Cellular immune responses in mice infected with the intestinal nematode Trichuris muris.

CBA and B10.BR mice show variation in immune response to the intestinal nematode Trichuris muris. CBA mice develop strong resistance, eliminating worms from the intestine; B10BR mice are permissive and develop chronic infections. It is already known that resistance and permissiveness reflect differential T helper responses. The data reported here show that resistant CBA mice express good antigen-specific lymphocyte proliferative responses to infection, whereas cells from B10.BR mice are relatively anergic, although still responsive to Concanavalin A (ConA). The possibility that the altered proliferative responsiveness seen in infected B10.BR mice reflected quantitative or qualitative changes in T helper cells was examined by comparing cytokine production and expression of cell surface markers (CD4, CD8, and CD28) in mesenteric lymph node cells and spleen cells from both strains and comparing these with the characteristics of cells from resistant CBA mice and from CBA mice that had been rendered permissive to infection by a combination of irradiation and corticosteroid treatment. As expected, cells from B10.BR mice produced high levels of interferon-gamma (IFN-gamma), whereas those from CBA mice released high levels of IL-5, whether stimulated with adult worm somatic antigens, excretory/secretory antigens, or ConA. Immunosuppressed CBA mice produced high levels of both IFN-gamma and IL-5 throughout the experiment. FACS analysis revealed a decrease of CD4+ and an initial increase in CD8+ cells in all infected mice. No major changes occurred in the relative proportion of CD28(+) cells. Further evaluation of the CD28 costimulatory molecule, measured as mean fluorescence intensity, displayed down-regulation in permissive and immunosuppressed mice. The data obtained suggest that lymphocyte unresponsiveness and permissiveness to T. muris infection may be associated with a down-regulation or an initially reduced expression of costimulatory CD28 molecules.     

Improved reduced representation bisulfite sequencing for epigenomic profiling of clinical samples

Background

DNA methylation plays crucial roles in epigenetic gene regulation in normal development and disease pathogenesis. Efficient and accurate quantification of DNA methylation at single base resolution can greatly advance the knowledge of disease mechanisms and be used to identify potential biomarkers. We developed an improved pipeline based on reduced representation bisulfite sequencing (RRBS) for cost-effective genome-wide quantification of DNA methylation at single base resolution. A selection of two restriction enzymes (Taq^αI and MspI) enables a more unbiased coverage of genomic regions of different CpG densities. We further developed a highly automated software package to analyze bisulfite sequencing results from the Solexa GAIIx system.

Results

With two sequencing lanes, we were able to quantify ~1.8 million individual CpG sites at a minimum sequencing depth of 10. Overall, about 76.7% of CpG islands, 54.9% of CpG island shores and 52.2% of core promoters in the human genome were covered with at least 3 CpG sites per region.

Conclusions

With this new pipeline, it is now possible to perform whole-genome DNA methylation analysis at single base resolution for a large number of samples for understanding how DNA methylation and its changes are involved in development, differentiation, and disease pathogenesis.     

Biomass changes and trophic amplification of plankton in a warmer ocean

Ocean warming can modify the ecophysiology and distribution of marine organisms, and relationships between species, with nonlinear interactions between ecosystem components potentially resulting in trophic amplification. Trophic amplification (or attenuation) describe the propagation of a hydroclimatic signal up the food web, causing magnification (or depression) of biomass values along one or more trophic pathways. We have employed 3‐D coupled physical‐biogeochemical models to explore ecosystem responses to climate change with a focus on trophic amplification. The response of phytoplankton and zooplankton to global climate‐change projections, carried out with the IPSL Earth System Model by the end of the century, is analysed at global and regional basis, including European seas (NE Atlantic, Barents Sea, Baltic Sea, Black Sea, Bay of Biscay, Adriatic Sea, Aegean Sea) and the Eastern Boundary Upwelling System (Benguela). Results indicate that globally and in Atlantic Margin and North Sea, increased ocean stratification causes primary production and zooplankton biomass to decrease in response to a warming climate, whilst in the Barents, Baltic and Black Seas, primary production and zooplankton biomass increase. Projected warming characterized by an increase in sea surface temperature of 2.29 ± 0.05 °C leads to a reduction in zooplankton and phytoplankton biomasses of 11% and 6%, respectively. This suggests negative amplification of climate driven modifications of trophic level biomass through bottom‐up control, leading to a reduced capacity of oceans to regulate climate through the biological carbon pump. Simulations suggest negative amplification is the dominant response across 47% of the ocean surface and prevails in the tropical oceans; whilst positive trophic amplification prevails in the Arctic and Antarctic oceans. Trophic attenuation is projected in temperate seas. Uncertainties in ocean plankton projections, associated to the use of single global and regional models, imply the need for caution when extending these considerations into higher trophic levels.     

