Persistent nuclear ribosomal DNA sequence polymorphism in the Amelanchier agamic complex (Rosaceae)

Individual plants of several Amelanchier taxa contain many polymorphic nucleotide sites in the internal transcribed spacers (ITS) of nuclear ribosomal DNA (nrDNA). This polymorphism is unusual because it is not recent in origin and thus has resisted homogenization by concerted evolution. Amelanchier ITS sequence polymorphism is hypothesized to be the result of gene flow between two major North American clades resolved by phylogenetic analysis of ITS sequences. Western North American species plus A. humilis and A. sanguinea of eastern North America form one clade (A), and the remaining eastern North American Amelanchier make up clade B. Five eastern North American taxa are polymorphic at many of the nucleotide sites where clades A and B have diverged and are thought to be of hybrid origin, with A. humilis or A. sanguinea as one parent and various members of clade B as the other parent. Morphological evidence suggests that A. humilis is one of the parents of one of the polymorphic taxa, a microspecies that we refer to informally as A. "erecta." Sequences of 21 cloned copies of the ITS1- 5.8S gene-ITS2 region from one A. "erecta" individual are identical to A. humilis sequence or to the clade B consensus sequence, or they are apparent recombinants of A. humilis and clade B ITS repeats. Amelanchier "erecta" and another polymorphic taxon are suspected to be relatively old because both grow several hundred kilometers beyond the range of one of their parents. ITS sequence polymorphisms have apparently persisted in these two taxa perhaps because of polyploidy and/or agamospermy (asexual seed production), which are prevalent in the genus.      

Clonal Differences in Expression of 25-Hydroxyvitamin D3-1α-hydroxylase, of 25-Hydroxyvitamin D3-24-hydroxylase, and of the Vitamin D Receptor in Human Colon Carcinoma Cells: Effects of Epidermal Growth Factor and 1α,25-Dihydroxyvitamin D3

Human colon carcinoma cells express 25-hydroxyvitamin D₃-1α-hydroxylase (CYP27B1) and thus produce the vitamin D receptor (VDR) ligand 1α,25-dihydroxyvitamin D₃ (1,25-D3), which can be metabolized by 25-hydroxyvitamin D₃-24-hydroxylase (CYP24). Expression of VDR, CYP27B1, and CYP24 determines the efficacy of the antimitotic action of 1,25-D3 and is distinctly related to the degree of differentiation of cancerous lesions. In the present study we addressed the question of whether the effects of epidermal growth factor (EGF) and of 1,25-D3 on VDR, CYP27B1, and CYP24 gene expression in human colon carcinoma cell lines also depend on the degree of cellular differentiation. We were able to show that slowly dividing, highly differentiated Caco-2/15 cells responded in a dose-dependent manner to both EGF and 1,25-D3 by up-regulation of VDR and CYP27B1 expression, whereas in highly proliferative, less differentiated cell lines, such as Caco-2/AQ and COGA-1A and -1E, negative regulation was observed. CYP24 mRNA was inducible in all clones by 1,25-D3 but not by EGF. From the observed clonal differences in the regulatory effects of EGF and 1,25-D3 on VDR and CYP27B1 gene expression we suggest that VDR-mediated growth inhibition by 1,25-D3 would be efficient only in highly differentiated carcinomas even when under mitogenic stimulation by EGF.     

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.     

Testosterone: the culprit for producing splenocyte immune depression after trauma hemorrhage

Studies indicate that, whereas immune functions in males aredepressed, they are enhanced in females after trauma hemorrhage. Moreover, castration of male mice (i.e., androgen depletion) before trauma hemorrhage prevented the depression of cell-mediated immunity. Nonetheless, it remains unknown whether or not testosterone per se isresponsible for producing the immune depression. To study this, femaleC3H/HeN mice (n = 7 animals/group)were pretreated with 5-dihydrotestosterone (DHT) or vehicle for 19 days, then subjected to laparotomy (e.g., trauma) and hemorrhagic shock(blood pressure 35 ± 5 mmHg for 90 min) followed by fluidresuscitation or sham operation. Nontreated males underwent eithertrauma hemorrhage or sham operation. Twenty-four hours thereafter,splenocyte immune functions as well as plasma DHT, estradiol, andcorticosterone levels were measured. DHT-pretreated females hadsignificantly (P < 0.05) increasedDHT levels, comparable to those seen in males. Conversely, estradiollevels in such females were similar to control males. Splenocyteproliferation as well as interleukin-2 and interleukin-3 release werenot depressed in vehicle-treated females, whereas it was in DHT-treatedfemales after trauma hemorrhage, comparable to hemorrhaged males. Thushigh testosterone and/or low estradiol levels appear to beresponsible for producing splenocyte immune depression in males aftertrauma hemorrhage. Agents that block testosterone receptors or increaseestradiol levels may therefore be helpful in improving depressed immunefunctions in male trauma patients.

     

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.     

