Use of endogenous, stable lead isotopes to determine release of lead from the skeleton.

The stable lead isotope methodology can be used to study the release of lead from bone into the circulation because of its potential to distinguish circulatory lead from "older" and isotopically different skeletal lead that may have been accumulated years or decades earlier. Here we report the initial results from a larger ongoing study that evaluates the skeleton as a source of lead to the circulation in environmentally exposed human subjects. Lead concentrations and stable lead isotopic compositions were measured in blood and trabecular bone samples obtained from five patients who underwent total hip or knee joint replacement. All subjects contained low blood (1-6 micrograms/dl) and bone (0.6-7 micrograms/g dry weight) lead concentrations typical of environmentally exposed individuals. There were relatively large differences in the lead isotopic compositions between the paired blood and bone samples from each subject. These isotopic differences are attributed to differences in the lead isotopic compositions of past versus current lead exposures and to the long elimination half-life of lead in the skeleton compared to lead in the circulation. Based on these data, we determined that the skeleton contributed 40-70% of the lead in the blood of these subjects. This initial study demonstrates the utility of the stable lead isotope methodology for investigating the release of lead from the skeleton. It also shows that the skeleton can be an important endogenous source of lead exposure in environmentally exposed humans.     

Criteria for definition of overweight in transition: background and recommendations for the United States

Overweight and obesity are leading nutrition-related disorders of clinical and public health concern. Assessment and classification of these conditions are dependent on specific body mass index (BMI; in kg/m(2)) cutoff points. US government agencies are making the transition to a revised BMI definition of overweight from that previously recommended for general use. The purpose of this article is to inform the broader medical and scientific communities of the transition that is underway in the United States to identify and classify overweight among adults by using BMI. Historical background on the use of BMI in a variety of applications, as reported in US federal government agency documents, provides an understanding of previous and current weight-for-height guidelines and the basis for arriving at them. On the basis of the current Dietary Guidelines for Americans, US government agencies are moving toward the use of criteria for overweight and obesity that are consistent with current international standards. Clinicians, researchers, and journal editors should be aware of the transition toward a common definition of healthy weight, overweight, and obesity. To facilitate comparisons and reporting of data, others are encouraged to consider making this transition as well.     

Principles of Anesthesia Monitoring—Body Temperature

In this article we discuss the importance of monitoring body temperature. Some effects of hypothermia are covered, along with the benefits of careful monitoring. Also discussed are the basic use and application of the most common monitoring methods, as well as the methods we used to help maintain body temperature.     

Aging and brain fitness (Commentary on Voelcker‐Rehage et al.)

The human extrastriate visual cortex contains functionally distinct regions where neuronal populations exhibit signals that are selective for objects. How such regions might play a causal role in underpinning our ability to recognize objects across different viewpoints remains uncertain. Here, we tested whether two extrastriate areas, the lateral occipital (LO) region and occipital face area (OFA), contained neuronal populations that play a causal role in recognizing two‐dimensional shapes across different rotations. We used visual priming to modulate the rotation‐sensitive activity of neuronal populations in these areas. State‐dependent transcranial magnetic stimulation (TMS) was applied after the presentation of a shape and immediately before a subsequent probe shape to which participants had to respond. We found that TMS applied to both the LO region and OFA modulated rotation‐invariant shape priming but, whereas the LO region was modulated by TMS for small rotations, the OFA was modulated for larger rotations. Importantly, our results demonstrate that a node in the face‐sensitive network, the OFA, participates in causally relevant encoding of non‐face stimuli.     

The effects of age categorization on estimates of overweight prevalence for children

OBJECTIVE: The objective of this study is to investigate the effects of methods of age grouping on estimates of overweight prevalence for children and adolescents based on reference body mass index (BMI) percentiles. METHODS: Data for children aged 6-17 y came from three nationally representative US surveys, the Third National Health and Nutrition Examination Survey (1988-1994) and Cycles II and III of the National Health Examination Survey (1963-1965, 1966-1970). Month-specific BMI percentile values were taken from the revised US growth charts. Ages were grouped into categories 3, 6 or 12 months in length. Cut-off points were selected as the low or the mean percentile value within the category. Overweight prevalences for these groupings were compared with prevalences calculated using the month-specific values. RESULTS: The effects of grouping and cut-off point selection on overweight prevalence estimates were generally small; however, the combination of 12 month groupings and the low value led to an overestimation by up to 3 percentage points. Within the 12 month groupings, the first 6 months differed systematically from the second 6 months. CONCLUSIONS: Although age categorization may often have little effect on prevalence estimates, prevalence may sometimes be overestimated by as much as 3 percentage points. Use of narrower age categorizations than those used to construct the reference values may result in systematic biases. It is important to understand how age was handled in the construction of the reference population and to select age categories consistent with those used for the reference population.