Iron-binding proteins in milk and resistance to Escherichia coli infection in infants

Vitamin B12-binding proteins of r-type, cobalophilin

A gradient was developed for isoelectric focusing in the pH range 2-5. Cobalophilin (earlier called R proteins or vitamin B12-binding proteins of R-type) was isolated from saliva and amniotic fluid in homogeneous form. It was found to be a glycoprotein with a molecular weight of 59,300-69,100. The preparation from amniotic fluid contained 33% carbohydrate. Cobalophilin variants in plasma, serum, granulocytes, platelets, amniotic fluid, milk, saliva and gastric juice were characterized by isoelectric focusing. Most fluids and cells contained the same isoproteins, with pI values between 2.3 and 5.0. Isoproteins of presumably myelogenic origin (e.g. those in granulocytes and plasma) had pI values below 4.2, whereas those of glandular origin (in milk and saliva) had a pI range of 4.0-5.0. Serum contained more cobalophilin than plasma, owing to release of this protein from granulocytes during clotting. This phenomenon also changed the isoprotein pattern. Plasma and serum from newborn infants and from patients with leucocytosis, polycythaemia vera and chronic myelogenous leukaemia contained the same isoproteins as were found in plasma from healthy subjects. In addition to these, isoproteins with lower than 'normal' pI values were often found in chronic myelogenous leukaemia and occasionally in leucocytosis. It is concluded that cobalophilin from different fluids and cells is a single microheterogeneous protein with a variable carbohydrate composition. The distribution of cobalophilin in different body fluids and cells supports the suggestion that cobalophilin is an antimicrobial protein (Gullberg 1972) like lactoferrin and lysozyme.

Inhibition of Escherichia coli by bovine colostrum and post-colostral milk. II. The bacteriostatic effect of lactoferrin on a serum susceptible and serum resistant strain of E. coli

Two strains of Escherichia coli were inhibited by complement-inactivated cow serum and to a lesser extent by precolostral calf serum devoid of specific antibodies. They were not inhibited by undiluted colostral whey or milk but colostral whey became bacteriostatic after dialysis or dilution in Kolmer saline and addition of precolostral calf serum or lactoferrin. The inhibition in all these fluids was due to iron-binding proteins (transferrin or lactoferrin). Undiluted dialysed milk was not inhibitory because of its low content of lactoferrin but became inhibitory after addition of 1 mg/ml of lactoferrin. The lack of inhibition in undiluted whey is due to the high concentration of citrate in colostral whey (and milk) and it is suggested that citrate competes with the iron-binding proteins for iron and makes it availabe to the bacteria. Addition of bicarbonate, which is required for the binding of iron by transferrin and lactoferrin, can overcome the effect of citrate; hence, the bacteriostatic effect of cow serum and precolostral calf serum is due to the presence of both transferrin and bicarbonate as well as the low lefel of citrate.

Defense mechanisms in the mouth and their possible role in the prevention of dental caries: a review

The mouth harbors organisms in great abundance; yet their variety is limited and it is noteworthy that some species present in the mouth are not found elsewhere. There are many antibacterial substances in the mouth, some of which may contribute to the control of the microbial flora in the mouth. The activity of some is enhanced in the presence of specific antibody, e.g. lactoferrin, although others appear unaffected, e.g. lactoperoxidase. Opinions differ as to whether the level of immunoglobulins in human saliva can be related to caries. Although it has been established in principle that caries can be prevented in animals by means of vaccination, substantial work remains to be done before a vaccine will be available for testing in humans.

Virulence and the role of iron in Pseudomonas aeruginosa infection

The virulence of Pseudomonas aeruginosa can be enhanced by passage in mice or rabbits. Enhanced virulence has some specificity for the host in which the passage is done. Experimental infection in the peritoneal cavity of cannulated rabbits has shown that the injection of iron compounds can lead to a rapid and fatal growth of an otherwise nonlethal dose of bacteria. In vitro the unsaturated iron-binding proteins present in the peritoneal fluid can halve the growth rate of P. aeruginosa. The restricted rate of growth is restored to normal if the iron-binding proteins are saturated with iron. Exactly the same results are achieved with purified transferrin. Both fatal and nonfatal infections with P. aeruginosa cause a sharp fall in the percentage of saturation with Fe of the plasma and peritoneal fluid. In both normal and infected animals the peritoneal fluid is invariably less saturated than the plasma. Specific antiserum not only protects against death but also against the fall in iron saturation of the plasma and peritoneal fluid. In both fatal and nonfatal infections a high proportion of viable bacteria are unphagocytized in the peritoneal cavity.

