Photoperiodism is a day-length-dependent seasonal change of physiological or developmental activities that is widely found in plants and animals. Photoperiodic flowering in plants is regulated by photosensory receptors including the red͞far-red light-receptor phytochromes and the blue͞UV-A light-receptor cryptochromes. However, the molecular mechanisms underlying the specific roles of individual photoreceptors have remained poorly understood. Here, we report a study of the day-length-dependent response of cryptochrome 2 (cry2) and phytochrome A (phyA) and their role as day-length sensors in Arabidopsis. The protein abundance of cry2 and phyA showed a diurnal rhythm in plants grown in short-day but not in plants grown in long-day. The short-day-specific diurnal rhythm of cry2 is determined primarily by blue light-dependent cry2 turnover. Consistent with a proposition that cry2 and phyA are the major day-length sensors in Arabidopsis, we show that phyA mediates far-red light promotion of flowering with modes of action similar to that of cry2. Based on these results and a finding that the photoperiodic responsiveness of plants depends on light quality, a model is proposed to explain how individual phytochromes and cryptochromes work together to confer photoperiodic responsiveness in Arabidopsis.P hotoperiodic flowering in plants was the first photoperiodism phenomenon documented (1). The flowering of longday (LD) or short-day (SD) plants occurs or is accelerated in the LD or SD condition, respectively. Arabidopsis is a facultative LD plant for which flowering-time regulation has been extensively studied (2-5). Although the detailed mechanism underlying photoperiodism is not well understood, extensive plant physiological studies support a hypothesis referred to as the external coincidence model (6-8). According to this hypothesis, the light signal must interact at the appropriate time of the day (or ''coincide'') with the photoperiodic response rhythm (PRR) of a cellular activity to confer photoperiodic responsiveness. It has been found that mRNA expression of flowering-time genes in Arabidopsis, including CO, GI, and FT, exhibited circadian rhythms, which have different phase shapes in plants grown in LD compared with plants grown in SD (9-12). Therefore, the day-length-dependent circadian expression of one or more flowering-time genes may represent the PRR.Arabidopsis relies on at least nine photosensory receptors, including five phytochromes (phyA-phyE), two cryptochromes (cry1 and cry2), and two phototropins (phot1 and phot2), to regulate most of its light responses (13-16). Among these photoreceptors, phytochromes and cryptochromes are known to regulate flowering time (5). It has also been found that phyA and cry2 protein abundance is regulated by light (17, 18) and that cry2 expression changes in response to photoperiod (19). These studies indicate that cry2 and phyA may act as major day-length sensors. Indeed, it has been found that the coincidence of light perception by cry2 and phyA with the peak circadian ...

Most mammalian tissue cells experience oxygen partial pressures in vivo equivalent to 1–6% O2 (i.e., physioxia). In standard cell culture, however, headspace O2 levels are usually not actively regulated and under these conditions are ~18%. This drives hyperoxia in cell culture media that can affect a wide variety of cellular activities and may compromise the ability of in vitro models to reproduce in vivo biology. Here, we review and discuss some specific O2-consuming organelles and enzymes, including mitochondria, NADPH oxidases, the transplasma membrane redox system, nitric oxide synthases, xanthine oxidase, and monoamine oxidase with respect to their sensitivities to O2 levels. Many of these produce reactive oxygen and/or nitrogen species (ROS/RNS) as either primary end products or byproducts and are acutely sensitive to O2 levels in the range from 1% to 18%. Interestingly, many of them are also transcriptional targets of hypoxia-inducible factors (HIFs) and chronic cell growth at physioxia versus 18% O2 may alter their expression. Aquaporins, which facilitate hydrogen peroxide diffusion into and out of cells, are also regulated by HIFs, indicating that O2 levels may affect intercellular communication via hydrogen peroxide. The O2 sensitivities of these important activities emphasize the importance of maintaining physioxia in culture.

Objective: Anhedonia, or loss of pleasure, is related to deficits in reward processing across a variety of psychiatric disorders. In light of research suggesting abnormal reward processing in eating disorders (EDs), the study of anhedonia in EDs may yield important insights into the role of reward in eating pathology. This meta-analysis and review aimed to provide both a quantitative and qualitative synthesis of the existing literature on this topic. Method:We conducted this research (or these meta-analyses) according to PRISMA guidelines. We searched four databases for both peer-reviewed and unpublished literature, and included studies only if a self-report or clinical interview measure of anhedonia was administered to a sample with an ED diagnosis. Results:We included 21 studies in the systematic review, and 10 studies in two meta-analyses that compared anhedonia between ED and control samples (n = 9 studies) and within different ED diagnoses (n = 5 studies). Meta-analyses revealed that anhedonia was significantly higher in ED groups compared to healthy controls, but there was no significant difference in anhedonia between ED diagnostic groups.A qualitative review of the literature also suggested that anhedonia may be correlated with increased ED symptom severity.Discussion: Findings indicated that anhedonia is elevated in EDs and may be a relevant treatment target. Future research should examine how self-reported anhedonia may correlate with components of reward processing in EDs in order to improve theoretical models as well as targeted interventions. ResumenObjetivo: La anhedonia, o pérdida de placer, está relacionada con déficits en el procesamiento de recompensas en una variedad de trastornos psiquiátricos. A la luz de la investigaci on que sugiere una anormalidad en el proceso de la recompensa en los trastornos de la conducta alimentaria (TCA), el estudio de la anhedonia en los TCA puede producir informaci on importante sobre el papel de la recompensa en la patología alimentaria. Este metanálisis y revisi on tuvo como objetivo proporcionar una síntesis cuantitativa y cualitativa de la literatura existente sobre este tema.Erin E. Reilly and Kamryn T. Eddy shared senior authorship.

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