Exploring adults' experiences of sedentary behaviour and participation in non-workplace interventions designed to reduce sedentary behaviour: a thematic synthesis of qualitative studies.

BACKGROUND: Sedentary behaviour is any waking behaviour characterised by an energy expenditure of ≤1.5 metabolic equivalent of task while in a sitting or reclining posture. Prolonged bouts of sedentary behaviour have been associated with negative health outcomes in all age groups. We examined qualitative research investigating perceptions and experiences of sedentary behaviour and of participation in non-workplace interventions designed to reduce sedentary behaviour in adult populations. METHOD: A systematic search of seven databases (MEDLINE, AMED, Cochrane, PsychINFO, SPORTDiscus, CINAHL and Web of Science) was conducted in September 2017. Studies were assessed for methodological quality and a thematic synthesis was conducted. Prospero database ID: CRD42017083436. RESULTS: Thirty individual studies capturing the experiences of 918 individuals were included. Eleven studies examined experiences and/or perceptions of sedentary behaviour in older adults (typically ≥60 years); ten studies focused on sedentary behaviour in people experiencing a clinical condition, four explored influences on sedentary behaviour in adults living in socio-economically disadvantaged communities, two examined university students' experiences of sedentary behaviour, two on those of working-age adults, and one focused on cultural influences on sedentary behaviour. Three analytical themes were identified: 1) the impact of different life stages on sedentary behaviour 2) lifestyle factors influencing sedentary behaviour and 3) barriers and facilitators to changing sedentary behaviour. CONCLUSIONS: Sedentary behaviour is multifaceted and influenced by a complex interaction between individual, environmental and socio-cultural factors. Micro and macro pressures are experienced at different life stages and in the context of illness; these shape individuals' beliefs and behaviour related to sedentariness. Knowledge of sedentary behaviour and the associated health consequences appears limited in adult populations, therefore there is a need for provision of accessible information about ways in which sedentary behaviour reduction can be integrated in people's daily lives. Interventions targeting a reduction in sedentary behaviour need to consider the multiple influences on sedentariness when designing and implementing interventions.

Parafermionic Zero Modes in Ultracold Bosonic Systems.

Exotic topologically protected zero modes with parafermionic statistics (also called fractionalized Majorana modes) have been proposed to emerge in devices fabricated from a fractional quantum Hall system and a superconductor. The fractionalized statistics of these modes takes them an important step beyond the simplest non-Abelian anyons, Majorana fermions. Building on recent advances towards the realization of fractional quantum Hall states of bosonic ultracold atoms, we propose a realization of parafermions in a system consisting of Bose-Einstein-condensate trenches within a bosonic fractional quantum Hall state. We show that parafermionic zero modes emerge at the end points of the trenches and give rise to a topologically protected degeneracy. We also discuss methods for preparing and detecting these modes.

Mec1p regulates Pds1p levels in S phase: complex coordination of DNA replication and mitosis.

Genetic evidence suggests that the securin Pds1p is the target of a late-S-phase checkpoint control. Here we show that Pds1p becomes essential once two-thirds of the genome has been replicated and that the coupling of the completion of genome replication with mitosis relies on the regulation of Pds1p levels. Mec1p is needed to maintain Pds1p levels under S-phase checkpoint conditions. In contrast, Rad53p and Chk1p, needed for the stabilization of Pds1p in the context of the G2 DNA-damage checkpoint pathway, are dispensable. Thus, the Pds1p-dependent late-S-phase checkpoint pathway couples replication with mitosis but is mechanistically distinct from the G2 DNA-damage checkpoint. Finally, we show that the inhibition of spindle elongation in early S phase, controlled by the Mec1p/Rad53p branch, is not regulated via Pds1p/Esp1p. This can mechanistically explain the need for branched S-phase checkpoint controls.

Role of Aurora B and Haspin kinases in the metaphase Topoisomerase II checkpoint.

DNA Topoisomerase II (TopoII) uses ATP hydrolysis to decatenate chromosomes so that sister chromatids can faithfully segregate in mitosis. When the TopoII enzyme cycle stalls due to failed ATP hydrolysis, the onset of anaphase is delayed, presumably to allow extra time for decatenation to be completed. Recent evidence revealed that, unlike the spindle assembly checkpoint, this TopoII checkpoint response requires Aurora B and Haspin kinases and is triggered by SUMOylation of the C-terminal domain of TopoII.

Probing the tri-trophic interaction between insects, nematodes and Photorhabdus.

