The influences of sleep duration,chronotype, and nightwork on the ovarian cycle

ABSTRACT

Despite research indicating that sleep disorders influence reproductive health, the effects of sleep on reproductive hormone concentrations are poorly characterized. We prospectively followed 259 regularly menstruating women across one to two menstrual cycles (the BioCycle Study, 2005–2007), measuring fasting serum hormone concentrations up to eight times per cycle. Women provided information about daily sleep in diaries and chronotype and night/shift work on a baseline questionnaire. We evaluated percent differences in mean hormone concentrations, the magnitude of shifts in the timing and amplitude of hormone peaks, and the risk for sporadic anovulation associated with self-reported sleep patterns and night/shift work. We estimated chronotype scores – categorizing women below and above the interquartile range (IQR) as “morning” and “evening” chronotypes, respectively. For every hour increase in daily sleep duration, mean estradiol concentrations increased by 3.9% (95% confidence interval [CI] 2.0, 5.9%) and luteal phase progesterone by 9.4% (CI 4.0, 15.2%). Receiving less than 7 hours of sleep per day was associated with slightly earlier rises in peak levels for several hormones. Women reporting night/shift work (n = 77) had lower testosterone relative to women employed without night/shift work (percent difference: ?9.9%, CI ?18.4, ?0.4%). Women with morning chronotypes (n = 47) had earlier rises in estradiol during their cycles and potentially an earlier rise in luteinizing hormone. Compared to those who had intermediate chronotypes, women with evening chronotypes (n = 42) had a later luteinizing hormone peak of borderline statistical significance. A reduced risk for sporadic anovulation was suggested, but imprecise, for increasing hours of daily sleep leading up to ovulation (risk ratio 0.79, CI 0.59, 1.06), while an imprecise increased risk was observed for women with morning chronotypes (risk ratio 2.50, CI 0.93, 6.77). Sleep-related hormonal changes may not greatly alter ovarian function in healthy women, but have the potential to influence gynecologic health.     

Bridging the Mechanical and the Human Mind: Spontaneous Mimicry of a Physically Present Android

The spontaneous mimicry of others'' emotional facial expressions constitutes a rudimentary form of empathy and facilitates social understanding. Here, we show that human participants spontaneously match facial expressions of an android physically present in the room with them. This mimicry occurs even though these participants find the android unsettling and are fully aware that it lacks intentionality. Interestingly, a video of that same android elicits weaker mimicry reactions, occurring only in participants who find the android “humanlike.” These findings suggest that spontaneous mimicry depends on the salience of humanlike features highlighted by face-to-face contact, emphasizing the role of presence in human-robot interaction. Further, the findings suggest that mimicry of androids can dissociate from knowledge of artificiality and experienced emotional unease. These findings have implications for theoretical debates about the mechanisms of imitation. They also inform creation of future robots that effectively build rapport and engagement with their human users.     

Amino Acid-Induced Translation of TOP mRNAs Is Fully Dependent on Phosphatidylinositol 3-Kinase-Mediated Signaling, Is Partially Inhibited by Rapamycin, and Is Independent of S6K1 and rpS6 Phosphorylation

Vertebrate TOP mRNAs contain an oligopyrimidine tract at their 5' termini (5'TOP) and encode components of the translational machinery. Previously it has been shown that they are subject to selective translational repression upon growth arrest and that their translational behavior correlates with the activity of S6K1. We now show that the translation of TOP mRNAs is rapidly repressed by amino acid withdrawal and that this nutritional control depends strictly on the integrity of the 5'TOP motif. However, neither phosphorylation of ribosomal protein (rp) S6 nor activation of S6K1 per se is sufficient to relieve the translational repression of TOP mRNAs in amino acid-starved cells. Likewise, inhibition of S6K1 activity and rpS6 phosphorylation by overexpression of dominant-negative S6K1 mutants failed to suppress the translational activation of TOP mRNAs in amino acid-refed cells. Furthermore, TOP mRNAs were translationally regulated by amino acid sufficiency in embryonic stem cells lacking both alleles of the S6K1 gene. Inhibition of mTOR by rapamycin led to fast and complete repression of S6K1, as judged by rpS6 phosphorylation, but to only partial and delayed repression of translational activation of TOP mRNAs. In contrast, interference in the phosphatidylinositol 3-kinase (PI3-kinase)-mediated pathway by chemical or genetic manipulations blocked rapidly and completely the translational activation of TOP mRNAs. It appears, therefore, that translational regulation of TOP mRNAs, at least by amino acids, (i) is fully dependent on PI3-kinase, (ii) is partially sensitive to rapamycin, and (iii) requires neither S6K1 activity nor rpS6 phosphorylation.     

