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Biomedical subjects

G Sarwar

Publications and source records attributed to G Sarwar.

At least 55 records · Page 3Linked to original sources
PubMed1988

Differences in uricogenic effects of dietary purine bases, nucleosides and nucleotides in rats.

The uricogenic effects of dietary free purines (adenine, guanine, hypoxanthine and xanthine), their nucleosides (adenosine, monophosphate, guanosine monophosphate and inosine monophosphate) were studied in rats. Casein-based diets (20% protein) supplemented with 30 mmol/kg diet of each of the free purine base, nucleoside or nucleotide were fed to male Sprague-Dawley rats (100 +/- 5 g) for 14 d. Addition of adenine resulted in less weight gain than in controls, greater kidney weight, greater urine volume and higher levels of blood urea nitrogen, serum uric acid, creatinine and allantoin but lower urinary levels of allantoin, uric acid and creatinine. The adenine diet also caused nephropathy characterized by nephromegaly and deposition of crystals. A microscopic examination of the kidneys revealed deposition of crystals mainly in the lumen of convoluted tubules of the cortex. Feeding of diets containing other purine bases, nucleosides and nucleotides had no adverse effects on kidney weight or structure, urine volume, serum uric acid or creatinine. Urinary allantoin excretion, however, was greater in rats fed hypoxanthine, xanthine, nucleoside and nucleotide diets than in control rats. Adenine produced adverse effects only when fed in the free form and not when fed as the nucleoside or nucleotide, suggesting a metabolic significance for free adenine in predicting hyperuricemic effects of foods.

Adenine↗
PubMed1987

Purification of a kappa-carrageenase from marine Cytophaga species.

A mixture of extracellular carrageenases was isolated from the cell-free medium of a culture of marine Cytophaga sp. 1k-C783 grown on ZoBell 2216 E broth with 0.1% commercial carrageenan. A single active peak of kappa-carrageenase was separated and purified from the mixture by ammonium sulfate precipitation, ion-exchange chromatography, and Sephadex G-200 gel filtration chromatography. Molecular weight of the purified kappa-carrageenase was estimated as 100,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The purified kappa-carrageenase had pH optimum 7.6 and temperature optimum 25 C.

Bacteria↗
PubMed1986

Comparisons between true digestibility of total nitrogen and limiting amino acids in vegetable proteins fed to rats.

Values (%) for true digestibility (TD) of protein and individual amino acids in some vegetable proteins were determined by the rat balance (fecal) method. Diets containing 8% crude protein (N X 6.25) from soaked and autoclaved samples of Trapper and Century field peas, lentil, pinto bean, seafarer bean, black bean or fababean and autoclaved samples of soybean, peanut, sunflower, rolled oat, rice + soybean and corn + pea were tested in two rat balance studies. In the case of blends, each protein source provided 50% of total protein. The beans, peas and lentil proteins were limiting in sulphur amino acids, tryptophan and threonine, whereas sunflower and rolled oat were most limiting in lysine. In beans, peas and lentil, the TD values of methionine (51-82), cystine (46-85), tryptophan (47-90) and threonine (62-84) were considerably lower than the TD values of total nitrogen (72-90). Similarly, in sunflower and rolled oat, the TD values of lysine (81-83) were lower than the TD values of total nitrogen (90-91). These data suggested that crude protein digestibility may not be a good predictor of bioavailability of limiting amino acids in vegetable proteins. Amino acid scores of the vegetable proteins were 62-96%. The corrections for true digestibility of protein and individual amino acids lowered the scores by 6-15 and 11-47 percentage units, respectively.

Amino Acids↗
PubMed1985

Potentiality of artificial sea water salts for the production of carrageenase by a marine Cytophaga sp.

