Chronotype and sleep duration: The influence of season of assessment

Little is known about human entrainment under natural conditions, partly due to the complexity of human behavior, torn between biological and social time and influenced by zeitgebers (light–dark cycles) that are progressively “polluted” (and thereby weakened) by artificial light. In addition, data about seasonal variations in sleep parameters are scarce. We, therefore, investigated seasonal variation in cross-sectional assessments of sleep/wake times of 9765 subjects from four European populations (EGCUT?=?Estonian Genome Centre, University of Tartu in Estonia; KORA?=?Cooperative Health Research in the Region of Augsburg in Germany; KORCULA?=?The Korcula study in Croatia; and ORCADES?=?The Orkney Complex Disease Study in Scotland). We identified time-of-year dependencies for the distribution of chronotype (phase of entrainment assessed as the mid-sleep time point on free days adjusted for sleep deficit of workdays) in cohorts from Estonia (EGCUT) and Germany (KORA). Our results indicate that season (defined as daylight saving time – DST and standard zonetime periods – SZT) specifications of photoperiod influence the distribution of chronotype (adjusted for age and sex). Second, in the largest investigated sample, from Estonia (EGCUT; N?=?5878), we could detect that seasonal variation in weekly average sleep duration was dependent on individual chronotype. Later chronotypes in this cohort showed significant variation in their average sleep duration across the year, especially during DST (1?h advance in social time from the end of March to end of October), while earlier chronotypes did not. Later chronotypes not only slept less during the DST period but the average chronotype of the population assessed during this period was earlier than during the SZT (local time for a respective time zone) period. More in detail, hierarchical multiple regression analyses showed that, beyond season of assessment (DST or SZT), social jetlag (SJl; the discrepancy between the mid sleep on free and work days – which varied with age and sex) contributed to a greater extent to the variation in sleep duration than chronotype (after taking into account factors that are known to influence sleep duration, i.e. age, sex and body mass index). Variation in chronotype was also dependent on age, sex, season of assessment and SJl (which is highly correlated with chronotype – SJl was larger among later chronotypes). In summary, subjective assessments of sleep/wake times are very reliable to assess internal time and sleep duration (e.g. reproducing sleep duration and timing tendencies related to age and sex across the investigated populations), but season of assessment should be regarded as a potential confounder. We identified in this study photoperiod (seasonal adaptation) and SJl as two main factors influencing seasonal variation in chronotype and sleep duration. In conclusion, season of assessment, sex and age have an effect on epidemiological variation in sleep duration, chronotype and SJl, and should be included in studies investigating associations between these phenotypes and health parameters, and on the development of optimal prevention strategies.     

The effect of size and age on depuration rates of diarrhetic shellfish toxins (DST) in mussels (Mytilus edulis L.)

Depuration or elimination of diarrhetic shellfish toxins (DST) was followed for 73 days in 1- and 2-year-old mussels. The age groups also differed in size, providing a broad approach to studying the effect of the differences in physiology accompanying the differences in size. Content of DST was analysed both on groups and individual mussels. Environmental variables were measured to evaluate their effect on depuration.We found no significant differences in elimination rate of DST between 1- and 2-year-old mussels under natural conditions. This suggests that size and age do not affect the elimination rate of the DST. The present study is the first study on the effect of age and size on the elimination rate of algal toxins in bivalves. The natural variations in food levels and temperature were not found to affect the elimination rate of DST.The digestive gland weights in the 1-year-old mussels increased four times while the DST content per individual decreased eight times. This demonstrated that dilution of toxins due to tissue growth could have an important contribution to declines in toxin concentrations. Changes in tissue mass are affected by environmental variables via growth or starvation, and when such changes lead to concentration or dilution of toxins this does not reflect the accumulation or removal of toxins from the tissues. We hence suggest that when evaluating the actual elimination capacity of the mussels, as in the present study, the total content of toxins per individual should be used, rather than toxin concentrations.The 1-year-old mussels had faster growth compared to the 2-year-old mussels in both total soft tissue and digestive glands. The mechanism of DST elimination is still unknown. If this process involves metabolism of the toxins, one could expect the rates of elimination to follow overall metabolic rates. However, the results from the present study suggest that large differences in growth rates, which also include difference in feeding and metabolic rates, do not affect the elimination rate of DST. Our results support the assumption that the depuration rates cannot be accelerated, even in artificial systems, as a cost-effective way to solve the problem with toxic mussels for the industry.     

