Carbon:chlorophyll <Emphasis Type="Italic">a</Emphasis> ratio,assimilation numbers and turnover times of Lake Kinneret phytoplankton

Carbon to chlorophyll a (C:Chl) ratios, assimilation numbers (A.N.) and turnover times of natural populations of individual species and taxonomic groups were extracted from a long-term database of phytoplankton wet-weight biomass, chlorophyll a concentrations, and primary production in Lake Kinneret, Israel. From a database spanning more than a decade, we selected data for samples dominated by a single species or taxonomic group. The overall average of C:Chl was highest for cyanophytes and lowest for diatoms, while chlorophytes and dinoflagellates showed intermediate values. When converting chlorophyll a to algal cellular carbon this variability should be taken into account. The variability in C:Chl within each phylum and species (when data were available) was high and the variability at any particular sampling date tended to be greater than the temporal variability. The average chlorophyll a-normalized rate of photosynthetic activity of cyanophytes was higher and that of the dinoflagellates lower than that of other phyla. Turnover time of phytoplankton, calculated using primary productivity data at the depth of maximal photosynthetic rate, was longest in dinoflagellates and shortest in cyanophytes, with diatoms and chlorophytes showing intermediate values. The more extreme C:Chl and turnover times of dinoflagellates and cyanobacteria in comparison with chlorophytes and diatoms should be taken into consideration when employed in ecological modeling.     

Accumulation of DNA damage and reduced levels of nicotine adenine dinucleotide in the brains of Atm-deficient mice.

Ataxia-telangiectasia (A-T) is a human genetic disorder caused by mutational inactivation of the ATM gene. A-T patients display a pleiotropic phenotype, in which a major neurological feature is progressive ataxia due to degeneration of cerebellar Purkinje and granule neurons. Disruption of the mouse Atm locus creates a murine model of A-T that exhibits most of the clinical and cellular features of the human disease, but the neurological phenotype is barely expressed. We present evidence for the accumulation of DNA strand breaks in the brains of Atm(-/-), supporting the notion that ATM plays a major role in maintaining genomic stability. We also show a perturbation of the steady state levels of pyridine nucleotides. There is a significant decrease in both the reduced and the oxidized forms of NAD and in the total levels of NADP(T) and NADP(+) in the brains of Atm(-/-) mice. The changes in NAD(T), NADH, NAD(+), NADP(T), and NADP(+) were progressive and observed primarily in the cerebellum of 4-month-old Atm(-/-) mice. Higher rates of mitochondrial respiration were also recorded in 4-month-old Atm(-/-) cerebella. Taken together, our findings support the hypothesis that absence of functional ATM results in continuous stress, which may be an important cause of the degeneration of cerebellar neurons in A-T.     

High‐density molecular characterization and association mapping in Ethiopian durum wheat landraces reveals high diversity and potential for wheat breeding

Durum wheat (Triticum turgidum subsp. durum) is a key crop worldwide, and yet, its improvement and adaptation to emerging environmental threats is made difficult by the limited amount of allelic variation included in its elite pool. New allelic diversity may provide novel loci to international crop breeding through quantitative trait loci (QTL) mapping in unexplored material. Here, we report the extensive molecular and phenotypic characterization of hundreds of Ethiopian durum wheat landraces and several Ethiopian improved lines. We test 81 587 markers scoring 30 155 single nucleotide polymorphisms and use them to survey the diversity, structure, and genome‐specific variation in the panel. We show the uniqueness of Ethiopian germplasm using a siding collection of Mediterranean durum wheat accessions. We phenotype the Ethiopian panel for ten agronomic traits in two highly diversified Ethiopian environments for two consecutive years and use this information to conduct a genome‐wide association study. We identify several loci underpinning agronomic traits of interest, both confirming loci already reported and describing new promising genomic regions. These loci may be efficiently targeted with molecular markers already available to conduct marker‐assisted selection in Ethiopian and international wheat. We show that Ethiopian durum wheat represents an important and mostly unexplored source of durum wheat diversity. The panel analysed in this study allows the accumulation of QTL mapping experiments, providing the initial step for a quantitative, methodical exploitation of untapped diversity in producing a better wheat.     

The COP9 signalosome is vital for timely repair of DNA double-strand breaks

The DNA damage response is vigorously activated by DNA double-strand breaks (DSBs). The chief mobilizer of the DSB response is the ATM protein kinase. We discovered that the COP9 signalosome (CSN) is a crucial player in the DSB response and an ATM target. CSN is a protein complex that regulates the activity of cullin ring ubiquitin ligase (CRL) complexes by removing the ubiquitin-like protein, NEDD8, from their cullin scaffold. We find that the CSN is physically recruited to DSB sites in a neddylation-dependent manner, and is required for timely repair of DSBs, affecting the balance between the two major DSB repair pathways—nonhomologous end-joining and homologous recombination repair (HRR). The CSN is essential for the processivity of deep end-resection—the initial step in HRR. Cullin 4a (CUL4A) is recruited to DSB sites in a CSN- and neddylation-dependent manner, suggesting that CSN partners with CRL4 in this pathway. Furthermore, we found that ATM-mediated phosphorylation of CSN subunit 3 on S410 is critical for proper DSB repair, and that loss of this phosphorylation site alone is sufficient to cause a DDR deficiency phenotype in the mouse. This novel branch of the DSB response thus significantly affects genome stability.     

