Dual-energy X-ray absorptiometry (DXA) to measure bone mineral density (BMD) for diagnosis of osteoporosis - experimental data from artificial vertebrae confirms significant dependence on bone size.

Introduction: The WHO definition of osteoporosis, and published BMD (Bone Mineral Density) references ranges, do not consider differences in bone size. Because it is a two-dimensional technique, and cannot measure bone depth, aBMD (areal BMD) measured using DXA (Dual-energy X-Ray Absorptiometry) is affected by bone size variability. Mathematical models have been devised to correct aBMD for bone size, but these are confounded by variations in soft tissue surrounding bone. Confirmation of the actual quantitative effect on clinical results for patients requires precise changes in bone size and mineral density, but studies of humans and animals are limited by the inability to precisely control these in natural bones. Purpose: The objectives of this experiment were to obtain precise, repeatable, quantitative data from sets of artificial vertebrae to confirm the dependence of aBMD on bone size in clinical practice, and to test the effect of applying corrections based on assumptions that the vertebrae were simple geometric shapes to produce corrected BMAD (Bone Mineral Apparent Density). Methods and materials: Four sets of artificial bones, each set containing four cylinders of different diameters but identical in height, were constructed by casting a mixture of epoxy resin and calcium carbonate powder into a mould. The cylinders were considered to be artificial vertebrae L1 to L4 so that all four in a set may be tested in a single scan. The X-Ray attenuation of the material used was varied between the sets, to represent differences in BMD. Each set of vertebrae was inserted into a soft-tissue analogue and DXA scanned, in the anteroposterior position, with the GE Lunar Prodigy and the Hologic Discovery. Results: The results verify the theoretical direct proportionality between aBMD and diameter, confirming that aBMD is significantly affected by bone size. Applying a BMAD correction, by assuming the vertebrae to be cylinders, reduced the effect of change in bone diameter by approximately two orders of magnitude to an insignificant level. Conclusion: This experiment has confirmed that BMD measured using DXA, accepted in clinical practice as the "gold standard" means of diagnosing osteoporosis, could lead to misdiagnosis because it is significantly affected by differences in bone size.

The early biopsychosocial development of boys and the origins of violence in males.

We apply a biopsychosocial approach to introduce early-in-life experiences that explain a significant part of the male preponderance in the perpetration of violence. Early caregiver abuse and neglect, father absence, and exposure to family and neighborhood violence exacerbate boys' greater risk for aggressive behavior and increase the probability of carrying out violent acts later in life. We examine the development of the psychological self and explore conditions that encourage physical aggression, focusing on the impact on the infant and toddler's emergent mental representation of self, others, and self-other relationships. Boys' slower developmental timetable in the first years of life may enhance their vulnerability for disorganization in emergent neurobiological networks mediating organization of socioemotional relationships. Emergent attachment and activation relationship systems may differentially affect risk and resilience in boys and girls, particularly in single-parent families. Evidence has suggested that the dramatic increase in single-parent families is especially linked to corresponding increases in behavioral undercontrol, antisocial behavior, and the emergence of violence in boys.

Experimental folate deficiency in human subjects: what is the influence of vitamin C status on time taken to develop megaloblastic anaemia?

BACKGROUND: In 1962 Victor Herbert developed megaloblastic anaemia four months after commencing a severely folate-deficient diet whereas, in his self-experiment 50 years later, this author took 19 months to fully deplete his liver folate store. This author proposed that his own larger initial liver folate store, due to his vegetarian diet and consumption of fortified foods, was the cause of the time difference. MAIN TEXT: This author now proposes that Herbert was also likely to have been deficient in vitamin C, thus shortening the time taken to develop folate deficiency. Several human experiments have confirmed the role of vitamin C in protecting reduced forms of folate from oxidation. Although there has historically been no consensus on the required intake of vitamin C, and official recommendations set a level below that required to ensure plasma saturation, recent research supports an intake that would ensure saturation. There have been no longitudinal experiments on human subjects since the introduction of voluntary or mandatory folic acid fortification of food, and the few published models differ significantly in their estimates of human liver folate storage capacity. CONCLUSION: Because of the importance of folate in one-carbon metabolism, the potential influence of vitamin C intake on the time taken to deplete the liver folate store should be experimentally investigated.

