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Biomedical subjects

F E McDonough

Publications and source records attributed to F E McDonough.

At least 19 recordsLinked to original sources
PubMed1989

A collaborative study of methods of protein evaluation: introductory paper.

The USDA's collaborative study of methods of protein quality evaluation is introduced. It was intended primarily to provide a basis for the evaluation of possibly improved procedures for the labelling of foods as a source of dietary protein. In general, the usefulness of in vitro digestibility procedures has been confirmed, but problems remained for the in vitro evaluation of heat-damaged materials and of some types of pinto beans.

Amino Acids, Essential↗
PubMed1989

Bioavailability of lysine in selected foods by rat growth assay.

Lysine bioavailabilities in reference protein and 16 test protein diets were estimated using 10 day rat growth assays. A standard growth curve was obtained by feeding 5 diets containing casein, zein and synthetic amino acids ranging in total lysine concentration from 0.3 to 0.7%. Experimental foods were added to the basal diet at the expense of zein and/or synthetic amino acids to provide 2 specific lysine concentrations, i.e., 0.4 and 0.6%. Availabilities were established by comparing growth responses from the test food diets to the regression line of the standard growth data. Availabilities were over 88% for 13 of 16 products. Utilization was poor in pinto beans (73%), rice-wheat gluten cereal (70%), and skim milk powder heated to 100 degrees C for 12 h (66%). Addition of excess lysine (700 mg/100 g diet) to the pinto bean diet did not improve growth response; thus poor digestibility or some unidentified growth inhibitor is indicated.

Animals↗
PubMed1989

Rat bioassays for methionine availability in 16 food sources.

Methionine availabilities of 16 test proteins were assessed by comparing ten day rat growth response to the test diets and reference (casein) diets. In a preliminary study, various concentrations of methionine and cystine were fed to determine methionine requirements and effect of excess cystine. Results indicated a methionine requirement of about 550 mg per 100 g diet. Cystine had a sparing affect of 50-55%, i.e., about 300 mg could be used to meet methionine requirements. Further additions of cystine (up to 2.6 times methionine) did not affect rat growth. Methionine availabilities were excellent (88-100%) for 15 of the 16 test foods; only pinto beans (58%) were low, but prior evidence indicates that the poor growth response was due to some factor other than availability.

Animals↗
PubMed1989

Bioavailability of tryptophan in selected foods by rat growth assay.

Tryptophan bioavailabilities were estimated in 16 protein sources using 10 day rat growth assays with casein as the reference protein. Growth responses of rats fed test food diets were compared to growth responses of rats fed basal diets with graded levels of tryptophan ranging from 50 to 100 mg of tryptophan/100 g diet. Estimates of tryptophan availabilities were 85-100% for all products except whole wheat cereal (73%) and pinto beans (59%). Results of a previous study on lysine availability indicated that poor response to pinto beans was due either to poor digestibility or to the presence of some unidentified growth inhibitor.

Animals↗
PubMed1989

The use of Escherichia coli mutants to measure the bioavailability of essential amino acids in foods.

The beta-galactosidase-based assay for lysine developed by Tuffnell & Payne was used to measure the bioavailabilities of cyst(e)ine, methionine, threonine and tryptophan in pronase digests of 17 foods. The digests were assayed by estimating the beta-galactosidase synthesis responses of five Escherichia coli mutants, each requiring one of the respective amino acids for protein synthesis. Deletion mutants were used whenever possible in order to ensure strain stability. Single digests of each food were assayed with 3 or 4 separate cultures of each mutant and the results were compared with those from the corresponding chemical assay. Omitting the anomalously low values for one food, the rank correlation coefficients of the bio- and chemo-assay values were 0.61 (cysteine), 0.91 (lysine), 0.95 (methionine), 0.64 (threonine) and 0.85 (tryptophan). Mean (+/- S.D.) relative amino acid bioavailabilities (casein = 100%) for the 17 foods were: cysteine, 53 +/- 23; lysine, 90 +/- 10; methionine, 95 +/- 18; threonine, 89 +/- 13; and tryptophan, 89 +/- 25. The cysteine mutant appeared to give unusually low bioavailability values except for the milk products. These amino acid mutants afford a rapid method for assaying the bioavailabilities of at least four of the five amino acids studied.

Amino Acids, Essential↗
PubMed1989

Prophylactic and therapeutic aspects of fermented milk.

Many claims have been made concerning prophylactic and therapeutic effects of fermented bovine milk consumption. Of these, the amelioration of lactose intolerance symptoms in humans and rats due to the reduced lactose level caused by fermentation is convincingly documented and corroborated. In addition, some kinds of fermentation microbes can contribute to lactose digestion in vivo thus augmenting the preingestive fermentative decrease of lactose. Relief of the growth inhibition and the gastrointestinal infection susceptibility due to high dietary lactose levels can also be achieved by fermentation of milk lactose. The hypocholesterolemic activity of fermented milk is apparently related to a similar uncharacterized activity of ordinary milk. Antitumorigenic effects in rats have been reported. Microfloral alterations due to dietary dairy microbes have been reported to retard the development of colon cancer. Purported human longevity effects have not been supported by appropriate data.

Animals↗
PubMed1987

Modification of sweet acidophilus milk to improve utilization by lactose-intolerant persons.