SUMMARY: Photorhabdus sp. are entomopathogenic bacteria which, upon experimental infection, interact with the insect immune system, but little is known about the roles of their symbiotic nematode partners Heterorhabditis sp. in natural infections. Here, we investigated the respective contributions of nematodes and bacteria by examining humoral and cellular immune reactions of the model lepidopteran insect Manduca sexta against Heterorhabditis carrying Photorhabdus, nematodes free of bacteria (axenic nematodes) and bacteria alone. Insect mortality was slower following infection with axenic nematodes than when insects were infected with nematodes containing Photorhabdus, or the bacteria alone. Nematodes elicited host immune responses to a lesser extent than bacteria. Transcription of certain recognition and antibacterial genes was lower when insects were naturally infected with nematodes carrying no bacteria compared to insects that received bacteria, either with or without nematodes. Axenic nematodes also did not elicit such high levels of phenoloxidase activity and haemocyte aggregates as did treatments involving Photorhabdus. By contrast, the phagocytic capability of host haemocytes was decreased by both axenic and bacteria-associated nematodes, but not by Photorhabdus alone. These results imply that both bacteria and nematodes contribute separately to the pathogenic modulation of host immune responses during natural infections by the mutualistic Heterorhabdus-Photorhabdus complex.

A festival of cell-cycle controls.

The second biennial Salk Cell Cycle meeting convened on 22 June 2001 in San Diego, California. Organized by Tony Hunter and Susan Forsburg of the Salk Institute, the five-day conference was highlighted by enlightening science and plenty of San Diego sunshine. Presentations covered a broad range of contemporary cell-cycle topics, ranging from regulation of DNA replication and mitosis to DNA damage recognition and checkpoint control.

Clb5-associated kinase activity is required early in the spindle pathway for correct preanaphase nuclear positioning in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, a single cyclin-dependent kinase, Cdc28, regulates both G1/S and G2/M phase transitions by associating with stage-specific cyclins. During progression through S phase and G2/M, Cdc28 is activated by the B-type cyclins Clb1-6. Because of functional redundancy, specific roles for individual Clbs have been difficult to assign. To help genetically define such roles, strains carrying a cdc28(ts) allele, combined with single CLB deletions were studied. We assumed that by limiting the activity of the kinase, these strains would be rendered more sensitive to loss of individual Clbs. By this approach, a novel phenotype associated with CLB5 mutation was observed. Homozygous cdc28-4(ts) clb5 diploids were inviable at room temperature. Cells were defective in spindle positioning, leading to migration of undivided nuclei into the bud. Occasionally, misplaced spindles were observed in cdc28-4 clb5 haploids; additional deletion of CLB6 caused full penetrance. Thus, CLB5 effects proper preanaphase spindle positioning, yet the requirement differs in haploids and diploids. The execution point for the defect corresponded to the time of Clb5-dependent kinase activation. Nevertheless, lethality of cdc28-4 clb5 diploids was not rescued by CLB2 or CLB4 overexpression, indicating a specificity of Clb5 function beyond temporality of expression.

A novel role of the budding yeast separin Esp1 in anaphase spindle elongation: evidence that proper spindle association of Esp1 is regulated by Pds1.

In Saccharomyces cerevisiae, the metaphase-anaphase transition is initiated by the anaphase-promoting complex-dependent degradation of Pds1, whereby Esp1 is activated to promote sister chromatid separation. Although this is a fundamental step in the cell cycle, little is known about the regulation of Esp1 and how loss of cohesion is coordinated with movement of the anaphase spindle. Here, we show that Esp1 has a novel role in promoting anaphase spindle elongation. The localization of Esp1 to the spindle apparatus, analyzed by live cell imaging, is regulated in a manner consistent with a function during anaphase B. The protein accumulates in the nucleus in G2 and is mobilized onto the spindle pole bodies and spindle midzone at anaphase onset, where it persists into midanaphase. Association with Pds1 occurs during S phase and is required for efficient nuclear targeting of Esp1. Spindle association is not fully restored in pds1 mutants expressing an Esp1-nuclear localization sequence fusion protein, suggesting that Pds1 is also required to promote Esp1 spindle binding. In agreement, Pds1 interacts with the spindle at the metaphase-anaphase transition and a fraction remains at the spindle pole bodies and the spindle midzone in anaphase cells. Finally, mutational analysis reveals that the conserved COOH-terminal region of Esp1 is important for spindle interaction.

A postprophase topoisomerase II-dependent chromatid core separation step in the formation of metaphase chromosomes.

