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G R Beecher

Publications and source records attributed to G R Beecher.

At least 55 records · Page 3Linked to original sources
PubMed1985

Decapreno-beta-carotene as an internal standard for the quantification of the hydrocarbon carotenoids by high-performance liquid chromatography.

The application of decapreno-beta-carotene as an internal standard in quantification of the hydrocarbon carotenoids extracted from raw carrots has been thoroughly examined. Decapreno-beta-carotene is a C50 beta-carotene that has most of the requirements of an internal standard and it can be commercially synthesized in high purity. An isocratic high-performance liquid chromatographic (HPLC) system has been developed that separated all-trans-alpha-carotene, all-trans-beta-carotene, and its 15,15'-cis-isomer from this internal standard. Quantitative determination of the hydrocarbon carotenoids in carrots by HPLC using the internal standard technique gave values for alpha- and beta-carotene similar to those obtained from alpha- and beta-carotene standards alone.

Carotenoids↗
PubMed1985

Amobarbital interactions with 25-hydroxycholecalciferol: effects on the extraction, quantification, and competitive protein binding in vitro.

Amobarbital has been found to coelute with 25-hydroxycholecalciferol (25OHD3) on a normal phase high performance liquid chromatographic system and cause subsequent interference in the UV detection and plasma transport competitive protein binding assay for this vitamin D metabolite. Concentrations of 25OHD3 were overestimated by 95% in the presence of 0.4 mg amobarbital in the competitive protein binding assay; as little as 0.1 mg amobarbital caused a 22% overestimation in the concentration of 25OHD3 in the assay. Separation of 25OHD3 from amobarbital on a reverse phase high performance liquid chromatographic system allowed for proper quantification without interference. Because of the similarity of chemical structures, other barbital-based compounds may cause similar interactions with 25OHD3 or other vitamin D metabolites as well.

Amobarbital↗
PubMed1984

Evaluation of vitamin A and carotenoid data in food composition tables.

Vitamin A and carotenoid data in food composition tables have been generated with the use of the Association of Official Analytical Chemists procedures. These procedures fractionate complex mixtures of retinoids and carotenoids into only three fractions, e.g., retinoids, carotenes, and xanthophylls. Food tables lack uniformity in the presentation of vitamin A and carotenoid data. For example, the revisions of Agriculture Handbook, No. 8 (Washington, D.C.: U.S. Govt Print Off, 1963), report both international units and retinol equivalents of vitamin A in foods. Food tables published in the United Kingdom (Paul AA, Southgate DA. McCance and Widdowson's: The composition of foods. Amsterdam: Elsevier/North-Holland, 1978) report preformed vitamin A as retinol and carotenoids as carotene on a weight basis (micrograms/100 g food). The vitamin A and carotenoid data currently available in food composition tables allow only the intake of total vitamin A activity to be estimated. Information about the intake of specific species of retinoids or carotenoids is not available and could not be calculated from existing food tables. Limited applications of new separation techniques and chemical instrumentation have demonstrated the potential for generating detailed analytic information in regard to the retinoid and carotenoid contents of foods.

Bibliographies as Topic↗
PubMed1983

Dietary protein and phosphorus: effect on calcium and phosphorus metabolism in bone, blood and muscle of the rat.

Four- or 12-week-old rats were fed diets containing either 25 or 45% casein and either 0.35 or 0.8% phosphorus (P) for 7 weeks. Calcium (Ca) level of each diet was 0.9%. In the young, fast-growing rat (expt 1), plasma P was increased (P less than 0.01) when 0.8%, rather than 0.35%, P was fed. In the more mature rats (expt 2), increased dietary P depressed Ca in plasma but elevated P; high protein intake elevated whole-blood Ca, but depressed plasma P. Dietary treatment had little effect on muscle of mature rats, but wet weight and total P content of muscle were higher in young rats fed 0.8%, rather than 0.35%, P. Femur dry weight and P concentration were greater when 0.8%, rather than 0.35%, P was fed to young rats; dietary P did not affect any other parameter of bone (expt 1, 2). Excessive protein intake elevated femur P concentration in young rats, but depressed length and strength of femurs in mature rats. Some parameters of bone, blood and muscle can be influenced by dietary levels of protein and P. The response, however, is dependent on the physical maturity of the rat when dietary treatment begins.

Animals↗
PubMed1981

B6 vitamer analysis in human plasma by high performance liquid chromatography: a preliminary report.

An extraction procedure that can be used successfully with a high performance liquid chromatography sample clean-up and analytical method is outlined for the determination of B6 vitamer and pyridoxic acid concentrations in human plasma. The method is a modification of ones developed for food and animal tissue investigations. Chromatographic traces, relatively clean of interfering compounds are obtained. The method has the advantage of speed and reproducibility and yields recoveries of from 90 to 100% for all vitamers and pyridoxic acid.

Chromatography, High Pressure Liquid↗
PubMed1981

Effect of dietary protein and phosphorus levels on calcium and phosphorus metabolism of the young, fast growing rat.

Utilizing a 2 X 2 factorial design, male weanling rats were fed diets containing either 25% or 45% casein with 0.35% or 0.8% phosphorus (P). Dietary calcium (Ca) was set at 0.9% for each diet. During the 7 weeks of this experiment, food intakes and body weights were measured weekly; urine and fecal samples were collected daily. Regardless of dietary P level, increasing dietary protein resulted in significantly decreased fecal Ca output accompanied by an increase in the Ca content of urine. Increasing dietary P resulted in significantly increased fecal Ca content, decreased absolute and percent Ca absorption, and decreased urinary Ca output. Increased fecal and urinary P excretion were obtained when dietary P levels were increased. Increasing dietary protein at the 0.35% P level slightly increased the values for absolute and percent Ca and P absorption. However, when 0.8% P was fed, increasing the protein level of the diet decreased these Ca (weeks 1-5) and P absorption values. Ca and P balances were positive at all times.

