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Biomedical subjects

B Lönnerdal

Publications and source records attributed to B Lönnerdal.

At least 253 records · Page 14Linked to original sources
PubMed1981

Developmental changes in the composition of Beagle dog milk.

The concentrations of iron, copper, zinc, manganese, calcium, magnesium, protein, carbohydrate, and fat were analyzed in dog milk during the first 45 days of lactation. The concentration of iron decreased significantly from 13 microgram/ml on day 0 to 6 microgram/ml. Zinc concentration decreased only slightly from 9.6 microgram/ml to 8.7 microgram/ml. Calcium concentration increased significantly during early lactation, from 1,366 microgram/ml to 1,757 microgram/ml on day 10, but changed little thereafter. Protein concentration increased throughout lactation, from 4.3% early in lactation to 6.3% late in lactation. Fat concentration increased from 2.4% to 4.5% in early lactation, and then decreased to 2.7% in late lactation. The concentrations of copper, manganese, magnesium, and carbohydrate did not show strong developmental patterns; average values were 1.8 microgram/ml, 0.14 microgram/ml, 59 microgram/ml, and 4.5%, respectively, throughout lactation. These data indicated that the nutrient intake of the pup changed markedly during the early neonatal period and that these changes should be taken into account in evaluating studies of suckling dogs.

Animals↗
PubMed1980

Copper in fetal and neonatal development.

The essentially of copper for normal fetal and neonatal development has been well documented, although copper metabolism during this period is poorly understood. The dietary requirement for copper is influenced by genetic background. The neurological phenotypic characteristics of the mutant gene quaking (qk) in mice resemble in part those of copper-deficient animals. Supplementation of the maternal diet with copper during pregnancy and lactation, or during lactation alone, greatly reduced the frequency of tremors characteristic of these mutants, and brought the otherwise low copper concentrations in the brain to normal. Prenatal copper supplementation of crinkled (cr) mice increased neonatal survival and produced nearly normal development of skin and hair. Non-supplemented cr/cr mice showed anaemia at 21 days of age which disappeared later. Similarly, copper concentration in liver and hair was low in young but normal in old cr/cr mice. However, activity of copper--zinc-superoxide dismutase (Cu-ZnSOD) remained low even at 60 days of age. Copper supplementation brought both SOD activity and copper concentration of liver and hair to normal. The errors in copper metabolism produced by qk and cr appear to be expressed at different periods of development. The hypothesis that there are rapid changes in the metabolism of copper is supported by the observation that molecular distribution of copper in rat intestine changes drastically during the neonatal period.

Aging↗
PubMed1980

Iron in human milk.

The distribution of iron among various fractions of human milk was determined by gel filtration, ultrafiltration, and atomic absorption spectrophotometry. Total iron varied between 0.26 and 0.73 microgram/ml; 1.5 to 46% of the iron was bound to the lipid fraction and 18 to 56% was found in a low molecular weight fraction. Only a small amount of iron was bound to lactoferrin, the major iron-binding protein of human milk; the iron saturation of this protein was found to be 1 to 4%, at the most. Thus, much less iron is bound to lactoferrin than earlier reported; this may be important in regard to the suggested role of this protein as a bacteriostatic agent. A correlation was found between iron and fat content during the course of a single nursing, but not between iron and lactoferrin.

Biological Availability↗
PubMed1980

Isolation of a low molecular weight zinc binding ligand from human milk.

A low molecular weight zinc binding compound from human milk has been purified by ultrafiltration, gel filtration, and ion-exchange chromatography. Evidence is provided that this compound is citrate. A higher amount of citrate-bound zinc was found in human milk than in cow's milk. It is suggested that the therapeutic value of human milk for patients with the genetic disorder of zinc metabolism acrodermatitis enteropathica (AE) derives from a greater content of bioavailable zinc citrate in human than in cow's milk.

Animals↗
PubMed1980

Effect of oral contraceptives on composition and volume of breast milk.

