Determinants of the energy costs of light activities: inferences for interpreting doubly labeled water data.

OBJECTIVE: To investigate the controversy regarding the means of adjusting the energy cost of physical activity measured by doubly labeled water for differences in body size. DESIGN: We performed a cross-sectional study of the energy costs of carefully reproduced light activities with careful control for fidgeting and other unnecessary movement. SUBJECTS: :The study was performed in 23 healthy, young to middle aged adults with body masses between 39 and 118 kg. MEASUREMENTS: Energy expenditure was measured by respiratory gas exchange while subjects performed controlled light activities representative of activities of daily life. Body composition was measured by bioelectrical impedance analysis. RESULTS: The energy costs of individual controlled light activities were proportional to body weight except for mock vacuum cleaning. When the energy costs of all five activities were taken together, allometric regression analysis indicated that the energy cost of these light activities was proportional to body weight (slope=0.88+/-0.07), but not to fat-free mass (1.24+/-0.10), fat mass (0.27+/-0.03) or resting metabolic rate (1.43+/-0.12). CONCLUSION: Normalization of energy expenditure of physical activity by division by body weight is an appropriate means for comparing the volume (intensity x time) of physical activity between individuals of different body size.     

When the negative is positive

In this issue of Blood, Hosking and colleagues report the lack of correlation between genetic variants within the MHC and the risk of ALL.     

Development of pituitary-adrenal endocrine function in the marmoset monkey: infant hypercortisolism is the norm

Early life stress, involving activation of the hypothalamic-pituitary-adrenal (HPA) system, is associated with altered functioning of stress-related systems in adulthood. In the rat, postnatal development is characterized by low basal HPA activity and stress hyporesponsiveness, and infant exposure to atypical glucocorticoid levels leads to chronic alteration of HPA function and HPA-dependent peripheral and central processes. There have been few studies of primate HPA ontogeny, and here we report a study of changes in pituitary-adrenal function between birth and adulthood in the common marmoset monkey. In this simian primate, basal plasma ACTH and cortisol levels were actually elevated in neonates (ACTH, 141 +/- 28 pg/ml; cortisol, 1903 +/- 326 microg/dl) and wk 4 infants (ACTH, 114 +/- 9 pg/ml; cortisol, 290 +/- 8 microg/dl) relative to month 2 infants, juveniles (month 6), subadults (month 12), and adults (>2 yr; ACTH, 37 +/- 4 to 61 +/- 8 pg/ml; cortisol, 101 +/- 2 to 195 +/- 4 microg/dl). In contrast to older life stages, neonates lacked circadian change in their plasma cortisol levels, and this state of consistently high cortisol was associated with large adrenal glands in addition to high ACTH levels. Cerebrospinal fluid cortisol levels were, in accord with plasma levels, higher in wk 4 infants than in juveniles and subadults. In terms of stress response, month 2 infants demonstrated ACTH and cortisol peak stress responses similar to those at older life stages (infant stress cortisol, 185 +/- 36% of basal; subadult stress cortisol, 174 +/- 6% of basal); whereas infant ACTH recovery was also similar to that in older subjects, their cortisol poststress recovery was retarded. This primate, it is proposed, provides an excellent complementary model in which to test hypotheses derived from the rat model relating to HPA system ontogeny and the chronic effects and biomedical implications of hypercorticoidism during early life.     

Carotid stenting or carotid surgery in average surgical-risk patients: interpreting the conflicting clinical trial data

There are generic as well as carotid-specific trial design considerations that have the potential to materially affect the outcomes and interpretation of comparative studies between carotid artery stenting and carotid endarterectomy. Recently, a series of trials in patients who are at average risk for carotid surgery have been reported. The European trials have all suffered from allowing an imbalance in operator experience between stenting and surgery and have consistently allowed stenting procedures without embolic protection. The combination of inexperienced operators and lack of embolic protection may be responsible for their negative stenting results. The Carotid Revascularization with Endarterectomy vs. Stenting Trial avoided both of these problems, having a threshold of experience for operators as well as mandating embolic protection be used. The Carotid Revascularization with Endarterectomy vs. Stenting Trial demonstrated noninferiority for stenting compared with surgery in average-risk symptomatic and asymptomatic patients, leading to Food and Drug Administration approval of a stent and protection for this indication. This has been recently followed by guidelines supporting the role of stenting compared with surgery from a broad range of professional societies.     

When premature is not premature--the ASCOT study.

‘Controversy is the Lifeblood of Science’

SirGeorge Pickering¹

Almost 3 years ago, in the aftermath ofthe ALLHAT study,² the New York Times was carrying the headlines‘Older way to treat hypertension found best’.³ ALLHAT,the largest study ever done, showed no difference in primaryoutcome (coronary heart disease) among the three treatment armsbut seemed to favour chlorthalidone over amlodipine or lisinoprilwith regard to some secondary endpoints. Clearly, these headlineswill need to be amended in view of the