A field and experimental evaluation of the effect of data storage tags on the growth of cod

The effect of electronic data storage tags (DSTs) on the growth of cod Gadus morhua was evaluated in laboratory and field experiments. In the first laboratory experiment, large DSTs (60 × 18 mm, 3 g in water ) attached externally for 3 months did not have any effect ( anova , P  > 0·05) on the growth of adult cod (mean ±  s . d . 65 ± 4·5 cm total length) relative to untagged adult cod. In a second experiment, small DSTs (34 × 11 mm, 1·5 g in water) implanted into young cod (48·1 ± 4·4 cm) for an 8 month period did not have any effect upon the growth relative to untagged controls ( anova , P  > 0·05). Length data returned from tagging experiments conducted on adult cod (57·3 ± 7·5 cm) in the North Sea showed that the growth of fish tagged either externally or internally with large DSTs was not different ( t ‐test, P  > 0·05). Attachment wounds, however, provided evidence that external attachment of DSTs should be avoided unless sensor configuration requires access to the external environment, and that internal implantation should be preferred whenever possible.     

Arabidopsis STAYGREEN-LIKE (SGRL) promotes abiotic stress-induced leaf yellowing during vegetative growth

During leaf senescence in Arabidopsis, STAYGREEN 1 (SGR1) and SGR2 regulate chlorophyll degradation positively and negatively, respectively. SGR-LIKE (SGRL) is also expressed in pre-senescing leaves, but its function remains largely unknown. Here we show that under abiotic stress, Arabidopsis plants overexpressing SGRL exhibit early leaf yellowing and sgrl-1 mutants exhibit persistent green color of leaves. Under salt stress, SGR1 and SGRL act synergistically for rapid Chl degradation prior to senescence. Furthermore, SGRL forms homo- and heterodimers with SGR1 and SGR2 in vivo, and interacts with LHCII and chlorophyll catabolic enzymes. The role of SGRL under abiotic stress is discussed.     

Partitioning heterozygosity in subdivided populations: Some misuses of Nei's decomposition and an alternative probabilistic approach

Nei's decomposition of total expected heterozygosity in subdivided populations into within‐ and between‐subpopulation components, H_S and D_ST, respectively, is a classical tool in the conservation and management of genetic resources. Reviewing why this is not a decomposition into independent terms of within‐ and between‐subpopulation gene diversity, we illustrate how this approach can be misleading because it overemphasizes the within‐subpopulation component compared to Jost's nonadditive decomposition based on gene diversity indices. Using probabilistic partitioning of the total expected heterozygosity into independent within‐ and between‐subpopulation contributions, we show that the contribution of the within‐subpopulation expected heterozygosity to the total expected heterozygosity is not H_S, as suggested by Nei's decomposition, but H_S/s, with s being the number of subpopulations. Finally, we compare three possible approaches of decomposing total heterozygosity in subdivided populations (i.e., Nei's decomposition, Jost's approach, and probabilistic partitioning) with regard to independence between terms and sensitivity to unequal subpopulation sizes. For the conservation and management of genetic resources, we recommend using probabilistic partitioning and Jost's differentiation parameter rather than Nei's decomposition.     

Evidence for metapopulation structuring in cod from the west of Scotland and North Sea

The scale of population structuring in cod Gadus morhua from the west of Scotland (ICES stock area VIa) and northern North Sea was investigated using a combination of non-genetic methods. Site fidelity of spawning aggregations was examined using historic tag-recapture experiments and individual geolocation estimates from data storage tagged fish. The extent of movements from spawning areas indicated by these two tagging approaches was broadly similar. Between 67 and 97% of adult cod remained within 100 km of spawning areas throughout the year, suggesting resident spawning groups. A small proportion of cod, however, did appear to stray between spawning areas. A comparison of the elemental signature of the otoliths of 0 year-group and the 0 year-group component from the same year-class at age 2 years indicated that most adults originate from local nursery areas. Moreover, there did not appear to be detectable exchange between spawning areas >200 km apart, such as the Clyde and Minch or Shetland and the Inner Hebrides. As such, population processes may operate at a smaller spatial scale than the stock level, with spawning aggregations functioning as local populations within a metapopulation. The relevance of this scale of dynamics is discussed in relation to recently imposed closed areas in the region.     

