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Reanalyzed data from Goodman's 1965 study of whether increased reading fluency related to increased dependence on context in the process of word recognition and repeated Goodman's procedure with first-third graders. Results found that reading fluency was not significantly associated with context use, though third graders improved significantly more in the context condition than first graders. (SM)

The partitioning of whole body carbon flux between fat and lean compartments affects body composition. We hypothesized that it is possible to simultaneously determine whole body carbon (energy) balance and the dynamics of lipids and proteins in specific tissues in vivo. Growing C57BL/6J mice fed a high-fat low-carbohydrate diet were injected with a bolus of 'doubly labeled' water (i.e., [sup.2][H.sub.2]O and [H.sub.2][sup.18]O). The rate of C[O.sub.2] production was determined from the difference between the elimination rates of [sup.2]H and [sup.18]O from body water. The rates of synthesis and degradation of triglycerides extracted from epididymal fat pads and of proteins extracted from heart muscle were determined by mathematically modeling the [sup.2]H labeling of triglyceride-bound glycerol and proteinbound alanine, respectively. We found that mice were in positive carbon balance (~20% retention per day) and accumulated lipid in epididymal fat pads (~9 [micro]mol triglyceride accumulated per day). This is consistent with the fact that mice were studied during a period of growth. Modeling the [sup.2]H labeling of triglycerides revealed a substantial rate of lipid breakdown during this anabolic state (equivalent to ~25% of the newly synthesized triglyceride). We found equal rates of protein synthesis and breakdown in heart muscle (~10% of the pool per day), consistent with the fact that the heart muscle mass did not change. In total, these findings demonstrate a novel application of the doubly labeled water method. Utilization of this approach, especially in unique rodent models, should facilitate studies aimed at quantifying the efficacy of interventions that modulate whole body carbon balance and lipid flux while in parallel determining their impact on (cardiac) muscle protein turnover. Last, the simplicity of administering doubly labeled water and collecting samples allows this method to be used in virtually any laboratory setting. metabolic regulation; carbon-energy balance; triglyceride turnover; protein turnover; stable isotope tracer kinetics

Previs, Stephen F., Richard Fatica, Visvanathan Chandramouli, James C. Alexander, Henri Brunengraber, and Bernard R. Landau. Quantifying rates of protein synthesis in humans by use of [sup.2.H.sub.2.0]: application to patients with end-stage renal disease. Am J Physiol Endocrinol Metab 286: E665-E672, 2004. First published December 23, 2003; 10.1152/ajpendo.00271.2003.--A method is introduced for quantitating protein synthetic rates in humans by use of [sup.2.H.sub.2.O]. Its validity was tested in subjects with end-stage renal disease. Six clinically stable subjects, hemodialyzed three times weekly, ingested [sup.2.H.sub.2.0] to a body water [sup.2.H] enrichment of ~0.4%. On dialysis, body water enrichment declined to ~0.1%. Enrichment of the [alpha]-hydrogen of plasma free alanine was also ~0.4% before and ~0.1% after dialysis. [3-Hydrogen enrichment was ~80-100% of [alpha]-hydrogen enrichment. [sup.2.H.sub.2.0] was ingested to replace [sup.2.H.sub.2.0] removed after each dialysis for 15-51 days, returning enrichment to ~0.4%. Enrichment of alanine from plasma albumin gradually increased, with again ~80-100% as much [sup.2.H] in [beta]- as in [alpha]-hydrogens. With continued dialyses, without [sup.2.H.sub.2.0] replacement, alanine from albumin enrichment gradually declined, whereas free alanine and water enrichments were negligible. The fractional albumin synthesis rate, calculated from the increase in enrichment in alanine from albumin, was 4.0 [+ or -] 0.5%/day, and from the decrease, 4.6 [+ or -] 0.2%/day. Thus body water enrichment in a subject given [sup.2.H.sub.2.0] can be maintained constant long term. A rapid exchange, essentially complete, occurs between the hydrogens of alanine and body water. An integrated measure over a long period of albumin's synthetic rate can be estimated from both the rise in enrichment of alanine from the protein during [sup.2.H.sub.2.0] ingestion and fall on [sup.2][H.sub.2O] withdrawal, while the subject's living routine is uninterrupted. Estimates are in subjects with renal disease, but the method should be applicable to estimates of protein synthetic rates in normal subjects and in other pathological states. protein; albumin; alanine; deuterium oxide; hemodialysis

We have studied the accretion of lipids in growing mice. We measured the rates of synthesis and degradation of triglycerides in epididymal fat pads of mice maintained for 44 days on a low-fat, high-carbohydrate diet (I) or a high-fat, low-carbohydrate diet (H). [sup.2][H.sub.2]O was added to the drinking water for 14 days. Rates of incorporation/washout of [sup.2]H to/from C1 of triglyceride-glycerol showed that triglyceride synthesis was greater than triglyceride degradation (net triglyceride balance was ~2.5 times greater in H than in I). The data also show that the contribution of de novo lipogenesis to triglyceride-bound palmitate was ~3 times greater in I than in H. This was consistent with a greater relative intake of carbohydrate in I vs. H. The rates of incorporation and washout of newly synthesized ([sup.2]H-labeled) palmitate into and from triglycerides were also measured. Those data suggested a remodeling of triglyceridebound fatty acids. On measuring the profile of triglyceridebound fatty acids, we observed a decrease in the relative abundance of triglyceride-bound palmitate and stearate and an increase in triglyceride-bound oleate and linoleate. This was observed in I and II. In summary, diet substantially affects the deposition and modeling of triglycerides in adipose tissue during growth. [sup.2][H.sub.2]0 can be used to examine the mechanisms responsible for the accumulation of triglycerides, e.g., factors that affect 1) triglyceride synthesis and degradation and 2) the source of fatty acids that are used in esterification. deuterium; stable isotopes; lipid metabolism; pediatric obesity; insulin resistance