Absorption↗
PubMed1981

Influence of exercise on free amino acid concentrations in rat tissues.

Levels of free amino acids in muscle, liver, and plasma were measured in rats that had either swum (1 or 2 h) or run (until exhausted). Exercise lowered alanine levels in all three tissues except for liver of exhausted rats. Exercise decreased the plasma levels of the acidic amino acids and their amides. Glutamate and glutamine levels were depressed in muscle, and the glutamine level was lowered in liver by exercise. Aspartate concentration was lowered by exercise in liver but elevated in muscle. The branched-chain amino acids were generally elevated by exercise as were tyrosine, phenylalanine, methionine, and lysine. Plasma 3-methylhistidine concentration was also elevated by an exercise bout. The changes observed in the amino acid contents of muscle, liver, and plasma are consistent with the increase in protein degradation during exercise that we previously reported. The lowered levels of some amino acids (e.g., alanine, glutamine, glutamate) seem to suggest that amino acid catabolism and/or gluconeogenesis is increased by exercise.

Amino Acids↗
PubMed1981

The ovariectomized female rat as a model animal for the study of adaptation to endurance training.

The effect of a 6-week endurance training program on food consumption and weight gain was investigated in intact and castrated male and female rats. Training decreased on weight gain and food consumption in both intact and castrated male rats. Intact female rats increased food consumption during training and had larger lean body weights than untrained-intact females at the end of the training program. However, the trained-ovariectomized rats consumed the same amount of food as the untrained-ovariectomized group and had similar lean body weights at the end of the training program. Thus, the ovariectomized female rat appears to be a good model for the study of adaptation to endurance training.

Adaptation, Physiological↗
PubMed1980

Effect of exercise on synthesis and degradation of muscle protein.

Several reports have shown that amino acid utilization via oxidation and gluconeogenesis is increased during exercise. The purpose of this study was to investigate whether these changes are accompanied by alterations in protein synthesis and degradation in the muscle of exercising rats. One group of rats was made in swim for 1h and then protein synthesis and protein degradation were measured in a perfused hemicorpus preparation. Protein synthesis was decreased and protein degradation was increased in exercised rats compared with sedentary control rats. Exercise also decreased amino acid incorporation by isolated polyribosomes from muscle. Measurement of several muscle proteinase activities demonstrated that exercise had no effect on alkaline proteinase or Ca2+-activated proteinase. However, the free (unbound) cathepsin D activity was elevated in muscle of exercised rats, whereas the total activity of catepsin D was unchanged. This increase in the proportion of free cathepsin D activity suggests that lysosomal enzymes may be involved in the increased protein degradation that was observed.

Animals↗
PubMed1980

Automated multiple flow-injection analysis in clinical chemistry: determination of albumin with bromcresol green.

We describe an adaptation of automated multiple flow-injection analysis instrumentation to an analysis for albumin in serum. The bromcresol green reaction was used to test the utility of the system. The approach yielded albumin results with excellent sensitivity, no measurable carryover, a relative standard deviation of less than 1%, good correlations with published procedures, and no measurable interferences. The simplicity and flexibility of the instrumentation and its performance integrity, as indicated by the analytical results, make this a viable clinical chemical tool.

Bromcresol Green↗
PubMed1978

Design assembly of an inexpensive, automated microbore amino acid analyzer: separation and quantitation of amino acids in physiological fluids.

An amino acid analyzer capable of separating and quantitating 0.5 to 20 n moles of each ninhydrin-positive compound in physiological fluids has been designed and assembled from commercially available components. The buffer sequence, column temperature change and sample application are controlled by an automatic programmer constructed from a series of timers. The liquid delivery protion of the instrument consists of a series of polystyrene and stainless steel chambers pressurized with argon and connected through valves and manifolds to conventional positive displacement pumps. The column is highly polished stainless steel tubing (0.21-cm ID) packed with 9-mu cation exchange resin. Micro colorimeters, equipped with appropriate interference filters and small-volume (2-8 mu 1) flow cells, are used as detectors. The sample loader is a dual 20-port automatic valve containing 25-mu1 sample loops. Small-bore teflon tubing (32 AWG), interconnected with tubing adapters and connectors, is used for buffer lines and reaction coil (100 degree C); ninhydrin lines are 1/16-inch stainless steel tubing. Separation of 42 ninhydrin positive compounds, including column equilibration, is accomplished in 5 hours. Procedures for the extraction of amino acids from physiological fluids and tissues as well as the preliminary clean-up of these extracts are also described.

Amino Acids↗
PubMed1977

Adaptation of protein metabolism to endurance training. Increased amino acid oxidation in response to training.

This study was conducted to investigate alterations in excretion of urea and total nitrogen after6-8 weeks of daily exercise and to establish if the capacity for amino acid oxidation in muscle is influenced by endurance training. Urea nitrogen excretion was increased in trained compared with untrained rats and nitrogen balance was less positive in trained than in untrained rats. Increased [14C]leucine oxidation with training was observed both in vivo and in vitro. The results of this study demonstrate that amino acid catabolism is increased during exercise training and that the muscle enzymes involved in leucine oxidation adapt to endurance training in a manner similar to the enzymes of carbohydrate and fat catabolism.

Adaptation, Physiological↗