Nitrogen and protein composition was determined in milk from women using oral contraceptives during lactation. Total nitrogen and nonprotein nitrogen as well as lactose and the individual milk proteins lactoferrin, alpha-lactalbumin, and serum albumin were analyzed before introduction of oral contraceptives and thereafter throughout the lactation period. Twenty-four hour milk volumes were registered by weighing the infant before and after each feeding. The four oral contraceptives used consisted of different combinations of d-norgestrel, megestrolacetate, and ethinylestradiol. Significant changes were observed between groups and controls for all parameters studied. However, the changes observed were generally within the physiological variation of normal breast milk. It is suggested that the use of oral contraceptives during lactation should be limited.

Contraceptives, Oral↗
PubMed1980

Effect of protein intake on protein and nitrogen composition of breast milk.

The effect of a low and a high protein diet (approximately 8 and 20% energy from protein, respectively) on the contents of different nitrogen-containing substances in breast milk was studied on three healthy Swedish mothers in full lactation. Each experimental diet was fed during a 4-day period and milk samples were collected during the last day. The milk volume was estimated by weighing the child before and after each feeding. The 24-hr outputs as well as concentrations of total nitrogen, true protein, and nonprotein nitrogen were significantly higher when the subjects consumed the high protein rather than the low protein diet. The higher content of nonprotein nitrogen was due to increased urea levels as well as to increased levels of free amino acids. Milk urea levels were closely correlated with plasma urea levels in samples obtained after overnight fasting when the subjects had consumed the experimental diets for 4 days. The 24-hr output of lactoferrin, alpha-lactalbumin, and serum albumin were higher when the subject consumed the high protein diet as compared to the low protein diet but the differences were not significant.

Adult↗
PubMed1980

Molecular localization of zinc in rat milk and neonatal intestine.

The molecular localization of zinc in rat milk and pup intestine was determined by gel chromatography. Commerical gels were found to give low recoveries of zinc and also caused anomalous elution patterns. Treatment of the gel with sodium borohydride corrected these problems. With treated gels, all of the zinc in rat milk eluted with high molecular weight proteins (MW greater than or equal to 30,000). In neonatal intestine, zinc eluted in two major peaks with molecular weights 30,000 and 6,000-8,000, respectively. However, incubating intestinal homogenates at 37 degrees for 30 minutes produced a redistribution of zinc with a new major low molecular weight (less than or equal to 1,500) peak. These results demonstrate the importance of sample preparation and chromatographic conditions when studying trace element ligands and also suggest that rat milk is not analogous to human milk in regard to zinc binding.

Animals↗
PubMed1979

Protein evaluation in growing rats of breast milk and breast milk substitutes with special reference to the content of non-protein nitrogen.

The levels of individual proteins and other nitrogen containing substances differ considerably between cow's milk and human milk. Therefore, during manufacture of infant formulas, attempts are made to simulate the protein composition of human milk. However, the composition and nutritional characteristics of human milk protein are incompletely known. In this paper, the protein quality of breast milk protein with and without the non-protein-nitrogen (NPN) substances present in human milk was studied with growing rats and compared to two formulas, one "adapted" commercial infant formula and a suggested further modified, possibly improved, infant formula. Detailed examinations of protein and amino acid composition of the test diets are given. Breast milk protein with added NPN substances showed a lower protein quality than all other test proteins. Breast milk protein without NPN substances and the protein of the suggested infant formula were of similar quality while the protein of the commercial adapted formula was significantly better than all other test proteins. The use of rat growth assays in the evaluation of protein quality of infant formulas is discussed.

Amino Acids↗
PubMed1978

Nitrogen and protein components of human milk.

The true protein content of human milk is 0.9%, in well-nourished as well as malnourished mothers. Casein constitutes only about 20% of the protein nitrogen in human milk. The remaining 80% is derived from the whey proteins, the three dominant components being alpha-lactalbumin, lactoferrin and secretory IgA. alpha-lactalbumin is a subunit of lactose synthetase. Lactoferrin is an iron-binding glycoprotein which plays a role in the defence against gastro-intestinal infections and is probably also involved in iron transport in the gut. Secretory IgA is comparatively stable at low pH; it is resistant to proteolytic enzymes and plays an essential role in the immunological defence against gastro-intestinal infections. Lysozyme is a minor component of the whey proteins and represents an active enzyme with a bactericidal effect. The nutritional and immunological significance of the marked differences with respect to the nitrogen and protein compositions of human milk and cow's milk should not be underestimated, but need further elucidation.

Animals↗