ConA激活小鼠胸腺T淋巴细胞增殖过程中c-myc与核骨架蛋白的结合

采用DNA-蛋白质体外吸附的方法研究伴刀豆球蛋白激活小鼠胸腺T淋巴细胞增殖过程中c-myc与核骨架蛋白的结合.实验结果显示,c-myc与核骨架蛋白的结合具有特异性,在淋巴细胞激活过程中c-myc与P₃₄/P₃₆核骨架蛋白及核纤层蛋白结合,并发生动态变化.     

Efficiencies of different genes and different tree-building methods in recovering a known vertebrate phylogeny

The relative efficiencies of different protein-coding genes of the mitochondrial genome and different tree-building methods in recovering a known vertebrate phylogeny (two whale species, cow, rat, mouse, opossum, chicken, frog, and three bony fish species) was evaluated. The tree-building methods examined were the neighbor joining (NJ), minimum evolution (ME), maximum parsimony (MP), and maximum likelihood (ML), and both nucleotide sequences and deduced amino acid sequences were analyzed. Generally speaking, amino acid sequences were better than nucleotide sequences in obtaining the true tree (topology) or trees close to the true tree. However, when only first and second codon positions data were used, nucleotide sequences produced reasonably good trees. Among the 13 genes examined, Nd5 produced the true tree in all tree-building methods or algorithms for both amino acid and nucleotide sequence data. Genes Cytb and Nd4 also produced the correct tree in most tree-building algorithms when amino acid sequence data were used. By contrast, Co2, Nd1, and Nd41 showed a poor performance. In general, large genes produced better results, and when the entire set of genes was used, all tree-building methods generated the true tree. In each tree-building method, several distance measures or algorithms were used, but all these distance measures or algorithms produced essentially the same results. The ME method, in which many different topologies are examined, was no better than the NJ method, which generates a single final tree. Similarly, an ML method, in which many topologies are examined, was no better than the ML star decomposition algorithm that generates a single final tree. In ML the best substitution model chosen by using the Akaike information criterion produced no better results than simpler substitution models. These results question the utility of the currently used optimization principles in phylogenetic construction. Relatively simple methods such as the NJ and ML star decomposition algorithms seem to produce as good results as those obtained by more sophisticated methods. The efficiencies of the NJ, ME, MP, and ML methods in obtaining the correct tree were nearly the same when amino acid sequence data were used. The most important factor in constructing reliable phylogenetic trees seems to be the number of amino acids or nucleotides used.      

Protein sequencing: thermal conversion of thiazolinone derivatives of amino acids to thiohydantoins.

A tlc method is presented for the separation on PEI-cellulose of adenine derivatives from the acid-soluble fraction of brain tissue. The procedure permits the quantitative estimation of radioactivity distributed among adenine nucleotides and the determination of ATP specific activity following labeling with [¹⁴C] adenosine. Two rapid one-dimensional separations produce excellent resolution of AMP, ADP, ATP, adenine, and adenosine from each other and from the corresponding guanosine derivatives. A two-dimensional procedure gives excellent separation of ATP from all other deoxy- and ribonucleotides. The recovery of the separated components by elution is better than 94% and requires few technical manipulations. The technique possesses the advantages of simplicity and sensitivity and is applicable to small amounts of biological material.     

Secretion of human serum albumin from Bacillus subtilis.

We have fused the structural gene (hsa) for human serum albumin (HSA) to the expression elements and signal sequence coding region of each of two genes from Bacillus amyloliquefaciens P, an alpha-amylase gene (amyBamP) and a neutral protease gene (nprBamP). Bacillus subtilis strains harboring either of these gene fusions synthesized a protein with the antigenic characteristics and size (68 kilodaltons) of HSA. Results from pulse-labeling studies indicated that the bacterially produced HSA was secreted from cells which had been converted to protoplasts. Results from similar studies with intact cells suggested that the signal sequence was removed from the hybrid protein, providing further evidence that B. subtilis can translocate this foreign protein across the cell membrane. Signal sequence removal was efficient when the level of HSA synthesis was low. However, in strains which synthesized HSA at a high level, signal sequence removal was less efficient.     

Phosphatidylcholine and cholesterol interactions in model membranes

Various phosphatidylcholines differing either in the stereochemistry around their chiral center or in the position of a cis double bond along the acyl chains were synthesized in order to study critical contact regions in the phospholipid molecule with adjacent cholesterol in model membranes. Microviscosities calculated from fluorescence depolarization of diphenylhexatriene and chain order from spin label studies were measured to monitor physical membrane properties. The enhancing effect of cholesterol on the microviscosity of membranes containing phosphatidylcholines with comparable acyl chain length was largest when the two acyl chains were saturated and smallest when both were unsaturated. Membranes prepared from phosphatidylcholines having a single cis double bond at different positions along the sn-2 acyl chain showed roughly the same changes of microviscosity or chain order upon incorporation of cholesterol. No discrimination was evident in the interaction between cholesterol and enantiomeric phosphatidylcholines or between the enantiomeric phosphatidylcholine molecules themselves. We conclude that the rigidifying effect of cholesterol in membranes does not depend on specific sites of interaction and that with respect to physical membrane properties phosphatidylcholine behaves as an achiral molecule.     

Active immunotherapy in treatment of acute leukaemia

Active non-specific immunotherapy has been used to prolong remissions in acute lymphoblastic leukaemia. The series reported here used Bordetella pertussis vaccine in a controlle trial after intensive chemotherapy. Possibly immunotherapy delayed the onset of relapse in the treated patients, but no long-term remissions were obtained. Further work is needed to establish the role of immunotherapy in general, and the use of B. pertussis vaccine in particular, in the treatment of acute leukaemia.     

