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K L Erickson

Publications and source records attributed to K L Erickson.

114 records · Page 7Linked to original sources
PubMed1976

The effect of MSH on thymidine incorporation by keratinocytes in the epidermal melanin unit.

Epidermal melanocytes were observed in the black but not in the white skin of black-and-white spotted guinea pigs. In experiments designed to determine whether melanocyte-stimulating hormone (MSH) affects the incorporation of thymidine by kerationcyte nuclei of the epidermal melanin unit, the labeling index was the same in all skin before MSH administration. After MSH injections, the level of (3H)thymidine incorporation in keratinocytes increased significantly in black skin but not in white. We suggest that through the mediation of melanocytes MSH indirectly afffects keratinocytes in the epidermal melanin unit.

Animals↗
PubMed1976

The role of divalent cations in epidermolysis.

In experiments designed to elucidate the role of divalent cations in maintaining the integrity of the epidermis, newborn mouse skin was incubated in ethylenediamine tetraacetic acid (EDTA) or ethylene glycol tetraacetic acid (EGTA). In EDTA, epidermolysis occurred and was confirmed by rubbing the specimen to demonstrate that a sheet of epidermis could be split off. After 30 min incubation in 0-01 mol/EDTA the split occurred in the lower granular-upper spinous layer; after 45 min, it was in a spinous-suprabasilar location and at 60 min and later at the dermal-epidermal junction. Ultrastructurally, a clear zone of apparent intracellular oedema occurred along the cell membranes. The split then occurred intracytoplasmally through this clear zone and the adjacent cell membrane was lost. Since incubation in EGTA at pH 7-4 did not result in epidermolysis, we suggest that the removal of magnesium rather than calcium is responsible for epidermolysis. Thirty min after the addition of either calcium or magnesium to EDTA-treated specimens, epidermolysis could no longer be demonstrated.

Animals↗
PubMed1975

The induction of melanogenesis by ultraviolet light in the pigmentary system of Rhesus monkeys.

Except for the face, eyelids, friction surfaces, and lips, the epidermis of the rhesus monkey contains no discernible melanocytes. After ultraviolet irradiation, however, dopa-positive dendritic cells appeared. With daily sequential irradiation, the number of histochemically demonstrable dopa-positive dendritic cells peaked after 30 exposures, then declined to a basal level which was maintained for the duration of the experiment (216 exposures or 43 weeks). Pigment cells can be restimulated by shading part of the irradiated area and then reirradiating after 3 months. While shaded, dopa-positive cells disappeared; but when reirradiated, they reappeared, increased, then declined again to a basal level. These melanocytes, unlike those in other primates, require high threshold levels of irradiation to produce a response, have a definite period during which they are active, and transfer very little melanin to the surrounding keratinocytes. Long-term ultraviolet irradiation has no discernible effect on dermal pigment-containing cells.

Animals↗
PubMedDate not supplied

Regulation of cellular differentiation and apoptosis by fatty acids and their metabolites.

We have reviewed the literature regarding the effects of fatty acids and their metabolites on cellular differentiation and apoptosis. Results obtained in different studies have been variable, but some generalizations can be made. Differentiation was increased by incubation of cells with arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), prostaglandin E1 (PGE1), prostaglandin E2 (PGE2), or leukotriene D4 (LTD4). Effects of these agents on differentiation could be magnified with the simultaneous addition of other differentiation-inducing agents like dimethylsulfoxide or retinoic acid. AA and gamma-linolenic acid increased apoptosis while the effects of n-3 fatty acids (EPA and DHA) and of eicosanoids varied from stimulation to inhibition. These inconsistencies are attributed to the differences in methods used to evaluate differentiation and apoptosis, concentrations of fatty acids and serum, exposure time and the cell models used. Studies using the physiological concentrations of the fatty acids and standardized experimental conditions need to be conducted to establish effects of fatty acids and their metabolites on these cellular processes.

Animals↗
PubMedDate not supplied

Differential mRNA expression of prostaglandin receptor subtypes in macrophage activation.

Assessing the regulation of macrophage receptors for prostaglandin (PGE2) is essential to understanding the control which that potent lipid mediator has in modulating macrophage activities. The purpose of this study was to assess the differential mRNA expression of PGE2 receptor subtypes (EP) during macrophage exposure to activating and transducing agents. RAW 264.7 macrophages constitutively expressed mRNA for EP2,EP3 and EP4 receptor subtypes. Messenger RNA for EP4 was expressed at a much higher level when compared to EP2 in unstimulated macrophages as assessed by kinetic quantitative RT-PCR. When macrophages were stimulated with LPS, EP2 m RNA levels were 12-fold higher when compared to unstimulated macrophages, while EP4 m RNA remained unchanged. Conversely, mRNA levels of both EP2 and EP4 receptors were lower after macrophages were treated with IFN-gamma. Messenger RNA levels of both receptors were lower in macrophages after treatment with PGE2 or dibutyryl (db) cAMP Addition of the PKA inhibitor H89 reversed the effects of PGE2 and dbcAMP to varying degrees. Proteosome and p38 MAP kinase inhibitors blocked the LPS-stimulated increase in EP2 mRNA levels. Those inhibitors had no effect on EP4 mRNA.Thus, activating agents such as LPS and IFN-gamma may differentially regulate mRNAfor PGE2 receptor types in macrophages but the ligand and its associated signal transducing factors probably have similar regulatory effects.

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