Lanthanum staining of the epidermal intercellular spaces. An electron microscopic study

Localization of lanthanum tracer in oral epithelium using transmission electron microscopy and the electron microprobe

Although water soluble tracers have been used to localize intercellular permeability barriers with the transmission electron microscope, there is the possibility of translocation or loss of the tracer during processing. This study compares the localization of lanthanum tracer in keratinized oral epithelium after routine processing with lanthanum seen after using freeze drying to avoid aqueous fixation and dehydration. The electron probe was used to identify the lanthanum tracer in the tissue and to distinguish it from other electron-dense material. After incubating small biopsies of rat palate mucosa in 1% lanthanum nitrate, specimens were either routinely processed for electron microscopy or quick frozen, dehydrated, fixed in osmium vapour and infiltrated with epoxy resin. Examination in the transmission electron microscope indicated that preservation of the freeze dried tissue did not compare favourably with that of normally processed tissue, but the distribution of the electron-dense tracer in the intercellular spaces and the extent of the penetration through the epithelia was similar in the two types of preparations. Confirmation of the tracer as lanthanum was obtained by wavelength dispersive X-ray analysis with the electron probe. The results indicate that no appreciable shift in the localization of the tracer is introduced by routine aqueous fixation and dehydration for electron microscopic examination.

A study of the permeability barrier in epidermis and oral epithelium using horseradish peroxidase as a tracer in vitro

Small biopsies of skin, and of keratinized and non-keratinized oral mucosa were incubated with horseradish peroxidase, fixed and reacted to demonstrate peroxidase activity at the light and electron microscope level. In all tissues peroxidase extended through the intercellular spaces of the epithelium up to, but not into, the stratum corneum of keratinized, or the superficial layer of non-keratinized, tissue. This distribution corresponds to that seen in studies using the tracer in vivo where the presence of an intercellular permeability barrier has been demonstrated in the upper cell layers. It is suggested that the method is a useful way of investigating the permeability of normal and pathological human epithelial tissues.

Glycocalyx of epidermal cells in vitro: demonstration and enzymatic removal

Guinea-pig epidermal cells in culture possess a glycocalyx coat similar to that in vivo, as revealed by the ruthenium red stating technique. Trypsin, phospholipase C, and lysozyme do not produce any changes of the glycocalyx, while hyaluronidase and neuraminidase lead to partial and subcomplete removal respectively. Cells stripped of their glycocalyx coat by neuraminidase do not detach from the support and do not show any signs of toxicity. There is complete reconstitution of the glycocalyx within 24 hr.