Characterization of a parathyroid hormonelike peptide secreted by human keratinocytes.
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Adenylyl Cyclases↗
Biomedical subjects
L M Milstone
Publications and source records attributed to L M Milstone.
In vivo fluorescence of human skin. A potential marker of photoaging.
Fluorescence is a feature of elastin and collagen, both major compounds of human dermis that are altered by age and photoexposure. We studied the intrinsic fluorescence of skin in vivo in 28 human volunteers to determine whether photoaging and chronologic aging of the skin could be evaluated by this noninvasive technique. We demonstrate that the excitation of skin autofluorescence by laser ultraviolet radiation yields characteristic tissue fluorescence spectra that are unrelated to age, pigmentation, or skin thickness. The differences in skin autofluorescence appear to be related to photoexposure. Thus, laser-induced fluorimetry, a noninvasive technique, may be adaptable as a marker of photoaging.
Adult↗
A parathyroid hormone-like protein from cultured human keratinocytes.
Parathyroid hormone-like factors have been found in extracts of tumors associated with humoral hypercalcemia of malignancy, many of which are of squamous epithelial origin. Cultured, nonmalignant human keratinocytes were examined for the production of similar factors. Keratinocyte-conditioned medium from ten cultures stimulated the production of cyclic adenosine monophosphate in clonally derived rat osteosarcoma cells sensitive to parathyroid hormone. Bovine [Nle8,18, Tyr34]PTH-(3-34)NH2, a competitive inhibitor of parathyroid hormone, stopped the adenylate cyclase production stimulated by keratinocyte-conditioned medium, but antisera to parathyroid hormone had no effect on such adenylate cyclase activity. The active component of keratinocyte-conditioned medium has a molecular weight exceeding that of native parathyroid hormone. These characteristics are shared by the parathyroid hormone receptor agonists associated with humoral hypercalcemia of malignancy, which suggests that normal human keratinocytes may produce a factor related to that produced by malignant tumors associated with humoral hypercalcemia of malignancy.
Adenylyl Cyclases↗
Prescribing retinoids. The art and the science.
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Endocarditis, Bacterial↗
Heterogeneity of basal keratinocytes: nonrandom distribution of thymidine-labeled basal cells in confluent cultures is not a technical artifact.
Basal surface autoradiography of [3H]dThd-labeled, confluent, keratinocyte cultures reveals that proliferating cells have a nonrandom, patterned distribution. Unlabeled cells, likewise, appear nonrandomly in clusters. We show here that failure to detect DNA synthesis in some basal cells in culture is not an artifact caused either by physical separation of the labeled nuclei from the radiographic emulsion or by a diffusion barrier that would prevent [3H]dThd from reaching basal cells.
Autoradiography↗
2,3,7,8-Tetrachlorodibenzo-p-dioxin induces hyperplasia in confluent cultures of human keratinocytes.
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is the prototype for a group of halogenated aromatic hydrocarbons which can be potent modulators of growth and differentiation of epithelial tissues. TCDD causes chloracne and can act as a skin tumor promoter, but these actions have been demonstrated only in animals in which TCDD causes epidermal hyperplasia. Study of the hyperplastic response to TCDD has been hampered by lack of an in vitro model; all previous investigations indicated that TCDD had no in vitro effect on cell growth. We show here that nanomolar concentrations of TCDD cause hyperplasia in confluent cultures of human keratinocytes and suggest that this model system will be useful for analyzing mechanisms of TCDD-induced epithelial hyperplasia and genetic differences in responsiveness to TCDD.
Cells, Cultured↗
Epidermal cell confluence and implications for a two-step mechanism of wound closure.
In contrast to freshly isolated cells, some cultured keratinocytes have the ability to adhere and spread in protein-free media. Reported here are experiments testing the hypothesis that the social history of keratinocytes influences their ability to spread in defined media. The experiments indicate that confluent cells lack the ability to spread in defined media while subconfluent cells have this property. The inability of dissociated confluent cells to spread in protein-free media is referred to phenomenologically as a "confluent block." The confluent block is acquired rapidly (1-3 days) and lost slowly (5-7 days). The ability of subconfluent cells to spread in the absence of media protein is sensitive to cycloheximide. Aortic endothelial cells and dermal fibroblasts do not demonstrate a confluent block. These observations are consonant with a two-step mechanism of epidermal wound repair: the first occurs immediately after wounding during which the cells require substratum-active proteins, and the second occurs 5-7 days later when the cells are able to synthesize their own substratum.
Aorta↗
GABA from putrescine is bound in macromolecular form in keratinocytes.
We report for the first time that the neurotransmitter gamma-aminobutyric acid (GABA) exists in macromolecular form in keratinocytes. GABA derived from putrescine (Pu) has been identified as a component of acid-precipitable material of cultured human keratinocytes. Confluent, stratified cultures of human foreskin keratinocytes exposed to [3H]-Pu for 4 hours took up about 14% of the radioactivity from the medium and 1% of the total cell-associated radioactivity was precipitable by trichloroacetic acid (TCA). Both attached and shed cells were examined by HPLC for Pu and its radioactive metabolites in TCA-insoluble and TCA-soluble fractions. GABA accounted for the major portion (54%) of the radioactivity derived from Pu in the TCA-precipitable material of attached keratinocytes. Pu and spermidine represented lesser amounts, 35% and 9% respectively, of the total TCA-precipitable radioactivity. In addition, a large portion of acid soluble radioactivity derived from Pu (63%) was GABA, whereas Pu and spermidine represented 29% and 6% respectively of the total TCA-soluble radioactivity. The exact origin of GABA in acid-precipitable material, as well as its form of attachment, is currently under investigation.