Functional changes in the conformation of thrombospondin-1 during complexation with fibronectin or heparin

Thrombospondin-1 (TSP-1) interacts specifically with heparin and fibronectin in vitro and colocalizes with fibronectin and heparan sulfate in the extracellular matrix (ECM). Its conformation is strongly dependent on Ca2+ concentration. We have previously shown that both heparin and fibronectin have two binding sites on the TSP-1 subunit which may require conformational change for their occupancy (R. Dardik and J. Lahav, 1987, Eur. J. Biochem. 168, 347; ibid 1989, 185, 581). To investigate the effect of TSP-1 binding to fibronectin and heparin on its functional conformation, TSP-1 was subjected to proteolysis in the presence and absence of ligands and of Ca2+. We found that while trypsin cleavage of free TSP-1 resulted in the inactivation of ligand binding, TSP-1 bound to either fibronectin or heparin remained stably associated with these ligands. Cleavage by thrombin or tissue plasminogen activator (tPA) showed that Ca2+-depleted TSP-1, when bound to fibronectin or to heparin, yielded proteolytic cleavage patterns typical of the Ca2+-containing form. Cleavage by chymotrypsin was not affected by binding to fibronectin or heparin; hence loss of proteolytic susceptibility was not due to steric hindrance by the ligands. Taken together, these results indicate that: (A) binding of TSP-1 to fibronectin or heparin is a two-step mechanism where binding to one site leads to conformational changes that enable binding to the second site; (B) TSP-1 in complex with fibronectin or heparin adopts the Ca2+-containing conformation in the absence of Ca2+; and (C) such complexes are highly resistant to cleavage by tPA and, if cleaved by other enzymes, the TSP-1 fragments remain bound to other ECM components. These characteristics have profound significance for platelet adhesion and cell migration into wounds where Ca2+ concentrations are reduced.     

Recombinant antibodies with MHC-restricted, peptide-specific, T-cell receptor-like specificity: new tools to study antigen presentation and TCR-peptide-MHC interactions

The advent in recent years of the application of tetrameric arrays of class I peptide-MHC complexes now enables us to detect and study rare populations of antigen-specific CD8+ T cells. However, available methods cannot visualize or determine the number and distribution of these TCR ligands on individual cells or detect antigen-presenting cells (APCs) in tissues. Here we describe a new approach that enables study of human class I peptide-MHC ligand-presentation as well as TCR-peptide-MHC interactions. Such studies are facilitated by applying novel tools in the form of peptide-specific, HLA-A2-restricted human recombinant antibodies directed toward a large variety of tumor-associated as well as viral T-cell epitope peptides. Using a large human antibody phage display library, a large panel of recombinant antibodies that are specific for a particular peptide-MHC class I complex in a peptide-dependent, MHC-restricted manner was isolated. These antibodies were used to directly visualize the specific MHC-peptide complex on tumor cells, antigen-presenting cells or virus-infected cells by flow cytometry. They enabled direct quantitation of the number of MHC-peptide complexes as well as in situ detection of the complex on the surface of APCs after naturally occurring active intracellular processing of the cognate antigen. These studies will enable also the development of a new class of targeting molecules to deliver drugs or toxins to tumor or virus-infected cells. Thus, we demonstrate our ability to transform the unique fine specificity but low intrinsic affinity of TCRs into high-affinity soluble antibody molecules endowed with a TCR-like specificity toward human tumor or viral epitopes. These molecules may prove to be crucial useful tools for studying MHC class I antigen presentation in health and disease as well as for therapeutic purposes in cancer, infectious diseases and autoimmune disorders.     