大肠杆菌FC40系统静止期突变中的F因子转移

本研究采用大肠杆菌GM133 rifr细胞和营养收集细胞HB214 strr进行适应性突变实验。在混合30min和2d 后添加链霉素杀死GM133基因型细胞,继续培养5d后,在选择平板上出现了一定数量的lac+strr基因型回复突变菌落。根据这些突变菌落的数量,估计在lac+突变产生之前,GM133和HB214细胞之间的接合频率分别为0.07%和7.47%。在培养了7d的选择平板上添加含链霉素的M9选择培养基,2d 后也观察到大量发生lac+突变但没有形成肉眼可见菌落的营养收集细胞。此外,在lac+突变发生后,也有F因子从GM133细胞转移进入HB214细胞。这些事实表明,在FC40系统的适应性突变实验中发生了真正的F因子转移。 Abstract:The experiment of adaptive mutation was performed by using Escherichia coli GM133 rifr as test cells and HB214 strr as scavenger cells.Transfer frequency between GM133 and HB214 was estimated,based on the number of revertants appeared on the selective plates when GM133 were killed by addition of M9 selective medium containing 100μg/mL of streptomycin at different time.After 30 minutes the cells of GM133 and HB214 were mixed,the estimated transfer frequency was about 0.07%,and two days,7.47%.After selection of 7 days,some HB214 cells with F` factor from GM133 cells and lac+ mutation were observed,but these cells failed to form the colonies which can be seen by the naked-eye.It was demonstrated that actual F` factor transfer events from test cells GM133 to scavenger cells HB214 occurred during the selection.     

The role of the immune response in helminth population regulation

In natural host-parasite relationships the immune response represents the most effective control against parasitism by those species adapted to life within the environment specified by the host genotype. The parasite population is regulated by immunologically-mediated, often density-dependent, responses which influence establishment, survival and fecundity. The mechanisms underlying such responses have been largely determined by experimental studies using laboratory infections in rodent hosts and are reviewed. The influence of genetic factors which enhance or depress antiparasite immune responses is discussed.     

Electrostatic components of drug-receptor recognition. II. The DNA-binding antibiotic actinomycin

The semiempirical molecular orbital method PCILO has been used to study the electronic charge distribution and conformation of the antibiotic actinomycin. Molecular electrostatic potential fields have been constructed in three-dimensional space round the molecule and displayed stereoscopically together with contour maps in the orthogonal planes relative to that of the chromophore. It was found that the drug has a considerable dipole moment and that the electrostatic fields can be separated into two large regions; an area of positive potential surrounds the chromophore and one of negative potential is directed away from the peptide rings. In this and the preceding paper these observations are discussed with respect to drug-receptor recognition phenomena. Pattern-matching of complementary electrostatic fields between the drug and polynucleotide receptor can be discerned.     

DNA-binding compounds--synthesis and intercalating properties of a peptide-diamino diacridine

A novel diacridine has been prepared in which two acridines are linked by a flexible peptide chain composed of gamma-aminobutyric acid, tyrosine, lysine and glycine. Synthesis of N-[9-acridinyl)-4-aminobutanoyl-tyrosyl-lysyl-lysyl-glycyl)-N'-(9- acridinyl)-1, 3-diaminopropane (VII) was achieved in 8% overall yield by a solution phase stepwise procedure. This compound binds to DNA by intercalation of both chromophores with at least a 140-fold enhancement of affinity compared to 9-aminoacridine.     

NMR studies of the interaction of the antibiotic nogalamycin with the hexadeoxyribonucleotide duplex d(5'-GCATGC)2

1H resonance assignments in the NMR spectra of the self-complementary hexadeoxyribonucleoside pentaphosphate d(5'-GCATGC)2 and its complex with the antibiotic nogalamycin, together with interproton distance constraints obtained from two-dimensional nuclear Overhauser effect (NOE) spectra, have enabled us to characterize the three-dimensional structure of these species in solution. In the complex described, two drug molecules are bound per duplex, in each of two equivalent binding sites, with full retention of the dyad symmetry. Twenty-eight NOE distance constraints between antibiotic and nucleotide protons define the position and orientation of the bound drug molecule. Nogalamycin intercalates at the 5'-CA and 5'-TG steps with the major axis of the anthracycline chromophore aligned approximately at right angles to the major axes of the base pairs. The nogalose sugar occupies the minor groove of the helix and makes many contacts with the deoxyribose moieties of three nucleotides along one strand of the duplex in the 5'-TGC segment. The charged dimethylamino group and hydroxyl functions of the bicyclic sugar lie in the major groove juxtaposed to the guanine base, the bridging atoms of the bicyclic sugar making contacts with the methyl group of the thymine. Thus the antibiotic is not symmetrically disposed in the intercalation site but is in close contact in both grooves with atoms comprising the 5'-TGC strand. The intercalation cavity is wedge-shaped, the major axes of the base pairs forming the site being tilted with respect to one another. All base-pair hydrogen-bonding interactions are maintained in the complex, and there is no evidence for Hoogsteen pairing. The free duplex adopts a regular right-handed B-type conformation in which all glycosidic bond angles are anti and all sugar puckers lie in the C2'-endo range. In the complex the glycosidic bond angles and the sugar puckers deviate little from those observed for the duplex alone. The presence of two bound nogalamycin molecules substantially slows the "breathing" motions of the base pairs forming the intercalation cavity, and the observation of two downfield-shifted resonances in the 31P NMR spectrum of the complex suggests a pronounced local helix unwinding at the drug binding site. The footprinting data of Fox and Waring [Fox, K.R., & Waring, M.J. (1986) Biochemistry 25, 4349-4356] imply that the highest affinity binding sites of nogalamycin have the sequence 5'-GCA (or 5'-TGC).(ABSTRACT TRUNCATED AT 400 WORDS)