细菌中2-甲基柠檬酸循环研究进展

2-甲基柠檬酸循环广泛分布于细菌中,参与丙酸或丙酰-CoA的分解代谢。我们一直致力于微生物代谢调控方面的研究,并以苏云金芽胞杆菌为研究对象在2-甲基柠檬酸循环的代谢调控及生理功能方面取得了新的进展。本文将从2-甲基柠檬酸循环关键酶基因的组成、关键酶基因的转录调控和该循环参与的生理功能3个方面介绍细菌中2-甲基柠檬酸循环的研究进展。同时,对该循环研究中存在的相关科学问题和未来的研究重点作简要评述,并对该循环关键酶作为药物靶标在病原菌感染防治方面的应用进行展望。     

Diferencias en función de la edad y la autopercepción del envejecimiento en ansiedad,tristeza, soledad y sintomatología comórbida ansioso-depresiva durante el confinamiento por la COVID-19

ObjectivesTo analyze differences by age group in anxiety, depression, loneliness and comorbid anxiety and depression in young people, middle aged adults and older adults during the lock-down period at home due to the COVID-19 pandemic, and to explore the association between negative self-perceptions of aging and psychological symptoms controlling by age group.MethodParticipants are 1501 people (age range 18 to 88 years). Anxiety, sadness, loneliness and self-perceptions of aging were assessed. The sample was divided according to the age group and quartiles (lower, intermediate levels, and higher) of anxiety, sadness, loneliness and self-perceptions of aging.ResultsOlder adults reported lower levels of anxiety and sadness than middle aged adults, and middle aged adults reported lower levels than younger participants. Middle aged adults reported the lowest loneliness, followed by older adults and younger participants. For each age group, those with more negative self-perceptions of aging reported higher anxiety, sadness and loneliness. More comorbid anxiety and sadness was found in younger adults and less in older adults; more depressed participants in the middle aged group, and more older adults and less younger participants were found in the group with the lowest levels of anxiety and sadness. For all the age groups, participants with high levels of comorbid anxiety and sadness are those who report the highest scores in negative self-perceptions of aging.ConclusionsOlder adults reported lower psychological anxiety, sadness and loneliness than the other age groups. Having negative self-perceptions of aging damage psychological health irrespective of the chronological age.     

Exposure to nectar-realistic sugar concentrations negatively impacts the ability of the trypanosome parasite (Crithidia bombi) to infect its bumblebee host

1. The ideal conditions for a parasite are typically found with its preferred host. However, prior to transmission to a naïve host and successful infection, a parasite may have to withstand extrinsic environmental conditions. Some parasites have adapted to time away from hosts, for example, by co-opting vectors or by having drought-resistant growth stages. However, other parasites may have no obvious adaptations to persist during prolonged transmission cycles. Consequently, the environment may detrimentally impact parasite fitness and ultimately epidemiology. 2. Here, we investigate the impact of nectar-realistic sugar concentrations on the ability of the trypanosome parasite Crithidia bombi, which may be transmitted between conspecifics at flowers, to infect its bumblebee host Bombus terrestris and to reproduce during the infection (parasitaemia). Our results show, following 30 min exposure to our experimental nectars that as sugar concentration increases, infection prevalence and parasitaemia decrease. This is likely due to the increased osmotic stress C. bombi experiences in high sugar, aqueous environments. 3. Consequently, if C. bombi transmission is facilitated by nectar or a high-sugar environment, it may have a negative impact on parasite fitness.     

Evening chronotype is associated with poor cardiovascular health and adverse health behaviors in a diverse population of women

