Temporal associations between daytime physical activity and sleep in children

Objectives

We examined temporal associations between objectively-measured physical activity (PA) during the day and in the evening, and sleep quantity and quality.

Study Design

PA and sleep were measured by actigraphs for an average of one week in an epidemiological cohort study of 275 eight-year-old children.

Results

For each one standard deviation (SD) unit of increased PA during the day, sleep duration was decreased by 0.30, sleep efficiency by 0.16, and sleep fragmentation increased by 0.08 SD units that night. For each one SD unit increase in sleep duration and efficiency the preceding night, PA the following day decreased by 0.09 and 0.16 SD units, respectively. When we contrasted days with a high amount of moderate to vigorous activity during the day or in the evening to days with a more sedentary profile, the results were essentially similar. However, moderate to vigorous PA in the evening shortened sleep latency.

Conclusions

The relationship between a higher level of PA and poorer sleep is bidirectional. These within-person findings challenge epidemiological findings showing that more active people report better sleep. Since only a few studies using objective measurements of both PA and sleep have been conducted in children, further studies are needed to confirm/refute these results.     

Identification and Validation of Novel Contraction-Regulated Myokines Released from Primary Human Skeletal Muscle Cells

Proteins secreted by skeletal muscle, so called myokines, have been shown to affect muscle physiology and additionally exert systemic effects on other tissues and organs. Although recent profiling studies have identified numerous myokines, the amount of overlap from these studies indicates that the secretome of skeletal muscle is still incompletely characterized. One limitation of the models used is the lack of contraction, a central characteristic of muscle cells. Here we aimed to characterize the secretome of primary human myotubes by cytokine antibody arrays and to identify myokines regulated by contraction, which was induced by electrical pulse stimulation (EPS). In this study, we validated the regulation and release of two selected myokines, namely pigment epithelium derived factor (PEDF) and dipeptidyl peptidase 4 (DPP4), which were recently described as adipokines. This study reveals that both factors, DPP4 and PEDF, are secreted by primary human myotubes. PEDF is a contraction-regulated myokine, although PEDF serum levels from healthy young men decrease after 60 min cycling at VO₂max of 70%. Most interestingly, we identified 52 novel myokines which have not been described before to be secreted by skeletal muscle cells. For 48 myokines we show that their release is regulated by contractile activity. This profiling study of the human skeletal muscle secretome expands the number of myokines, identifies novel contraction-regulated myokines and underlines the overlap between proteins which are adipokines as well as myokines.     

Measles IgG antibody index correlates with T2 lesion load on MRI in patients with early multiple sclerosis

Background

B cells and humoral immune responses play an important role in the pathogenesis and diagnosis of multiple sclerosis (MS). A characteristic finding in patients with MS is a polyspecific intrathecal B cell response against neurotropic viruses, specifically against measles virus, rubella virus, and varicella zoster virus, also known as an MRZ reaction (MRZR). Here, we correlated from the routine clinical diagnostics individual IgG antibody indices (AIs) of MRZR with magnetic resonance imaging (MRI) findings in patients with first MS diagnosis.

Methods/Results

MRZR was determined in 68 patients with a clinically isolated syndrome (CIS) or early relapsing-remitting MS (RRMS). Absolute AI values for measles virus, rubella virus, and varicella zoster virus were correlated with T2 lesion load and gadolinium enhancing lesions on cerebral MRI (cMRI) and cMRI combined with spinal MRI (sMRI). Measles virus AI correlated significantly with T2 lesion load on cMRI (p = 0.0312, Mann-Whitney U test) and the sum of lesions on cMRI and sMRI (p = 0.0413). Varicella zoster virus AI also showed a correlation with T2 lesion load on cMRI but did not reach statistical significance (p = 0.2893).

Conclusion

The results confirm MRZR as part of the polyspecific immune reaction in MS with possible prognostic impact on MRI and clinical parameters.Furthermore, the data indicate that intrathecal measles virus IgG production correlates with disease activity on cMRI and sMRI in patients with early MS.     

