Comparative assessment of soy and milk protein quality in infant cebus monkeys

Protein qualities of lactalbumin (L), casein (C), soy concentrate (SC), soy isolate (SI), and soy isolate plus 15.3 mg methionine/g protein (SIM) were investigated in a slope-ratio assay using 32, 8-wk old cebus monkeys. Growth (28 days) and nitrogen balance (NB) (days 19-28) data were evaluated in a multiple-regression format with nitrogen intake and body weight as the independent variables. Based upon growth, potencies compared to L were: C, 72.1; SC, 52.5; SI, 40.6; and SIM, 72.2. Based upon NB, comparable potencies were: C, 62.2; SC, 69.0; SI, 46.8; and SIM, 90.7. NB data showed that the potency of SC was significantly greater than SI and that methionine supplementation of SI improved it to a potency not distinguishable from the standard. The marked improvement from SI to SIM emphasizes the beneficial effect of sulfur amino acid supplementation of soy protein for an infant primate species.

Protein quantity and quality in term and preterm infants: effects on urine creatinine and expression of amino acid excretion data

The effect of dietary protein quantity and quality on the excretion of creatinine in preterm and term neonatal infants has been investigated. Whey protein predominant formulas result in increased creatinine excretion as compared with either casein protein predominant formulas or with pooled human milk in preterm infants (p less than 0.001 by ANOVA). The volume of human milk (170 versus 185 versus 200 ml/kg/day) appears to have little effect in these infants. In term infants, few differences among the feeding groups were observed, although creatinine excretion did increase with time. The pattern of creatinine excretion among feeding groups was similar regardless of whether or not the data were expressed in milligrams per deciliter or in milligrams per 24 hours. Small correlations of creatinine excretion with birth weight were observed, but these appeared to vary, depending on the type of feeding. These diet-induced differences in creatinine excretion indicate the need for caution in expressing other urinary metabolites, such as amino acids, relative to creatinine excretion.

Utilization of zinc from picolinic or citric acid complexes in relation to dietary protein source in rats

Young male Sprague-Dawley rats were divided in 18 groups of eight animals each and were fed ad libitum for 24 d a purified diet with 20% casein, whey protein or serum albumin as protein source. Each diet was supplemented with zinc picolinate, zinc citrate or zinc sulfate to a level of dietary zinc equal to 5 or 10 ppm. The source of zinc had no significant effect on zinc utilization with any of the three dietary proteins or at either dietary zinc concentration. With the 5 ppm Zn diet zinc concentration in the serum, but not weight gain or the zinc concentration in femur, testis or whole body was lower in rats fed the casein diet than in those fed the whey diet. Zinc concentrations in serum, femur, testis and whole body, but not weight gain, were lower in rats fed the casein diet than in those fed the serum albumin diet. With the 10 ppm Zn diet, zinc concentrations in serum, femur and whole body, but not weight gain nor zinc concentration in testis, were lower in rats fed the casein diet than in those fed either of the other diets. These results suggest that the reason for the lower utilization of zinc from cow milk in comparison to human milk may be the higher casein concentration in cow milk.

Purification of a mammary-derived growth factor from human milk and human mammary tumors

A growth factor, mammary-derived growth factor 1 (MDGF1), has been purified to apparent homogeneity from human milk. The factor is a pepsin-sensitive, reducing agent-insensitive protein with a molecular mass of 62 kDa and a pI of 4.8. An apparently identical factor has been isolated from human mammary tumors, suggesting that MDGF1 might be made by and act as an autocrine growth factor for mammary cells. High affinity receptors for MDGF1 have been detected on mouse mammary cells, normal rat kidney cells, and A431 epidermoid cells (KD = 2 X 10(-10) M). MDGF1 at picomolar levels stimulates the growth of mammary cells and greatly amplifies their production of collagen, apparently via elevating collagen mRNA levels, an effect that is demonstrated for normal rat kidney cells. The responsiveness of mammary cells to MDGF1 is attenuated when the cells are grown on a basement membrane collagen substratum, a component of the extracellular matrix upon which these cells normally rest in vivo. MDGF1 thus may regulate the production of new basement membrane as mammary epithelium invades the stroma during proliferation.