Production of an extracellular enzyme complex (carrageenase) was studied by examining cell-free fluids from cultures of a marine Cytophaga, 1k-C783, growing on different media. Among artificial sea water salts, only NaCl and MgCl2 were utilized by the organism to produce carrageenase. The minimal concentrations of suitable combinations of NaCl and MgCl2 were found to be 0.05 M NaCl plus 0.25 M MgCl2, and 0.15 M NaCl plus 0.15 M MgCl2. KCl and CaCl2 did not have any role in carrageenase production in ZoBell 2216 E broth medium. Carrageenase was synthesized continuously within the resting cells and was released from the cells as well as in the growing cells, when nutrient had been supplied.

Bacterial Proteins↗
PubMed1982

In vitro assay for predicting protein efficiency ratio as measured by rat bioassay: collaborative study.

Seven laboratories collaborated in testing the calculated protein efficiency ratio (C-PER and DC-PER). The collaborative study required each laboratory to analyze 6 foods and a control protein (ANRC casein) for in vitro apparent protein digestibility, amino acid composition, and PER via rat bioassay. The 6 foods or food ingredients tested were nonfat dry milk, cooked chicken muscle, protein-fortified dry breakfast cereal, textured soy protein, oat-based dry breakfast cereal, and durum wheat flour. Data obtained from the study were analyzed statistically for the intralaboratory variation for each method of analysis (i.e., amino acid analysis, PER, etc.). The ability of the C-PER to rapidly predict rat PER was also measured. The C-PER and DC-PER methods were adopted official first action.

Amino Acids↗
PubMed1980

Determination of bioavailability of some long-chain N-substituted derivatives of L-methionine and L-lysine.

The bioavailability of N-acyl-L-methionine derivatives has been determined using microbiological assay with Tetrahymena pyriformis. It was found that palmitoyl- and stearoyl-L-methionine, stearoyl-L-methionine ethyl ester, and stearoyl-L-methionine sodium salt were partially utilized (14-38%) for growth of the microorganism. These compounds partially inhibited utilization of free methionine added to the media. The shorter derivatives, acetyl-, hexanoyl-, lauroyl-, and myristoyl-L-methionine completely inhibited the growth of T. pyriformis. This effect was not reversed when DL-methionine was added to the media. N6-fatty acyl L-lysine derivatives gave low availability values (3-18%) in microbiological assessment with T. pyriformis. N2-Acetyl-and N6-acetyl-lysine did not inhibit the utilization of the added parent amino acid. Nutritional evaluation of L-methionine derivatives by the rat growth method using net protein ratio (NPR) as the performance index indicated complete availability of stearoyl-L-methionine, stearoyl-L-methionine sodium salt, and partial availability of stearoyl-L-methionine ethyl ester (52%), stearoyl-L-methionylglycine (32%), and lauroyl-L-methionine (75%).

Animals↗
PubMed1980

Assessment of rat growth methods for estimating protein quality: interlaboratory study.

An interlaboratory study involving protein efficiency ratio (PER), net protein ratio (NPR), relative NPR (RNPR) and relative nitrogen utilization (RNU) was carried out. Six collaborators assayed 6 samples, including casein plus methionine which was used as a reference protein. Collaborators prepared their own diets and analyzed the diets for nitrogen. Test proteins were added at the 8% level (N X 6.25). PER values varied more than NPR values which varied more than either RNPR or RNU. RNU and RNPR produced almost identical values, but RNPR remains the official method of choice, because it is a well established method.

Animals↗
PubMed1978

Nutritional evaluation of oilseeds and legumes as protein supplements to cereals.