Carnobacterium divergens - a dominating bacterium of pork meat juice

Nonspoiled food that nevertheless contains bacterial pathogens constitutes a much more serious health problem than spoiled food, as the consumer is not warned beforehand. However, data on the diversity of bacterial species in meat juice are rare. To study the bacterial load of fresh pork from ten different distributors, we applied a combination of the conventional culture-based and molecular methods for detecting and quantifying the microbial spectrum of fresh pork meat juice samples. Altogether, we identified 23 bacterial species of ten different families analyzed by 16S rRNA gene sequencing. The majority of isolates were belonging to the typical spoilage bacterial population of lactic acid bacteria (LAB), Enterococcaceae, and Pseudomonadaceae. Several additional isolates were identified as Staphylococcus spp. and Bacillus spp. originating from human and animal skin and other environmental niches including plants, soil, and water. Carnobacterium divergens, a LAB contributing to the spoilage of raw meat even at refrigeration temperature, was the most frequently isolated species in our study (5/10) with a bacterial load of 10(3) - 10(7) CFU mL(-1). In several of the analyzed pork meat juice samples, two bacterial faecal indicators, Serratia grimesii and Serratia proteamaculans, were identified together with another opportunistic food-borne pathogen, Staphylococcus equorum. Our data reveal a high bacterial load of fresh pork meat supporting the potential health risk of meat juice for the end consumer even under refrigerated conditions.     

Habitat preferences and distribution characteristics are indicative of species long-term persistence in the Estonian flora

Large-scale changes in regional floras provide direct information about changes in biodiversity through time and enable the evaluation of conservation targets. We compared the distribution ranges in 2004 of Estonian native terrestrial flora with the distribution ranges before 1970, using the Atlas of Estonian Flora. Relative persistence was related to species endemism, commonness, occurrence at its border of the global distribution range, main habitat type, sensitivity to human impact, life-form, conservation category, and Red List category. A literature-based database of the flora of Estonian habitat types was used to evaluate relative persistence of the flora of different habitats. Changes in the flora are largely dependent on human activities. The decrease in mire and grassland habitats and the increase in forests are reflected in the persistences of related species. Flora of mire habitats decreased the most. The fact that an almost ten-fold decrease of grasslands has not resulted in as large a decrease in the ranges of grassland species could serve as evidence of the extinction debt of these habitats. We also found a greater decrease among habitat specialists than habitat generalists and lower average persistence of the species of species-rich habitats. Our data show that current prioritization of species for conservation is in concordance with needs, as reflected in the changes in the range of species. However, conservation has not been entirely successful: the decrease of protected species continues. Our simple method for summarizing large databases was effective for the evaluation of large scale effects of conservation actions.     

Do female leaf beetles Galerucella nymphaeae choose their mates and does it matter?

The role of active female choice in sexual selection is frequently difficult to ascertain, and this is particularly the case for many insect species. Also, it is uncertain whether choosing between males would affect offspring viability. We designed an experiment to investigate the presence of female choice in a Coleoptera species (Galerucella nymphaeae). We also estimated whether mate choice would have any effect on offspring performance. Females were first placed with two males in a test arena to see which of the males copulated with the virgin female, and how quickly. Subsequently the loser male was offered a new virgin female to test for any change in latency time until mating. The two-male tests indicated that males with wider upper prothoraxes were more likely to mate with the female, and the latency time until mating was shorter when the winner male had relatively long wings. When the loser males were placed singly with females the latency time was not correlated with male size, and was the same as when two males were used. These results suggest that male-male competition is the most likely cause of sexual selection on size, and if females have any preferences they are not very strong. The seemingly passive female strategy may be sufficient to ensure that females mate with the most vigorous males, since in the field several males usually compete for access to each female. Finally, the benefits of female choosiness were estimated to be low and non-significant. The eggs of the winner males were no more likely to hatch, offspring survival into adulthood was no greater among descendants of winner males, and the offspring did not differ in adult size. Received: 3 March 1997 / Accepted: 13 October 1997     