ABSTRACT

Chronotype reflects time of day preferences for performing daily activities. Previous research within Asian and European cohorts indicates evening chronotype is associated with elevated cardiometabolic risk. However, evidence is limited from population-based US cohorts, particularly among women in whom evening chronotype prevalence may become higher after middle-age, coinciding with life stages associated with higher cardiovascular disease (CVD) risk. This cross-sectional study evaluated associations of chronotype with overall cardiovascular health (CVH), health behaviors, and cardiometabolic risk factors among 506 women (mean age = 37 ± 16y, 62% racial/ethnic minority) in the American Heart Association (AHA)’s Go Red for Women Strategically-Focused Research Network cohort at Columbia University (New York City, NY, USA). Chronotype was assessed using the validated Morningness-Eveningness Questionnaire (MEQ) and categorized as “evening”, “intermediate”, and “morning” chronotypes. Health behaviors (diet, physical activity, and sleep) were assessed using validated questionnaires. Anthropometrics, clinical blood pressure, and blood biomarkers were assessed at the clinic visit. CVH was evaluated using the AHA Life’s Simple 7 (LS7) metrics; LS7 scores of 0–8 and 9–14 were considered indicative of poor and moderate-to-high CVH, respectively. Linear and logistic regression models adjusted for age, race/ethnicity, education, health insurance, and menopausal status were used to examine associations of MEQ scores and chronotype categories with overall CVH, clinical cardiometabolic risk factors, and health behaviors. Overall, 13% of women identified as evening chronotypes, while 55% and 32% reported being intermediate and morning types. In linear models, higher MEQ scores were associated with higher AHA LS7 scores (β(SE) = 0.02(0.01); p = .014), indicative of more favorable CVH, and with health behaviors not included in the LS7. Higher MEQ scores were also associated with lower Pittsburgh Sleep Quality Index, i.e. better sleep quality, (β(SE) = ?0.07(0.02), p < .0001), lower insomnia severity (β(SE) = ?0.14(0.01), p < .0001), shorter time to fall asleep (β(SE) = ?0.28(0.14), p = .044), and less sedentary time (β(SE) = ?0.11(0.03), p = .001). In logistic regression models, evening chronotype, compared to intermediate/morning type, was associated with higher odds of having poor CVH (OR(95%CI):2.41(1.20–4.85)), not meeting AHA diet (OR(95%CI):2.89(1.59–5.23)) and physical activity guidelines (OR(95%CI):1.78(1.03–3.07)), and having short sleep (OR(95%CI):2.15(1.24–3.73)) or insomnia (OR(95%CI):2.69(1.53–4.75)). The evening type compared to morning type was also associated with being a current smoker (OR(95%CI):2.14(1.02–4.52)) and having poor sleep quality (OR(95%CI:2.35(1.27–4.37)) and long sleep onset latency (OR(95%CI:1.89(1.00–3.56)). In our cohort of women, evening chronotype was related to poor CVH, likely driven by its influence on health behaviors. These findings, although warranting confirmation prospectively in other populations, suggest chronotype is an important factor to consider and possibly target when designing lifestyle interventions for CVD prevention.     

Host thermoregulatory constraints predict growth of an amphibian chytrid pathogen (Batrachochytrium dendrobatidis)

1. The course and outcome of many wildlife diseases are context-dependent, and therefore change depending on the behaviour of hosts and environmental response of the pathogen.2. Contemporary declines in amphibian populations are widely attributed to chytridiomycosis, caused by the pathogenic fungus Batrachochytrium dendrobatidis. Despite the thermal sensitivity of the pathogen and its amphibian hosts, we do not understand how host thermal regimes experienced by frogs in the wild directly influence pathogen growth.3. We tested how thermal regimes experienced by the rainforest frog Litoria rheocola in the wild influence pathogen growth in the laboratory, and whether these responses differ from pathogen growth under available environmental thermal regimes.4. Frog thermal regimes mimicked in the laboratory accelerated pathogen growth during conditions representative of winter at high elevations more so than if temperatures matched air or stream water temperatures. By contrast, winter frog thermal regimes at low elevations slowed pathogen growth relative to air temperatures, but not water temperatures.5. The growth pattern of the fungus under frog thermal regimes matches field prevalence and intensity of infections for this species (high elevation winter > high elevation summer > low elevation winter > low elevation summer), whereas pathogen growth trajectories under environmental temperatures did not match these patterns.6. If these laboratory results translate into field responses, tropical frogs may be able to reduce disease impacts by regulating their body temperatures to limit pathogen growth (e.g., by using microhabitats that facilitate basking to reach high temperatures); in other cases, the environment may limit the ability of frogs to thermoregulate such that individuals are more vulnerable to this pathogen (e.g., in dense forests at high elevations).7. Species-specific thermoregulatory behaviour, and interactions with and constraints imposed by the environment, are therefore essential to understanding and predicting the spatial and temporal impacts of this global disease.     

