ABSTRACT
In developed countries, the years from Age 30 to 45 are, for many, the most intense, demanding, and rewarding years of adult life. During this period of the life span most adults must negotiate the intersecting demands of progressing in a chosen career, maintaining an intimate partnership, and caring for children. Successes or difficulties in meeting these simultaneous demands have the potential to profoundly influence the direction of a person's adult life. As such, we believe that it is of critical importance to better understand this developmental period that we call established adulthood. This article provides a new theoretical conceptualization of established adulthood, outlining its distinctiveness from emerging adulthood and midlife in terms of physical health, well-being, cognitive development, and the career-and-care-crunch of competing work and family responsibilities. We also consider variations in the timing and experience of established adulthood, including variations by gender and social class, and provide suggestions for future research. As economic and social arrangements continue to evolve, so too will this developmental period, providing fertile ground for developmental theory and research. (PsycInfo Database Record (c) 2020 APA, all rights reserved).
Subject(s)
Human Development , Adult , Female , Gender Role , Humans , Interpersonal Relations , Longevity , Male , Middle Aged , Psychology, Developmental , Sexual Behavior , Social Class , Work-Life BalanceABSTRACT
BACKGROUND: Khellin is a naturally occurring furochromone which, when combined with artificial ultraviolet (UV) A or solar irradiation (KUVA), is reported to repigment vitiligo skin as effectively as PUVA photochemotherapy. The exact mechanism of KUVA-induced repigmentation is unknown. OBJECTIVES: The aim of this study was to test the effect of khellin and KUVA on proliferation and melanogenesis of normal human melanocytes and Mel-1 melanoma cells in vitro. METHODS: Cultured normal human melanocytes, Mel-1 melanoma cells and fibroblasts were treated with khellin, UVA and KUVA and the effect on proliferation determined by cell counting. The effect on melanogenesis was determined by a radiometric melanin formation assay. Changes in gene expression and protein synthesis were determined by Northern blot, reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot analyses. RESULTS: Khellin stimulated proliferation of Mel-1 melanoma cells and melanocytes at concentrations between 1 nmol L-1 and 0.5 mmol L-1 with a peak effect at 0.01 mmol L-1 khellin. In contrast, khellin inhibited proliferation of fibroblasts over the entire concentration range tested. At concentrations above 0.5 mmol L-1, khellin was cytotoxic to both melanocytic cells and fibroblasts. Exposure of khellin-treated cells to single doses of UVA between 150 and 280 mJ cm-2 resulted in an enhanced proliferative effect. Khellin and KUVA also stimulated the melanogenic enzyme activity of pigmented cells, with the most effective treatment being 0.01 mmol L-1 khellin with 250 mJ cm-2 UVA. Western blot, Northern blot and RT-PCR analysis revealed that these increases in melanogenic enzyme activity were not due to increases in gene expression or protein synthesis. UVA treatment resulted in an increase in enzyme glycosylation and this correlated with the increase in melanogenesis. CONCLUSIONS: We conclude that khellin activated by UVA stimulates melanocyte proliferation and melanogenesis. Our results point to the possibility that current treatment regimens might be improved if reduced khellin doses are applied and suggest that improved delivery vehicles be tested.