Functional characterization of three novel tissue-specific anion exchangers SLC26A7, -A8, and -A9

A second distinct family of anion exchangers, SLC26, in addition to the classical SLC4 (or anion exchanger) family, has recently been delineated. Particular interest in this gene family is stimulated by the fact that the SLC26A2, SLC26A3, and SLC26A4 genes have been recognized as the disease genes mutated in diastrophic dysplasia, congenital chloride diarrhea, and Pendred syndrome, respectively. We report the expansion of the SLC26 gene family by characterizing three novel tissue-specific members, named SLC26A7, SLC26A8, and SLC26A9, on chromosomes 8, 6, and 1, respectively. The SLC26A7-A9 proteins are structurally very similar at the amino acid level to the previous family members and show tissue-specific expression in kidney, testis, and lung, respectively. More detailed characterization by immunohistochemistry and/or in situ hybridization localized SLC26A7 to distal segments of nephrons, SLC26A8 to developing spermatocytes, and SLC26A9 to the lumenal side of the bronchiolar and alveolar epithelium of lung. Expression of SLC26A7-A9 proteins in Xenopus oocytes demonstrated chloride, sulfate, and oxalate transport activity, suggesting that they encode functional anion exchangers. The functional characterization of the novel tissue-specific members may provide new insights to anion transport physiology in different parts of body.     

Next Generation Sequencing of Fecal DNA Reveals the Dietary Diversity of the Widespread Insectivorous Predator Daubenton’s Bat (Myotis daubentonii) in Southwestern Finland

Understanding predator-prey dynamics is a fundamental task in the evaluation of the adaptive capacities of species. However, direct observations or morphological identification of fecal remains do not offer an effective way to study the dietary ecology of elusive species, such as nocturnal insectivorous bats. However, recent advances in molecular techniques have opened a new method for identifying prey species from fecal samples. In this study, we amplified species-specific mitochondrial COI fragments from fecal DNA extractions from 34 individual Daubenton’s bats (Myotis daubentonii) collected between 2008 and 2010 from southwestern Finland. Altogether, 128 different species of prey were identified based on a comprehensive local DNA reference library. In our study area, Daubenton’s bats feed most frequently on insects of the orders Diptera (found in the diet of 94% individuals), Trichoptera (69%) and Lepidoptera (63%). The most frequent dipteran family in the diet was Chironomidae, which was found in 31 of 34 individuals. Most common prey species were chironomids Microtendipes pedellus (found in 50% of bats), Glyptotendipes cauliginellus (44%), and Procladius ferrugineus (41%). For the first time, an accurate species level list of the diet of the insectivorous Daubenton’s bat (Myotis daubentonii) in Finland is presented. We report a generally applicable method for describing the arthropod diet of vertebrate predators. We compare public databases to a national database to highlight the importance of a local reference database.     

Urinary excretion of epsilondA is not predictive of cancer development: a prospective nested case-control study

Human biomonitoring of the lipid peroxidation DNA modification 1,N⁶-ethenodeoxyadenosine (εdA) excreted into urine is thought to be a potential marker for oxidative stress-related DNA damage and human cancer. We have tested this hypothesis in a prospective, nested case-control study. During the years 1984-1989, 24-h urines were collected from 1956 men in the Kuopio Ischaemic Heart Disease (KIHD) Risk Factor Study. εdA concentrations were measured by LC-MS/MS in 24-h urine samples from 47 men with cancer diagnosed at follow up until 2001 and from 31 cancer free smoking-matched control subjects. Odds ratio for having higher than control median εdA excretion rate and cancer, estimated by binary logistic regression, was 0.73 (95% CI 0.29-1.80, p=0.49). In this study, the urinary excretion of εdA provides no additional prediction of cancer development in males after controlling for smoking.     

Predator control and the density and reproductive success of grouse populations in Finland

The impact of predator removal or protection on the reproductive success and density of grouse populations was studied experimentally in southern and northern Finland. In predator removal areas small and medium-sized carnivores wore efficiently hunted, while in predator protection areas hunting was prohibited. Both predator (red fox, raccoon dog, pine marten and stoat) and grouse populations were monitored. The breeding success of grouse, indicated by the young/adults ratio, decreased in the predator protection area in northern Finland during a vole low. Despite a decline in the vole population, the breeding success of grouse did not decline in the predator removal area. The mean brood size during the experiment was significantly higher in the removal areas than in the protection areas both in southern and northern Finland. Predator removal/protection thus affected the reproductive success of grouse, but the impact of control on adult grouse populations was not as evident.     