Some observations on the possible nutritional significance of vitamin B12-and folate-binding proteins in milk

1. The folate and vitamin B12in milk are strongly bound to minor whey proteins. These binder proteins are present in excess, and so milk has capacity – which varies between milks of different mammalian species – to sequester added cyanocobalamin and folic acid.

2. A study was made of the influence of different milks on uptake of [3H]cyanocobalamin and [3H]folic acid in selected bacteria, mostly of types that are commonly found in the intestine.

3. None of the test cultures required exogenous vitamin B12. Nevertheless, when free cyanocobalamin was added, in seven of nine cultures it was rapidly taken up into the cells, though there were large differences between the different bacterial species in their absorptive capacity. In presence of sow's milk, little or none of the added cyanocobalamin was taken up, even after incubation of the test mixture for 1 h at 37°. The avidity of sow's milk for cyanocobalamin, as judged from its retention of the vitamin against competition by bacterial cells, was greater than that of a preparation of porcine Intrinsic Factor of similar binding capacity.

4. Of ten cultures of bacteria representing seven species, only the five cultures that required exogenous folate took up added folic acid into the cells. Uptake was severely depressed by the simultaneous addition of goat's colostrum, even after incubation of the test mixture for 1 h at 37°.

5. The physiological role of the binders is discussed. It is postulated that they may act in the mammary gland as trapping mechanisms to accumulate the vitamins from blood plasma into milk and in the gut to facilitate their absorption, both directly, and indirectly by preventing their uptake by intestinal micro-organisms. It is concluded that the binders might well influence the vitamin economy in the neonatal period, and the ecology of the gut microflora.

Significance of milk pH in newborn infants

Bottle-fed infants do not gain weight as rapidly as breast-fed babies during the first week of life. This weight lag can be corrected by the addition of a small amount of alkali (sodium bicarbonate or trometamol) to the feeds. The alkali corrects the acidity of cow's milk which now assumes some of the properties of human breast milk. It has a bacteriostatic effect on specific Escherichia coli in vitro, and in infants it produces a stool with a preponderance of lactobacilli over E. coli organisms. When alkali is removed from the milk there is a decrease in the weight of an infant and the stools contain excessive numbers of E. coli bacteria.A pH-corrected milk appears to be more physiological than unaltered cow's milk and may provide some protection against gastroenteritis in early life. Its bacteriostatic effect on specific E. coli may be of practical significance in feed preparations where terminal sterilization and refrigeration are not available. The study was conducted during the week after birth, and no conclusions are derived for older infants. The long-term effects of trometamol are unknown. No recommendation can be given for the addition of sodium bicarbonate to milks containing a higher content of sodium.

Phenotypic expression of immune secretory function in focal pregnancy-like change of the human breast

Fibrocystic disease of the breast in middle-aged women characteristically shows focal epithelial lesions of a very varied nature. The functional immunohistochemical changes in such lesions have been little studied. Focal Pregnancy-like Change in the breast has a striking morphological similarity to the secretory breast lobules in pregnancy and in lactation. We show that the epithelial cells in all the lesions of Focal Pregnancy-like Change studied simultaneously express secretory component, Ig A and J chain in their cytoplasm. Additionally these epithelial cells, unlike those in resting breast lobules, contain lysozyme and lactoferrin. All these phenotypic immunohistochemical changes in Focal Pregnancy-like Change resemble the breast lobules of late pregnancy and lactation. Possibly, the very focality of Focal Pregnancy-like Change reflects a peculiar and local sensitivity of 'resting' breast lobules to unidentified hormonal stimulation.