Several oilseed and legume protein products were fed to rats as the sole source of dietary protein, and in blends with cereals for the determination of protein efficiency ratio (PER) and biological availability of amino acids. In addition oilseed protein isolates were fed to mice for the determination of PER. Results of the mouse study revealed that the adjusted PER (casein = 100)for Target rapeseed isolate (108) was higher than those of sunflower (74), safflower (77), soybean (86) or flax (92) isolates. Results of the rat trials revealed that the adjusted PER for Twoer rapeseed meal (88) was higher than those of fababean (21), field pea (59) and soybean meal (72). Supplementation with methionine (0.2%) resulted in improved PER for fababean (84), field pea (101) and soybean meal (97). Mustard flour and rapeseed flour gave PER of 109 and 106, respectively, while the value of sunflower flour was low (56). Protein isolates of Tower rapeseed and soybean gave PER of 92 and 80, respectively. Blending of legumes and oilseeds with wheat flour (PER = 28) gave high PER values (60--85), as also occurred in rice blends (71--88). Supplementation of wheat-legume blends with lysine (0.4%), methionine (0.2%) and threonine (0.1%) brought all PER values above 100. It appeared that differences in PER of the diets paralleled the levels of the first limiting amino acid for rat growth. Results of balance trials indicated that the availability of the limiting amino acid(s) was lower than other essential amino acids for each protein source.

Amino Acids↗
PubMedDate not supplied

Evaluation of protein digestibility-corrected amino acid score method for assessing protein quality of foods.

The current concepts of protein quality evaluation were reviewed. A detailed examination of existing animal assays and more promising amino acid scoring methods has been carried out by an Ad Hoc Working Group on Protein Quality Measurement for the Codex Committee on Vegetable Proteins during the last 5 years. Several factors such as inadequacies of protein efficiency ratio (PER, the poorest test) and other animal assays, advancements made in standardizing methods for amino acid analysis and protein digestibility, availability of data on digestibility of protein and individual amino acids in a variety of foods, and reliability of human amino acid requirements and scoring patterns were evaluated. On the basis of this evaluation, amino acid score, corrected for true digestibility of protein, was recommended to be the most suitable routine method for predicting protein quality of foods for humans. Amino acid scores corrected for true digestibility of protein (as determined by rat balance method) were termed "protein digestibility-corrected amino acid scores." A detailed method for the determination of the protein digestibility-corrected amino acid score was proposed, and information about the range of scores to be expected in foods or food products was provided in the present investigation. The protein digestibility-corrected amino acid score method is a simple and scientifically sound approach for routine evaluation of protein quality of foods. Accuracy of the method would, however, be confirmed after validation with growth or metabolic balance studies in humans.

Amino Acids↗
PubMedDate not supplied

In vitro assay for protein digestibility: interlaboratory study.

True protein digestibilities of 17 protein sources were estimated by 6 laboratories using an in vitro, 3-enzyme digestion system in a pH stat. Samples from animal, vegetable, and mixed food sources were freeze-dried (if not already dried), ground, mixed, and shipped to each collaborator along with a sodium caseinate standard and trypsin, chymotrypsin, and peptidase. The uptake of titrant during enzymatic digestion was used to calculate estimates of digestibility. Digestibilities ranged from 100% for casein to 89.9% for whole wheat cereal. Mean relative standard deviations for repeatability were 1.4% for rolled oats and less than 1% for the remaining 16 samples. Mean relative standard deviations for reproducibility ranged from 5.0 to 0.8%; values were less than 2.5% for 13 of the 17 samples.

Animals↗
PubMedDate not supplied

In vivo rat assay for true protein digestibility: collaborative study.

Eight laboratories participated in a collaborative study to estimate precision of a standardized rat assay for determining true protein digestibility in selected animal, fish, and cereal products. Each of 7 test protein sources (casein, tuna fish, macaroni/cheese, pea protein concentrate, rolled oats, pinto beans, and nonfat dried milk) was fed as the sole source of protein at a 10% protein level in mixed diets. Each diet was fed to 2 replicate groups of 4 rats each for a 4-day acclimation period and a 5-day balance period. Mean digestibilities ranged from 98.6% for casein to 72.6% for pinto beans. Repeatability standard deviations ranged from 0.5 to 2.0%; the mean relative standard deviation for repeatability was 0.9% (range 0.5-2.8%). Reproducibility standard deviations ranged from 1.2 to 3.2%, and the mean relative standard deviation for reproducibility was 2.4% (range 1.3-4.4%). The method has been approved interim official first action for determining true protein digestibility in foods and ingredients.

