Negligible release of cardiolipin during milk secretion by the ruminant

The presence of cardiolipin (diphosphatidyl glycerol) in lactating mammary tissue (cow and goat) was investigated. The tissue was separated into subcellular fractions by sedimentation; the identities of the fractions were confirmed by electron microscopy. Polar lipids recovered from the fractions, the whole tissues, and milks were analyzed by two-dimensional thin-layer chromatography and the percentages of cardiolipin were determined. The phospholipids of whole mammary tissue from the cow and goat contain 3-5% cardiolipin which is concentrated largely, if not exclusively, in the mitochondria. Although milk may on occasion have up to 1% cardiolipin in its phospholipids, some normal milks contain less than 0.15%. Since tissue contains 20-30 times the amount (mg/g) of phospholipids in milk, the quantitative ratio of tissue to milk cardiolipin is several hundred to one. We interpret this to mean that the mechanism of milk secretion is highly selective and insures retention of mitochondria within the cell even though they are decidedly smaller than milk fat globules which are continuously secreted. Our findings substantiate the conception that there is very little disintegration of the cell or disruption of the plasma membrane during milk secretion. The fatty acids of cardiolipin from lactating mammary tissue of cow, goat, and pig are highly unsaturated; they contain 50% or more octadecadienoic acid.     

Systematic status of the large squirrels (subgenus urosciurus) of the western Amazon basin

Patterns of geographic variation within and between regional samples of the large rufous western Amazon squirrels (Sciurus) are described based on univariate and multivariate analyses. Two species are clearly recognizable by independent patterns of geographic variation in measured characters, non‐overlapping qualitative cranial features, and certain pelage color characteristics. These species are a long‐muzzled, narrow‐skulled 5. spadiceus Olfers and a more normal‐muzzled, broader‐skulled S. igniventris Wagner. The two are sympatric over all of eastern Ecuador and most of Perú; only spadiceus is known from Bolivia.