[Effect of animal protein supplementation and energy on the protein quality of diets based on rice and beans in adult males]

Four short nitrogen balance index studies were carried out in adult subjects to evaluate the biological quality of a mixture based on rice and beans, and also to measure the effect of animal protein and/or energy supplementation on the nutritive value of the mixture. In the first study, rice supplied 60% and beans, 40% of the protein's diet, which was administered at an energy level of 45.5 kcal/kg/day of metabolizable energy. A regression coefficient of 0.76 +/- 0.11 was found between ingested nitrogen and nitrogen balance, and a value for nitrogen maintenance of 96.2 +/- 13.7 mg/kg/day. When this same diet was administered in the second study at a 51.2 kcal/kg/day of metabolizable energy, the regression coefficient was 0.80 +/- 0.13, and that of nitrogen for maintenance, 90.1 +/- 8.7 mg/kg/day, without differences being significant (P less than 0.05) for any of the two measures. In the third study, 10% of the mixture's protein was substituted by milk protein, and given at a level of 45.2 kcal/kg/day of metabolizable energy. In this case, the regression coefficient found was 0.96 +/- 0.08, and that of nitrogen for maintenance, 78.6 +/- 10.2 mg/kg/day. These values do differ significantly (P less than 0.05) from those found in the two previous studies. When the diet of the third study was administered to the same subjects at a level of 48.9 kcal/kg/day of metabolizable energy, the regression coefficient of the equation was 0.86 +/- 0.17, and that for maintenance nitrogen, 82.4 +/- 10.2 mg/kg/day. These values are statistically equal to those found in the third study and do differ significantly from those of the first two studies. Information indicates that the supplementary effect of protein and milk occurs mainly at the digestive level. It is therefore concluded that when rice and beans are consumed jointly, in the adequate proportions, they constitute an excellent-quality food for adult humans.

BALB/c mice fed milk or beef protein: differences in response to 1,2-dimethylhydrazine carcinogenesis

The development of 1,2-dimethylhydrazine (DMH)-induced colon tumors and immune responses were investigated in male BALB/c mice fed six different equicaloric diets. Milk or beef at a low (11%) or high (33%) level supplied the dietary protein, and corn oil (primarily) at a low (5%) or high (30%) level supplied the fat. Eleven weekly injections of DMH (at 20 mg/kg mouse) or saline were administered. At 59 weeks of age, the milk-fed mice had a significantly higher (P less than or equal to .05) colon tumor incidence than the beef-fed mice, 67 and 16%, respectively. Tumor volume and colon weight in the milk-fed mice were also significantly greater. Low natural killer cell activity against [125I]5-iodo-2'-deoxyuridine-labeled colon tumor cells and high serum blocking of antitumor cell activity were observed in the milk-fed-mice. These mice also exhibited higher T-lymphocyte cytotoxicity against colon tumor cells. These results differ from those of our previous studies and those of numerous epidemiologic investigations.

The specificity of wheat protein reactivity in coeliac disease

The purpose of this study was to compare the effects of seven wheat protein fractions on the cell-mediated immune response of coeliac patients and normal individuals, by means of the leukocyte migration inhibition factor (LMIF) assay. Two preparations of milk protein were used as control antigens. Whereas milk protein had no effect on the release of LMIF by cells from either normal or coeliac patients, wheat protein preparations stimulated two types of response. A non-specific reaction was elicited from both coeliac and normal cells by crude preparations such as gliadin and Frazer's fraction III (an enzyme digest of gluten), whereas purified fractions (alpha gliadin and alpha-pel) stimulated a specific response from the cells of coeliac patients only. These results suggest that only a pure wheat protein preparation such as alpha gliadin or alpha-pel is of value in studying immunological parameters in coeliac disease.

Influence of folate-binding protein from bovine milk on the absorption of folate in gastrointestinal tract of rat

The absorption of [14C]pteroylglutamic acid (PteGlu) bound to the folate-binding protein of bovine milk was investigated in rat gastrointestinal tract in vivo and in situ. When bound [14C]PteGlu was given to rat intragastrically via oral intubation, a considerable amount of PteGlu was released from folate-binding protein under the acidic conditions in stomach, and it recombined with folate-binding protein in jejunum in vivo. Compared with free PteGlu, bound PteGlu was more gradually absorbed in small intestine, but finally the total amount of bound PteGlu absorbed was almost the same as that of free PteGlu. In all experiments in situ, bound PteGlu was only slightly absorbed in jejunum, where free PteGlu was rapidly absorbed under the same conditions. On the other hand, the absorption rates of the two forms of PteGlu were almost similar to each other in ileum. These results suggest that PteGlu bound to folate-binding protein is absorbed by a manner different from that of free PteGlu in rat gastrointestinal tract.

