Milk fat globule membrane material in skim-milk

Abstract

SummaryIt has been claimed by Stewart, Puppione & Patton (1972) that milk is a valuable source of cell membrane in a ‘relatively pure’ state originating from shed mammary secretory cell microvilli and golgi vesicles. The morphological basis for this has been re-examined in this paper. It is shown that the vesicular and elongated membranous structures found in skim-milk are identical to structures present as part of the initial milk fat globule membrane (MFGM) of alveolar and expressed milk, and that both structures survive extraction with chloroform–methanol. It is therefore suggested that a major part of the skim-milk membrane is material shed from the freshly secreted milk fat globule and consists of a specialised derivative of the secretory cell plasmalemma, the initial MFGM.

Heterogeneity of milk fat globule membrane structure and composition as observed using fluorescence microscopy techniques

“…The non-bilayer patches may be circular or non-circular in shape. Further work is needed to verify whether parts of the bilayer are indeed lost through so-called membrane blebbing, as has previously been suggested on the basis of electron microscopy (Wooding, 1974).…”

“…4) -sheds new light upon an existing controversy in the literature. On the basis of electron microscopy, it had been suggested that most of the bilayer is lost from milk fat globules in bovine milk post-secretion by the secretory cell (Bauer, 1972;Henson et al, 1971;Wooding, 1971Wooding, , 1974. In contrast, biochemical data have suggested that the structure of the MFGM is largely preserved in secreted milk (Mather & Keenan, 1998).…”

Study on the susceptibility of the bovine milk fat globule membrane proteins to enzymatic hydrolysis and organization of some of the proteins

“…Several authors have provided evidence, by means of electron microscopy, that some membrane material is shed from some globules following secretion (Bauer, 1972;Henson et al, 1971;Wooding, 1971Wooding, , 1974. Recently, by means of a novel technique using specific stains and fluorescence microscopy, Evers et al (2008), have confirmed that a certain proportion of milk fat globules are denuded from the bilayer membrane.…”

“…In contrast, Kobylka and Carraway (1973) and Shimizu et al (1979) found that the proteins in washed cream (intact globules) and isolated MFGM (broken membrane) were similarly digested, leading them to conclude that the MFGM was not a continuous membrane, thus facilitating action by enzymes. After secretion, the membrane bilayer can be gradually lost (Bauer, 1972;Evers et al, 2008;Henson, Holdsworth, & Chandon, 1971;Wooding, 1971Wooding, , 1974.…”

Intracellular Origin of Milk Fat Globules and the Nature of the Milk Fat Globule Membrane

“…Some of the membrane that initially surrounds fat globules is lost following secretion, either within the mammary gland or in expressed milk (Wooding, 1971b(Wooding, , 1974. Estimates of the extent of this loss vary considerably (Mather and Keenan, 1983).…”