Quantifying the contribution of dietary protein to whole body protein kinetics: examination of the intrinsically labeled proteins method.

Intrinsically labeled dietary proteins have been used to trace various aspects of digestion and absorption, including quantifying the contribution of dietary protein to observed postprandial amino acid and protein kinetics in human subjects. Quantification of the rate of appearance in peripheral blood of an unlabeled (tracee) amino acid originating from an intrinsically labeled protein (exogenous R) requires the assumption that there is no dilution of the isotope enrichment of the protein-bound amino acid in the gastrointestinal tract or across the splanchnic bed. It must also be assumed that the effective volume of distribution into which the tracer and tracee appear can be reasonably estimated by a single value and that any recycling of the tracer is minimal and thus does not affect calculated rates.

Skeletal Muscle Acute and Chronic Metabolic Response to Essential Amino Acid Supplementation in Hypertriglyceridemic Older Adults.

Supplementation with essential amino acids (EAAs) + arginine is a promising nutritional approach to decrease plasma triglyceride (TG) concentrations, which are an independent risk factor for ischemic heart disease. The objective of this study was to examine the effects of 8 wk of EAA supplementation on skeletal muscle basal metabolite concentrations and changes in metabolic response to acute EAA intake, with an emphasis on mitochondrial metabolism, in adults with elevated TGs to better understand the mechanisms of lowering plasma TGs. Older adults with elevated plasma TG concentrations were given 22 g EAAs to ingest acutely before and after an 8-wk EAA supplementation period.

A New Derivatization Reagent for HPLC-MS Analysis of Biological Organic Acids.

Small molecules containing carboxylic acid functional groups are ubiquitous throughout biology, playing vital roles in biological chemistry ranging from energy metabolism to cellular signaling. This paper describes a new derivatization reagent, 4-bromo--methylbenzylamine, which was selected for its potential to derivatize mono-, di- and tri-carboxylic acids, such as the intermediates of the tricarboxylic acid (TCA) cycle. This derivatization procedure facilitated the use of positive electrospray ionization (ESI) tandem mass spectrometry (MS/MS) detection of derivatized species allowing for clear identification thanks to the easily recognizable isotope pattern of the incorporated bromine.

Nanosilver suppresses growth and induces oxidative damage to DNA in Caenorhabditis elegans.

Studies on the effects of nanomaterial exposure in mammals are limited, and new methods for rapid risk assessment of nanomaterials are urgently required. The utility of Caenorhabditis elegans cultured in axenic liquid media was evaluated as an alternative in vivo model for the purpose of screening nanomaterials for toxic effects. Spherical silver nanoparticles of 10 nm diameter (10nmAg) were used as a test material, and ionic silver from silver acetate as a positive control.

Active transcriptomic and proteomic reprogramming in the C. elegans nucleotide excision repair mutant xpa-1.

Transcription-blocking oxidative DNA damage is believed to contribute to aging and to underlie activation of oxidative stress responses and down-regulation of insulin-like signaling (ILS) in Nucleotide Excision Repair (NER) deficient mice. Here, we present the first quantitative proteomic description of the Caenorhabditis elegans NER-defective xpa-1 mutant and compare the proteome and transcriptome signatures. Both methods indicated activation of oxidative stress responses, which was substantiated biochemically by a bioenergetic shift involving increased steady-state reactive oxygen species (ROS) and Adenosine triphosphate (ATP) levels.

Pro-oxidant induced DNA damage in human lymphoblastoid cells: homeostatic mechanisms of genotoxic tolerance.

Oxidative stress contributes to many disease etiologies including ageing, neurodegeneration, and cancer, partly through DNA damage induction (genotoxicity). Understanding the i nteractions of free radicals with DNA is fundamental to discern mutation risks. In genetic toxicology, regulatory authorities consider that most genotoxins exhibit a linear relationship between dose and mutagenic response.

NIST gold nanoparticle reference materials do not induce oxidative DNA damage.

One primary challenge in nanotoxicology studies is the lack of well-characterised nanoparticle reference materials which could be used as positive or negative nanoparticle controls. The National Institute of Standards and Technology (NIST) has developed three gold nanoparticle (AuNP) reference materials (10, 30 and 60 nm). The genotoxicity of these nanoparticles was tested using HepG2 cells and calf-thymus DNA.

The role of iron redox state in the genotoxicity of ultrafine superparamagnetic iron oxide nanoparticles.

Ultrafine superparamagnetic iron oxide nanoparticles (USPION) hold great potential for revolutionising biomedical applications such as MRI, localised hyperthermia, and targeted drug delivery. Though evidence is increasing regarding the influence of nanoparticle physico-chemical features on toxicity, data however, is lacking that assesses a range of such characteristics in parallel. We show that iron redox state, a subtle though important physico-chemical feature of USPION, dramatically modifies the cellular uptake of these nanoparticles and influences their induction of DNA damage.