Effects of whey protein, casein, soya-bean and sunflower proteins on the serum, tissue and faecal steroids in rats

Four groups of rats were fed for 49 d on one of four semi-purified diets, without added cholesterol and containing 230 g/kg of the following isolated proteins: casein, whey, soya-bean or sunflower. Whey, soya-bean and sunflower proteins, when compared with casein, decreased the level of serum high-density-lipoprotein (HDL)-cholesterol. These low cholesterol levels were accompanied by an increase in the daily faecal excretion of neutral sterols and bile acids in the case of soya-bean protein, and by a decrease in the liver cholesterol content, when rats were fed on whey protein. Considering the amino acid composition of the four purified proteins, we observed that serum total and HDL-cholesterol levels had a significant positive correlation with tyrosine and glutamic acid, and a negative correlation with cystine and alanine. The present study showed that the hypocholesterolaemic effect of dietary proteins was not related to their animal or vegetable origin.

Trace-nutrient-binding proteins in milk and the growth of bacteria in the gut of infant rabbits

1. The influence of trace-nutrient-binding proteins on the growth of coliforms, streptococci and lactobacilli in the gastrointestinal tract was examined in neonatal rabbits delivered germ-free and dosed with an artificial flora (ESL), or born conventionally and dosed with ESL or rabbit faeces. 2. In the stomach and small intestine of both gnotobiotic and conventional animals the counts of coliforms were usually atypically high and those of streptococci were always low. In the colon the counts of coliforms and streptococci were high. Lactobacilli usually became established in the gut of the gnotobiotic animals but were not found in the conventional rabbits. 3. Sterilization (freeze-drying followed by gamma-irradiation) of the milk decreased its capacity to bind added iron by 45% and vitamin B12 by 30%. When compared with raw milk, feeding of radiation-sterilized milk did not affect the viable count of coliforms and streptococci in the gut of gnotobiotic animals. 4. Saturating the nutrient-feeding proteins in milk with Fe, folic acid and vitamin B12 had no effect on the numbers of coliforms, streptococci and lactobacilli recovered from the intestine.

Postprandial changes in the levels of lipids, glucose, urea and nonprotein nitrogen in the serum of veal calves fed milk replacers containing either skim milk powder or soybean protein concentrate

Postprandiale Veränderungen in der Serumkonzentration an Fetten, Glucose, Harnstoff und NPN bei Kälbern nach Zufuhr von Milchaustauschern mit Magermilchpulver oder Sojaproteinkonzentrat

Kälber im Alter von 7 Wochen (5–6 Tiere je Gruppe) erhielten Milchaustauscher mit Magermilchpulver oder Sojaproteinkonzentrat über 14 Wochen. Die Gewichtsentwicklung der Tiere zeigt bei der Magermilchgruppe eine höhere Tendenz.

Am Ende der Versuchsperiode wurden Blutproben kurz vor der Fütterung und etwa 3 Stunden nach der Fütterung genommen. Die Proteinquellen hatten keinen signifikanten Einfluß auf den Serumgehalt an Glucose, Harnstoff, NPN, Triglyceriden, Cholesterin und Phospholipiden vor der Fütterung. Ca. 3 Stunden nach der Aufnahme des Milchaustauschers mit Sojaproteinkonzentrat waren die Konzentrationen an NPN, Triglyceriden, Phospholipiden und Cholesterin erhöht. Die Unterschiede im Phospholipidgehalt und Cholesteringehalt waren signifikant. In der Magermilchgruppe war die Glucosekonzentration erhöht.

Die Erhöhung des Cholesteringehaltes wird auf die Freisetzung von Cholesterin bei der Umwandlung von HDL in LDL bei Sojaprotein‐Milchaustauscher zurückgeführt. Es wird vermutet, daß ein Teil der aufgezeigten postprandialen Veränderungen darauf beruhten, daß das Kasein im Gegensatz zum Sojaproteinkonzentrat im Abomasum des Kalbes koaguliert.