Cell Differentiation↗
Population dynamics in cultures of stratified squamous epithelia.
Stratified squamous epithelia, such as those covering the skin, esophagus, and cervix, are normally in a dynamic steady state: production of new cells (proliferation) is matched by loss of terminally differentiated cells into the environment (desquamation). The parameters that describe population dynamics in stratified epithelia--number of dividing cells, number of cell layers, transit time, and rate of desquamation--can be closely monitored in cultures of stratified epithelial cells. Analysis of these data show that cultures of stratified epithelial cells can be maintained in a dynamic steady state for at least 1 month and thus have a dynamic behavior similar to stratified epithelia in vivo. Although this in vitro behavior may be intuitively reasonable based on the in vivo behavior of these cells, it is remarkable in that it is contrary to the general experience with other normal cell types in culture. The usefulness of measuring population dynamics in cultures is demonstrated by an analysis of the actions of retinoids on human keratinocytes. In addition, we show that because of favorable geometry and ease of manipulation, these cultures are well-suited to the analysis of heterogeneity in the proliferating population of cells.
Animals↗
Classification and therapy of atrophie blanche.
Atrophie blanche usually appears as painful purpuric papules that evolve into ulcerations and, finally, angular scars on the lower extremities. The literature on this subject presents a confusing picture of its causes, pathogenesis, and treatment. From our review of the literature and our experience in evaluating and treating cases of atrophie blanche, we conclude that it is best categorized as a clinicopathologic entity with multiple causes. Its characteristic histopathologic features and clinical evolution indicate that the common pathologic event is occlusion of vessels in the middle and deep dermis. No single form of therapy has been consistently effective for the treatment of atrophie blanche, but drugs that inhibit platelet thrombus formation or stimulate endogenous fibrinolytic activity arrest the disease in most patients.
Adult↗
Premature epiphyseal closure in a child receiving oral 13-cis-retinoic acid.
A boy with epidermolytic hyperkeratosis was treated systemically for 4 1/2 years with 13-cis-retinoic acid. At the age of 10 1/2 years, he developed pain in his right knee and radiographic evidence of partial closure of the proximal epiphysis of the right tibia. Similar radiographic changes have been described in individuals ingesting excessive amounts of vitamin A.
Bone Diseases↗
Retinoic acid causes premature desquamation of cells from confluent cultures of stratified squamous epithelia.
Cells from 2 types of stratified squamous epithelia were grown to confluence in vitro. In these cultures highly differentiated cells were shed into the culture medium at a constant rate for at least 4 weeks, thus providing a unique system in which to study factors that influence desquamation. Retinoic acid (RA) decreased the rate of desquamation in calf esophagus epithelial cell (CEEC) cultures and increased the rate of desquamation in human foreskin epithelial cell(HFEC) cultures. Cells shed from CEEC and HFEC cultures treated with RA were less differentiated, as assessed by their protein/DNA ratio, than cells shed from control cultures. These data indicate that retinoic acid induces premature desquamation from stratified squamous epithelia.
Animals↗
Different polypeptides form the intermediate filaments in bovine hoof and esophageal epithelium and in aortic endothelium.
Polypeptides that form 10-nm filaments in vitro were isolated from three different bovine tissues: the viable portion of the hoof epithelium, the epithelium of the esophagus, and cultured endothelial cells derived from aorta. The seven polypeptides from hoof, the two from esophagus, and the one from endothelial cells were different with respect to mobility in SDS polyacrylamide gels and/or limited proteolytic digestion. Peptide maps of the different filament-forming polypeptides (FFP's) showed that none of the smaller FFP's was a fragment of any of the larger FFP's. Several isomobile fragments were found in the peptide maps of different FFP's, suggesting that they might contain regions of amino acid sequence homology. We present a hypothesis that suggests how the different 10-nm filament-forming proteins may be related.
Amino Acid Sequence↗
Isolation and characterization of two polypeptides that form intermediate filaments in bovine esophageal epithelium.
Cells in the stratified squamous epithelium of bovine esophagus contain abundant tonofilaments measuring 6-10 nm in diameter. Two polypeptides, extracted from esophageal epithelium with 0.05 M Tris, pH 7.4, containing 8 M urea and 25 mM beta-mercaptoethanol, comprise 35% of the total extractable protein. These polypeptides have apparent molecular weights of 46,000 and 56,000 daltons and are rich in glutamic acid-glutamine, glycine, and serine. Each polypeptide can be partially purified by DEAE-cellulose chromatography. Mixtures of the purified polypeptides from filaments in vitro that measured 6-10 nm in diameter. Neither polypeptide formed filaments by itself. Filaments formed in vitro give an alpha-keratin type x-ray diffraction pattern.. These data indicate that the tonofilaments in esophageal epithelium are formed primarily from these two polypeptides.
Amino Acids↗
delta-Crystallin gene expression in embryonic chick lens epithelia cultured in the presence of insulin.
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Animals↗
Delta-crystallin mRNA in chick lens cells: mRNA accumulates during differential stimulation of delta-crystallin synthesis in cultured cells.
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Animals↗