Differential cellulolytic activity of native-form and C-terminal tagged-form cellulase derived from Coptotermes formosanus and expressed in E. coli

An endogenous cellulase gene (CfEG3a) of Coptotermes formosanus, an economically important pest termite, was cloned and overexpressed in both native form (nCfEG) and C-terminal His-tagged form (tCfEG) in Escherichia coli. Both forms of recombinant cellulases showed hydrolytic activity on cellulosic substrates. The nCfEG was more active and stable than tCfEG even though the latter could be purified to near homogeneity with a simple procedure. The differential activities of nCfEG and tCfEG were also evidenced by hydrolytic products they produced on different substrates. On CMC, both acted as an endoglucanase, randomly hydrolyzing internal β-1,4-glycosidic bonds and resulting in a smear of polymers with different lengths, although cellobiose, cellotriose, and cellotetraose equivalents were noticeable. The hydrolytic products of tCfEG were one unit sugar less than those produced by nCfEG. Using filter paper as substrate, however, the major hydrolytic products of nCfEG were cellobiose, cellotriose and trace of glucose; those of tCfEG were cellobiose, cellotriose and trace of cellotetraose, indicating a property similar to that of cellobiohydrolase, an exoglucanase. The results presented in this report uncovered the biochemical properties of the recombinant cellulase derived from the intact gene of Formosan subterranean termites. The recombinant cellulase would be useful in designing cellulase-inhibiting termiticides and incorporating into a sugar-based biofuel production program.     

Oxygen sensing drives predictable migrations in a microbial community

Oxygen sensing is widely practised by aerobic organisms ranging from bacteria to vertebrates, and a dominant oxygen-sensing mechanism may persist among all aerobes. We traced population migrations of 10 species of the larger aerobic ciliated protozoa living in lake sediment, and in the 15 m water column of Esthwaite Water in the English Lake District (UK). In so doing, we discovered that the character and dynamics of the lake sediment and water column were remarkably predictable in performance over a continuous period of almost 2 years. Increasing warming of the lake sediment, coupled with low oxygen tension, resulted in the emergence of aerobic ciliates out of the sediment and their migration into the water column. And with the annual collapse of thermal stratification in the water column, the whole annual cycle was repeated. In an unusual discovery, we found that particular ciliate species seemed to be 'linked' to other (functionally different) ciliate species partners via the ambient oxygen tension. The favoured hypothesis is that all ciliate species in a particular body-size range seek out a particular, preferred oxygen tension. If that is the case, the 'cement' providing the cohesion of the ciliate community might actually be the preferred oxygen tension. The principal aim of our study is to clarify the microbial migration itself, not the response of the different ciliate species to oxygen gradients once they have established themselves in the water column. The latter happens once the organisms have migrated out of the sediment together, driven by the ambient oxygen tension.     

Mixotrophy in ciliates

Mixotrophy is the occurrence of phagotrophy and phototrophy in the same organism. In ciliates the intracellular phototroph can be unicellular green algae (zoochlorellae), dinoflagellates (zooxanthellae), cryptomonads or sequestered chloroplasts from ingested algae. An intermediate mixotrophic mechanism is that where the phagotroph ingests algal cells, maintains them intact and functional in the cytoplasm for some time, but the algae are afterwards digested. This seems to occur in some species of Mesodinium. Ciliates with phototrophic endosymbionts have evolved independently in marine and freshwater habitats. The enslaved algal cells or chloroplasts provide host cells with organic matter. Mixotrophs flourish in oxygen-rich, but also in micro-aerobic waters and in the complete absence of oxygen. In the latter case, the aerobic host retains aerobic metabolism, sustained by the oxygen produced by the phototrophic endosymbionts or the sequestered chloroplasts. Mixotrophic ciliates can attain spectacular abundances in some habitats, and entirely dominate the ciliate community.     

Mutations in CSTA, encoding Cystatin A, underlie exfoliative ichthyosis and reveal a role for this protease inhibitor in cell-cell adhesion

Autosomal-recessive exfoliative ichthyosis presents shortly after birth as dry, scaly skin over most of the body with coarse peeling of nonerythematous skin on the palms and soles, which is exacerbated by excessive moisture and minor trauma. Using whole-genome homozygosity mapping, candidate-gene analysis and deep sequencing, we have identified loss-of-function mutations in the gene for protease inhibitor cystatin A (CSTA) as the underlying genetic cause of exfoliative ichthyosis. We found two homozygous mutations, a splice-site and a nonsense mutation, in two consanguineous families of Bedouin and Turkish origin. Electron microscopy of skin biopsies from affected individuals revealed that the level of detachment occurs in the basal and lower suprabasal layers. In addition, in vitro modeling suggests that in the absence of cystatin A protein, there is a cell-cell adhesion defect in human keratinocytes that is particularly prominent when cells are subject to mechanical stress. We show here evidence of a key role for a protease inhibitor in epidermal adhesion within the lower layers of the human epidermis.