Bioavailability of zinc from a diet based on isolated soy protein: application in young men of the stable isotope tracer, 70Zn

With the aid of the stable isotope, 70Zn, as a tracer and neutron activation analysis, a combination of extrinsic labeling of meals and fecal monitoring of isotope excretion was used as a safe and noninvasive approach for assessing the effects of the vegetable (soy) and animal (milk, beef) proteins on the absorption of zinc in healthy, adult human volunteers. A known amount of 70Zn was added as ZnCl2, to six consecutive meals over a 2-day period during which either one of three isonitrogenous liquid formulas (skim milk; soy isolate; or a 50:50 mixture) or one of two bologna sausages (soy isolate of beef) were given. The mean absorption of 70Zn from milk, soy and soy/milk was 41 +/- 4, 34 +/- 4, and 41 +/- 7% (mean +/- SEM), respectively, the presence of soy protein having no effect on absorption of the extrinsic label. For beef bologna and soy bologna, fractional absorption of the 70Zn tracer was 41 +/- 4 and 30 +/- 3%, respectively. Beef might favor absorption of extrinsic zinc. The kinetics of isotope excretion, pooling procedures, for stool samples and the utility of fecal markers were also evaluated.

Inhibition of the pokeweed mitogen-induced response of normal peripheral blood lymphocytes by humoral components of colostrum

Colostral whey at dilutions up to 1 : 100 inhibited both the uptake of tritium-labelled thymidine and the differentiation of pokeweed mitogen-stimulated peripheral blood lymphocytes from normal adults into immunoglobulin-containing plasma cells. Upon gel filtration (Sephadex G-200), inhibitory activity was associated with high molecular weight fractions. Secretory component, but not monomeric, polymeric or colostral IgA, IgM, IgG, lactoferrin, casein or alpha-lactalbumin, inhibited the response to mitogen. Supernatants from cultures of colostral cells did not induce the differentiation of adult peripheral or cord blood lymphocytes into IgA-containing cells and did not stimulate the uptake of tritium-labelled thymidine.

Artificial rearing of pigs. 10. Effect of replacing dried skim-milk by a single-cell protein (Pruteen) on performance and digestion of protein

1. Spray-dried diets were prepared containing (g/kg): dried skim-milk 665, dried whey 65, soya-bean oil 270 (diet U); or single-cell protein (Pruteen; SCP) 308, dried whey 440, soya-bean oil 252 (diet X). The diets had a crude protein (nitrogen × 6·25) content (g/kg) of 250 (diet U) and 240 (diet X), excluding nucleic acids (36 g/kg) in diet X.

2. The diets were reconstituted (200 g dry matter/l) and mixtures of diets U and X prepared to give diets supplying 0 (diet U), and approximately 400 (diet V), 600 (diet W) and 800 (diet X) g crude protein from SCP/kg total protein. All diets were supplemented with vitamins, and minerals to equalize the calcium, phosphorous, sodium and potassium concentrations.

3. Pigs weaned at 2 d of age were given the diets at hourly intervals on a scale based on live weight. At 28 d age the experiment was terminated and pigs killed 1 h after a feed for a study of protein digestion. Polyethylene glycol (PEG) was fed in the diets (0.5 g/l) for 24 h before slaughter.

4. Performance of pigs fed on diet V was as good as on the all-milk diet U. Greater levels of replacement by SCP (diets W and X) reduced performance. Mortality was greater on the all-milk diet, but protein source had no effect on the incidence of scouring. N retention (g/d per kg live weight) was similar for all diets but declined with age.

5. SCP appeared to stimulate secretion of pepsin and chymotrypsin, and reduced the pH value in digesta in the stomach. Enzyme adaptation may have been insufficient to digest high levels of SCP in the diet, and together with the decreased transit time observed using PEG as a marker, may account for the poorer performance when 600 or 800 g/kg milk protein was replaced.

6. Nucleic acids from SCP were metabolized and not retained for tissue synthesis. Allantoin excretion accounted for 75% of the theoretical maximum for complete excretion of nucleic acids, and uric acid excretion was also increased.