The highest kingdom of Anolis: Thermal biology of the Andean lizard Anolis heterodermus (Squamata: Dactyloidae) over an elevational gradient in the Eastern Cordillera of Colombia

Vertebrate ectotherms may deal with changes of environmental temperatures by behavioral and/or physiological mechanisms. Reptiles inhabiting tropical highlands face extreme fluctuating daily temperatures, and extreme values and intervals of fluctuations vary with altitude. Anolis heterodermus occurs between 1800 m to 3750 m elevation in the tropical Andes, and is the Anolis species found at the highest altitude known. We evaluated which strategies populations from elevations of 2200 m, 2650 m and 3400 m use to cope with environmental temperatures. We measured body, preferred, critical maximum and minimum temperatures, and sprint speed at different body temperatures of individuals, as well as operative temperatures. Anolis heterodermus exhibits behavioral adjustments in response to changes in environmental temperatures across altitudes. Likewise, physiological traits exhibit intrapopulation variations, but they are similar among populations, tended to the “static” side of the evolution of thermal traits spectrum. The thermoregulatory behavioral strategy in this species is extremely plastic, and lizards adjust even to fluctuating environmental conditions from day to day. Unlike other Anolis species, at low thermal quality of the habitat, lizards are thermoconformers, particularly at the highest altitudes, where cloudy days can intensify this strategy even more. Our study reveals that the pattern of strategies for dealing with thermal ambient variations and their relation to extinction risks in the tropics that are caused by global warming is perhaps more complex for lizards than previously thought.     

Assessment of the efficacy of the utilisation of conventional and electric toothbrushes by the older adults

Objective: To evaluate the efficacy of electric and conventional toothbrushes for a group of elderly individuals. Background: Although the electric toothbrush has been recommended for elderly individuals, there had previously never been a study regarding its efficacy. Material and methods: Sixty independent elders of both genders with different oral conditions from the Center Adult Day Vitória, Espírito Santo, Brazil, were randomly divided into two groups of 30 individuals. One group received the Oral B CrossAction Power electric toothbrush, whereas the other received a conventional Bitufo Class 32 soft toothbrush to perform oral hygiene. The bacterial plaque index (O’Leary Plaque Index) and DMFT index were assessed as a measure of oral hygiene and oral health. The data were analysed using the Shapiro–Wilk, Mann–Whitney and Wilcoxon tests. Results: The results of the efficacy of the Oral B Cross Action Power electric toothbrush demonstrated that on the 7th and 15th days, the bacterial plaque indexes were 24.91 ± 12.81 and 22.11 ± 14.46, respectively, which corresponds to a 50.24% removal of bacterial plaque on the 7th and 55.83% on the 15th days. Although the electric toothbrush removed more bacterial plaque than the conventional toothbrush, the difference was not statistically significant. Conclusion: Both the conventional and the electric toothbrushes were effective in removing bacterial plaque within the elderly group. More studies are necessary to test the efficacy of electric toothbrushes in relation to conventional toothbrushes for elderly patients.     

Exact results for fixation probability of bithermal evolutionary graphs

One of the most fundamental concepts of evolutionary dynamics is the “fixation” probability, i.e. the probability that a mutant spreads through the whole population. Most natural communities are geographically structured into habitats exchanging individuals among each other and can be modeled by an evolutionary graph (EG), where directed links weight the probability for the offspring of one individual to replace another individual in the community. EGs have recently spurred huge interest, as it has been shown that some topology can amplify or suppress the effect of beneficial mutations. Very few exact analytical results however are known for EGs. In this article we show that the use of a new technique, the fixed point of probability generating function, allows us to compute the exact fixation probability for a large subset of bithermal graphs. We also show by numerical simulations that the computed solution holds for all bithermal graphs. Moreover, the analytical solution allows us to clarify the opposing consequences of birth–death versus death–birth processes as amplifier or suppressor of beneficial mutations for the same bithermal topology.