A new method for calculation of height centiles for preadolescent children.

A new method of calculation of cross-sectional attained height centiles is proposed. This exploits the variance-stabilizing transformation, which has the form log(a+b height) up to age 11 years. Residuals of transformed height about the expected value for age are antilogged to give a single Gaussian distribution from which centiles can be calculated. In contrast to previous methods the standard errors of the centiles can be estimated without imprecise adjustment for smoothing. The parameters a and b of the transformation do not need precise estimation and the method can be used for population subgroups from which large samples cannot be obtained.     

Long-term variation of urinary albumin excretion in insulin-dependent diabetes mellitus: some practical recommendations for monitoring microalbuminuria

Seven measurements of albumin excretion in overnight, recumbent (OR) and daytime, ambulant (DA) urine samples were carried out at successive intervals of 3 months in 172 insulin-dependent diabetic patients; at entry into the study, all had a resting albumin excretion rate less than 300 micrograms/min. Urinary albumin excretion in both collections was expressed as a concentration (UA, mg/l), as a creatinine ratio (UA/UC, mg/mmol) and as an excretion rate (UAV, micrograms/min). The pooled within-subject standard deviation (log. (base e) transformed data) for each expression of the albumin excretion was: (1) OR sample--UA 0.6824 mg/l, UA/UC 0.5257 mg/mmol, UAV 0.5940 micrograms/min; (2) DA sample--UA 0.7830 mg/l, UA/UC 0.5780 mg/mmol, UAV 0.6334 micrograms/min. The results were used to calculate the 95% range for a difference between two measurements within an individual patient which was lowest with OR UA/UC (chi/divided by 4.42) and highest with the DA UA (chi/divided by 9.16). Variation in the OR sample was also studied in terms of the patterns of microalbuminuria (M; UAV greater than 15 micrograms/min) which were found to be closely associated with the initial level of albumin excretion: persistent non-M was most common in patients with a baseline UAV less than 15 micrograms/min; established M was most common in those with a baseline UAV greater than 70 micrograms/min, some of whom developed clinical albuminuria. The frequency with which patients should be re-screened for M may be determined by the initial value of albumin excretion and by the threshold used to define M.     

Exercise primes a molecular memory for brain-derived neurotrophic factor protein induction in the rat hippocampus

Exercise is an important facet of behavior that enhances brain health and function. Increased expression of the plasticity molecule brain-derived neurotrophic factor (BDNF) as a response to exercise may be a central factor in exercise-derived benefits to brain function. In rodents, daily wheel-running exercise increases BDNF gene and protein levels in the hippocampus. However, in humans, exercise patterns are generally less rigorous, and rarely follow a daily consistency. The benefit to the brain of intermittent exercise is unknown, and the duration that exercise benefits endure after exercise has ended is unexplored. In this study, BDNF protein expression was used as an index of the hippocampal response to exercise. Both daily exercise and alternating days of exercise increased BDNF protein, and levels progressively increased with longer running duration, even after 3 months of daily exercise. Exercise on alternating days was as effective as daily exercise, even though exercise took place only on half as many days as in the daily regimen. In addition, BDNF protein remained elevated for several days after exercise ceased. Further, after prior exercise experience, a brief second exercise re-exposure insufficient to cause a BDNF change in naïve animals, rapidly reinduced BDNF protein to levels normally requiring several weeks of exercise for induction. The protein reinduction occurred with an intervening “rest” period as long as 2 weeks. The rapid reinduction of BDNF by an exercise stimulation protocol that is normally subthreshold in naïve animals suggests that exercise primes a molecular memory for BDNF induction. These findings are clinically important because they provide guidelines for optimizing the design of exercise and rehabilitation programs, in order to promote hippocampal function.     

Positron emission tomography scan to determine the need for neck dissection after chemoradiation for head and neck cancer: timing is everything

We present a case of a negative positron emission tomography (PET) scan in a patient with pathologic viable cancer at neck dissection. STUDY DESIGN: Case Report. METHODS: A 69-year-old man presented with clinical stage T2N2c squamous cell cancer of the left tonsil and was treated with definitive chemoradiation. Left-sided adenopathy decreased but remained palpable after therapy. RESULTS: PET scan performed 23 days after completion of treatment showed no suspicious uptake in the left neck. Neck dissection performed at 2 months post-therapy revealed viable tumor in left cervical nodes. CONCLUSIONS: Persistent adenopathy after chemoradiation for head and neck cancer remains a clinical dilemma. A negative PET scan is accurate but only if the scan is performed 3 to 4 months after therapy.     

Bone density at the os calcis: reference values, reproducibility, and effects of fracture history and physical activity

Aims: To establish reference values for bone mineral density (BMD) measured at the os calcis (OC) in healthy UK Caucasian children. Secondary objectives were to assess the reproducibility of the measurement and the effects of fracture history and habitual physical activity. Methods: A total of 403 children aged 5–18 were studied. Main outcome measures were: BMDOC measured by peripheral DXA, total BMD measured by whole body axial scanner, age, anthropometry, pubertal status, self-reported fracture history, and physical activity (PA) expressed as a three point score. Results: Complete data were available on 171 girls and 123 boys free of a history of fracture. BMDOC was related positively to age, body size, and total BMD, and could be predicted using a proportional model based on height alone (R²: 65% girls, 77% boys). Mean BMDOC appears to plateau in girls at 15 years and attain a value that concurs with the mean peak value in adult women. The 95% limits of agreement in repeated measures were –0.029 to 0.029 g/cm² (n = 53). Compared with sedentary children, those doing regular sports or PA for more than five hours a week had an increased BMDOC (by about 0.03 g/cm² or about 7% of the overall mean). A history of fracture (n = 81) was associated with a reduced BMDOC in boys but not in girls, though our study may have been underpowered for a subgroup analysis. Conclusions: BMDOC can be measured easily and quickly in children older than 5 years and provides an objective measure of areal bone density for clinical and research studies using a reference range derived from its relation to height.