Metaphase chromatids are believed to consist of loops of chromatin anchored to a central scaffold, of which a major component is the decatenatory enzyme DNA topoisomerase II. Silver impregnation selectively stains an axial element of metaphase and anaphase chromatids; but we find that in earlier stages of mitosis, silver staining reveals an initially single, folded midline structure, which separates at prometaphase to form two chromatid axes. Inhibition of topoisomerase II prevents this separation, and also prevents the contraction of chromatids that occurs when metaphase is arrested. Immunolocalization of topoisomerase II alpha reveals chromatid cores analogous to those seen with silver staining. We conclude that the chromatid cores in early mitosis form a single structure, constrained by DNA catenations, which must separate before metaphase chromatids can be resolved.

Coordinated spindle assembly and orientation requires Clb5p-dependent kinase in budding yeast.

The orientation of the mitotic spindle along a polarity axis is critical in asymmetric cell divisions. In the budding yeast, Saccharomyces cerevisiae, loss of the S-phase B-type cyclin Clb5p under conditions of limited cyclin-dependent kinase activity (cdc28-4 clb5Delta cells) causes a spindle positioning defect that results in an undivided nucleus entering the bud. Based on time-lapse digital imaging microscopy of microtubules labeled with green fluorescent protein fusions to either tubulin or dynein, we observed that the asymmetric behavior of the spindle pole bodies during spindle assembly was lost in the cdc28-4 clb5Delta cells. As soon as a spindle formed, both poles were equally likely to interact with the bud cell cortex. Persistent dynamic interactions with the bud ultimately led to spindle translocation across the bud neck. Thus, the mutant failed to assign one spindle pole body the task of organizing astral microtubules towards the mother cell. Our data suggest that Clb5p-associated kinase is required to confer mother-bound behavior to one pole in order to establish correct spindle polarity. In contrast, B-type cyclins, Clb3p and Clb4p, though partially redundant with Clb5p for an early role in spindle morphogenesis, preferentially promote spindle assembly.

The Pds1 anaphase inhibitor and Mec1 kinase define distinct checkpoints coupling S phase with mitosis in budding yeast.

In most eukaryotic cells, DNA replication is confined to S phase of the cell cycle [1]. During this interval, S-phase checkpoint controls restrain mitosis until replication is complete [2]. In budding yeast, the anaphase inhibitor Pds1p has been associated with the checkpoint arrest of mitosis when DNA is damaged or when mitotic spindles have formed aberrantly [3] [4], but not when DNA replication is blocked with hydroxyurea (HU). Previous studies have implicated the protein kinase Mec1p in S-phase checkpoint control [5]. Unlike mec1 mutants, pds1 mutants efficiently inhibit anaphase when replication is blocked. This does not, however, exclude an essential S-phase checkpoint function of Pds1 beyond the early S-phase arrest point of a HU block. Here, we show that Pds1p is an essential component of a previously unsuspected checkpoint control system that couples the completion of S phase with mitosis. Further, the S-phase checkpoint comprises at least two distinct pathways. A Mec1p-dependent pathway operates early in S phase, but a Pds1p-dependent pathway becomes essential part way through S phase.

Dosage suppressors of pds1 implicate ubiquitin-associated domains in checkpoint control.

In budding yeast, anaphase initiation is controlled by ubiquitin-dependent degradation of Pds1p. Analysis of pds1 mutants implicated Pds1p in the DNA damage, spindle assembly, and S-phase checkpoints. Though some components of these pathways are known, others remain to be identified. Moreover, the essential function of Pds1p, independent of its role in checkpoint control, has not been elucidated. To identify loci that genetically interact with PDS1, we screened for dosage suppressors of a temperature-sensitive pds1 allele, pds1-128, defective for checkpoint control at the permissive temperature and essential for viability at 37 degrees C. Genetic and functional interactions of two suppressors are described. RAD23 and DDI1 suppress the temperature and hydroxyurea, but not radiation or nocodazole, sensitivity of pds1-128. rad23 and ddi1 mutants are partially defective in S-phase checkpoint control but are proficient in DNA damage and spindle assembly checkpoints. Therefore, Rad23p and Ddi1p participate in a subset of Pds1p-dependent cell cycle controls. Both Rad23p and Ddi1p contain ubiquitin-associated (UBA) domains which are required for dosage suppression of pds1-128. UBA domains are found in several proteins involved in ubiquitin-dependent proteolysis, though no function has been assigned to them. Deletion of the UBA domains of Rad23p and Ddi1p renders cells defective in S-phase checkpoint control, implicating UBA domains in checkpoint signaling. Since Pds1p destruction, and thus checkpoint regulation of mitosis, depends on ubiquitin-dependent proteolysis, we propose that the UBA domains functionally interact with the ubiquitin system to control Pds1p degradation in response to checkpoint activation.