Animals↗
PubMedDate not supplied

Rapid analysis of nutritionally important free amino acids in serum and organs (liver, brain, and heart) by liquid chromatography of precolumn phenylisothiocyanate derivatives.

An amino acid analysis method for protein hydrolysates, using precolumn phenylisothiocyanate (PITC) derivatization and liquid chromatography, was modified for its application in rapid analysis of commonly occurring free amino acids in serum and other physiological samples. The modifications included changes in column temperature (47.5 degrees C compared to 25-35 degrees C used in analyzing protein hydrolysates), method of preparing standard and test samples, and gradient conditions. By using a Waters Pico-Tag amino acid analysis 15 cm long column (which is also used for analyzing protein hydrolysates), separation of 27 PTC-amino acids in human serum and rat liver, brain, or heart was completed in 20 min by the modified method. The total time for analysis and equilibration was 30 min. The modified method was much faster than the traditional ion-exchange methods (2-3 h) or the existing liquid chromatographic methods using PITC derivatization (66-80 min) for determining nutritionally important free amino acids in physiological fluids and tissues. Variability of the method (expressed as coefficients of variation) for the determination (including deproteinization, derivatization, and liquid chromatography) of all amino acids was less than 5%, which compared favorably with the reproducibility of ion-exchange methods.

Amino Acids↗
PubMedDate not supplied

Amino acid rating method for evaluating protein adequacy of infant formulas.

Amino acid profiles and/or protein digestibility (by the rat balance method) were determined for various forms (powder, ready-to-use, liquid concentrate, etc.) of cow's milk- and soy-based infant formulas obtained from 4 manufacturers. The essential amino acid data of the formulas were compared with that of human milk for the calculation of amino acid scores (based on the single most limiting amino acid). The product of amino acid score and total protein (g/100 kcal) was then termed "amino acid rating." Amino acid scores for the milk- and soy-based formulas ranged from 59 to 90 and from 59 to 81%, respectively, due to deficiencies in sulfur amino acids and/or tryptophan. Because of significantly higher total protein contents (g/100 kcal) of soy- (2.65-3.68) and milk-based (2.20-2.95) infant formulas compared to human milk (1.5), the relative amino acid ratings (human milk = 100) for all infant formulas except 2 liquid concentrates (having values of 87%) were above 100%. Values for true digestibility of protein in milk- and soy-based formulas ranged from 87 to 97 and from 92 to 95%, respectively. When corrected for protein digestibility, the relative amino acid ratings for all the milk-based liquid concentrates were below 100% (77-98%).

Amino Acids↗
PubMedDate not supplied

Complete amino acid analysis in hydrolysates of foods and feces by liquid chromatography of precolumn phenylisothiocyanate derivatives.

The amino acid analysis method using precolumn phenylisothiocyanate (PITC) derivatization and liquid chromatography was modified for accurate determination of methionine (as methionine sulfone), cysteine/cystine (as cysteic acid), and all other amino acids, except tryptophan, in hydrolyzed samples of foods and feces. A simple liquid chromatographic method (requiring no derivatization) for the determination of tryptophan in alkaline hydrolysates of foods and feces was also developed. Separation of all amino acids by liquid chromatography was completed in 12 min compared with 60-90 min by ion-exchange chromatography. Variation expressed as coefficients of variation (CV) for the determination of most amino acids in the food and feces samples was not more than 4%, which compared favorably with the reproducibility of ion-exchange methods. Data for amino acids and recoveries of amino acid nitrogen obtained by liquid chromatographic methods were also similar to those obtained by conventional ion-exchange procedures.