Overwintering survival in relation to body mass in a field population of the wolf spider (Hygrolycosa rubrofasciata)

Body size is often considered to be an important trait affecting individual fitness. In arthropods, females commonly benefit from larger size directly through increased fecundity (Roff, 1992), and males through increased mating success (Andersson, 1994). It has also been suggested that larger individuals may in general have a better survival than smaller individuals (Calder, 1983; Peters, 1983). From this suggestion it may be predicted that during stressful environmental conditions larger individuals should do better than smaller individuals.     

Secretome profiling of primary human skeletal muscle cells

The skeletal muscle is a metabolically active tissue that secretes various proteins. These so-called myokines have been proposed to affect muscle physiology and to exert systemic effects on other tissues and organs. Yet, changes in the secretory profile may participate in the pathophysiology of metabolic diseases. The present study aimed at characterizing the secretome of differentiated primary human skeletal muscle cells (hSkMC) derived from healthy, adult donors combining three different mass spectrometry based non-targeted approaches as well as one antibody based method. This led to the identification of 548 non-redundant proteins in conditioned media from hSkmc. For 501 proteins, significant mRNA expression could be demonstrated. Applying stringent consecutive filtering using SignalP, SecretomeP and ER_retention signal databases, 305 proteins were assigned as potential myokines of which 12 proteins containing a secretory signal peptide were not previously described. This comprehensive profiling study of the human skeletal muscle secretome expands our knowledge of the composition of the human myokinome and may contribute to our understanding of the role of myokines in multiple biological processes. This article is part of a Special Issue entitled: Biomarkers: A Proteomic Challenge.     

