean flour (50% protein), the protein product exhibited higher water and oil absorption, but lower emulsifying activity, emulsion stability, foaming capacity, and foam stability, the last one increase at higher pH. Emulsifying activity, foaming capacity, and foam stability were ionic strength dependent. C. orinocense protein product increased its emulsifying activity steadily from 0.05M to 0.75M NaCl, while it remained almost constant for soybean flour. Foaming capacity increased drastically at pH 10. The minimum time and concentration to form a gel was 20% in 4 min and 10% in 8 min for the Caryodendron protein product and soybean flour, respectively. The bulk density was 0.5056+/-0.0041 g/mL.     

Influence of post‐extrusion parameters on the final morphology of polystyrene/high density polyethylene blends

The deformation of the dispersed phase in polystyrene/high density polyethylene (PS/HDPE) blends produced by ribbon extrusion was studied numerically and experimentally. A mathematical model for the deformation of the dispersed phase in ribbon extrusion processing of polymer blends was developed assuming uniaxial deformation of the ribbon and the equilibrium shapes of the dispersed particles with a pressure balance over a drop. Simulated morphologies as function of the post‐extrusion parameters were obtained and compared with experiments. The analysis of the ribbon extrusion process showed that parameters such as draw ratio (DR) and ribbon‐water contact length (X) significantly influence the ribbon dimensions, the extensional stress, and the stretching force. The results also showed that deformation and coalescence of the dispersed phase in the ribbon extrusion processing of polymer blends increase at higher DR and/or lower X values. The comparison between the model and the experimental morphologies of PS/HDPE produced a good agreement.     

Photobleaching with phloxine B sensitizer to reduce food matrix interference for detection of Escherichia coli serotype O157:H7 in fresh spinach by flow cytometry

A flow cytometric method (RAPID-B™) with detection sensitivity of one viable cell of Escherichia coli serotype O157:H7 in fresh spinach (Spinacia oleracea) was developed and evaluated. The major impediment to achieving this performance was mistaking autofluorescing spinach particles for tagged target cells. Following a 5 h non-selective enrichment, artificially inoculated samples were photobleached, using phloxine B as a photosensitizer. Samples were centrifuged at high speed to concentrate target cells, then gradient centrifuged to separate them from matrix debris. In external laboratory experiments, RAPID-B and the reference method both correctly detected E. coli O157:H7 at inoculations of ca. 15 cells. In a follow-up study, after 4 cell inoculations of positives and 6 h enrichment, RAPID-B correctly identified 92% of 25 samples. The RAPID-B method limit of detection (LOD) was one cell in 25 g. It proved superior to the reference method (which incorporated real time-PCR, selective enrichment, and culture plating elements) in accuracy and speed.     

Mechanical Characterization of Copper-Copper Wires Joined by Friction Welding Using Instrumented Indentation Technique

Friction welding samples of both the fire-refined high-conductivity (FRHC) and electrolytically tough pitch (ETP) copper alloy wires have been mechanically characterized by instrumented indentation technique and tensile test. Hardness profiles in the perpendicular direction to the weld interface, in both the central and peripheral zones, of the as-welded FRHC-FRHC and ETP-ETP samples have been investigated at nano-/micrometric scale. The microstructures of welds have been observed using both the optical microscopy and scanning electronic microscopy. The results show the typical friction welding zones: the interface zone, the thermo-mechanically affected zone (TMAZ), and the transition zone between the TMAZ and the base metal zone (BMZ) that present a microstructure and hardness close to the base metal. No presence of a heat-affected zone is observed. Although both welds show the same tendency in hardness distribution, FHRC-FHRC weld presents a TMAZ narrower than ETP-ETP one, which produces a stronger drop in hardness with increasing of the distance from welding central line, and a higher difference in hardness between the central and peripheral zones. The tensile tests of ETP-ETP welds showed that all samples broke by the BMZ that is far away from the interface of the welded joint, while the most of the FRHC-FRHC welds are broken at the TMAZ region at low strengths. These appreciable differences in mechanical properties for the FHRC-FHRC welds are probably generated by a stronger variation in their microstructural properties. Therefore, it may justify the welding failures in the FHRC-FHRC weld at the typical tensile stress for an industrial cold-drawn process of wires.