Genetic load is associated with hypothalamic–pituitary–adrenal axis dysregulation in macaques

Dysregulation of the hypothalamic–pituitary–adrenal (HPA) axis pathway is associated with several neuropsychiatric disorders, including post‐traumatic stress disorder (PTSD), major depressive disorder (MDD), schizophrenia and alcohol abuse. Studies have demonstrated an association between HPA axis dysfunction and gene variants within the cortisol, serotonin and opioid signaling pathways. We characterized polymorphisms in genes linked to these three neurotransmitter pathways and tested their potential interactions with HPA axis activity, as measured by dexamethasone (DEX) suppression response. We determined the percent DEX suppression of adrenocorticotropic hormone (ACTH) and cortisol in 62 unrelated, male rhesus macaques. While DEX suppression of cortisol was robust amongst 87% of the subjects, ACTH suppression levels were broadly distributed from ?21% to 66%. Thirty‐seven monkeys from the high and low ends of the ACTH suppression distribution (18 ‘high’ and 19 ‘low’ animals) were genotyped at selected polymorphisms in five unlinked genes (rhCRH, rhTPH2, rhMAOA, rhSLC6A4 and rhOPRM). Associations were identified between three variants (rhCRH‐2610C>T, rhTPH2 2051A>C and rh5‐HTTLPR) and level of DEX suppression of ACTH. In addition, a significant additive effect of the ‘risk’ genotypes from these three loci was detected, with an increasing number of ‘risk’ genotypes associated with a blunted ACTH response (P = 0.0009). These findings suggest that assessment of multiple risk alleles in serotonin and cortisol signaling pathway genes may better predict risk for HPA axis dysregulation and associated psychiatric disorders than the evaluation of single gene variants alone.     

BPAG1 isoform-b: Complex distribution pattern in striated and heart muscle and association with plectin and α-actinin

BPAG1-b is the major muscle-specific isoform encoded by the dystonin gene, which expresses various protein isoforms belonging to the plakin protein family with complex, tissue-specific expression profiles. Recent observations in mice with either engineered or spontaneous mutations in the dystonin gene indicate that BPAG1-b serves as a cytolinker important for the establishment and maintenance of the cytoarchitecture and integrity of striated muscle. Here, we studied in detail its distribution in skeletal and cardiac muscles and assessed potential binding partners. BPAG1-b was detectable in vitro and in vivo as a high molecular mass protein in striated and heart muscle cells, co-localizing with the sarcomeric Z-disc protein α-actinin-2 and partially with the cytolinker plectin as well as with the intermediate filament protein desmin. Ultrastructurally, like α-actinin-2, BPAG1-b was predominantly localized at the Z-discs, adjacent to desmin-containing structures. BPAG1-b was able to form complexes with both plectin and α-actinin-2, and its NH₂-terminus, which contains an actin-binding domain, directly interacted with that of plectin and α-actinin. Moreover, the protein level of BPAG1-b was reduced in muscle tissues from plectin-null mutant mice versus wild-type mice. These studies provide new insights into the role of BPAG1-b in the cytoskeletal organization of striated muscle.     

Development of a single multiplex amplification refractory mutation system PCR for the detection of rifampin-resistant Mycobacterium tuberculosis

A rapid and simple method for the detection of drug-resistant Mycobacterium tuberculosis is critical for the efficient treatment and control of this pathogen in developing country. Here we developed a single multiplex amplification refractory mutation system (M-ARMS) PCR, in which chimeric-primer and temperature switch PCR (TSP) strategy were included. Using this method, we detected rifampin resistance-associated mutations at codons 511, 516, 526 and 531 in the rifampin resistance-determining region of rpoB gene. The performance of M-ARMS-PCR assay was evaluated with 135 cultured isolates of M. tuberculosis. The sensitivity and specificity were 94.2% and 100%, respectively, compared with direct DNA sequencing, and 86.67% and 89.71%, respectively, compared with culture-based phenotypic drug susceptibility testing. Therefore, this newly-developed M-ARMS-PCR method is useful and efficient with an intended application in provincial Centers for Disease Control and Prevention for rapid detection of rifampin resistance-associated mutations.