Expression and characterization of the thylakoid lumen protease DegP1 from Arabidopsis

The Arabidopsis genome contains 14 genes encoding the serine protease DegP. Products of four of these genes are located in the chloroplast: three in the thylakoid lumen and one on the stromal side of the membrane. We expressed the gene encoding DegP1 as a His-tagged fusion protein in Escherichia coli, purified the protein by affinity chromatography, and characterized it biochemically. Size-exclusion chromatography suggested that DegP1 eluted from the column as a mixture of monomers and hexamers. Proteolytic activity was characterized using beta-casein as a model substrate. DegP1 demonstrated concentration-dependent activity, a pH optimum of 6.0 and increasing activity at elevated temperatures. DegP1 was capable of degrading two lumenal proteins, plastocyanin and OE33, suggesting a role as a general-purpose protease in the thylakoid lumen. The results of this work are discussed in the context of the recent elucidation of the structure of the E. coli homolog and the possible physiological role of the protease in the chloroplast lumen.     

MyD88-dependent immune activation mediated by human immunodeficiency virus type 1-encoded Toll-like receptor ligands

Immune activation is a major characteristic of human immunodeficiency virus type 1 (HIV-1) infection and a strong prognostic factor for HIV-1 disease progression. The underlying mechanisms leading to immune activation in viremic HIV-1 infection, however, are not fully understood. Here we show that, following the initiation of highly active antiretroviral therapy, the immediate decline of immune activation is closely associated with the reduction of HIV-1 viremia, which suggests a direct contribution of HIV-1 itself to immune activation. To propose a mechanism, we demonstrate that the single-stranded RNA of HIV-1 encodes multiple uridine-rich Toll-like receptor 7/8 (TLR7/8) ligands that induce strong MyD88-dependent plasmacytoid dendritic cell and monocyte activation, as well as accessory cell-dependent T-cell activation. HIV-1-encoded TLR ligands may, therefore, directly contribute to the immune activation observed during viremic HIV-1 infection. These data provide an initial rationale for inhibiting the TLR pathway to directly reduce the chronic immune activation induced by HIV-1 and the associated immune pathogenesis.     

The Emergence of Alternative 3′ and 5′ Splice Site Exons from Constitutive Exons

Alternative 3′ and 5′ splice site (ss) events constitute a significant part of all alternative splicing events. These events were also found to be related to several aberrant splicing diseases. However, only few of the characteristics that distinguish these events from alternative cassette exons are known currently. In this study, we compared the characteristics of constitutive exons, alternative cassette exons, and alternative 3′ss and 5′ss exons. The results revealed that alternative 3′ss and 5′ss exons are an intermediate state between constitutive and alternative cassette exons, where the constitutive side resembles constitutive exons, and the alternative side resembles alternative cassette exons. The results also show that alternative 3′ss and 5′ss exons exhibit low levels of symmetry (frame-preserving), similar to constitutive exons, whereas the sequence between the two alternative splice sites shows high symmetry levels, similar to alternative cassette exons. In addition, flanking intronic conservation analysis revealed that exons whose alternative splice sites are at least nine nucleotides apart show a high conservation level, indicating intronic participation in the regulation of their splicing, whereas exons whose alternative splice sites are fewer than nine nucleotides apart show a low conservation level. Further examination of these exons, spanning seven vertebrate species, suggests an evolutionary model in which the alternative state is a derivative of an ancestral constitutive exon, where a mutation inside the exon or along the flanking intron resulted in the creation of a new splice site that competes with the original one, leading to alternative splice site selection. This model was validated experimentally on four exons, showing that they indeed originated from constitutive exons that acquired a new competing splice site during evolution.