Neutron activation analysis determination of body composition

Antimicrobial Dosing in Specific Populations and Novel Clinical Methodologies: Obesity

Obesity and its related comorbidities can negatively influence the outcomes of certain infectious diseases. Specific dosing recommendations are often lacking in the product label for patients with obesity that leads to unclear guidance in practice. Higher rates of therapeutic failure have been reported with some fixed dose antibiotics and pragmatic approaches to dose modification are limited for orally administered agents. For i.v. antimicrobials dosed on weight, alternate body size descriptors (ABSDs) have been used to reduce the risk of overdosing. These ABSDs are mathematical transformations of height and weight that represent fat-free weight and follow the same principles as body surface area (BSA)-based dosing of cancer chemotherapy. However, ABSDs are rarely studied in pivotal phase III studies and so can risk the underdosing of antimicrobials in patients with obesity when incorrectly applied in the real-world setting. Specific case examples are presented to highlight these risks. Although general principles may be considered by clinicians, a universal approach to dose modification in obesity is unlikely. Studies that can better distinguish human body phenotypes may help reduce our reliance on height and weight to define dosing. Simple and complex technologies exist to quantify individual body composition that could improve upon our current approach. Early evidence suggests that body composition parameters repurposed from medical imaging data may improve upon height and weight as covariates of drug clearance and distribution. Clinical trials that can integrate human body phenotyping may help us identify new approaches to optimal dose selection of antimicrobials in patients with obesity.

Engineering approaches to energy balance and obesity: opportunities for novel collaborations and research: report of a joint national science foundation and national institutes of health workshop

Energy balance disorders account for a large public health burden. The obesity epidemic in particular is one of the most rapidly evolving public health problems of our day. At present, two-thirds of American adults and one-sixth of American children and adolescents are considered either overweight or obese. Public health concern about obesity is high because of the increased risk and increased mortality of cardiovascular disease, Type 2 diabetes, many forms of cancer, gallbladder disease, and osteoarthritis. These risks increase with the severity of the obesity. Excess adipose tissue, representing fat storage, ultimately derives from an imbalance between energy intake and energy expenditure. Conversely, undesirable and inadvertent loss of body weight and muscle mass, as seen in aging and cachectic states of chronic diseases such as heart failure and cancer, have serious clinical and functional consequences without satisfactory clinical or behavioral solutions. Innovative engineering technologies could help to address unresolved problems in energy balance, intake, and expenditure. Novel sensors, devices, imaging technologies, nanotechnologies, biomaterials, technologies to detect biochemical markers of energy balance, mathematical modeling, systems biology, and other approaches could be developed, evaluated, and leveraged through multidisciplinary collaborations. Engineers, physical scientists, and mathematicians can work with scientists from other relevant disciplines who possess expertise in obesity and nutrition. Furthermore, the possibility of re-engineering the "built environment" to encourage higher levels of physical activity has been suggested as another promising and important approach to which engineers can contribute (see http://www.obesityresearch.nih.gov). Ultimately, systematic application of the "Engineering Approach" can help in developing the needed technologies and tools to facilitate research and eventually support therapeutic advances and behavioral change. This article summarizes important public health concerns related to disordered energy balance and describes research priorities identified at a recent National Science Foundation-National Institutes of Health workshop. Research funding opportunities are described as posted on the NIH Guide to Grants and Contracts (see http://www.nih.gov/grants/guide).

Monte Carlo simulation of neutron irradiation facility developed for accelerator based in vivo neutron activation measurements in human hand bones

The neutron irradiation facility developed at the McMaster University 3 MV Van de Graaff accelerator was employed to assess in vivo elemental content of aluminum and manganese in human hands. These measurements were carried out to monitor the long-term exposure of these potentially toxic trace elements through hand bone levels. The dose equivalent delivered to a patient during irradiation procedure is the limiting factor for IVNAA measurements. This article describes a method to estimate the average radiation dose equivalent delivered to the patient's hand during irradiation. The computational method described in this work augments the dose measurements carried out earlier [Arnold et al., 2002. Med. Phys. 29(11), 2718-2724]. This method employs the Monte Carlo simulation of hand irradiation facility using MCNP4B. Based on the estimated dose equivalents received by the patient hand, the proposed irradiation procedure for the IVNAA measurement of manganese in human hands [Arnold et al., 2002. Med. Phys. 29(11), 2718-2724] with normal (1 ppm) and elevated manganese content can be carried out with a reasonably low dose of 31 mSv to the hand. Sixty-three percent of the total dose equivalent is delivered by non-useful fast group (> 10 keV); the filtration of this neutron group from the beam will further decrease the dose equivalent to the patient's hand.

Bone resorption in anorexia nervosa and rehabilitated patients

OBJECTIVE

To assess the impact of anorexia nervosa and that of nutritional rehabilitation on bone resorption.

DESIGN

Cross-sectional, observational study.

SETTING

Rome, Italy

SUBJECTS

Twenty-eight female patients affected by anorexia nervosa (AN, BMI<or=17.0 kg/m(2)), 18 females rehabilitated from anorexia nervosa and weight-stable for at least 6 months (RE, BMI >or=18.5 kg/m(2)) and 34 age- and sex-matched healthy controls (CO, BMI >or=18.5 kg/m(2)). Among AN patients, 16 were affected by the 'restrictive' (ANr) and 12 by the 'purging' type (ANp) of anorexia nervosa.

METHOD

Body weight, height and skeletal diameters were measured on each individual. The skeletal mass (SKM) was predicted from the skeletal diameters of the elbow, wrist, knee and ankle, using the equation of Martin. Twenty-four-hour urinary excretion of pyridinium crosslinks of collagen (pyridinoline (Pyd) and deoxypyridinoline (Dpd)) and creatinine was assessed by reversed-phase HPLC with fluorimetric detection after solid-phase extraction and by the Jaffé-method with deproteinization, respectively.

RESULTS

Twenty-four-hour urinary output of Pyd and Dpd was not significantly different between AN and CO when expressed in absolute values, but AN showed higher bone resorption than CO when Pyd and Dpd excretion was adjusted by either creatinine (P<0.0000) or the SKM (P<0.05). Within the AN group, urinary excretion of both cross-links was significantly and consistently higher in ANp compared with ANr (P<0.05). However, these differences disappeared when crosslink output was adjusted either by urinary creatinine or SKM. RE subjects showed no differences in bone resorption with the AN group despite weight gain, being crosslink excretion consistently elevated compared to controls (Pyd: P<0.01 by creatinine and P<0.05 by SKM; Dpd: P<0.01 by creatinine and P<0.05 by SKM).

CONCLUSION

Bone resorption is elevated in anorexia nervosa and different strategies for low-weight maintenance do not seem to have a differential impact. Increased bone resorption persists in subjects with past diagnosis of anorexia nervosa despite rehabilitation lasting more than 6 months. This finding indicates that bone mass and turnover should be monitored in anorexia nervosa patients and ex-patients well beyond recovery of normal body mass. Further investigation is warranted to examine the long-term effect of such prolonged increase in bone turnover at a young age.