Enhanced digestion of yogurt by lactose-intolerant individuals is believed to be due to inherent beta-galactosidase (lactase) in the culture organisms that aids in the hydrolysis of ingested lactose. However, sweet acidophilus milk, which contains lactase-rich organisms, does not enhance lactose digestion. Using breath-hydrogen measurements to indicate malabsorption in 14 human subjects, we compared utilization of: milk, yogurt, heated yogurt, yogurt plus lactose, heated yogurt plus lactase, sweet acidophilus milk (SAM), and SAM made with sonicated cells. Results indicate that both the reduction of lactose during fermentation and the presence of indigenous bacterial lactase are responsible for the increased ability to tolerate lactose in yogurt. Improved utilization of SAM by sonication suggests that intracellular lactase is not available during digestion and that sonication releases the lactase activity from the cells.

Animals↗
PubMed1985

Amelioration of the adverse effect of a gastrointestinal challenge with Salmonella enteritidis on weanling rats by a yogurt diet.

The response of yogurt-fed rats and the corresponding unfermented milk-fed rats to an infectious gastrointestinal challenge has been compared. After 1 (2 trials), 7 (4 trials), 14 and 21 (1 trial each) days on freeze-dried milk or yogurt diets, the rats were inoculated intra-gastrically by intubation per os with 4.5 X 10(10) +/- 0.7 colony forming units (mean +/- SEM) of Salmonella enteritidis. Challenged and control rats were monitored during the 3 weeks post-inoculation for viability, weight gain, feed consumption, and feed efficiency. In general, challenged yogurt-fed rats exhibited significantly superior weight gain and feed efficiency (but not feed consumption) values in week 1 post-infection, but the differences were not significant in week 2 post-infection. Sick milk- and yogurt-fed rats convalesced in week 3. Pooled mortality data indicated that yogurt-fed rats survived better than milk-fed rats. Yogurt did not prevent salmonellosis per se but significantly reduced the mortality and weight gain deceleration.

Animals↗
PubMed1983

Contribution of Streptococcus thermophilus to growth-stimulating effect of yogurt on rats.

The origin of the growth-stimulating factor in yogurt was studied in rats fed liquid or freeze-dried diets of milk, yogurt, milks fermented individually by Streptococcus thermophilus and Lactobacillus bulgaricus, milks to which cells of Streptococcus thermophilus and Lactobacillus bulgaricus were added. Diets containing sonicated cells, cell supernatant, and cell fractions also were fed. Milk fermented by Streptococcus thermophilus and milk plus Streptococcus thermophilus cells stimulated growth as effectively as did yogurt. That finding and the absence of stimulation in rats fed Lactobacillus bulgaricus showed that Streptococcus thermophilus is responsible for stimulation of growth by yogurt. Growth was stimulated by an intracellular factor and not by fermentative changes in the milk.

Animals↗
PubMed1978

Minerals in whey and whey fractions.

Liquid and dried acid and sweet wheys and the concentrates and permeates obtained from ultrafiltration of whey were analyzed for major and trace minerals. Calcium, magnesium, sodium, and potassium were determined by atomic absorption and phosphorus by a colorimetric method. Zinc, iron, copper, and manganese were determined by flameless atomic absorption. The composition of all wheys and their fractions differed in nutritionally important minerals. Calcium was three times as great and zinc twenty times as great in acid whey as in sweet whey.

Animals↗
PubMed1975

Growth and carcass evaluation of Holstein steers fed liquid acid whey.

Thirty Holstein steer calves, 96.5 kg, were assigned to three groups. Two groups received liquid acid whey, and one was the water control. Grain was fed either restricted or ad libitum to the whey groups and ad libitum to the water control group over three 14-wk growth periods. Hay, up to .4% body weight, reduced symptoms of bloat. Period 1: Calves started on a 20% crude protein dry ration for 7 wk and then changed to a 16% crude protein dry ration for 7 wk gained faster and were heavier than calves statred on a 30% crude protein dry ration for 7 wk and then changed to a 20% crude protein dry ration for 7 wk. Period 2: Body weights among groups were not different by the end of the period. Intakes of whey were 33.6 kg daily with grain ad libitum and 49.7 kg daily with restricted grain feeding. Water intake was 22.2 kg daily. The steers obtained 28% of their total dry matter intake from acid whey under ad libitum feeding, and 48% from acid whey under restricted feeding. Period 3: Final body weights were decreased by restricted feeding, but acid whey intake increased to 55.6 kg daily. These steers obtained 57% of their total dry matter intake from acid whey. Acid whey treatment resulted in lower carcass dressing percent, rib fat cover, and loin eye area. Grades averaged Standard for acid whey, restricted grain feeding and Low Good for acid whey, ad libitum grain feeding. Lower panel scores were given for aroma and quantity of juice for restricted grain feeding. Acid whey treatment did not change tenderness, shear values, or overall carcass desirability.

Adipose Tissue↗
PubMed1969

Increased sensitivity of immunofluorescent assay for Salmonella in nonfat dry milk.

The necessity of developing a quick, sensitive, and reliable test for Salmonella in nonfat dry milk (NDM) is evident from the recent tracing of Salmonella outbreaks to this product. Normally, coagulation of casein occurs when assaying NDM under regular cultural conditions, raising the possibility of trapped bacteria. After 20 hr of incubation of NDM in preenrichment lactose broth, enrichment was achieved by using Selenite-Cystine Broth. Smears from the enrichment broth were examined by the fluorescent-antibody technique (FAT) with a commercially available polyvalent O globulin conjugated with fluorescein. Standard cultural methods (SCM) were performed for comparison with FAT. Sensitivity of FAT was definitely improved by the use of trypsin. Casein coagulation of NDM can be avoided by addition of trypsin to samples during initial preenrichment in lactose broth. Samples containing approximately one Salmonella per 10 g were easily detected by FAT with the use of trypsin-treated samples. The method required only 42 hr to complete. Additionally, the use of trypsin enhanced recovery of Salmonella by use of SCM, as evidenced by alteration in the observed coliform to Salmonella ratios.

Animals↗