荷木树干CO_2释放通量与木质部液流和CO_2浓度的关系

采用红外气体分析仪,于2008年10月17-19日连续3个昼夜原位监测了荷木的树干CO_2释放通量、树干温度、木质部液流密度和CO_2浓度.结果表明:树干CO_2释放通量(EA)日变化呈S形曲线,不同径级间差异显著.EA与树干温度呈显著幂函数关系(0.24

Abstract：

By using a Li-820 infra-red CO_2 gas analyzer, an in situ measurement of Schima super-ba stem CO_2 efflux was conducted for three consecutive days from 17 to 19 October 2008. In the meantime, the stem temperature, xylem sap efflux density, and xylem CO_2 concentration were measured. The stem CO_2 efflux had a diurnal variation of "S" pattern, and differed significantly with stem diameter. There was a significant exponential relationship between stem CO_2 efflux and stem temperature (0. 24 < R~2 < 0. 78). The temperature coefficient (b) and regression coeffi-cient (R~2) were higher at nighttime than at daytime, and the Q_(10) value ranged from 2. 01 to 2. 79. The stem CO_2 efflux correlated significantly with the xylem CO_2 concentration, and the best regression curve was cubic (R~2= 0. 48). Excluding the effects of stem temperature, the stem CO_2 efflux showed a significant negative correlation with xylem sap flux density (r =-0.462). Therefore, only using simple temperature function to estimate stem CO_2 efflux would yield a significant error, and xylem sap flux should be taken into consideration in the stem CO_2 emux estimation.     

Nestedness of Ectoparasite-Vertebrate Host Networks

Determining the structure of ectoparasite-host networks will enable disease ecologists to better understand and predict the spread of vector-borne diseases. If these networks have consistent properties, then studying the structure of well-understood networks could lead to extrapolation of these properties to others, including those that support emerging pathogens. Borrowing a quantitative measure of network structure from studies of mutualistic relationships between plants and their pollinators, we analyzed 29 ectoparasite-vertebrate host networks—including three derived from molecular bloodmeal analysis of mosquito feeding patterns—using measures of nestedness to identify non-random interactions among species. We found significant nestedness in ectoparasite-vertebrate host lists for habitats ranging from tropical rainforests to polar environments. These networks showed non-random patterns of nesting, and did not differ significantly from published estimates of nestedness from mutualistic networks. Mutualistic and antagonistic networks appear to be organized similarly, with generalized ectoparasites interacting with hosts that attract many ectoparasites and more specialized ectoparasites usually interacting with these same “generalized” hosts. This finding has implications for understanding the network dynamics of vector-born pathogens. We suggest that nestedness (rather than random ectoparasite-host associations) can allow rapid transfer of pathogens throughout a network, and expand upon such concepts as the dilution effect, bridge vectors, and host switching in the context of nested ectoparasite-vertebrate host networks.     

The presence of serum anti-Ascaris lumbricoides IgE antibodies and of Trichuris trichiura infection are risk factors for wheezing and/or atopy in preschool-aged Brazilian children

Background

The elucidation of factors that trigger the development of transient wheezing in early childhood may be an important step toward understanding the pathogenesis of asthma and other allergic diseases later in life. Transient wheezing has been mainly attributed to viral infections, although sensitisation to aeroallergens and food allergens may occur at an early age. In developing countries, intestinal helminthic infections have also been associated with allergy or atopy-related disorders.

Objective

The aim of this study was to explore the association of Trichuris trichiura and Ascaris lumbricoides infections with wheezing and atopy in early childhood.

Study design

A cross-sectional study using a Portuguese-language ISAAC phase I questionnaire, adapted for preschool-aged children, nested in a cohort study of childhood diarrhoea, was conducted on 682 children. Two faecal samples per child were examined for the presence of intestinal helminthic infection. IgE antibodies against three allergenic preparations (Dermatophagoides pteronyssinus, Blomia tropicalis and common child food), as well as against A. lumbricoides antigens, were measured in a sub-sample of these children, whose parents allowed the procedure. Atopy was defined by the presence of levels of serum IgE antibodies ≥0.35 kU/L against at least one of the three tested allergenic preparations.

Results

Active T. trichiura infection but not A. lumbricoides infection was positively associated with wheezing in the total studied children population [adjusted OR = 2.60; CI = 1.54;4.38] and in the atopic children sub-population [adjusted OR = 3.07; CI = 1.00;9.43]. The association with atopy was also positive and statistically significant only in the brute analysis [OR = 2.13; CI = 1.03;4.40]. Anti-A. lumbricoides IgE antibodies, but not current A. lumbricoides infection, were positively associated with wheezing in atopic children [adjusted OR = 2.01; CI = 1.00;4.50] and in non-atopic children [adjusted OR = 3.07; CI = 1.13;8.35] and it was also associated with atopy [adjusted OR = 7.29; CI = 3.90; 13.4]. On the other hands, reports of wheezing were not significantly associated with atopy.

Conclusions

These data corroborate previous studies showing that wheezing is predominantly associated with infection in early childhood and shows that anti-A. lumbricoides IgE antibodies, but not active Ascaris infections, are associated with wheezing and atopy. Additionally, the data demonstrate that T. trichiura infection may play a role in the pathogenesis of atopic wheezing in early childhood.