Investigation of noble metal nanoparticle ζ-potential effects on single-cell exocytosis function in vitro with carbon-fiber microelectrode amperometry.

Since noble metal nanoparticles are increasingly found in consumer goods, there is a need for information about potential impacts of these nanoparticles on cellular function to avoid environmental and health risks associated with exposure. In this study, spherical Au and Ag nanoparticles of similar size were synthesized and modified to assess the effects of ζ-potential on immune cell function. Nanoparticle ζ-potential was controlled by employing surfactant exchange to generate nanoparticles with positive or negative surface charge.

Evaluating the effects of immunotoxicants using carbon fiber microelectrode amperometry.

Carbon fiber microelectrode amperometry (CFMA) is explored as a technique for studying the effects of immunotoxicants on single-cell in vitro exocytosis function in a mouse peritoneal mast cell (MPMC)/fibroblast co-culture model. MPMCs were acutely exposed to between 10 and 100 μM of the immunotoxicants mono-2-ethylhexyl phthalate (MEHP) and bisphenol A (BPA), and release of serotonin was evaluated by CFMA. A significant decrease in the quantal content of serotonin was measured for all levels of exposure to both MEHP and BPA.

Amperometric assessment of functional changes in nanoparticle-exposed immune cells: varying Au nanoparticle exposure time and concentration.

A mast cell/fibroblast co-culture system is used as a model to assess the toxicity of Au nanoparticles over the course of 72 hours of exposure. Cellular uptake of nanoparticles was found to increase over the 72 hr exposure period and the nanoparticles localized within granular bodies of the primary culture mast cells. These granules were found to increase in volume with the addition of nanoparticles.

Analytical methods to assess nanoparticle toxicity.

During the past 20 years, improvements in nanoscale materials synthesis and characterization have given scientists great control over the fabrication of materials with features between 1 and 100 nm, unlocking many unique size-dependent properties and, thus, promising many new and/or improved technologies. Recent years have found the integration of such materials into commercial goods; a current estimate suggests there are over 800 nanoparticle-containing consumer products (The Project on Emerging Nanotechnologies Consumer Products Inventory, , accessed Oct. 2008), accounting for 147 billion USD in products in 2007 (Nanomaterials state of the market Q3 2008: stealth success, broad impact, Lux Research Inc.

Toxicity of therapeutic nanoparticles.

A total of six nanotherapeutic formulations are already approved for medical use and more are in the approval pipeline currently. Despite the massive research effort in nanotherapeutic materials, there is relatively little information about the toxicity of these materials or the tools needed to assess this toxicity. Recently, the scientific community has begun to respond to the paucity of information by investing in the field of nanoparticle toxicology.

The effects of co-culture of fibroblasts on mast cell exocytotic release characteristics as evaluated by carbon-fiber microelectrode amperometry.

In this work, carbon-fiber microelectrode amperometry (CFMA) is employed to probe changes in the biophysical mechanism of exocytosis under varied cell culture conditions. Degranulation and serotonin exocytosis from mouse peritoneal mast cells (MPMCs) were measured both without and with co-cultured Swiss-albino 3t3 fibroblasts using CFMA. After 24 h in culture, there are distinct differences in the exocytotic characteristics of MPMCs cultured with and without fibroblast support cells, as detected by CFMA, including an increased number of secreted serotonin molecules, number of granule fusion events, secretion rate, and granule membrane tension.

Dynamic measurement of altered chemical messenger secretion after cellular uptake of nanoparticles using carbon-fiber microelectrode amperometry.

In this work, carbon-fiber microelectrode amperometry is used to characterize serotonin exocytosis from murine peritoneal mast cells cocultured with fibroblasts in the presence of Au nanoparticles. In the case of mast cell exposure to 1 nM 28 nm diameter spherical Au nanoparticles, there is a decrease of greater than 30% in the number of successful granule transport and fusion events, greater than 30% increase in the rate of intragranular matrix expansion, and greater than 20% increase in the number of secreted serotonin molecules per granule. These results suggest that nanoparticles interrupt the dense-core biopolymer intragranular matrix and present the potential for systematic studies showing how exocytotic function is influenced by nanoparticle size, shape, and composition.

Secondary organic aerosol from limona ketone: insights into terpene ozonolysis via synthesis of key intermediates.

Limona ketone was synthesized to explore the secondary organic aerosol (SOA) formation mechanism from limonene ozonolysis and also to test group-additivity concepts describing the volatility distribution of ozonolysis products from similar precursors. Limona ketone SOA production is indistinguishable from alpha-pinene, confirming the expected similarity. However, limona ketone SOA production is significantly less intense than limonene SOA production.