Artificial rearing of pigs. 11. Effect of replacement of dried skim-milk by an isolated soya-bean protein on the performance of the pigs and digestion of protein

1. Pigs (twenty-one/diet) were weaned at 2 d of age and given liquid diets (200 g dry matter/l) at hourly intervals during a 26 d experiment. The pigs were fed on a scale based on live weight. The diets contained (g/kg DM): dried skim-milk 730 (diet A), dried whey 508.5, isolated soya-bean protein 218, DL-methionine 3.5 (diet S), and soya-bean oil 270 (diets A and S). Diet T contained equal proportions of diets A and S. Soya-bean supplied 0, 370 and 740 g crude protein (nitrogen x 6.25) kg total crude protein in diets A, T and S respectively. 2. Performance was similar for both diets A and T (P > 0.05). Pigs given diet S scoured severely, and fourteen died. The survivors grew very poorly. Nitrogen retention (g/d per kg live weight) was greater for diet A compared with diet T (P < 0.01), and decreased with age (P < 0.001). 3. Protein digestion was examined in the pigs killed at 28 d of age. The amount of soya-bean protein in the diet did not affect the amount of digesta in the stomach, but soya-bean protein decreased the pH, DM and total N content of the digesta (P < 0.01), and increased, though not significantly (P > 0.05), pepsin activity in the digesta and stomach tissue. Acid secretion into the stomach appeared to be enhanced in pigs given a diet containing soya-bean protein. 4. Amounts of trypsin, chymotrypsin, total N and proportion of non-protein-N in the digesta from the small intestine were similar for both diets A and T. The amounts for both diets were greater in the distal compared with the proximal region of the small intestine (P < 0.05). Chymotrypsin activity in the pancreas was reduced (P < 0.05) in pigs given diet T, although this reduction did not seem to impair digestion in 28-d-old pigs. Trypsin activity in the pancreas was similar for both diets A and T. 5. It seems likely that the neonatal pig does not have the digestive capacity to tolerate the large daily intakes of soya-bean protein when dried skim-milk was totally replaced in the diet (diet S). When half the dried skim-milk was replaced, protein digestion was not impaired in 28-d-old pigs.

[Effect of component 5 of the proteose-peptone fraction of milk on blood circulation indices]

Under study was the influence exerted by peroral administration of component 5 of the proteosoic-peptone milk fraction on the pulse rate, arterial pressure and cerebral circulation in dogs with the subcutaneously exteriorized carotid and under a functional load on the central nervous system (with photostimulation used as a load). The resulting data on the slowing down of the cardiac contractions rhythm and diminished reaction on the level of the minimum pressure and the stroke volume of the cerebral blood flow in response to the functional load testify to a certain regulating effect exerted by component 5 on the circulation, when the central nervous system is subjected to a functional load.

Milk protein quantity and quality in low-birth-weight infants: II. Effects on selected aliphatic amino acids in plasma and urine

The optimal quantity and quality of protein for low-birth-weight infants is undefined. In this study, 106 well, appropriate-for-gestational-age, low-birth-weight infants weighing 2,100 gm or less were divided into three gestational age groups and assigned randomly within each age group to one of five feeding regimens: pooled human milk; formula 1 (protein content, 1.5 gm/100 ml- 60 parts bovine whey proteins to 40 parts bovine caseins); formula 2 (3.0 gm/100 ml, 60:40); formula 3 (1.5 gm/100 ml, 18:82); and formula 4 (3.0 gm/100 ml, 18:82). The concentrations of the free amino aicds in the plasma and urine of these infants were determined. The plasma concentrations of free amino acids were generally far greater in the infants fed the 3.0-gm/100 ml protein diets than they were in the infants fed pooled human milk. The plasma concentrations of free amino acids of the infants fed the 1.5-gm/100 ml protein diets were intermediate. In general, the concentrations of the free amino acids in the plasma of the infants fed the 3.0-gm/100 ml casein-predominant formula (F4) were furthest from those fed pooled human milk. Glutamate showed the highest plasma amino acid concentrations in infants fed the 3.0-gm/100 ml casein-predominant formula (F4) were furthest from those fed pooled human milk. Glutamate showed the highest plasma amino acid concentrations in infants fed both the high- and low-protein casein-predominant formulas. This was true despite the fact that the intake of glutamate on the high-protein, whey-predominant formula was twice that on the low-protein, casein-predominant formula. The differences between groups in the essential amino acids in plasma were generally greater than those of the nonessential amino acids. The concentrations of amino acids in the urine tended to parallel those of the plasma.