Amino Acids↗
PubMedDate not supplied

Comparison of interlaboratory variation in amino acid analysis and rat growth assays for evaluating protein quality.

Estimates of inter- and intralaboratory variation of protein efficiency ratio (PER), relative PER (RPER), net protein ratio (NPR), relative NPR (RNPR), and nitrogen utilization (NU) were compared with those of amino acid analysis in the same batches of 7 protein sources (ANRC casein, egg white solids, minced beef, soy assay protein, rapeseed protein concentrate, pea flour, and whole wheat flour). Interlaboratory variation (estimated as between-laboratories coefficients of variation, CV) of NPR and RNPR (up to 6.0%) was lower than that of PER (up to 20.2%) and RPER (up to 18.5%). The interlaboratory determination of NPR and RNPR was also more reproducible than that of most essential amino acids (CV up to 10.0%), especially tryptophan (CV up to 23.7%), cystine (CV up to 17.6%), and methionine (CV up to 16.1%). Intralaboratory variation (estimated as within-laboratories CV) of amino acid analysis (up to 4.7%), however, was comparable to that of protein quality indices in most protein sources (up to 6.0%). The significant (P less than 0.01) positive correlations (r = 0.68-0.74) between amino acid scores and protein quality indices based on rat growth were further improved when amino acid scores were corrected for digestibility of protein (r = 0.73-0.78) or individual amino acids (r = 0.79-0.82).

Amino Acids↗
PubMedDate not supplied

Corrected relative net protein ratio (CRNPR) method based on differences in rat and human requirements for sulfur amino acids.

The requirement for sulfur amino acids was calculated for growing rats fed 8% protein diets. The rat and human requirements for sulfur amino acids were compared and a correction factor was developed to reflect the differences. This correction factor was used to determine corrected relative net protein ratio (CRNPR) values for a number of potential meat extenders and their mixtures with beef. The methionine + cystine requirement of growing rats was estimated to be 4% of protein for 8% protein diets. The methionine + cystine requirement of rats was about 50% higher than that of humans (2.65% of protein). Based on this comparison (rat/human), a correction factor of 1.5 was developed to correct RNPR values of those protein products that were deficient in sulfur amino acids for rat growth. The CRNPR values of beef, casein, soybean protein products, pea concentrate, and peanut meal were 100, 100, 91-97, 75, and 73, respectively. Mixtures (50:50 protein basis) of beef with casein, soybean concentrate, soybean isolate, pea concentrate, peanut meal, rapeseed concentrate, rapeseed isolate, sunflower isolate, or wheat gluten were equal to beef in CRNPR values. The CRNPR method is a good predictor of protein quality for humans of those protein products that are deficient in sulfur amino acids.

Amino Acids↗
PubMedDate not supplied

Inter- and intra-laboratory variability in rat growth assays for estimating protein quality of foods.

Protein efficiency ratio (PER), relative PER (RPER), net protein ratio (NPR), relative NPR (RNPR), and nitrogen utilization (NU) methods were investigated in an interlaboratory rat growth study. Six collaborating laboratories studied 7 protein sources (ANRC casein; minced beef; soya assay protein, SAP; pea flour; whole wheat flour, WW; rapeseed protein concentrate, RPC; and egg white solids, EW), and their 10 supplementary or complementary mixtures (casein + Met, SAP + Met, pea flour + Met, WW + Lys, WW + casein, WW + beef, WW + SAP, WW + pea flour, WW + RPC, WW + EW). Test protein(s) were added at the 8% level (N X 6.25). Casein + Met was used as the reference protein. Interlaboratory variation (estimated as between-laboratories coefficients of variation) of PER (up to 17.2%) was greater than that of RPER (up to 14.9%), NU (up to 9.5%), NPR (up to 7.0%), and RNPR, which had the lowest variability (up to 4.7%). In most cases, intralaboratory variation (estimated as within-laboratories coefficients of variation) for all the methods was less than 5%.

Animals↗