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Biomedical subjects

B A Friend

Publications and source records attributed to B A Friend.

8 recordsLinked to original sources
PubMed1983

The effect of processing and storage on key enzymes, B vitamins, and lipids of mature human milk. I. Evaluation of fresh samples and effects of freezing and frozen storage.

A study was initiated to evaluate the effects of several methods of processing and storage on key enzymes, B vitamins, and lipid components of mature human milk. In order to establish standard values for the nutrient components with which to compare processed samples, a total of 30 individual raw samples of mature human milk were analyzed. There was considerable sample to sample variation as indicated by the large range of values for each component. Freezing and frozen storage had little effect on the enzymes of pooled samples of milk. Lactoperoxidase activity decreased from 36 in raw pooled samples to 17 in pooled samples slow frozen and stored for 3 months at -25 degrees C (P less than 0.05). Similarly, quick freezing and storage for 3 months significantly decreased the lactoperoxidase activity of pooled samples from 93 to 14 (P less than 0.05). Quick freezing and frozen storage tended to increase lipase activity although the changes were not significant. Freezing and frozen storage did not significantly affect the levels of biotin, niacin, and folic acid. Similarly, the total lipid fatty acid level and relative % of each fatty acid were not significantly different in the frozen samples as compared to the raw samples.

Enzymes↗
PubMed1982

Ion exchange separation of the antitumor component(s) of yogurt dialyzate.

The active antitumor component of yogurt obtained by dialysis was further fractionated by ion exchange chromatography into acidic, basic, and neutral fractions, which were analyzed for activity by in vitro agar diffusion, cell culture, and in vivo mouse assay. Neither dialysate nor fractions showed any antitumor activity when tested by agar diffusion or cell culture techniques. When tested by in vivo mouse assay, the dialyzate as well as the anionic fraction showed significant inhibitory activity. The cationic fraction showed no activity. There was no direct relationship between stage of purification and antitumor activity. Moreover, the response of the dialyzate or anionic fraction was not linear with concentration. The antitumor activity of the yogurt fraction(s) may be related to a host-mediated immunological reaction or "activation" of the "inactive" component(s).

Animals↗
PubMed1980

Human milk ribonuclease.

Two components having ribonuclease (EC 3.1.27.5) activity were isolated from human milk. Each component of human milk ribonuclease (RNAase) moved at a slightly different rate when electrophoresed on polyacrylamide gel but at the same rate when ultracentrifuged. The major component had a molecular weight of approx. 14 000, an isoelectric point of pH 7.9, and exhibited a broad absorbance maximum between 277 and 281 nm. Human milk RNAase hydrolyzed yeast RNA, poly(cytidylic acid) and poly(uridylic acid) but not DNA, poly(adenylic acid) or poly(guanylic acid). Maximum activity occurred at pH 7.7 and 60 degrees C. Amino acid analysis of the major component revealed a large number of alanine, valine, glycine and aspartic acids but no tryptophan or free sulfhydryl groups. Lysine was the N-terminal amino acid. Tryptic hydrolysis yielded 18 peptides, some of which are similar to those from bovine pancreatic RNAase. Human milk RNAase activity was increased in the presence of NaCl, KCl and sodium citrate and decreased by CaCl(2), MgCl(2), FeSO(4), ZnSO(4) and CuSO(4).

Amino Acid Sequence↗
PubMed1980

Role and significance of enzymes in human milk.

Although human milk generally contains higher levels of enzymes than bovine milk, little definitive information is available concerning their role or significance. The enzyme levels in human milk as compared to bovine milk and levels in human colostrum versus normal milk are summarized. The few most widely studied human milk enzymes are discussed in more detail. Evidence is presented to support the views that 1) lipoprotein lipase and ribonuclease are probably spilled into the milk from the blood; 2) lysozyme is spilled from the secretory epithelial cells; 3) lactate and malate dehydrogenases, glucose-6-phosphate dehydrogenase, and lactose synthetase are synthesized in the mammary gland in response to hormonal stimuli; and 4) bile salt stimulated lipase, diastase, protease, and lysozyme are present in sufficient quantities to aid infants in growth and nutrition. Consideration must be given to standardizing the various enzyme assay procedures and activity units so that meaningful comparisons between various studies could be made.

Animals↗
PubMed1976

Relationship between composition and stability of bovine milk lysozyme.

The amino acid analysis, peptide mapping, and heat stability of bovine milk lysozyme are presented. The bovine milk lysozyme molecule contains approximately 154 amino acids and is strikingly different in amino acid content from human milk lysozyme and egg white lysozyme. Tryptic hydrolysis yielded 26 peptides, all of which are unique from tryptic peptides of human milk lysozyme and egg white lysozyme. In addition, bovine milk lysozyme was more heat stable than human milk lysozyme at pH 4.0 but more labile at pH 7.0 and 9.0. Possible explanations for the differences in heat stability are discussed.

Amino Acids↗