Stanton S Segal

Gas chromatography-mass spectrometry was utilized to study the metabolism of [15N]glutamate, [2-15N]glutamine, and [5-15N]glutamine in isolated renal tubules prepared from control and chronically acidotic rats. The main purpose was to determine the nitrogen sources utilized by the kidney in various acid-base states for ammoniagenesis. Incubations were performed in the presence of 2.5 mM 15N-labeled glutamine or glutamate. Experiments with [5-15N]glutamine showed that in control animals ...

The plasma concentration of galactose and galactitol was measured in 27 patients with galactose-1-phosphate uridyltransferase (GALT) deficiency galactosemia on a lactose-restricted diet, 17 infants on lactose-free formula, and 21 infants and children on a normal diet, by a newly devised isotope dilution gas chromatograph/mass spectrometry (GC/MS) method. The method was linear in the range of 0.1 to 10 micromol/L for galactose and 1 to 20 micromol/L for galactitol with good ...

Isolated renal cortical tubules prepared from adult male Sprague-Dawley rats were used to study the nature of cystine entry into tubule cells and its transport interactions with dibastic amino acids. The uptake of cystine over time was progressive, reaching a steady-state after 60 min of incubation. Analysis of the intracellular pool after incubation revealed that a significant fraction of the transported cystine was reduced to cysteine. A kinetic analysis of uptake demonstrated that two ...

Galactose 1-phosphate uridyltransferase (EC 2.7.7.12: UDP-glucose:α-d-galactose-1-phosphate uridylyltransferase) activity in the developing rat liver, gut, and kidney is presented. The activity in liver tissue increased from 3 days before birth to a maximum in the 10-day-old animal and then declined to adult levels between 35 and 45 days. No observed rise in transferase activity occurred in gut and kidney from term until 10 days with a subsequent decrease until 35 days. Adult rat brain ...

Protein turnover was studied in eight premature infants of conceptual age 26-37 weeks. A stochastic model based upon [15N]urea or [15N]ammonia excretion following a single injection of [15N]glycine was used to estimate rates of whole body protein synthesis and catabolism. The urinary 3-methylhistidine/creatinine ratio was determined to differentiate skeletal muscle protein breakdown from total protein catabolism. The rates of whole body protein synthesis ranged from 5.2 to 13.2 g X kg-1 ...

The ability of mice deficient in galactose-1-phosphate uridyltransferase (GALT) to metabolize galactose was determined in animals weaned to a mouse chow diet for a 4-wk period. When given [14C]galactose intraperitoneally, these animals slowly oxidized the sugar, excreting only 5.5% of the dose as 14CO2 in 4 h, whereas normal animals excreted 39.9%. These results mimic those seen in human galactosemic patients given isotopic galactose. When given 10 μmol of [1-13C]galactose, normal ...

We measured galactitol, galactonate, and galactose-1-phosphate in the red blood cell (RBC) to elucidate the biochemical phenotype of infants with a Duarte/galactosemia (D/G) genotype by isotope dilution GC/MS. The RBC galactonate, galactitol and Gal-1-P were quantified in 14 D/G newborns on a lactose containing formula or breast milk, eight D/G newborns on a galactose-free formula, and 18 D/G children between 1 and 2 years of age that were on a regular diet. The results were compared ...

Urinary excretion of galactitol was determined in 95 normals (N/N), 67 galactosemic (G/G), and 39 compound heterozygotes for the Duarte and galactosemia genotype (D/G). Galactitol excretion is age-dependent in both normal individuals and patients with classic galactosemia on lactose-restricted diets. In galactosemic patients who are homozygous for the Q188R mutation, urinary galactitol levels were fivefold to 10-fold higher than those of normal subjects of comparable age. All but a few ...

Glutamine uptake by rat renal brushborder vesicles occurred via two distinct saturable processes withKm values of 0.145 and 8.5 mM which were stimulated by both ionic and sodium gradients with a pH optimum of 6.8–7.1 Glutamic acid uptake also occurred by a two-component system withKm values of 0.016 and 3.60 mM. Both components were stimulated specifically by a sodium gradient. The lowKm system for glutamic acid had a pH optimum of 7.2–7.4. Glutamine entry at 0.06 mM was inhibited by a ...

Mice deficient in galactose-1-phosphate uridyltransferase (GALT) demonstrate abnormal galactose metabolism but no obvious clinical phenotype. To further dissect the pathways of galactose metabolism in these animals, galactose oxidation and metabolite levels were studied in 16-day-old sucklings and the effect of a 4 week prior exposure to a 40% glucose or 40% galactose diet was determined in 7-week-old mice. Suckling GALT-deficient (G/G) mice slowly oxidized [1-14C]galactose to 14CO2, ...

The red blood cell (RBC) concentration of galactitol and galactonate was measured in 27 patients with galactose-1-phosphate uridyltransferase (GALT) deficiency galactosemia and 19 non-galactosemic subjects by a newly devised isotope dilution gas chromatography/mass spectrometry (GC/MS) method. The method utilizing UL[13C]galactitol and UL[13C]galactonate was reproducible with excellent precision and recovery of 99%. The RBC galactitol in galactosemic patients on galactose-restricted ...

Uptake of L-proline and glycine by rat renal brushborder membrane vesicles was seen to be osmotically sensitive, pH dependent,and occurred in the absence of proline and glycine metabolism. The uptake system for proline was Na+ gradient dependent, and exhibited a dual system for entry, Km1 = 0.067 mM and Km2 = 5.26 mM. The uptake of glycine was also Na+ gradient dependent, and exhibited a two Km system, Km1 = 0.22 mM and Km2 = 4.00 mM. Studies of proline and glycine interactions indicate ...

The levels of uridine diphosphogalactose (UDPGal) and uridine diphosphoglucose (UDPGlu) in trichloroacetic acid extracts of human red blood cells (RBC) were measured by 31P NMR spectroscopy. Individual determinations were compared to results obtained by enzymatic and high-pressure liquid chromatographic (HPLC) methods. The characteristic doublet of the P beta resonance signals of both UDPGal and UDPGlu were detected in proton-decoupled spectra of extracts. Quantitative analyses were ...

1.1. Active transport of amino acids in rat kidney cortex slices diminished as the Na+ concentration of the medium was decreased below physiologic levels. In Na+-free media, active transport of glycine and α-amino [i-14C]isobutyric acid was abolished, but active transport of lysine persisted.2.2. Lysine transport was found to be mediated by two mechanisms—one Na+ dependent and ouabain sensitive, and the other independent of Na+ and insensitive to ouabain.3.3. Maximal transport of amino ...

Even on a lactose-restricted diet, urinary galactitol excretion and erythrocyte galactose-1-phosphate levels are persistently elevated in patients with galactose-1-phosphate uridyltransferase deficiency. In order to determine the contribution of galactose in dietary fruits and vegetables to this phenomenon, (1) the content of galactose in a lactose-free diet was directly measured when a galactosaemic patient's diet was specifically enriched in those fruits and vegetables which contain ...