Cross-sectional and longitudinal analysis of bone age maturation during peri-pubertal growth in children with type I, III and IV osteogenesis imperfecta.

Osteogenesis imperfecta (OI)is a rare genetically heterogeneous disorder caused by changes in the expression or processing of type I collagen. Clinical manifestations include bone fragility, decreased linear growth, and skeletal deformities that vary in severity. In typically growing children, skeletal maturation proceeds in a predictable pattern of changes in the size, shape, and mineralization on the hand and wrist bones that can be followed radiographically known at the bone age. Assessment of bone age can be clinically used to assess time remaining for linear growth, and the onset and duration of puberty, both of which can be useful in determining the timing of some surgeries or the interpretation of other imaging modalities such as bone densitometry. Additionally, deviations in the expected maturation process of the bone age may prompt or assist in the work up of a significant delay or advancement in a child's growth pattern. The primary aim of our study was to determine whether the bone age in children with a skeletal disorder such as OI follow the same pattern and rate of bone maturation compared to a control population. Using participants from the Natural History Study of the Brittle Bone Disorders Consortium, we analyzed 159 left hand and wrist radiographs (bone age) for a cross-sectional analysis and 55 bone ages repeated at approximately 24 months for a longitudinal analysis of skeletal maturation. Bone ages were read by a pediatric endocrinologist and by an automated analysis using a program called BoneXpert. Our results demonstrated that in children with mild-to-moderate OI (types I and IV), the skeletal maturation is comparable to chronological age-mated controls. For those with more severe forms of OI (type III), there is a delayed pattern of skeletal maturation of less than a year (10.5 months CI 5.1-16) P = 0.0012) at baseline and a delayed rate of maturation over the two-year follow up compared to type I (P = 0.06) and type III (P = 0.02). However, despite these parameters being statistically different, they may not be clinically significant. We conclude the bone age, with careful interpretation, can be used in the OI population in a way that is similar to the general pediatric population.

Sodium-dependent copper uptake across epithelia: a review of rationale with experimental evidence from gill and intestine.

The paper reviews the evidence for apparent sodium-dependent copper (Cu) uptake across epithelia such as frog skin, fish gills and vertebrate intestine. Potential interactions between Na(+) and Cu during transfer through epithelial cells is rationalized into the major steps of solute transfer: (i) adsorption on to the apical/mucosal membrane, (ii) import in to the cell (iii) intracellular trafficking, and (iv) export from the cell to the blood. Interactions between Na(+) and Cu transport are most likely during steps (i) and (ii). These ions have similar mobilities (lambda) in solution (lambda, Na(+), 50.1; Cu(2+), 53.6 cm(2) Int. ohms(-1) equiv(-1)); consequently, Cu(2+) may compete equally with Na(+) for diffusion to membrane surfaces. We present new data on the Na(+) binding characteristics of the gill surface (gill microenvironment) of rainbow trout. The binding characteristics of Na(+) and Cu(2+) to the external surface of trout gills are similar with saturation of ligands at nanomolar concentrations of solutes. At the mucosal/apical membrane of several epithelia (fish gills, frog skin, vertebrate intestine), there is evidence for both a Cu-specific channel (CTR1 homologues) and Cu leak through epithelial Na(+) channels (ENaC). Cu(2+) slows the amiloride-sensitive short circuit current (I(sc)) in frog skin, suggesting Cu(2+) binding to the amiloride-binding site of ENaC. We present examples of data from the isolated perfused catfish intestine showing that Cu uptake across the whole intestine was reduced by 50% in the presence of 2 mM luminal amiloride, with 75% of the overall inhibition attributed to an amiloride-sensitive region in the middle intestine. Removal of luminal Na(+) produced more variable results, but also reduced Cu uptake in catfish intestine. These data together support Cu(2+) modulation of ENaC, but not competitive entry of Cu(2+) through ENaC. However, in situations where external Na(+) is only a few millimoles (fish gills, frogs in freshwater), Cu(2+) leak through ENaC is possible. CTR1 is a likely route of Cu(2+) entry when external Na(+) is higher (e.g. intestinal epithelia). Interactions between Na(+) and Cu ions during intracellular trafficking or export from the cell are unlikely. However, effects of intracellular chloride on the Cu-ATPase or ENaC indicate that Na(+) might indirectly alter Cu flux. Conversely, Cu ions inhibit basolateral Na(+)K(+)-ATPase and may increase [Na(+)](i).