Element concentrations in boreal,coniferous forest humus layers in relation to moss chemistry and soil factors

Concentrations of 15 elements (Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, S and Zn) in the current annual growth increments of the ectohydric feather moss, Hylocomium splendens, were compared with those in the humus layer (Of+Oh) of coniferous forests at 353 sites throughout Finland. Moss concentrations in the moss increments were considered measures of atmospheric deposition of these elements. Concentrations in both moss and humus layer samples were negatively correlated with latitude, except Mn (moss) and Cr and Ni (humus layer), indicating a direct effect of deposition. Spearman correlations between concentrations in moss and humus layer samples were significant (P<0.05) for all elements; that for Pb concentrations was the highest (r_s=0.60) while those for the other elements were ≤0.48. Using thickness and organic matter content of the humus layer, clay content of the mineral soil (5–20 cm layer) and the concentration in the moss explained between 8% (Cd) and 44% (Cr, Mg) of the variation in the concentrations in the humus layer samples. It was concluded that, for most elements, concentration in the humus layer are a poor indicator of current atmospheric deposition levels, at least in relatively unpolluted regions such as Finland.     

A systematic review of MRI studies of language development from birth to 2 years of age

Neurocognitive functions supporting language development start to develop well before first words are spoken during the first years of life. This process coincides with the initial growth spurt of the brain. While the core components of the language network are well characterized in adults and children, the initial neural correlates of language skills are still relatively unknown. We reviewed 10 studies identified via a systematic search that combined magnetic resonance imaging and language‐related measures in healthy infants from birth to 2 years of age. We aimed to describe the current knowledge as well as point out viable future directions for similar studies. Expectedly, the implicated cerebral areas included many established components of the language networks, including frontal and temporal regions. A volumetric leftward asymmetry of the brain was suggested as a determinant of language skills, yet with marked interindividual variation. Overall, temporal and frontal brain volumes associated positively with language skills. Positive associations were described between the maturation of language related white matter tracts and language skills. The language networks showed adult‐like structural similarities already in neonates, with weaker asymmetry compared to adults. In summary, we found some evidence that the language circuit described in older age groups is also associated to language skills during the first 2 years of life. However, across the reviewed studies there were no systematic neural correlates of language skills, which is partly explained by a modest number of studies, scattered representation of ages in measurements and the variance in the used methods.     

Polyelectrolyte brushes grafted from cellulose nanocrystals using Cu-mediated surface-initiated controlled radical polymerization

Herein we report the synthesis of cellulose nanocrystals (CNCs) grafted with poly(acrylic acid) (PAA) chains of different lengths using Cu-mediated surface initiated-controlled radical polymerization (SI-CRP). First, poly(tert-butylacrylate) (PtBA) brushes were synthesized; then, subsequent acid hydrolysis was used to furnish PAA brushes tethered onto the CNC surfaces. The CNCs were chemically modified to create initiator moieties on the CNC surfaces using chemical vapor deposition (CVD) and continued in solvent phase in DMF. A density of initiator groups of 4.6 bromine ester groups/nm(2) on the CNC surface was reached, suggesting a dense functionalization and a promising starting point for the controlled/living radical polymerization. The SI-CRP of tert-butylacrylate proceeded in a well-controlled manner with the aid of added sacrificial initiator, yielding polymer brushes with polydispersity values typically well below 1.12. We calculated the polymer brush grafting density to almost 0.3 chains/nm(2), corresponding to high grafting densities and dense polymer brush formation on the nanocrystals. Successful rapid acid hydrolysis to remove the tert-butyl groups yielded pH-responsive PAA-polyelectrolyte brushes bound to the CNC surface. Individually dispersed rod-like nanoparticles with brushes of PtBA or PAA were clearly visualized by AFM and TEM imaging.     

Contributions of leaf photosynthetic capacity, leaf angle and self-shading to the maximization of net photosynthesis in Acer saccharum: a modelling assessment

Background and Aims

Plants are expected to maximize their net photosynthetic gains and efficiently use available resources, but the fundamental principles governing trade-offs in suites of traits related to resource-use optimization remain uncertain. This study investigated whether Acer saccharum (sugar maple) saplings could maximize their net photosynthetic gains through a combination of crown structure and foliar characteristics that let all leaves maximize their photosynthetic light-use efficiency (ɛ).

Methods

A functional–structural model, LIGNUM, was used to simulate individuals of different leaf area index (LAI_ind) together with a genetic algorithm to find distributions of leaf angle (L_A) and leaf photosynthetic capacity (A_max) that maximized net carbon gain at the whole-plant level. Saplings grown in either the open or in a forest gap were simulated with A_max either unconstrained or constrained to an upper value consistent with reported values for A_max in A. saccharum.

Key Results

It was found that total net photosynthetic gain was highest when whole-plant PPFD absorption and leaf ɛ were simultaneously maximized. Maximization of ɛ required simultaneous adjustments in L_A and A_max along gradients of PPFD in the plants. When A_max was constrained to a maximum, plants growing in the open maximized their PPFD absorption but not ɛ because PPFD incident on leaves was higher than the PPFD at which ɛ_max was attainable. Average leaf ɛ in constrained plants nonetheless improved with increasing LAI_ind because of an increase in self-shading.

Conclusions

It is concluded that there are selective pressures for plants to simultaneously maximize both PPFD absorption at the scale of the whole individual and ɛ at the scale of leaves, which requires a highly integrated response between L_A, A_max and LAI_ind. The results also suggest that to maximize ɛ plants have evolved mechanisms that co-ordinate the L_A and A_max of individual leaves with PPFD availability.