Evaluation of microwave digestion systems for mercury recovery in an oil matrix

The scope of this document is to characterize three microwave systems developed by CEM Corporation. The purpose of this investigative work was to evaluate the performance of each system for dissolution qualities and the recovery of mercury in an oil based matrix. The microwave systems evaluated were the heavy duty vessel system (HDV), the advanced composite system (ACV), and the open vessel system (OVS). All three systems have automated features, but all systems are limited by one factor or another. EPA method 3051 was the procedure used for sample preparation for this project. This particular microwave digestion method can also be used for other metal analytes of interest. Of the three different systems, only the HDV (now UDV) demonstrated complete digestion of the oil based matrix in a one step process and acceptable mercury recoveries

Mercury recovery results of microwave digested tritium facility pump oil

This report is a follow up of work done earlier this year and recorded in document WSRC-RP-97-322. The scope of this document is to demonstrated the viability of digesting two non-radioactive Tritium facility pump oils, Welch Duoseal and Spindura, neat and spiked with low-level mercury to determine completeness of digestion and recoverability of mercury. As noted in document WSRC-RP-97-322 a microwave digestion methodology was developed with CEM`s ultimate digestion vessel system (UDV) and is the technique used for the follow up task of digesting the above mention pump oils for the preparatory step of cold-vapor mercury analysis.All analytical development for this project was performed at TNX. The determination of the mercury concentration in each digested sample was by cold vapor atomic absorption. The instrument used was a Varian SpectrAA 800 with a vapor generation attachment. This flameless AA procedure is a physical method based on the absorption of radiation at 253.7 nm of mercury vapor. Organo-mercury compounds will not respond to the cold vapor atomic absorption technique, therefore, to acquire a total mercury value it is necessary for a complete digestion to oxidize and convert the organo-mercury species to the mercuric ion

Developing oral chronotherapy for cortisol replacement in congenital adrenal hyperplasia

The sun imposes a 24-h periodicity to life and circadian rhythms have evolved to maintain homoeostasis through the day/night cycle. In humans, there is a central clock that controls the sleep/wake cycle which is paralleled metabolically by a fast/feed cycle. The clock maintains homoeostasis by synchronising metabolism to the time of feeding. Loss of synchrony between the clock and hormonal rhythms results in loss of homoeostasis as evidenced by obesity, depression, and diabetes in people undertaking shift work. Cortisol has a distinct circadian rhythm; peaking on waking and low at sleep onset. Loss of this rhythm in adrenal insufficiency is associated with a poor quality of life and increased mortality. To replace the cortisol rhythm requires chronotherapy and for this you need to define the key parameters of the target rhythm, create a formulation to replicate that rhythm, and then prove clinical benefit. The physiology of hormones is more complex than that of nonnative drugs. Hormones are secreted with varied rhythms, bound to multiple cognate binding proteins, and actively transported and cleared through enzymatic pathways in multiple organs. We have examined the diurnal rhythm of cortisol in healthy volunteers, created physiologically-based pharmacokinetic models, and tested various oral delayed and sustained formulations of hydrocortisone (development name, Chronocort) in clinical trials. The outcome from this work was the manufacture of modified-release hydrocortisone hard capsules (tradename Efmody, Diurnal Ltd), that replicate the cortisol diurnal rhythm and improve the disease control of congenital adrenal hyperplasia the commonest hereditary form of adrenal insufficiency

Bioavailability of oral hydrocortisone corrected for binding proteins and measured by LC-MS/MS using serum cortisol and salivary cortisone

Context: The assessment absolute bioavailability of oral hydrocortisone is complicated by its saturable binding to cortisol binding globulin (CBG). Previous assessment of bioavailability used a cortisol radioimmunoassay which has cross reactivity with other steroids. Salivary cortisone is a measure of free cortisol and LC-MS/MS is the gold standard method for measuring steroids. We here report the absolute bioavailability of hydrocortisone calculated using serum cortisol and salivary cortisone measured by LC-MS/MS. Methods: 14 healthy male dexamethasone suppressed volunteers were administered 20 mg hydrocortisone either intravenously or orally by tablet. Samples of serum and saliva were taken and measured for cortisol and cortisone by LC-MS/MS. Serum cortisol was corrected for saturable binding using published data and pharmacokinetic parameters derived using the program WinNonlin. Results: The mean (95% CI) bioavailability of oral hydrocortisone calculated from serum cortisol, unbound serum cortisol and salivary cortisone was 1.00 (0.89-1.14); 0.88 (0.75-1.05); and 0.93 (0.83-1.05), respectively. Conclusion: The data confirm that, after oral administration, hydrocortisone is completely absorbed. The data derived from serum cortisol corrected for protein binding, and that from salivary cortisone, are similar supporting the concept that salivary cortisone reflects serum free cortisol levels and that salivary cortisone can be used as a non-invasive method for measuring the pharmacokinetics of hydrocortisone

Subject-specific, multiscale simulation of electrophysiology: a software pipeline for image-based models and application examples

