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Biomedical subjects

K J Carpenter

Publications and source records attributed to K J Carpenter.

At least 55 records · Page 3Linked to original sources
PubMed1982

The bioavailability for humans of bound niacin from wheat bran.

Ethanolic wheat bran extracts were dialyzed and dried on starch. One portion [bound niacin (BN)] was cooked in steam; another [alkali-treated bound niacin (ABN)] was made alkaline with calcium oxide and then cooked. The niacin in BN was bound to large molecules (gel filtration); in ABN it was free. Three subjects each consumed a standard daily diet containing approximately 20 mg niacin equivalents. Urine was collected throughout. From day 14, each received three doses in random order at 8-day intervals. The doses, each spread over 2 days, were of BN and ABN, containing 35 mg niacin and 24 mg pure nicotinic acid. The above base-line response in urinary metabolites (N1-methylnicotinamide + N1-methyl-2-pyridone-5-carboxamide) over the 6 days from the beginning of each dose was equivalent to 24% of ingested niacin after BN, 62% after ABN and 89% after nicotinic acid. The niacin in BN appeared mostly unavailable.

Adult↗
PubMed1982

The available niacin values of foods for rats and their relation to analytical values.

A bioassay for niacin was developed using weight gain or "gain/food eaten" of young rats as the response measure. The best basal diet contained casein 70 and gelatin 65.5 g/kg together with supplementary tryptophan to a total of 0.97 g/kg and other amino acids to meet requirements. After a 4-day depletion period, rats gained ca. 1 g/day over the next 20 days on the basal diet alone, or ca. 7 g/day and 12 mg/kg added nicotinic acid. Test foods were added at two levels with diets adjusted to keep constant amino acid composition. The results were compared with chemical analyses for total niacin (i.e., in extracts prepared from samples digested with alkali) and for free niacin (using extracts made at neutral pH) with separation of nicotinic acid and nicotinamide on thin-layer chromatograms or Sephadex columns. Eight samples of mature cooked cereals, with their niacin largely in bound forms, gave rat assay values equivalent to ca. 35% of their total niacin content. Alkali-cooked tortilas, steamed sweet corn, beans and liver, with their niacin all in free form, gave assay values close to their total niacin content. Baked potatoes and peanut flour were intermediate in both respects.

Animals↗
PubMed1982

The effects of alkali-cooking of corn and supplementation with amaranth seed on its deficiencies in lysine and tryptophan.

Corn, made into tortillas (flat cakes baked from lime-treated corn) is the staple food of Mexico. The amino acid deficiencies of tortillas (TT) and boiled corn (BC), and the supplementary value of amaranth seed (PA), another traditional Mexican food, roasted to the point of "popping", were studied. The feeding tests were 14-day PER trials using weanling rats; each diet contained 8.95% crude protein, all from corn, or with PA providing 3.6% protein and corn the remainder, with vitamin and mineral supplements. In addition each diet was supplemented with lysine (lys) so that tryptophan (trp) would be the first limiting amino acid or vice versa. In no comparison did TT give a significantly different value from BC. With trp limiting, the mean PER for the two corn preparations alone was 1.55, and with PA, 2.22. The amaranth had shown a high trp value (1.55 g/16g N). g N). With lys limiting, the mean PER for corn was 1.15; adding PA failed to improve this. Popping amaranth also reduced its reactive lysine value (by dye-binding) from 5.9 to 4.0 g/16g N. It appears that making tortillas has no adverse effect on protein value, but that 'popping' can reduce the value of amaranth seeds. The higher PER for corn with trp as the limiting amino acid (rather than lys) was due to lower ad libitum food intake with the same weight gain.

Animals↗
PubMed1978

The effect of a high level of dietary leucine on the niacin status of chicks and rats.

Baby chicks were fed purified diets containing 90 g/kg casein and 100 g/kg gelatin. With low levels of niacin and tryptophan, niacin deficiency resulted: this was not exacerbated by the addition of supplementary leucine (17.4 g/kg). With levels of niacin and tryptophan that supported rapid growth the further addition of supplementary leucine depressed food consumption and weight gain; in most instances this was statistically significant. No evidence was obtained to indicate that a high level of dietary leucine could result in niacin deficiency in chicks. Comparable experiments were carried out with weanling rats given a basal diet containing 60 g/kg casein and 60 g/kg gelatin. Adding 15 g/kg L-leucine gave results similar to those obtained with chicks and the same conclusions were drawn.

Amino Acids↗
PubMed1978

The effect of a high level of dietary leucine on the niacin status of dogs.

Two feeding trials were designed to precipitate niacin deficiency in puppies receiving low levels of niacin by adding 15 g/kg supplementary l-leucine to a diet containing 180 g/kg casein. We failed to produce such an effect and, as niacin levels were gradually reduced, the times at which control dogs became deficient (and then responded to injections of the vitamin) were not significantly different from those for dogs receiving the leucine supplement. Differences between the conditions of our experiments and of the experiment in which this effect was found are discussed. Two pairs of littermates in trial 2 died suddenly while apparently in fairly good condition, but revealing fatty livers and/or changes in heart muscle on autopsy. Similar observations have been reported by others using purified diets with dogs over long periods; there is no certain explanation.

Amino Acids↗
PubMed1977

Nutritional significance of cross-link formation during food processing.

