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Biomedical subjects

S Lippincott

Publications and source records attributed to S Lippincott.

8 recordsLinked to original sources
PubMed1990

Comparison of serum and plasma taurine values in Bengal tigers with values in taurine-sufficient and -deficient domestic cats.

A white Bengal tiger was determined to have a central retinal lesion and a central visual defect. Because of the known association between feline central retinal degeneration (CRD) and taurine deficiency in domestic cats, plasma concentrations of taurine were measured in this tiger. Serum concentrations of taurine, methionine, and cystine also were measured in white Bengal tigers, orange Bengal tigers, taurine-sufficient domestic cats, and taurine-deprived and tissue-taurine-depleted visually impaired cats with CRD. Hepatic and brain enzymes responsible for taurine synthesis were identified in tissue specimens from an orange Bengal tiger. Serum taurine concentrations were lower in white vs orange tigers, but were not as low as those in cats with CRD. Thus, we concluded that taurine depletion did not account for the central retinal lesion in the white Bengal tiger.

Animals↗
PubMed1989

Rapid determination of total hydroxyproline (HYP) in human urine by HPLC analysis of the phenylisothiocyonate (PITC)-derivative.

A recent development in the preparation for amino acid analysis is the use of phenylisothiocyanate (PITC) as a precolumn derivatizing agent prior to analysis to form a stable derivative. These derivatives can then be separated by reversed phase high pressure liquid chromatography (HPLC). Because of interest in the accurate measurement of urinary hydroxyproline (HYP), PITC was used for derivatization followed by HPLC analysis. Using an automated computer-controlled sampler system, up to 75 samples can be analyzed each 24 h. Technical details, specificity, and reliability of this method are provided. Duplicate measurements of HYP had a coefficient of variation (CV) of 5.5% and with a recovery of HYP in spiked urine samples of 94 to 104%. A sample frozen and thawed 10 times showed no change in the concentration of HYP. When total HYP was measured in 230 healthy women between 20 and 39 years of age, it was found to be 236.62 +/- 146.41 mumoles/L. These samples were researched in 3.5 days using this technique.

Adult↗
PubMed1988

Development of beta-amino acid transport in the kidney.

This study focuses on the maturation of the renal beta-amino acid transport system and uses dietary manipulation as a probe. The epithelial surface of the renal proximal tubule is responsible for the conservation of ions and organic solutes including beta-amino acids. This beta-amino acid transport system is stimulated during periods of reduced dietary intake and permits increased excretion following dietary excess. We have examined transport of the sulfur-containing beta-amino acid, taurine, as a measure of this renal adaptive response to fluctuations in dietary sulfur amino acid intake and as a substrate for the beta-amino acid transport system. A precession of taurine uptake values by brush border membrane vesicles (BBMV) prepared from nursing rats from youngest to oldest was evident. However, these membranes demonstrate the full renal adaptive response to altered sulfur amino acid intake after the first week of life. This adaptive response is expressed at the brush border surface by transport changes in both directions ("up regulation" and "down regulation"), through changes in the initial rate (15 sec) of Na+-taurine cotransport. No alterations in the lipid microenvironment of the membrane, as detected by altered membrane fluidity, were uncovered. Although vesicles from 7-day-old pups demonstrate adaptation and accumulate taurine to a limited extent, the accumulation of Na+, which energizes uptake, may be altered, thereby preventing full expression of the adaptive response and of transport capacity at this age.

Amino Acids↗
PubMed1986

Studies on renal adaptation to altered dietary amino acid intake: tissue taurine responses in nursing and adult rats.

This study examines the effect of a low sulfur amino acid diet (LTD) and a high taurine diet (HTD), compared with a normal diet, on the plasma, urine, muscle, brain and renal cortex levels of taurine in immature and adult rats. Milk taurine from lactating dams reflected the taurine content of the diet, being low in LTD-fed and high in HTD-fed animals. Nursing pups (7, 14 and 21 d old) often had plasma, urine and tissue--renal cortex, heart, skeletal muscle--levels of taurine related to dietary exposure, a situation also found in adult animals. These diets did not influence the urinary excretion of the sulfur-containing alpha-amino acids methionine and cystine but a sulfur aminoaciduria of immaturity was evident. By contrast, the content of taurine in brain was constant regardless of dietary intake of sulfur amino acids. An age-related decline in brain taurine content was found--as noted by others--but this too was influenced by diet. This dual finding of brain taurine constancy despite wide differences in sulfur amino acid intake and changes in the renal handling of taurine as influenced by diet suggest that the renal adaptive response serves to maintain the stability of brain taurine content.

Adaptation, Physiological↗
PubMed1986

Effect of amino acid intake on brush-border membrane uptake of sulfur amino acids.

Alterations in the intake of sulfur amino acids (SAA) changes the rat renal brush-border membrane uptake of the beta-amino acid, taurine. A low-SAA diet enhances and a high-taurine diet reduces uptake (Chesney et al., Kidney Int. 24: 588-594, 1983). Neither the low-SAA diet nor the high-taurine diet alters the time course or concentration-dependent accumulation of the sulfur amino acids methionine and cystine or of inorganic sulfate. By contrast the uptake of beta-alanine, another beta-amino acid that competes with taurine, is greater in animals on the low-SAA diet. The high-taurine diet does not change beta-alanine uptake. The plasma levels of taurine are altered by dietary change, but not the values for methionine and cystine. This study indicates that renal adaptation is expressed for beta-alanine, a nonsulfur-containing beta-amino acid. By contrast, methionine, cystine, and sulfate, which participate in a variety of synthetic and conjugative processes, are not conserved by the renal brush-border surface following ingestion of either a low-methionine and -cystine diet or high-taurine diet.

Amino Acids↗