Many simulation studies in biomedicine are based on a similar sequence of processing steps, starting from images and running through geometric model generation, assignment of tissue properties, numerical simulation and visualization of the results—a process known as image-based geometric modelling and simulation. We present an overview of software systems for implementing such a sequence both within highly integrated problem-solving environments and in the form of loosely integrated pipelines. Loose integration in this case indicates that individual programs function largely independently but communicate through files of a common format and support simple scripting, so as to automate multiple executions wherever possible. We then describe three specific applications of such pipelines to translational biomedical research in electrophysiology

Development and verification of an endogenous PBPK model to inform hydrocortisone replacement dosing in children and adults with cortisol deficiency

The goal of hormone replacement is to mirror physiology. Hydrocortisone granules and modified release formulations are being developed to optimise cortisol replacement in the rare disease of adrenal insufficiency. To facilitate clinical development, we built and verified a physiologically based pharmacokinetic (PBPK) model for the endogenous hormone cortisol (hydrocortisone) in healthy adults, and children and adults with adrenal insufficiency. The model predicted immediate-release hydrocortisone pharmacokinetics in adults across the dose range 0.5 to 20 mg, with predicted/observed AUCs within 0.8 to 1.25-fold. The model also tightly predicted pharmacokinetic parameters for modified-release formulations, with AUCs within 0.8 to 1.25-fold after single and multiple dosing. Predicted modified-release formulation pharmacokinetics (PK) in 12 to 18-year olds showed PK to be similar to adults. This hydrocortisone PBPK model is a useful tool to predict adult and paediatric pharmacokinetics of both immediate- and modified-release hydrocortisone formulations, and develop clinical dosing regimens

Adrenal insufficiency in young children : a mixed methods study of parents' experiences

Research into adrenal insufficiency (AI) and congenital adrenal hyperplasia (CAH) in children has focused largely on clinical consequences for patients; and until recently, the wider experience of the condition from the perspective of other family members has been neglected. In a mixed methods study, we captured the experiences of parents of young children affected by AI/CAH, including their views on the psychosocial impact of living with and managing the condition. Semi-structured interviews were carried out in the UK and an online survey was developed, translated and disseminated through support groups (UK and the Netherlands) and outpatient endocrinology clinics (Germany). Challenges associated with diagnosis, treatment, support and the future were identified. For UK parents, the diagnosis period was characterised by a lack of awareness amongst healthcare professionals and occurrences of adrenal crisis. Parents reported burden, anxiety and disruption associated with the intensive treatment regimen. Parents adjusted and gained confidence over time yet found delegating responsibility for medication difficult and worried about the future for their child. Access to psychological support and contact with other families was reported as highly beneficial. The findings of the study provide critical context for future studies and for informing how parents and families can be better supported. Prenatal genetic counselling for parents who already have an affected child will include an explanation of recurrence risk but should also focus on providing information and reassurance about diagnostic testing and care for their newborn

Pore-scale Modeling of Viscous Flow and Induced Forces in Dense Sphere Packings

We propose a method for effectively upscaling incompressible viscous flow in large random polydispersed sphere packings: the emphasis of this method is on the determination of the forces applied on the solid particles by the fluid. Pore bodies and their connections are defined locally through a regular Delaunay triangulation of the packings. Viscous flow equations are upscaled at the pore level, and approximated with a finite volume numerical scheme. We compare numerical simulations of the proposed method to detailed finite element (FEM) simulations of the Stokes equations for assemblies of 8 to 200 spheres. A good agreement is found both in terms of forces exerted on the solid particles and effective permeability coefficients

Glucocorticoids regulate AKR1D1 activity in human liver in vitro and in vivo

Steroid 5β-reductase (AKR1D1) is highly expressed in human liver where it inactivates endogenous glucocorticoids and catalyses an important step in bile acid synthesis. Endogenous and synthetic glucocorticoids are potent regulators of metabolic phenotype and play a crucial role in hepatic glucose metabolism. However, the potential of synthetic glucocorticoids to be metabolised by AKR1D1 as well as to regulate its expression and activity has not been investigated. The impact of glucocorticoids on AKR1D1 activity was assessed in human liver HepG2 and Huh7 cells; AKR1D1 expression was assessed by qPCR and Western blotting. Genetic manipulation of AKR1D1 expression was conducted in HepG2 and Huh7 cells and metabolic assessments were made using qPCR. Urinary steroid metabolite profiling in healthy volunteers was performed pre- and post-dexamethasone treatment, using gas chromatography-mass spectrometry. AKR1D1 metabolised endogenous cortisol, but cleared prednisolone and dexamethasone less efficiently. In vitro and in vivo, dexamethasone decreased AKR1D1 expression and activity, further limiting glucocorticoid clearance and augmenting action. Dexamethasone enhanced gluconeogenic and glycogen synthesis gene expression in liver cell models and these changes were mirrored by genetic knockdown of AKR1D1 expression. The effects of AKR1D1 knockdown were mediated through multiple nuclear hormone receptors, including the glucocorticoid, pregnane X and farnesoid X receptors. Glucocorticoids down-regulate AKR1D1 expression and activity and thereby reduce glucocorticoid clearance. In addition, AKR1D1 down-regulation alters the activation of multiple nuclear hormone receptors to drive changes in gluconeogenic and glycogen synthesis gene expression profiles, which may exacerbate the adverse impact of exogenous glucocorticoids