PSYCHOLOGY OF BOYS AT RISK: INDICATORS FROM 0-5.

In utero and during the first 5 years of life, boys face unique risks as a result of neurobiological and environmental factors. This introductory article to the Special Issue describes the background of this gender-specific inquiry and outlines some of those risks, drawing attention to the areas that will be covered in depth in the following contributions. We also describe the basis of this inquiry as the link between early life and the subsequent difficulties that adolescent boys and many young men face, and pay particular attention to the circumstances of young men of color and to the growing knowledge about the contributions of fathers to boys' development.

Holotranscobalamin (HoloTC, Active-B12) and Herbert's model for the development of vitamin B12 deficiency: a review and alternative hypothesis.

The concentration of total vitamin B12 in serum is not a sufficiently sensitive or specific indicator for the reliable diagnosis of vitamin B12 deficiency. Victor Herbert proposed a model for the staged development of vitamin B12 deficiency, in which holotranscobalamin (HoloTC) is the first indicator of deficiency. Based on this model, a commercial immunoassay has been controversially promoted as a replacement for the total vitamin B12 test. HoloTC is cobalamin (vitamin B12) attached to the transport protein transcobalamin, in the serum, for delivery to cells for metabolism. Although there have been many published reports supporting the claims for HoloTC, the results of some studies were inconsistent with the claim of HoloTC as the most sensitive marker of vitamin B12 deficiency. This review examines the evidence for and against the use of HoloTC, and concludes that the HoloTC immunoassay cannot be used to measure vitamin B12 status any more reliably than total vitamin B12, or to predict the onset of a metabolic deficiency, because it is based on an erroneous hypothesis and a flawed model for the staged development of vitamin B12 deficiency. The author proposes an alternative model for the development of vitamin B12 deficiency.

Experimental vitamin B12 deficiency in a human subject: a longitudinal investigation of the performance of the holotranscobalamin (HoloTC, Active-B12) immunoassay.

Based on Victor Herbert's model for sequential stages in the development of vitamin B12 deficiency, the holotranscobalamin (HoloTC) immunoassay has controversially been promoted as a more specific and sensitive replacement for the total vitamin B12 test, for the diagnosis of deficiency. There have been no longitudinal studies, by means of experimental cobalamin deficiency, because ethical considerations prevent such risky studies on patients or healthy human volunteers. The objective was to provide a detailed record of the response of HoloTC, compared to total vitamin B12 and metabolites, to the development of experimental vitamin B12 deficiency in an initially replete human subject. This 54 year old male, with a vitamin B12 deficiency possibly caused by a defect in the intracellular cobalamin metabolism, ensured an initially replete condition by means of oral doses of cyanocobalamin supplements at 1000 µg/day for 12 weeks. The subject then depleted himself of vitamin B12, by withholding treatment and using a low-cobalamin diet, until significant metabolic disturbances were observed. The responses of serum total vitamin B12 and HoloTC and the two metabolites, plasma methylmalonic acid and homocysteine, were monitored by weekly blood tests. HoloTC was not significantly more sensitive than either total serum vitamin B12 or total homocysteine, and was much less sensitive than methylmalonic acid. HoloTC decreased from an initial concentration of >128 pmol/L to a minimum of 33 pmol/L on day 742, the only day on which it fell below the lower limit of the reference interval. Total vitamin B12 decreased from an initial concentration of 606 pmol/L to a minimum of 171 pmol/L on day 728. Total homocysteine increased from an initial concentration of 8.4 µmol/L to a maximum of 14.2 µmol/L on day 609. Methylmalonic acid unexpectedly contained four distinct peaks; initially at 0.17 µmol/L, it first exceeded the upper limit of the reference interval on day 386, finally reaching a maximum peak of 0.90 µmol/L on day 658. The results of this experiment are inconsistent with Herbert's hypothesis that HoloTC is the earliest marker of vitamin B12 deficiency, and therefore do not support his model for the staged development of vitamin B12 deficiency.