The dynamic behavior of the solution polymerization of styrene in a continuous stirred tank reactor is analyzed with a mixture of tert-butyl perbenzoate and benzoyl peroxide as an initiator system. In the modeling of the reactor, a viscosity dependent reactor wall heat transfer coefficient is used to account for the changing heat transfer efficiency as monomer conversion and polymer molecular weight increase. The steady state and bifurcation behaviors have been investigated with the reactor residence time, initiator feed composition, initiator concentration, feed solvent volume fraction, and coolant temperature as bifurcation parameters. Unlike the reactors with constant heat transfer coefficient, the present system exhibits relatively simple steady state and dynamic bifurcation behaviors. Oscillatory behavior is observed only when the solvent volume fraction in the feed exceeds 0.2. The dynamic simulation of the reactor also indicates that a feedback temperature controller may fail to maintain the reactor temperature when the heat transfer coefficient changes as a result of process disturbances., The behavior of continuous stirred tank reactors for styrene polymerization is investigated. A reactor was modeled with wall heat transfer coefficients dependent on monomer conversion and fluid viscosity. The reactor residence time, initiator feed composition and concentration, solvent feed volume fraction and coolant temperature were used as parameters to analyze reactor steady state behavior. Results show that reactors with heat transfer coefficients dependent on viscosity exhibit better steady state behavior than constant heat transfer coefficients.

A model to predict threshold and timing error rate versus position off-track is described. Missing bit and extra bit error rates are calculated separately, then combined to get the total threshold error rate. Timing error rate is calculated independent of threshold errors. The model illustrates the trade-offs in optimizing the threshold on-track versus off-track. The effect of erase width on off-track read performance is shown. The effect of thin film head undershoots on error rate is also shown. Results of the model compared favorably with experimental data.

The partitioning of whole body carbon flux between fat and lean compartments affects body composition. We hypothesized that it is possible to simultaneously determine whole body carbon (energy) balance and the dynamics of lipids and proteins in specific tissues in vivo. Growing C57BL/6J mice fed a high-fat low-carbohydrate diet were injected with a bolus of ‘doubly labeled’ water (i.e., ²H2O and H218O). The rate of CO2 production was determined from the difference between the elimination rates of ³H and 18O from body water. The rates of synthesis and degradation of triglycerides extracted from epididymal fat pads and of proteins extracted from heart muscle were determined by mathematically modeling the ²H labeling of triglyceride-bound glycerol and protein-bound alanine, respectively. We found that mice were in positive carbon balance (∼20% retention per day) and accumulated lipid in epididymal fat pads (∼9 μmol triglyceride accumulated per day). This is consistent with the fact that mice were studied during a period of growth. Modeling the ²H labeling of triglycerides revealed a substantial rate of lipid breakdown during this anabolic state (equivalent to ∼25% of the newly synthesized triglyceride). We found equal rates of protein synthesis and breakdown in heart muscle (∼10% of the pool per day), consistent with the fact that the heart muscle mass did not change. In total, these findings demonstrate a novel application of the doubly labeled water method. Utilization of this approach, especially in unique rodent models, should facilitate studies aimed at quantifying the efficacy of interventions that modulate whole body carbon balance and lipid flux while in parallel determining their impact on (cardiac) muscle protein turnover. Last, the simplicity of administering doubly labeled water and collecting samples allows this method to be used in virtually any laboratory setting. [ABSTRACT FROM AUTHOR]

A method is introduced for quantitating protein synthetic rates in humans by use of 2H20. Its validity was tested in subjects with end-stage renal disease. Six clinically stable subjects, hemodialyzed three times weekly, ingested 2H2O to a body water 2H enrichment of ∼0.4%. On dialysis, body water enrichment declined to ∼0.1%. Enrichment of the α-hydrogen of plasma free alanine was also ∼0.4% before and ∼0.1% after dialysis. [3-Hydrogen enrichment was ∼80–100% of α-hydrogen enrichment. 2H20 was ingested to replace 2H2O removed after each dialysis for 15–51 days, returning enrichment to ∼0.4%. Enrichment of alanine from plasma albumin gradually increased, with again ∼80–100% as much 2H in β- as in α-hydrogens. With continued dialyses, without 2H2O replacement, alanine from albumin enrichment gradually declined, whereas free alanine and water enrichments were negligible. The fractional albumin synthesis rate, calculated from the increase in enrichment in alanine from albumin, was 4.0 ± 0.5%/day, and from the decrease, 4.6 ± 0.2%/day. Thus body water enrichment in a subject given 2H2O can be maintained constant long term. A rapid exchange, essentially complete, occurs between the hydrogens of alanine and body water. An integrated measure over a long period of albumin's synthetic rate can be estimated from both the rise in enrichment of alanine from the protein during 2H2O ingestion and fall on 2H2O withdrawal, while the subject's living routine is uninterrupted. Estimates are in subjects with renal disease, but the method should be applicable to estimates of protein synthetic rates in normal subjects and in other pathological states. [ABSTRACT FROM AUTHOR]