Spatial and temporal electroselection patterns in electric field stimulation of polarized luminescence from photosynthetic membrane vesicles

Electroselection processes of charge recombination are manifested in the study of electric field induced polarized emission from photosynthetic membrane vesicles. The study explores the coupled spatial-temporal characteristics of electric field induced charge recombination by examining the dependence of the integrated polarized emission and the time dependent polarization on electric field strength. The experimental results were fitted to theoretical models by computer simulations employing empirical parameters. Simulation of the dependence of the integrated polarized components of emission on electric field strength, suggests field-dependent increased ratio between radiative and nonradiative rates of charge recombination. The observation that the initial polarization values are independent of electric field strength supports the assumption that electric field induced emission originates from the pole area and then spreads away from it towards the equator. The propagation rate of this electric field induced charge recombination from the pole area towards the equator is reflected by the decay of polarization which increases upon raising the electric field strength. Simulation of the polarization's decay, based on a calculated angle of 26.3 ± 0.4° between the transition moment of emission and the plane of the membrane, establishes coupled temporal spatial patterns of electroselection in intramembrane electron transfer invoked by exposing preilluminated photosynthetic vesicles to a homogeneous electric field.     

An Augmented SMS Intervention to Improve Access to Antenatal CD4 Testing and ART Initiation in HIV-Infected Pregnant Women: A Cluster Randomized Trial

BackgroundLess than one-third of HIV-infected pregnant women eligible for combination antiretroviral therapy (ART) globally initiate treatment prior to delivery, with lack of access to timely CD₄ results being a principal barrier. We evaluated the effectiveness of an SMS-based intervention to improve access to timely antenatal ART.MethodsWe conducted a stepped-wedge cluster randomized trial of a low-cost programmatic intervention in 20 antenatal clinics in Gaborone, Botswana. From July 2011-April 2012, 2 clinics were randomly selected every 4 weeks to receive an ongoing clinic-based educational intervention to improve CD₄ collection and to receive CD₄ results via an automated SMS platform with active patient tracing. CD₄ testing before 26 weeks gestation and ART initiation before 30 weeks gestation were assessed.ResultsThree-hundred-sixty-six ART-naïve women were included, 189 registering for antenatal care under Intervention and 177 under Usual Care periods. Of CD₄-eligible women, 100 (59.2%) women under Intervention and 79 (50.6%) women under Usual Care completed CD₄ phlebotomy before 26 weeks gestation, adjusted odds ratio (aOR, adjusted for time that a clinic initiated Intervention) 0.87 (95% confidence interval [CI]0.47–1.63, P = 0.67). The SMS-based platform reduced time to clinic receipt of CD₄ test result from median of 16 to 6 days (P<0.001), was appreciated by clinic staff, and was associated with reduced operational cost. However, rates of ART initiation remained low, with 56 (36.4%) women registering under Intervention versus 37 (24.2%) women under Usual Care initiating ART prior to 30 weeks gestation, aOR 1.06 (95%CI 0.53–2.13, P = 0.87).ConclusionsThe augmented SMS-based intervention delivered CD₄ results more rapidly and efficiently, and this type of SMS-based results delivery platform may be useful for a variety of tests and settings. However, the intervention did not appear to improve access to timely antenatal CD₄ testing or ART initiation, as obstacles other than CD₄ impeded ART initiation during pregnancy.     

Kinetics of Cr(VI) Removal by Iron Filings in Some Soils

In this research, kinetics of Cr(VI) reduction by iron filings was investigated through a batch study in seven different soils. Chromate reduction experiments were carried out for initial Cr(VI) concentrations ranging from 20 to 100 mgkg^?1 and iron filings dosage of 0 to 5% w/w. The experimental data were analyzed using various kinetic models including zero-order, pseudo first-order, power function, Elovich, and diffusion parabolic. Results showed that the Cr(VI) reduction efficiency in the presence of all studied soils increased with increasing iron filings dosage and decreased with increasing the initial Cr(VI) concentration. The reaction rates considerably depended on pH and were higher in acidic soils. The diffusion parabolic model was the best kinetic model as evidenced by the highest determination coefficient (r²) and the lowest standard error of the estimate (SE). The rate-limiting step(s) may be transport of chromate anions across a liquid film at the interface of soil-liquid, transport in liquid-filled macropores of iron filings aggregates, or diffusion in micropores and along the particle's surface.