Severe experimental folate deficiency in a human subject - a longitudinal investigation of red-cell folate immunoassay errors as megaloblastic anaemia develops.

BACKGROUND: The few published studies comparing results between commercial red-cell folate immunoassays have found significant differences. None have provided longitudinal data during the development of megaloblastic anaemia from severe folate deficiency. The objective was to produce longitudinal data, comparing results between three commercial immunoassays for red-cell folate, generated by means of severe experimental folate deficiency. METHODS: This 58 year old male, initially replete in folate, used a folate-deficient diet to severely deplete himself of folate until overt megaloblastic anaemia developed. The Siemens Advia Centaur, Roche Elecsys 2010 and Beckman UniCel DxI 800 Access immunoassay systems were used, by different clinical pathology laboratories, to perform weekly assays for red-cell folate throughout the depletion stage. The results were analysed graphically four ways: comparison with lines of equality; number of standard deviations difference against the means; number of standard deviations difference over time; variation over time. RESULTS: There were very significant differences, varying with time and folate concentration, between the results reported by the three laboratories. The differences were greatest, up to 17 standard deviations, between the Siemens Advia Centaur and each of the other two systems. Of the 85 results comparing the Siemens Advia Centaur and the Roche Elecsys 2010, two were within the 99.9% confidence interval. Of the 91 results comparing the Siemens Advia Centaur and the Beckman UniCel DxI 800 Access, 22 were within the 99.9% confidence interval. Of the 83 results comparing the Beckman UniCel DxI 800 Access and the Roche Elecsys 2010, 37 were within the 99.9% confidence interval. CONCLUSIONS: Comparative longitudinal data from clinical pathology laboratories, produced during experimental folate deficiency, have exposed very significant differences in results between commercial red-cell folate immunoassays. One immunoassay, the Roche Elecsys 2010, failed to detect overt megaloblastic anaemia of severe folate deficiency.

Severe experimental folate deficiency in a human subject - a longitudinal study of biochemical and haematological responses as megaloblastic anaemia develops.

BACKGROUND: The currently accepted theory, that the human liver store of folate is limited to about four months, is based on the findings of Victor Herbert and others of the era before folate fortification of food. A recent model, developed by Lin et al., predicts far greater liver folate storage capacity than reported by Herbert. The conflict between Herbert's and Lin's models needs to be resolved experimentally, however current research is restricted because ethical considerations prevent such risky experimentation on patients or healthy human volunteers. The objective was to provide a detailed record of the biochemical and haematological responses to the development of severe experimental folate deficiency in an initially replete human subject. METHODS: This 58 year old male severely depleted himself of folate, using a folate-deficient diet, until overt megaloblastic anaemia developed. The biochemical and haematological responses were monitored by routine blood tests. Daily intake of dietary supplements prevented deficiencies of other relevant nutrients. RESULTS: The rate of change of all analytes was significantly slower, and the delay before any change for several analytes was significantly longer, than reported for previous experiments. The time before reporting of abnormal biochemical and haematological results was therefore very significantly longer than reported by Herbert, but was consistent with the recent model of Lin et al. Serum folate and red-cell folate became abnormally low after 219 and 413 days respectively. Macrocytic anaemia was produced after 469 days, and megaloblastic anaemia was confirmed by bone marrow biopsy on day 575. Folate starvation ceased on day 586, and recovery was complete on day 772. CONCLUSIONS: The currently accepted four month time scale for development of megaloblastic anaemia from folate deficiency, based on the early work of Herbert and others, is not consistent with the results from this study. The > 300 day liver folate storage time, predicted by the model of Lin et al., is supported by this experiment. Self-experimentation has produced a detailed record of the biochemical and haematological responses to severe experimental folate deficiency, whereas using patients or healthy volunteers as subjects would be unethical.