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Ceglia L.,Tufts University | Abrams S.A.,Agricultural Research Service Childrens Nutrition Research Center | Harris S.S.,Tufts University | Rasmussen H.M.,Tufts University | And 2 more authors.
Experimental and Clinical Endocrinology and Diabetes | Year: 2010

The dual stable isotope method with a timed 24-h urine collection is the gold standard approach to measure fractional calcium absorption. However, the need to collect urine for 24h makes this technique time-consuming and laborious. Our study sought to determine whether a dual isotope method using a single serum sample obtained 4h after administration of the initial isotope provides a useful approach to measure fractional calcium absorption. Following a metabolic diet with a fixed calcium intake of 30mmol/day for 10 days, nineteen healthy subjects age 54-74 were given a test meal with an oral isotope (44Ca) followed 2h later by an intravenous isotope (42Ca). Once the oral isotope was administered, urine was collected for 24h, and a serum sample was obtained after 4h. The ratio of the oral to intravenous isotopes was measured in the urine and serum by mass spectroscopy. Fractional calcium absorption was 16.2±7.7% by the 4-h single serum method versus 18.5±7.5% by the 24-h urine method. There was a small mean difference between the urine and serum methods of 2.33% with a confidence interval -3.97 to 8.60%. The two methods showed a strong linear association (r=0.912, p<0.001). Use of dual stable isotopes with a 4-h single serum method gives fractional calcium absorption values that are 12.5% lower than with the 24-h urine method; however, it rank orders subjects accurately thus making it a useful alternative method in clinical research applications. © J. A. Barth Verlag in Georg Thieme Verlag KG Stuttgart - New York.

Lane M.M.,Baylor College of Medicine | Czyzewski D.I.,Baylor College of Medicine | Chumpitazi B.P.,Texas Childrens Hospital | Shulman R.J.,Texas Childrens Hospital | Shulman R.J.,Agricultural Research Service Childrens Nutrition Research Center
Journal of Pediatrics | Year: 2011

Objectives: This study sought to: evaluate the ability of children to reliably use a modified Bristol Stool Form Scale for Children (mBSFS-C), evaluate criterion-related validity of the mBSFS-C, and identify the lower age limit for mBSFS-C use. Study design: The mBSFS-C comprises 5 stool form types described and depicted in drawings. Children 3 to 18 years old rated stool form for 10 stool photographs. Because of low reliability when stool form descriptors were not read aloud (n = 119), a subsequent sample of children (n = 191) rated photographs with descriptors read. Results: Intraclass correlation coefficients for descriptor-unread versus -read samples were 0.62 and 0.79, respectively. Children were increasingly reliable with age. Percentage of correct ratings varied with stool form type, but generally increased with age. With descriptors unread, children 8 years and older demonstrated acceptable interobserver reliability, with >78% of ratings correct. With descriptors read, children 6 years and older demonstrated acceptable reliability, with >80% of ratings correct. Conclusions: The mBSFS-C is reliable and valid for use by children, with age 6 years being the lower limit for scale use with descriptors read and age 8 years being the lower limit without descriptors read. We anticipate that the mBSFS-C can be effectively used in pediatric clinical and research settings. © 2011 Mosby Inc. All rights reserved.

Marini J.C.,Agricultural Research Service Childrens Nutrition Research Center | Didelija I.C.,Agricultural Research Service Childrens Nutrition Research Center | Castillo L.,Agricultural Research Service Childrens Nutrition Research Center | Lee B.,Baylor College of Medicine | Lee B.,Howard Hughes Medical Institute
American Journal of Physiology - Endocrinology and Metabolism | Year: 2010

Although glutamine is considered the main precursor for citrulline synthesis, the current literature does not differentiate between the contribution of glutamine carbon skeleton vs. nonspecific nitrogen (i.e., ammonia) and carbon derived from glutamine oxidation. To elucidate the role of glutamine and nonspecific nitrogen in the synthesis of citrulline, L-[2- 15N]- and L-[5-15N]glutamine and 15N-ammonium acetate were infused intragastrically in mice. The amino group of glutamine labeled the three nitrogen groups of citrulline almost equally. The amido group and ammonium acetate labeled the ureido and amino groups of citrulline, but not the δ-nitrogen. D5-glutamine also infused in this arm of the study, which traces the carbon skeleton of glutamine, was utilized poorly, accounting for only 0.2-0.4% of the circulating citrulline. Dietary glutamine nitrogen (both N groups) incorporation was 25-fold higher than the incorporation of its carbon skeleton into citrulline. To investigate the relative contributions of the carbon skeleton and nonspecific carbon of glutamine, arginine, and proline to citrulline synthesis, U-13Cn tracers of these amino acids were infused intragastrically. Dietary arginine was the main precursor for citrulline synthesis, accounting for ∼40% of the circulating citrulline. Proline contribution was minor (3.4%), and glutamine was negligible (0.4%). However, the glutamine tracer resulted in a higher enrichment in the ureido group, indicating incorporation of nonspecific carbon from glutamine oxidation into carbamylphosphate used for citrulline synthesis. In conclusion, dietary glutamine is a poor carbon skeleton precursor for the synthesis of citrulline, although it contributes both nonspecific nitrogen and carbon to citrulline synthesis. Copyright © 2005 by the American Physiological Society.

Lin A.H.-M.,Purdue University | Lee B.-H.,Purdue University | Nichols B.L.,Agricultural Research Service Childrens Nutrition Research Center | Nichols B.L.,Baylor College of Medicine | And 5 more authors.
Journal of Biological Chemistry | Year: 2012

Background: α-Amylase was thought to be the sole enzyme that determines starch digestion rate. Mucosal α-glucosidases were considered to simply convert post-α-amylase dextrins to glucose. Results: The mucosal α-glucosidases can digest a wide range of α-limit dextrin molecules and digest starches from various sources differently. Conclusion: Starch chemical structure drives the digestion difference at the brush-border area. Significance: The findings provide new insight into controlling the glycemic response.

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