Response of plant species richness and primary productivity in shrublands along a north–south gradient in Europe to seven years of experimental warming and drought: reductions in primary productivity in the heat and drought year of 2003

We used a nonintrusive field experiment carried out at six sites – Wales (UK), Denmark (DK), the Netherlands (NL), Hungary (HU), Sardinia (Italy – IT), and Catalonia (Spain – SP) – along a climatic and latitudinal gradient to examine the response of plant species richness and primary productivity to warming and drought in shrubland ecosystems. The warming treatment raised the plot daily temperature by ca. 1 °C, while the drought treatment led to a reduction in soil moisture at the peak of the growing season that ranged from 26% at the SP site to 82% in the NL site. During the 7 years the experiment lasted (1999–2005), we used the pin‐point method to measure the species composition of plant communities and plant biomass, litterfall, and shoot growth of the dominant plant species at each site. A significantly lower increase in the number of species pin‐pointed per transect was found in the drought plots at the SP site, where the plant community was still in a process of recovering from a forest fire in 1994. No changes in species richness were found at the other sites, which were at a more mature and stable state of succession and, thus less liable to recruitment of new species. The relationship between annual biomass accumulation and temperature of the growing season was positive at the coldest site and negative at the warmest site. The warming treatment tended to increase the aboveground net primary productivity (ANPP) at the northern sites. The relationship between annual biomass accumulation and soil moisture during the growing season was not significant at the wettest sites, but was positive at the driest sites. The drought treatment tended to reduce the ANPP in the NL, HU, IT, and SP sites. The responses to warming were very strongly related to the Gaussen aridity index (stronger responses the lower the aridity), whereas the responses to drought were not. Changes in the annual aboveground biomass accumulation, litterfall, and, thus, the ANPP, mirrored the interannual variation in climate conditions: the most outstanding change was a decrease in biomass accumulation and an increase in litterfall at most sites during the abnormally hot year of 2003. Species richness also tended to decrease in 2003 at all sites except the cold and wet UK site. Species‐specific responses to warming were found in shoot growth: at the SP site, Globularia alypum was not affected, while the other dominant species, Erica multiflora, grew 30% more; at the UK site, Calluna vulgaris tended to grow more in the warming plots, while Empetrum nigrum tended to grow less. Drought treatment decreased plant growth in several studied species, although there were some species such as Pinus halepensis at the SP site or C. vulgaris at the UK site that were not affected. The magnitude of responses to warming and drought thus depended greatly on the differences between sites, years, and species and these multiple plant responses may be expected to have consequences at ecosystem and community level. Decreases in biodiversity and the increase in E. multiflora growth at the SP site as a response to warming challenge the assumption that sensitivity to warming may be less well developed at more southerly latitudes; likewise, the fact that one of the studied shrublands presented negative ANPP as a response to the 2003 heat wave also challenges the hypothesis that future climate warming will lead to an enhancement of plant growth and carbon sequestration in temperate ecosystems. Extreme events may thus change the general trend of increased productivity in response to warming in the colder sites.     

Estimation of spontaneous baroreflex sensitivity using transfer function analysis: effects of positive pressure ventilation.

To determine the short-term effects of non-invasive positive pressure ventilation (PPV) on spontaneous baroreflex sensitivity, we acquired time series of RR interval and beat-to-beat blood pressure in 55 healthy volunteers (mean age 46.5+/-10.5 years), who performed breathing tests on four occasions at frequencies of 12 and 15/min, with application of PPV of 5 mbar, and without positive pressure (control). Using spectral and transfer function analysis, we estimated RR interval variability (HRV) and systolic blood pressure variability (SBPV), as well as the gain (alpha-index) and phase shift (Phi) of the baroreceptor reflex for low- (LF) and high-frequency (HF) bands. Compared to control breathing, PPV at 12 and 15/min led to an increase in mean RR (p<0.001) and blood pressure (p<0.05). The alpha-index in the HF band increased significantly due to PPV for both respiratory frequencies (p<0.05). Phase shifts did not show significant changes in response to pressure ventilation. These results indicate that short-term administration of PPV in normal subjects elicits significant enhancement in the HF index of baroreflex gain. These findings may contribute to understanding the mechanisms, indications, and effectiveness of positive pressure breathing strategies in treating cardiorespiratory and other disease conditions.     

Transport of the ADP/ATP carrier of mitochondria from the TOM complex to the TIM22.54 complex.

Members of the mitochondrial carrier family such as the ADP/ATP carrier (AAC) are composed of three structurally related modules. Here we show that each of the modules contains a mitochondrial import signal recognized by Tim10 and Tim12 in the intermembrane space. The first and the second module are translocated across the outer membrane independently of the membrane potential, DeltaDeltapsipsi, but they are not inserted into the inner membrane. The third module interacts tightly with the TOM complex and thereby prevents complete translocation of the precursor across the outer membrane. At this stage, binding of a TIM9.10 complex confers a topology to the translocation intermediate which reflects the modular structure of the AAC. The precursor is then transferred to the TIM9.10.12 complex, still interacting with the TOM complex. Release of the precursor from the TOM complex and insertion into the inner membrane by the TIM22.54 complex requires a DeltaDeltapsipsi-responsive signal in the third module.     

