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

Chronotherapy based on modified-release hydrocortisone to restore the physiological cortisol diurnal rhythm

In this inspirational note, we describe the development of an endocrine chronotherapy to restore the physiological rhythm of the essential adrenal stress hormone, cortisol. The challenges included demonstrating the circadian rhythm of the drug target, creating a drug formulation that replicated that rhythm and then proving benefit in clinical trials. The physiological cortisol circadian rhythm is well defined with cortisol levels high on waking and low on going to sleep. We experimented with different formulation technologies including modified-release tablets and multi-particulates to replicate the cortisol rhythm where absent through disease. We describe the development of Efmody®, a modified-release formulation of hydrocortisone, which replicates the cortisol diurnal rhythm and improves the disease control of congenital adrenal hyperplasia, the commonest hereditary form of adrenal insufficiency. This program shows it is possible, through modified-release technology, to treat chronic endocrine diseases with physiological replacement to preserve health for life

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

Salivary cortisone to estimate cortisol exposure and sampling frequency required based on serum cortisol measurements

Context: Population studies frequently measure cortisol as a marker of stress and excess cortisol is associated with increased mortality. Cortisol has a circadian rhythm and frequent blood sampling is impractical to assess exposure. We investigated measuring salivary cortisone and examined sampling frequency required to determine cortisol exposure. Methods: Serum and saliva with cortisol and cortisone measured by LC-MS/MS in independent cohorts. The relationship between serum cortisol and salivary cortisone was analysed in cohort 1 using a linear mixed effects model and resulting fixed effects component was applied to cohort 2. Saliva cannot easily be collected when sleeping so we determined minimum sampling required to estimate cortisol exposure (eAUC) using 24-hour cortisol profiles (AUC24) and calculated the relative error (RE - a measure similar to the coefficient of variation) for the eAUC. Results: >90% of variability in salivary cortisone could be accounted for by change in serum cortisol. A single serum cortisol measurement was a poor estimate of AUC24 especially in the morning or last thing at night (RE > 68%), however 3 equally spaced samples gave a median RE of 0% (Interquartile range (IQR) between -15.6% and 15.1%). In patients with adrenal incidentalomas the eAUC based on 3 serum cortisol samples showed a difference between those with autonomous cortisol secretion and those without (p=0.03). Interpretation: Accepting that most people sleep 7-8 hours, using approximately 8-hourly salivary cortisone measurements provides a non-invasive method of estimating 24-hour cortisol exposure for population studies