Height Velocity Curves Research Articles

Effects of I ,25-Dihydroxyvitamin-D3 on Renal Function, Mineral Balance, and Growth in Children with Severe Chronic Renal Failure

To confirm and extend previous observations of enhanced linear growth in children with chronic renal disease being treated with 1,25-dihydroxyvitamin- D3 and to characterize further the calcium, phosphorus, magnesium, and zinc disorders in renal failure, 11 children (mean age 8 ± 5 years) with chronic renal insufficiency (glomerular filtration rate 18% ± 13% of normal) were evaluated on the basis of their reciprocal serum creatinine concentrations, height-velocity curves, mineral balances, and radiologic findings. Reciprocal serum creatinine concentrations analyzed retrospectively and prospectively during 32 months of 1,25-dihydroxyvitamin-D3 therapy showed progression of renal failure at rates linearly identical with those before treatment, thus suggesting that the treatment did not accelerate the rate of deterioration of glomerular filtration rate in chronic renal insufficiency. Indeed, one patient manifested a lesser decline in renal function (P sjlt .05). The height velocity of six of the children (75%) less than 12 years of age improved markedly over that expected for chronologic and bone ages after one year of treatment with orally administered 1,25-dihydroxyvitamin-D3, 15 to 35 ng/kg/day. All other medications except vitamin D2 were continued at their pretreatment dosage levels throughout the study. Growth velocity was unimproved in two of three children older than 12 years at the initiation of 1,25-dihydroxyvitamin- D3 therapy. Mineral balance data showed significant retention of calcium, phosphorus, magnesium, and zinc (357 ± 32 mg/sq m/day, 250 ± 82 mg/sq m/day, 38 ± 32 mg/sq m/day, and 1,157 ± 283 µ/sq m/day, respectively), after treatment for 12 months. In addition, serum calcium, alkaline phosphatase, and parathyroid hormone concentrations returned toward normal. Finally, healing of renal osteodystrophy was radiologically evident after six months of therapy.

Band dispersion in high-performance exclusion chromatography

The dispersion of polymer samples eluted in the exclusion mode from columns of Hypersil and SG60F (a highly porous silica gel) has been measured for a range of polymer standards over a range of elution velocities and from columns of different lengths. From experiments with columns of different lengths operated at the same velocity, the polydispersities of the polymer standards were obtained and ranged from 1.007 to 1.052. From experiments at different linear velocities, mass transfer coefficients were obtained from which the ratio of the diffusion rates of polymers in bulk eluent to the diffusion rates within the silica gel matrix could be found. For Hypersil these ranged from ca. 6 for PS2K and PS4K (MW 2000 and 4000 respectively) to ca. 17 for PS33K (MW 33,000) indicating fairly severe restrictions to diffusion within the pores of the matrix especially for nearly excluded materials. Measurements with a pure oligomer of polystyrene (MW ≈ 3000) confirmed the validity of the above method of separating spreading effects of polydispersity and kinetics and gave a reduced plate height—velocity curve overlapping that for benzene. Measurements of spreading of excluded polymer samples indicated anomalous behaviour at low flow-rates and with long columns. Measurements of the loading capacity in exclusion chromatography showed that samples should not exceed ca. 1 μg per cm 3 of column packing if overloading is to be avoided. It is concluded that the dispersion of bands of polymers eluted in the exclusion mode from silica gels obeys the same kinetic relationships as the dispersion of bands in retentive chromatography. The study confirms, however, that the major contributor to the dispersion of polymer samples eluted in the exclusion mode is their polydispersity.

A critical analysis of the double and triple logistic growth curves.

Recently a model of human growth from the age of one year to maturity, based on two logistic terms, has been proposed. The originators of the model claim that it provides biologically meaningful parameters, and allows total growth to be partitioned into a pre-pubertal and an adolescent component. More recently, they have suggested an improved model, with three logistic terms, which gives a better fit. While the double logistic model gives an adequate fit to the observed height curve, differentiating it leads to a height velocity curve which differs considerably from the observed velocity curve. The triple logistic model gives an excellent fit to both the attained height and height velocity curves. Both models, however, imply a considerable time interval during which both the pre-pubertal and adolescent components are simultaneously contributing to growth, a situation that is difficult to justify biologically. The double model should therefore be discarded, and the triple logistic model considered to be of descriptive, rather than of interpretative, value.

Height and weight growth patterns of school age deaf children.

AbstractDistance and velocity curves for height and weight were analyzed in a mixed longitudinal sample of American White, American Negro and Mexican‐American deaf children 6 through 17 years of age. The heights of deaf boys and girls are, on the average, consistently below an accepted pediatric standard from six through ten years of age. Between 11 and 17 years, deaf White and Negro boys approximate the standard, while White and Negro girls are at or slightly below the standard. Deaf Mexican‐American children are consistently below the height standard. For body weight, deaf boys are at or slightly below the standard from 6 to 11 years, and are at or slightly above the weight standard from 12 to 17 years of age. White and Negro deaf girls generally approximate the weight standard from eight years of age on. Mexican‐American deaf girls are consistently below the standard until 13 years of age, while between 14 and 17 years they are at or above the standard. Height and weight velocity curves for deaf children parallel closely the incremental standards of Falkner ('62). The height velocity curve, however, appears to peak, on the average, about one year earlier in deaf children.