Reduced Weight Gain Due to Subclinical Anaplasma phagocytophilum (Formerly Ehrlichia phagocytophila) Infection

Tick-borne fever (TBF) is caused by the rickettsia Anaplasma phagocytophilum (formerly Ehrlichia phagocytophila) and is a common disease in sheep in areas of Norway infested by Ixodes ricinus ticks. TBF can cause both direct and indirect losses to sheep kept on tick-infested pastures. In the present work we studied a sheep flock of 26 ewes and 50 lambs on pasture from May until September. No cases of TBF had earlier been observed on this pasture. Blood samples from lambs with a reduced weekly weight gain were collected and analysed for A. phagocytophilum infection by blood smear examination. In addition, at the end of the study, sera from all lambs were analysed by an indirect fluorescent antibody assay (IFA) to determine the antibody titre to E. equi. No clinical signs of tick-borne infections were observed, except in one lamb. However, 30 (60%) of the lambs grazing on this pasture became infected with A. phagocytophilum, and the infected lambs had a reduced weight gain (mean) of 3.8 kg compared with the uninfected lambs. The present study indicates that A. phagocytophilum infection may be widespread and contribute to considerable productivity losses even on pastures with no apparent tick infestation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Flexible weighted log-rank tests optimal for detecting early and/or late survival differences

At the present time, many AIDS clinical trials compare drug therapies by a time-to-event primary endpoint that measures the durability of suppression of HIV replication. For such studies, survival differences tend to occur early and/or late in the follow-up period due to drug differences in initial potency and/or durability of efficacy, and detecting these differences is of primary interest. We propose a weighted log-rank statistic that emphasizes early and/or late survival differences. We also consider some versatile tests that also emphasize these differences but are sensitive to a wider range of alternatives. The performances of the new tests are evaluated in numerical studies. For the alternatives of interest, the new tests show greater power and flexibility than commonly used weighted log-rank tests and related versatile tests. When the main interest is in detecting early and/or late survival differences, these tests may be preferable to the other versatile and weighted log-rank tests that have been studied.     

Study of high molecular weight wheat glutenin subunit 1Dx5 by 13C and 1H solid-state NMR spectroscopy. I. Role of covalent crosslinking

This work describes a carbon and proton solid-state NMR study of the hydration of a high molecular weight wheat glutenin subunit, 1Dx5. The effect of the presence of disulfide bonds on the hydration behavior of the subunit is investigated by a comparison of the unalkylated and alkylated forms of the protein. Hydration induces partial plasticization of the protein so that some segments become more mobile than others. The 13C cross-polarization and magic-angle spinning (MAS) spectra of the samples in the dry state and at two hydration levels (approximately 40 and approximately 65% D2O) were used to monitor the protein fraction resisting plasticization (trains). Conversely, 13C single pulse excitation and 1H-MAS experiments were used to gain information on the more plasticized segments (loops). The molecular motion of the two protein dynamic populations was further characterized by 13C T1 and 1H T(1rho), T2, and T1 relaxation times. The results suggest that hydration leads to the formation of a network held by a cooperative action of hydrogen bonded glutamines and some hydrophobic interactions. The looser protein segments are suggested to be glycine- and glutamine-rich segments. The primary structure is therefore expected to significantly determine the proportion of trains and loops in the network. The presence of disulfide bonds was observed to promote easier plasticization of the protein and the formation of a more mobile network, probably involving a higher number of loops and/or larger loops.     

Fractionation and characterization of polysaccharides from abaca fibre

Abaca fibre polysaccharides were fractionated into water soluble, pectic, 1% NaOH soluble, hemicellulosic and cellulose fractions by extraction with hot water, dilute hydrochloric acid (pH 1.6), aqueous 1% NaOH and 17.5% NaOH, respectively. Cellulose (60.4–63.6%) and hemicelluloses (20.8%) were the major polysaccharides in abaca fibres. The hot water soluble polysaccharides contained noticeable amounts of pectic substances and a large proportion of neutral polysaccharides. The pectic polysaccharide preparation was enriched in both galacturonic acid and neutral sugars, including xylose, glucose, galactose, arabinose, and rhamnose. Extraction of the fibre with aqueous 1% NaOH produced the hemicellulose–lignin complex, which was enriched in xylose and, to a lesser extent, glucose-, arabinose- and galactose-containing polysaccharides, together with 7.6% associated lignin. Further extraction of the delignified fibre residue with aqueous 17.5%. NaOH removed the hemicellulose fractions, which were strongly enriched in xylose-containing polysaccharides. Besides ferulic and p-coumaric acids, six other phenolic monomers were also detected in the mixtures of alkaline nitrobenzene oxidation of associated lignin in all the polysaccharide fractions. The content of bound lignin in water soluble, pectic, and 1% NaOH soluble polysaccharides (Fractions 1, 2, and 3), isolated directly from the lignified fibres, was 12 times that of the hemicellulosic preparations (Fractions 4 and 5) isolated from the delignified fibre residues.     

