A freeze-etching study on experimental murine mastitis.

Streptococcal mastitis was produced experimentally in mice inoculated by the intramammary route; freeze-etched preparations from the affected mammary glands were studied by electron microscopy. The inoculated cocci were seen free in the acinar lumen, within luminal phagocytes and within cells of the epithelium. No significant pathological changes were noted in the junctional complexes between secretory epithelial cells. The results were comparable to those obtained by ultrathin sectioning and indicated that, while cocci can transfer from the acinar lumen into the substance of the epithelium and towards a subepithelial location, the junctional complexes between epithelial cells present a potential barrier to movement through the intercellular spaces.