When proteins are severely heated, in the presence or absence of sugars, the fall in nutritional value appears to be largely, although not completely, explained by reduced protein digestibility. All amino acids are considerably reduced in availability; which is in contrast to early Maillard damage which occurs under mild conditions of heating or storage in the presence of reducing sugars and affects mainly lysine. It seems that corss-linkages are formed in the severely heated protein or protein-sugar mixes and that these reduce the rate of protein digestion. When freeze-dried chicken muscle (15% H2O content) was severely heated its protein shown a great fall in digestibility but its value for supporting growth in the rat had fallen even more. Aspartyl-lysine and glutamyl-lysine cross-linkages, which had been formed during heating, appeared to be as digestible as the total N component and it seems that once they are released from the protein chain they can be absorbed and utilized.

Amino Acids↗
PubMed1976

Mechanisms of heat damage in proteins. 7. The significance lysine-containing isopeptides and of lanthionine in heated proteins.

1. Studies have been made with solvent-extracted chicken muscle, bovine plasma albumin (BPA) and other proteins, all severely heated in the absence of carbohydrates so as to cause a large decrease in their fluorodinitrobenzene (FDNB)-reactive lysine contents. 2. epsilon-N-(beta-L-aspartyl)-L-lysine and epsilon-N-(gamma-L-glutamyl)-L-lysine isopeptides were determined after enzymic digestion of heated chicken muscle, and their content was found to increase as the material was subjected to more heat treatment. Heated chicken muscle was not found to contain lanthionine. Heated BPA, on the other hand, was found to contain lanthionine but not the isopeptides. Both lanthionine and isopeptide cross-linkages were detected in most of the other heated proteins. There was some difficulty in quantifying the amounts of isopeptides formed on heat treatment, because the enzymic digestion procedure used in their isolation appeared to be incomplete. Neither lysinoalanine nor ornithinoalanine was detected in any of the test materials.

Alanine↗
PubMed1975

Mechanisms of heat damage in proteins. 6. The digestibility of individual amino acids in heated and propionylated proteins.

1. The digestibilities of protein and amino acids have been estimated by two different techniques: the analysis of faeces (conventional method) and the analysis of ileal contents (ileal technique). 2. Freeze-dried muscle protein was found by both techniques to be almost completely digested. After autoclaving, the digestibility for the same protein was estimated by the conventional and ileal techniques to be 0.65 and 0.57 respectively. 3. Unmodified lactalbumin was found by both techniques to have digestibility of about 0.90. Propionylation of the lactalbumin reduced digestibility to 0.82 and 0.79 as indicated by faecal analysis and ileal content analysis respectively. 4. In general, the digestibilities of individual amino acids in any one protein sample were rather uniform, and reflected over-all protein digestibility. For each amino acid, digestibility, as determined by both methods, was lower for the modified protein than for the corresponding control protein: estimates based on ileal content analyses were consistently lower than those obtained by conventional analyses. The ileal technique was considered to be both more convenient and meaningful. 5. From the results obtained by the ileal technique it appears that reduced digestibility is an adequate explanation for the reduction found in nutritional value of the autoclaved protein. In contrast, for the propionylated protein, reduced digestibility of lysine is only a partial explanation of the low availability of this amino acid as estimated by chick growth assay. 6. In our experiments we found that the type of dietary protein used did influence the amino acid composition of the ileal contents. This was most marked with the least-digestible protein. These findings do not support the views of Nasset (1962).

Amino Acids↗
PubMed1975

The use of three dye-binding procedures for the assessment of heat damage to food proteins.

1. A study has been made of pure proteins heated either alone or in contact with sugars, so as to cause a severe fall in their reactive lysine contents, and also of commercial protein concentrations. 2. For unheated materials, and for bovine plasma albumin and fat-extracted, dried chicken muscle severely heated in the absence of sugar, Acid Orange 12 binding values (mmol bound dye/kg crude protein (nitrogen times 6-25)) were close to the sum of total histidine, total arginine and reactive lysine contents (mmol/kg crude protein (N times 6-25)), which we have termed HARL values. The dye-binding values and the HARL values were reduced similarly by heat treatment. 3. For materials in which protein and glucose had reacted under mild conditions (37 degrees), the dye-binding capacity with Acid Orange 12 was unchanged even though the HARL value of these materials was considerably reduced. When protein and glucose or sucrose were heated more severely, the dye-binding capacity was slightly lowered but not to the same extent as the reduction in the basic amino acids. 4. Animal feeding-stuffs, whether unheated, industrially processed or diliberately heated, appeared to react with Acid Orange 12 in the same way as the model systems (selected to represent three types of heat damage: 'advanced' and 'early' Maillard and protein-protein damage). 5. Remazol blue binding values and fluorodinitrobenzene (RDNB)-reactive lysine values were similarly reduced in materials that had been severely heated, either with or without added sugars; however, when protein and glucose had reacted under mild conditions the fall in Remazol blue binding was less than that in FDNB-reactive lysine. 6. For the model materials, binding with cresol red was, in general, higher for heated samples but the results showed no correlation with FDNB-reactive lysine values. For meat and groundnut meals, changes in values after heat treatment were smaller than those that have been reported for soya-bean meals.

Alkanesulfonates↗