Sustainability of Virulence in a Phage-Bacterial Ecosystem

Virulent phages and their bacterial hosts represent an unusual sort of predator-prey system where each time a prey is eaten, hundreds of new predators are born. It is puzzling how, despite the apparent effectiveness of the phage predators, they manage to avoid driving their bacterial prey to extinction. Here we consider a phage-bacterial ecosystem on a two-dimensional (2-d) surface and show that homogeneous space in itself enhances coexistence. We analyze different behavioral mechanisms that can facilitate coexistence in a spatial environment. For example, we find that when the latent times of the phage are allowed to evolve, selection favors “mediocre killers,” since voracious phage rapidly deplete local resources and go extinct. Our model system thus emphasizes the differences between short-term proliferation and long-term ecosystem sustainability.The replication strategies of phages fall into two major categories: virulent and temperate. A temperate phage has the ability to integrate its DNA into the host chromosome, where it is then replicated along with the bacterial DNA during cell division. This strategy allows the phage to slow down or completely stop exploitation of the bacteria, thus reducing the risk of driving its host to extinction. A virulent phage lacks this ability, and it is not fully understood how they manage to coexist with their bacterial prey (4, 19). Consider, for example, the highly effective T4 phage. For the sake of argument, let us assume a burst size of 100 offspring upon lysis. On average, not more than a single phage out of each burst of 100 should survive to infect another bacterium, or else the phage would rapidly outgrow the bacteria and drive them to extinction. The half-life (t_1/2) of a free T4 phage particle has been measured to be approximately 10 days in LB at 37°C (6). Therefore, on average, at least t_1/2 × log₂(100) ≈ 2 months should pass between infections to prevent runaway phage growth—a time span that seems highly unreasonable for many of the environments where phage and bacteria interact, such as soil or biofilm. Even a more considered calculation, inserting the above half-life measurement into more realistic Lotka-Volterra-like predator-prey models (9) does not change the conclusion that T4 and other virulent phages appear to be far too effective predators for coexistence to be feasible. It is, however, an undisputed fact that virulent phages and bacteria have coexisted for eons and do so still, everywhere around us and inside us. One possible explanation for this puzzle is that bacteria constantly evolve resistance to existing phages and that the phages evolve to attack resistant bacteria in a continuous arms race. This “Red Queen” argument (23) has, however, been criticized on the grounds that the rates of evolution of phages and bacteria are not symmetric (17, 12). Recent measurements support this: in soil, phages appear to be “ahead of the bacteria in the coevolutionary arms race” (24). We therefore wish to explore mechanisms other than bacterial resistance that may promote coexistence between virulent phages and bacteria.Historically, phage-bacterial ecosystem models have ignored the issue of space, utilizing zero-dimensional approaches, such as ordinary differential equations (e.g., see references 1, 5, 13, 14, 15, and 21). However, many real phage-bacterial ecosystems are found in environments with a complex spatial structure, such as soil, biofilms, or wounds in animal and plant tissue. Schrag and Mittler (20) showed that coexistence between virulent phage and bacteria is feasible in a chemostat but not in serial cultures, due to the heterogeneous nature of the environment in the chemostat. Further, experiments done by Brockhurst et al. (3) indicate that reduced phage dispersal can prolong coexistence for virulent phage and bacteria in spatial environments by creating ephemeral refuges for the bacteria. Kerr et al. (10) introduced a simple cellular automaton to model fragmented populations of phage and bacteria in which coexistence was more easily achieved when migration was spatially restricted. Thus, the main extension to the simple predator-prey framework that we examine will be to add a spatial dimension.We construct and compare two phage-bacterial ecosystem models: one model where the phage and bacteria exist in a two-dimensional space, such as the surface of an agar gel (referred to as the “spatial model”), and the other model where the phage and bacteria are repeatedly mixed, mimicking serial cultures or a well-mixed broth (referred to as the “well-mixed model”). We show that space does indeed enhance coexistence. We then move on to explore other mechanisms that phage could incorporate into their behavior to further enhance coexistence. These can broadly be classified as “hardwired” (where every phage follows the same deterministic strategy) versus “adaptive” (where each phage potentially behaves differently, thus allowing the population to explore different options).We have chosen to look at three specific mechanisms as examples of these categories: (i) phage effectiveness would be reduced if they were unable to register whether they were infecting live, infected, or dead bacteria (a hardwired behavior); (ii) phage could prolong their latent time, concurrently increasing burst size, depending on the number of multiple infections (also a hardwired behavior, but a more “active” sort, where each phage senses and responds to information from the environment; T4 is known to use such a lysis inhibition strategy), and (iii) phage offspring could have altered latent times due to mutations in the holin genes (an adaptive behavior). We will compare each of these mechanisms in the spatial and well-mixed models to investigate whether the heterogeneity possible in a spatial environment affects the outcome.     

Quantitative phosphoproteomic analysis of prion-infected neuronal cells

Following cultivation of distinct mesenchymal stem cell (MSC) populations derived from human umbilical cord under hypoxic conditions (between 1.5% to 5% oxygen (O₂)) revealed a 2- to 3-fold reduced oxygen consumption rate as compared to the same cultures at normoxic oxygen levels (21% O₂). A simultaneous measurement of dissolved oxygen within the culture media from 4 different MSC donors ranged from 15 μmol/L at 1.5% O₂ to 196 μmol/L at normoxic 21% O₂. The proliferative capacity of the different hypoxic MSC populations was elevated as compared to the normoxic culture. This effect was paralleled by a significantly reduced cell damage or cell death under hypoxic conditions as evaluated by the cellular release of LDH whereby the measurement of caspase3/7 activity revealed little if any differences in apoptotic cell death between the various cultures. The MSC culture under hypoxic conditions was associated with the induction of hypoxia-inducing factor-alpha (HIF-1α) and an elevated expression of energy metabolism-associated genes including GLUT-1, LDH and PDK1. Concomitantly, a significantly enhanced glucose consumption and a corresponding lactate production could be observed in the hypoxic MSC cultures suggesting an altered metabolism of these human stem cells within the hypoxic environment.