MCPH1, mutated in primary microcephaly, is required for efficient chromosome alignment during mitosis.

MCPH1 gene, mutated in primary microcephaly, regulates cell progression into mitosis. While this role has been extensively investigated in the context of DNA damage, its function during unperturbed cell cycles has been given less attention. Here we have analyzed the dynamics of chromosome condensation and cell cycle progression in MCPH1 deficient cells under undamaging conditions. Our study demonstrates that chromosome condensation is uncoupled from cell cycle progression when MCPH1 function is lacking, resulting in cells that prematurely condense their chromosomes during mid G2-phase and delay decondensation at the completion of mitosis. However, mitosis onset occurs on schedule in MCPH1 deficient cells. We also revealed active Cdk1 to be mandatory for the premature onset of chromosome condensation during G2 and the maintenance of the condensed state thereafter. Interestingly, a novel cellular phenotype was observed while monitoring cell cycle progression in cells lacking MCPH1 function. Specifically, completion of chromosome alignment at the metaphase plate was significantly delayed. This deficiency reveals that MCPH1 is required for efficient chromosome biorientation during mitosis.

UBA domains mediate protein-protein interactions between two DNA damage-inducible proteins.

The Saccharomyces cerevisiae genes RAD23 and DDI1 were identified in a screen for multicopy suppressors of the temperature-sensitivity of a mutant allele of S. cerevisiae PDS1. Pds1 is a regulator of anaphase that needs to accumulate and then be degraded by the ubiquitin-proteasome pathway at the metaphase-anaphase transition for cells to progress normally through mitosis. Both the Rad23 and Ddi1 pds1 suppression phenotypes depend on a shared motif known as a UBA domain found in a variety of proteins associated with ubiquitin metabolism. UBA domains were found to be essential for homodimerization of Rad23 and heterodimerization between Rad23 and Ddi1, but not for homodimerization of Ddi1. This observation, coupled with the findings that Rad23 and Ddi1 UBA domains bind ubiquitin and that dimerization of Rad23 blocks ubiquitin binding, suggests a possible mechanism for regulating Rad23 and Ddi1 function.

Identification of genes controlling growth polarity in the budding yeast Saccharomyces cerevisiae: a possible role of N-glycosylation and involvement of the exocyst complex.

The regulation of secretion polarity and cell surface growth during the cell cycle is critical for proper morphogenesis and viability of Saccharomyces cerevisiae. A shift from isotropic cell surface growth to polarized growth is necessary for bud emergence and a repolarization of secretion to the bud neck is necessary for cell separation. Although alterations in the actin cytoskeleton have been implicated in these changes in secretion polarity, clearly other cellular systems involved in secretion are likely to be targets of cell cycle regulation. To investigate mechanisms coupling cell cycle progression to changes in secretion polarity in parallel with and downstream of regulation of actin polarization, we implemented a screen for mutants defective specifically in polarized growth but with normal actin cytoskeleton structure. These mutants fell into three classes: those partially defective in N-glycosylation, those linked to specific defects in the exocyst, and a third class neither defective in glycosylation nor linked to the exocyst. These results raise the possibility that changes in N-linked glycosylation may be involved in a signal linking cell cycle progression and secretion polarity and that the exocyst may have regulatory functions in coupling the secretory machinery to the polarized actin cytoskeleton.

Competence for assembly of sister chromatid cores is progressively acquired during S phase in mammalian cells.

Condensed sister chromatids possess a protein scaffold or axial core to which loops of chromatin are attached. The sister cores are believed to be dynamic frameworks that function in the organization and condensation of chromatids. Chromosome structural proteins are implicated in the establishment of sister chromatid cohesion and in the maintenance of epigenetic phenomena. Both processes of templating are tightly linked to DNA replication itself. It is a question whether the structural basis of sister chromatid cores is templated during S phase. As cells proceed through the cell cycle, chromatid cores undergo changes in their protein composition. Cytologically, cores are first visualized at the start of prometaphase. Still, core assembly can be induced in G1 and G2 when interphase cells are fused with mitotic cells. In this study, we asked if chromatid cores are similarly able to assemble in S-phase cells. We find that the ability to assemble cores is transiently lost during local replication, then regained in chromosome regions shortly after they have been replicated. We propose that core templating occurs coincident with DNA replication and that the competence for the assembly of the sister chromatid cores is acquired shortly after passage of replication forks.

