流式细胞术在水体微型生物研究中的应用

综述了流式细胞术（flow cytometry)在水体微型生物研究中的应用。包括微型生物的识别、记数和生物量研究,微型生物的细胞周期分析以及生态与生理学研究。讨论了FCM在淡水微型生物和环境生物学中的应用。FCM技术与食品的改进将促进水体微型生物的研究,从而有助于对水生生态系统的深入认识。     

Trait variations of ground flora species disentangle the effects of global change and altered land‐use in Swedish forests during 20 years

Northern forest ecosystems are exposed to a range of anthropogenic processes including global warming, atmospheric deposition, and changing land‐use. The vegetation of northern forests is composed of species with several functional traits related to these processes, whose effects may be difficult to disentangle. Here, we combined analyses of spatio‐temporal dynamics and functional traits of ground flora species, including morphological characteristics, responses to macro‐ and microclimate, soil conditions, and disturbance. Based on data from the Swedish National Forest Inventory, we compared changes in occurrence of a large number of ground flora species during a 20‐year period (1994–2013) in boreal and temperate Sweden respectively. Our results show that a majority of the common ground flora species have changed their overall frequency. Comparisons of functional traits between increasing and declining species, and of trends in mean trait values of sample plots, indicate that current floristic changes are caused by combined effects of climate warming, nitrogen deposition and changing land‐use. Changes and their relations with plant traits were generally larger in temperate southern Sweden. Nutrient‐demanding species with mesotrophic morphology were favored by ongoing eutrophication due to nitrogen deposition in the temperate zone, while dwarf shrubs with low demands on nitrogen decreased in frequency. An increase of species with less northern and less eastern distribution limits was also restricted to temperate Sweden, and indicates effects of a moister and milder macroclimate. A trend toward dense plantation forests is mirrored by a decrease of light‐demanding species in both vegetation zones, and a decrease of grassland species in the temperate zone. Although denser tree canopies may buffer effects of a warmer climate and of nitrogen deposition to some extent, traits related to these processes were weakly correlated in the group of species with changing frequency. Hence, our results indicate specific effects of these often confounded anthropogenic processes.     

Skp1-Cul1-F-box Ubiquitin Ligase (SCFβTrCP)-mediated Destruction of the Ubiquitin-specific Protease USP37 during G2-phase Promotes Mitotic Entry

Ubiquitin-mediated proteolysis is a key regulatory process in cell cycle progression. The Skp1-Cul1-F-box (SCF) and anaphase-promoting complex (APC) ubiquitin ligases target numerous components of the cell cycle machinery for destruction. Throughout the cell cycle, these ligases cooperate to maintain precise levels of key regulatory proteins, and indirectly, each other. Recently, we have identified the deubiquitinase USP37 as a regulator of the cell cycle. USP37 expression is cell cycle-regulated, being expressed in late G₁ and ubiquitinated by APC^Cdh1 in early G₁. Here we report that in addition to destruction at G₁, a major fraction of USP37 is degraded at the G₂/M transition, prior to APC substrates and similar to SCF^βTrCP substrates. Consistent with this hypothesis, USP37 interacts with components of the SCF in a βTrCP-dependent manner. Interaction with βTrCP and subsequent degradation is phosphorylation-dependent and is mediated by the Polo-like kinase (Plk1). USP37 is stabilized in G₂ by depletion of βTrCP as well as chemical or genetic manipulation of Plk1. Similarly, mutation of the phospho-sites abolishes βTrCP binding and renders USP37 resistant to Plk1 activity. Expression of this mutant hinders the G₂/M transition. Our data demonstrate that tight regulation of USP37 levels is required for proper cell cycle progression.     

Estimating changes in mean population age using the death distributions of live‐captured medflies

1. A simple, low‐cost approach to estimating population ageing was introduced based on a modified version of the captive cohort method – a technique developed earlier (Carey et al., Aging Cell, 7 , 426–437, 2008) in which information on the remaining lifespans of live‐captured medflies of unknown age is used to estimate the overall population age structure. 2. To test this approach approximately 1200 medflies near Volos, Greece were live captured from daily sampling over a 3‐month field season. 3. This simplified method reported: (i) an extraordinary post‐capture longevity of wild medflies in early season (>200 days in longest lived); (ii) a decrease of 50–75 days in the mean longevity from early‐season to late‐season flies; (iii) seasonality of frailty as indicated by the shorter‐lived flies in late autumn; (iv) cessation of fly emergence in late season as indicated by the absence of long‐lived individuals (indicating newly emerged at capture) sampled in the autumn; and (v) increase in mean age from about 20 days in early season to approximately 60 days in late season. 4. The applications of this simplified captive cohort method are discussed, including its use in the analysis of insect vector populations, Drosophila ecology and ageing in the wild, demographic toxicology, and age bias in sampling.     

Effects of 2‐Chloro‐2′‐Deoxyadenosine on the Cell Cycle in the Human Leukemia EHEB Cell Line

To explain why 2‐chloro‐2′‐deoxyadenosine (CdA) is unable to block DNA synthesis and cell cycle progression, and paradoxically enhances progression from G1 into S phase in the CdA‐resistant leukemia EHEB cell line, we studied its metabolism and effects on proteins regulating the transition from G1 to S phase. A low deoxycytidine kinase activity and CdATP accumulation, and a lack of p21 induction despite p53 phosphorylation and accumulation may account for the inability of CdA to block the cell cycle. An alternative pathway involving pRb phosphorylation seems implicated in the CdA‐induced increase in G1 to S phase progression.     

Differential effects of circadian typology on sleep-related symptoms,physical fatigue and psychological well-being in relation to resilience

Various physiological and psychological functions are influenced by circadian typology (CT), which was reported to be related to resilience. However, few studies have assessed the effects of CT in relation to resilience. The aim of the present study was to assess the influence of CT on sleep-related symptoms, physical fatigue and psychological well-being in relation to resilience. The present study included a total of 1794 healthy hospital employees, and they completed the Morningness–Eveningness Questionnaire, Connor–Davidson Resilience Scale, Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale, Fatigue Severity Scale, Hospital Anxiety and Depression Scale and World Health Organization Quality of Life Scale Abbreviated Version. Subjects with evening type showed lower sleep quality, more daytime sleepiness and physical fatigue than neither types and morning types. Additionally, evening types were more depressed and anxious and reported a poorer quality of life. CT was found to be a significant predictor of sleep quality, but CT was minimally associated with physical fatigue and psychological well-being in the regression analysis. Instead, resilience was substantially related to all of the variables measured. In conclusion, CT independently predicts sleep quality, but the effects of CT on physical fatigue and psychological well-being are negligible compared to those of resilience.     

Dynamic discrete model of flashing light effect in photosynthesis of microalgae

For a photobioreactor for mass-culturing microalgae, it is known that flashing light effect enhances the efficiency of photosynthesis. A dynamic model for photosynthesis was developed to elucidate this effect. A particular feature of the model is that discrete RuBP particles circulate in the Calvin cycle and their speeds in the cycle are determined by the amount of ATP generated in the photon reception process. This can realise the light saturation under continuous light and the flashing light effect under fluctuating illumination. Laboratory experiments were conducted to obtain model parameters by curve-fitting for Chaetoceros calcitrans. The present model demonstrates the light flashing effect moderately well and elucidates its mechanism reasonably.