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Biomedical subjects

I C Mackenzie

Publications and source records attributed to I C Mackenzie.

89 records · Page 5Linked to original sources
PubMed1975

Labelling of murine epidermal Langerhans cells with H3-thymidine.

Epidermal Langerhans cells may be identified by light microscopy by their strongly positive reaction following incubation for ATPase activity. Intact sheets of epidermis from mice killed at various time intervals following a single pulse label of H3-thymidine were incubated to demonstrate ATPase activity and subsequently processed for autoradiography. In specimens taken one hour after labelling, many basal keratinocytes were labelled but very few ATPase-positive dendritic cells. At subsequent time periods a few pairs of labelled ATPase-positive cells were found but individually labelled cells were not observed. The findings suggest that epidermal Langerhans cells form a very stable (labelling index less than 0.01%) self-replicating population which divides to maintain cell spacing during growth. No evidence was found for migration and interchange of Langerhans cells with the connective tissue, or for an origin of Langerhans cells by transformation of another cell type.

Adenosine Triphosphatases↗
PubMed1975

Patterns of mitosis in hamster epidermis.

Alignment of the flattened keratinizing cells of the upper strata of mammalian epidermis leads to the formation of columnar units of structure. In mouse epidermis, mitoses have been found to occur relatively infrequently in the region beneath the center of each cell column where a non-keratinocyte dendritic cell, usually with freatures typical of an epidermal Langerhans cell, is situated. The observed pattern of mitosis could therefore be due either to displacement of central keratinocytes by Langerhans cells or indicate some control of keratinocyte proliferation related either to the Langerhans cells or to the over-lying cell columns. No relationship exists between the position of Langerhans cells and epidermal cell columns in hamster epidermis but measurement of the position of mitosis has shown a reduced frequency of occurrence of mitosis beneath the central region. This pattern of mitosis is therefore unrelated to Langerhans cells and appears to reflect differences in the mitotic potential of basal keratinocytes which could be associated with feedback from the overlying cell columns or with an intrinsic pattern of basal cell activity.

Animals↗
PubMed1975

Spatial distribution of mitosis in mouse epidermis.

The cells of the upper strata of mammalian epidermis are flattened and aligned to form regular columnar units. It has been suggested that the position of the smaller underlying basal cells is related to the overlying cell columns. Examination of the position of metaphase figures in sheets of mouse epidermis indicated that mitosis occurs principally in cells lying just within the periphery of the cell columns but that there is no alignment of interphase basal cells within the columnar peripheries which could account for this position of mitosis.

Animals↗
PubMed1975

Differences in the response of rodent oral mucosa and skin to repeated surface trauma.

The responses of oral mucosa and skin to daily application of controlled frictional stimuli were compared. In some respects, the epithelia of both oral mucosa and skin showed similar responses: Low levels of friction resulted in epithelial thickening, and higher levels resulted in ulceration. The mucosa, however, ulcerated more readily and, unlike the skin, failed to heal if friction was reapplied. The histologic appearance of the ulcers so produced was essentially similar to that of denture-induced traumatic ulcers. Healing of ulcerated skin was associated with the formation of a hard surface scab which protected the underlying healing tissues from further frictional damage. A similar protective scab was not formed over mucosal lesions, and a thickened epithelium resistant to further frictional damage was not re-formed. The low resistance of the oral mucosa to friction and its failure to heal if friction is reapplied suggest that an analogy between the responses to friction of oral mucosa and the skin does not form a sound basis for clinical therapy.

Animals↗
PubMed1975

Ordered structure of the epidermis.

Recent reports on the ordered structure of the epidermis are reviewed. The regular relationship between Langerhans cells and cell columns in the mouse is not typical of the epidermis of other animals. The pattern of mitotic activity previously described in mouse epidermis has also been demonstrated in the hamster, which suggests control of keratinocyte activity rather than the exclusion of keratinocytes from the central region beneath cell columns. These findings are discussed in relation to mechanisms which may be responsible for the formation of cell columns.

Adenosine Triphosphatases↗
PubMed1975

Cytochemical identification of ATPase-positive langerhans cells in EDTA-separated sheets of mouse epidermis.

Sheets of epidermis for incubation to demonstrate ATPase activity were obtained from specimens of mouse footpad using EDTA as the separation medium. The use of EDTA in place of the NaBr method previously described, resulted in a greatly reduced incubation time, precise localization of reaction product and preservation of ultrastructural detail. A population of closely and regularly spaced ATPase-positive dendritic cells was demonstrated by light microscopy. Electron microscopy demonstrated that, with short incubation times, reaction product was found only in the extracellular space adjacent to dendritic cells, the majority of which possessed the typical ultrastructural features of Langerhans cells.

Adenosine Triphosphatases↗