Mass and nutrient loss of fresh plant biomass in a small black-water tributary of Caura river, Venezuelan Guayana

Decomposition rates and nutrient dynamic (N, P, K, Ca and Mg) were determined for green leaves and fine branches immersed in the water of a small tributary of Caura river (SE-Venezuela). 16% of the original dry weight of leaves and 11% of branches were lost at the end of the first sampling period: first month for leaves and second month for branches. This dry weight reduction was probably due to leaching of soluble material. After a 9-month period, the mass loss was 60% for leaves and 20% for fine branches. The pattern of dry weight and nutrient losses are in general agreement with previous studies of decomposition of leaf litter in both terrestrial and aquatic ecosystems. Potassium and magnesium are the elements most rapidly lost, showing the dominance of leaching processes; at the end of the first month 7% of the initial amount of K and 18% of the initial amount of Mg remained in leaves. The loss of calcium and phosphorus was much slower: 61% of Ca and 47% of P remained in the leaf material after the first sampling period. In contrast to K, Mg, Ca and P, the initial amount of nitrogen in leaves remained relatively unchanged during the first month of decomposition; in the subsequent sampling period, the amount of N decreased. The elements K and Mg in branches behaved similar to leaves: 4% of K and 22% of Mg were left at the end of the first sampling period. The initial amount of Ca and P in branches decreased slightly: 88% of Ca and 83% of P remained in branches at the end of this first sampling. Nitrogen behaved differently in branches than that in leaves. In branches the amount of N remained relatively unchanged during the first 5 months of decomposition; afterwards, N showed gradual increases, probably due to immobilization. At the end of the experiment the amount of N in branches was 16% higher than the initial amount.     

DNA指纹图带与鸡的蛋重性状的遗传相关分析

用蛋重大的和蛋重小的北京白鸡做亲本交配获得F1代个体,再用F1代个体交配得125只F2代个体。以人源小卫星DNA33.6做探针以上述125只鸡进行D NA指纹分析,发现其中有两条指纹图带与蛋重性状有关,经简单线型相关分析表明,这两条图带(D6.2和D6.3)的出现频率与蛋重的相关系数分别为-0.80和-0.81。 Abstract:Beijing White Chickens laying larger eggs and those laying smaller eggs were used as parental individuals for mating to produce the F1 progeny and then the F1 progeny individuals were mated to produce 125 individuals of the F2 progeny.Two bands associated with the egg weight trait were identified by DNA fingerprints of the 125 individuals generated with human minisatellite probe 33.6. The simple linear correlation analysis showed that the coefficients of correlation between frequencies of the two bands(D6.2 and D6.3)and egg weights are –0.8 and –0.81.     

优雅蝈螽雌虫性选择

优雅蝈螽雌虫在交配过程中接受雄虫分泌的精包,并且在交配后一段时间内把精包吃掉。精包对雌虫的生殖是必需的,体重大的雄性分泌的精包较大。把2只鸣叫的且体重不同的雄虫放在一起,雌虫会选择体重大的个体交配。     

Inorganic Pi Increases Neuronal Survival in the Acute Early Phase Following Excitotoxic/Oxidative Insults

Abstract: Inorganic phosphate (P_i) plays a vital role in intracellular energy metabolism. Its many effects include stimulation of glucose use, enhancement of high-energy phosphate concentrations, and modulation of cytosolic free [Ca²⁺]. Cultured fetal rat cortical neurons constitutively import P_i, and cytosolic levels positively correlate with [ATP], [NADPH], and energy charge. In the present study, we demonstrate that the concentration of intracellular P_i is an important determinant of acute neuronal survival after an excitotoxic or oxidative insult to cultured fetal rat cortical neurons. Extracellular P_i dose-dependently enhanced survival of cortical neurons after exposure to NMDA at early (≤6 h) time points after termination of the insult. P_i similarly increased neuronal survival after exposure to kainic acid or H₂O₂. P_i-exposed neurons had higher basal intracellular [P_i], [ATP], and [GSH], and slightly lower cytosolic free [Ca²⁺], compared with P_i-deprived neurons. P_i-exposed neurons maintained increased [ATP] after exposure to NMDA and displayed reduced formation of reactive oxygen species after exposure to kainic acid or H₂O₂, compared with P_i-deprived neurons. These findings demonstrate that changes in extracellular and intracellular P_i can affect neuronal survival after excitotoxic or oxidative insults.     

Interactive effects of growth‐limiting N supply and elevated atmospheric CO2 concentration on growth and carbon balance of Plantago major

To assess the interactions between concentration of atmospheric CO₂ and N supply, the response of Plantago major ssp. pleiosperma Pilger to a doubling of the ambient CO₂ concentration of 350 µl l^?1 was investigated in a range of exponential rates of N addition. The relative growth rate (RGR) as a function of the internal plant nitrogen concentration (N_i), was increased by elevated CO₂ at optimal and intermediate N_i. The rate of photosynthesis, expressed per unit leaf area and plotted versus N_i. was increased by 20-30% at elevated CO₂ for N_i above 30 mg N g^?1 dry weight. However, the rate of photosynthesis, expressed on a leaf dry matter basis and plotted versus N_i, was not affected by the CO₂ concentration. The allocation of dry matter between shoot and root was not affected by the CO₂ concentration at any of the N addition rates. This is in good agreement with theoretical models. based on a balance between the rate of photosynthesis of the shoot and the acquisition of N by the roots. The concentration of total nonstructural carbohydrates (TNC) was increased at elevated CO₂ and at N limitation, resulting in a shift in the partitioning of photosynthates from structural to nonstructural and, in terms of carbon balance, unproductive dry matter. The increase in concentration of TNC led to a decrease in both specific leaf area (SLA) and N_i at all levels of nutrient supply, and was the cause of the increased rate of photosynthesis per unit leaf area. Correction of the relationship between RGR and Ni for the accumulation of TNC made the effect of elevated CO₂ on the relationship between RGR and N_i disappear. We conclude that the shift in the relationship between RGR and N_i was due to the accumulation of TNC and not due to differences in physiological variables such as photosynthesis and shoot and root respiration, changes in leaf morphology or allocation of dry matter.