Isolation and characterisation of a new hepatic bilirubin UDP-glucuronosyltransferase. Absence from Gunn rat liver.

A novel UDP-glucuronosyltransferase that conjugates bilirubin IX alpha, bilirubin monoglucuronide and an arylalkanoic acid was purified to homogeneity from clofibrate treated Wistar rats. The enzyme displayed a subunit molecular mass of 54 kDa, a pI of 7.6 and was demonstrated to be N-glycosylated. Sequence analysis of peptides derived by endoproteinase Glu-C cleavage of the purified enzyme indicated that it was a new member of the recently identified UGT1 subfamily. Immunoblot analysis demonstrated that this enzyme was absent from Gunn rat liver. The molecular derivation of this enzyme and the lack of it in Gunn rats is discussed.

Characterisation of a human bilirubin UDP-glucuronosyltransferase stably expressed in hamster lung fibroblast cell cultures.

A cDNA encoding a human bilirubin UDP-glucuronosyltransferase has been isolated and stably expressed in Chinese hamster V79 lung fibroblast cell line. Western blotting of cell homogenates with anti-UGT antibody revealed a highly expressed protein of approx. 55.5 kDa in size. The expressed enzyme specifically catalysed the formation of bilirubin mono- and diglucuronides, and also catalysed the glucuronidation of two phenolic compounds, which are good substrates for other human UGT isoenzymes, at low rates.

Host Corticostriatal Fibres Establish Synaptic Connections with Grafted Striatal Neurons in the Ibotenic Acid Lesioned Striatum.

The connections between host corticostriatal afferents and neurons in intrastriatal grafts of foetal striatal tissue have been studied with electron microscopic immunocytochemistry using Phaseolus vulgaris leucoagglutinin (PHA-L) as a label of the host corticostriatal fibres. Adult rats with unilateral ibotenic acid lesions of the head of the caudate putamen received foetal cell suspension grafts from E14-15 rat embryos into the lesioned striatal area. Ten months after transplantation, multiple iontophoretic injections of PHA-L were made into the host frontal cortex. These injections labelled large numbers of corticostriatal fibres which extended across the graft - host border to form a rich axonal network mainly in the peripheral portions of the grafts. At the ultrastructural level a total of 134 PHA-L-labelled terminals were identified to form asymmetric synaptic contacts with neurons within the grafts. Of these contacts, 83% were in contact with dendritic spines, 12% with dendritic shafts, and 5% with small shafts or spines. The synaptic contacts were similar to those identified in intact regions of the host striatum that were spared by the lesion. However, the synapses in the host striatum were almost exclusively in contact with spines (98%). These results demonstrate that the corticostriatal projection, which constitutes a major source of afferent control in the normal striatum, not only extends axons into the intrastriatal striatal grafts, but also establishes synaptic connections with the implanted neuronal elements.

Sites of [3H]taurine Uptake in the Rat Substantia Nigra in Relation to the Release of Taurine from the Striatonigral Pathway.

The autoradiographic localization of radiolabelled taurine taken up in the rat substantia nigra in vivo together with conditions of release of the [3H]taurine taken up into brain slices were studied to determine whether they are consistent with the hypothesis that taurine may act as a neurotransmitter in the striatonigral pathway. At the light microscopic level the main cellular elements that became radiolabelled following the injection of [3H]taurine into the substantia nigra could be identified as glial cells. Electron microscope autoradiography confirmed that a subpopulation of glial cells including astrocytes, pericytes, and oligodendrocytes were radiolabelled and that neuronal perikarya were not radiolabelled. In addition, axonal elements including both terminal and preterminal boutons were found to have silver grains overlying them and were thus considered to be radiolabelled. This was supported by a quantitative analysis of the distribution of the silver grains; whereas glial elements had a significantly higher number of grains associated with them than with any other structure, axonal elements had a significantly greater number of grains than dendritic structures. Release of the preloaded [3H]taurine from superfused slices of substantia nigra occurred in response to veratridine, was calcium-dependent and was sensitive to inhibition by high magnesium concentrations or tetrodotoxin. Following the destruction of neurons in the striatum by ibotenic acid injections, although the weight of the ipsilateral substantia nigra was reduced, the uptake of [3H]taurine was not altered. In contrast to this, the veratridine-stimulated release was markedly attenuated, implying that the destruction of striatal neurons causes the loss of sites in the substantia nigra from which exogenous taurine is released. These results add further support to previous suggestions that taurine might act as a neurotransmitter or neuromodulator in the striatonigral pathway.