Studies on R-phycoerythrins from two Antarctic marine red algae and a mesophilic red alga

R-phycoerythrin was purified from two benthic red algae, Iridaea cordata and Phyllophora antarctica, obtained growing at ?2°C under thick sea ice off the coast of Antarctica. For the I. cordata protein, the molecular mass was 245,000 Da, and its secondary structure was 60% α helix, 17% β sheet, 16% turn, and 7% other. The light-harvesting faculties of the I. cordata protein resembled those of R-phycoerythrins from mesophilic red algae and were distinctive from the novel R-phycoerythrin from P. antarctica. Deconvolution of the visible absorption spectrum of R-phycoerythrin from I. cordata indicated a minimum of five component bands having maxima at 568, 558, 534, 496, and 481?nm. R-phycoerythrins from the mesophilic Porphyra tenera and psychrophilic Phyllophora antarctica had the same five bands. The protein from Phyllophora antarctica obtained its unique spectrum from a more intense component at 482?nm, and a less intense band at 533?nm. This change was probably produced by a replacement of phycoerythrobilin by phycourobilin. A temperature study of the circular dichroism CD was obtained for R-phycoerythrin from I. cordata from 4 to 80°C. Laser time-resolved fluorescence studies on R-phycoerythrin showed bilin to bilin energy transfer with a 60.2-ps lifetime, which should occur by the Förster resonance. The similarities in spectra between the proteins from I. cordata and Porphyra tenera and the different spectrum for the protein from Phyllophora antarctica show that only particular antarctic habitats require unique R-phycoerythrins.     

Repercussions of the COVID-19 pandemic on athletes: a cross-sectional study

The COVID-19 pandemic has presented significant challenges and implications for the sports community. Thus, this study aimed to describe the prevalence of COVID-19 in Brazilian athletes and identify the epidemiological, clinical, athletic, life and health factors associated with the disease in these individuals. A cross-sectional study was performed involving 414 athletes from 22 different sports using an online questionnaire from August to November 2020. The association between the athletes’ characteristics and COVID-19 was evaluated using a logistic regression model. The prevalence of COVID-19 was 8.5%, although only 40% of athletes reported having been tested. Being under 27 years of age (3-fold), having children (~5-fold), having a teammate test positive for COVID-19 (2.5-fold), and smoking (14-fold) were associated with a possible higher risk of disease. Almost 20% of athletes self-reported musculoskeletal injuries during the period of the pandemic that was studied. Athletes with a university education (P = 0.02), a profession other than sports (P < 0.001), those from a low-income family (P = 0.01), and public health system users (P = 0.04) were significantly less frequently tested for COVID-19, whereas international competitors, athletes who received a wage, and athletes who had a teammate who tested positive for COVID-19 were 2-, 3-, and 15-fold more likely to be tested for COVID-19, respectively. Approximately 26% of the athletes who tested negative or were untested reported more than three characteristic COVID-19 symptoms, and 11% of athletes who tested positive for COVID-19 were asymptomatic. The identification of modifiable (have children, smoking, and teammates positively tested) and non-modifiable (age under 27 years) factors related to COVID-19 in athletes can contribute to implementing surveillance programmes to decrease the incidence of COVID-19 in athletes and its negative impacts in sports.     

Antioxidant system is essential to increase drought tolerance of sugarcane

Drought is one of the main factors affecting the productivity of agricultural crops, and plants respond to such stress by activating various physiological and biochemical mechanisms against dehydration. The present study investigated two varieties of sugarcane (Saccharum spp.) with contrasting responses to drought (RB867515, more tolerant; and RB855536, less tolerant) and subjected them to progressive drought conditions (2, 4, 6 and 8 days) followed by rehydration. Drought caused a decrease in water potential (ψ_w) and osmotic potential (ψ_os) in the leaves, which recovered to normal levels after rehydration only up to the fourth day of drought. Water stress changed the carbon metabolism of leaves by reducing starch and sucrose contents and increasing glucose and fructose contents in both varieties. Water deficit caused a significant reduction in the maximum quantum efficiency of photosystem II (F_v/F_m) and effective quantum yield (Φ_PSII) in both varieties; however, RB867515 recovered faster after rehydration. Under water stress, the more tolerant variety RB867515 exhibited increased activity of the antioxidant enzymes catalase, ascorbate peroxidase and superoxide dismutase compared with the RB855536 variety. The results suggest that RB867515 is more tolerant to drought conditions because of a more efficient antioxidant system, which results in reduced photosynthesis photoinhibition during water stress, thus revealing itself as a potential physiological marker for drought tolerance studies.     

Post‐traumatic stress disorder and beyond: an overview of rodent stress models

Post‐traumatic stress disorder (PTSD) is a psychiatric disorder of high prevalence and major socioeconomic impact. Patients suffering from PTSD typically present intrusion and avoidance symptoms and alterations in arousal, mood and cognition that last for more than 1 month. Animal models are an indispensable tool to investigate underlying pathophysiological pathways and, in particular, the complex interplay of neuroendocrine, genetic and environmental factors that may be responsible for PTSD induction. Since the 1960s, numerous stress paradigms in rodents have been developed, based largely on Seligman's seminal formulation of ‘learned helplessness’ in canines. Rodent stress models make use of physiological or psychological stressors such as foot shock, underwater trauma, social defeat, early life stress or predator‐based stress. Apart from the brief exposure to an acute stressor, chronic stress models combining a succession of different stressors for a period of several weeks have also been developed. Chronic stress models in rats and mice may elicit characteristic PTSD‐like symptoms alongside, more broadly, depressive‐like behaviours. In this review, the major existing rodent models of PTSD are reviewed in terms of validity, advantages and limitations; moreover, significant results and implications for future research—such as the role of FKBP5, a mediator of the glucocorticoid stress response and promising target for therapeutic interventions—are discussed.