Restoration of NK T cell development in fyn-mutant mice by a TCR reveals a requirement for Fyn during early NK T cell ontogeny

NK T cells are a unique lymphocyte population that have developmental requirements distinct from conventional T cells. Mice lacking the tyrosine kinase Fyn have 5- to 10-fold fewer mature NK T cells. This study shows that Fyn-deficient mice have decreased numbers of NK1.1(-) NK T cell progenitors as well. 5-Bromo-2'-deoxyuridine-labeling studies indicate that the NK T cells remaining in fyn(-/-) mice exhibit a similar turnover rate as wild-type cells. The fyn(-/-) NK T cells respond to alpha-galactosylceramide, a ligand recognized by NK T cells, and produce cytokines, but have depressed proliferative capacity. Transgenic expression of the NK T cell-specific TCR alpha-chain Valpha14Jalpha18 leads to a complete restoration of NK T cell numbers in fyn(-/-) mice. Together, these results suggest that Fyn may have a role before alpha-chain rearrangement rather than for positive selection or the peripheral upkeep of cell number. NK T cells can activate other lymphoid lineages via cytokine secretion. These secondary responses are impaired in Fyn-deficient mice, but occur normally in fyn mutants expressing the Valpha14Jalpha18 transgene. Because this transgene restores NK T cell numbers, the lack of secondary lymphocyte activation in the fyn-mutant mice is due to the decreased numbers of NK T cells present in the mutant, rather than an intrinsic defect in the ability of the other fyn(-/-) lymphoid populations to respond.     

A 1,500-year record of Antarctic seal populations in response to climate change

The historical seal populations at King George Island, Antarctica, for the past 1,500 years, have been estimated from the seal-hair abundance, bio-element concentrations, total organic carbon (TOC) and total nitrogen (TN) in one terrestrial sediment sequence influenced by seal excrement. Prior to human interference, the seal populations exhibited dramatic fluctuations with two peaks during 750–500 and 1400–1100 years before present (yr B.P.) and two troughs during 1100–750 and 500–200 yr B.P. A tentative comparison of the seal populations and historical climates in the Antarctic Peninsula region suggests that the seal populations may be linked to climate-related factors such as sea-ice coverage and atmospheric temperature.     

Terephthalamide derivatives as mimetics of the helical region of Bak peptide target Bcl-xL protein

A group of novel Bcl-xL/Bak antagonists, based on a terephthalamide scaffold, were designed to mimic the alpha-helical region of the Bak peptide. Good in vitro inhibition potencies in disrupting the Bak/Bcl-xL complex have been observed (terephthalamide 4, K(i)=0.78+/-0.07 microM).     

Increase in mitochondrial mass in human fibroblasts under oxidative stress and during replicative cell senescence

Abnormal proliferation of mitochondria generally occurs in muscle of aged individuals and patients with mitochondrial myopathy. An increase in the mitochondrial DNA (mtDNA) copy number has also been observed in aging human tissues. However, the molecular mechanism underlying the increase in mitochondrial mass and mtDNA is still unclear. In a previous study, we demonstrated that sublethal levels of oxidative stress caused an increase in mitochondrial mass in human lung cells. In this communication, we report our recent findings that the mitochondrial mass in human lung fibroblasts (MRC-5) in a later proliferation stage is significantly increased compared to that in the early stages of proliferation. The extent of the increase in mitochondrial mass in the senescent cells was similar to that in cells in the early stages of proliferation that had been treated with low concentrations ( 180 µM) of hydrogen peroxide (H₂O₂). Moreover, we found that the rate of reactive oxygen species (ROS) production was higher in cells in the later proliferation stage compared to cells in the early proliferation stages. A similar phenomenon was also observed in cells in the early proliferation stages under low levels of oxidative stress. On the other hand, the mRNA levels of many nuclear DNA-encoded proteins involved in mitochondrial biogenesis, particularly nuclear respiratory factor-1, were found to increase in cells in later proliferation stages and in cells in early proliferation stages that had been treated with 180 µM H₂O₂. Interestingly, the increase in mitochondrial mass in the cells under oxidative stress could be repressed by treatment with cycloheximide orm-chlorocarbonyl cyanide phenylhydrazone but not by chloramphenicol. Furthermore, the mitochondrial mass of mtDNA-less ° cells was also significantly increased by exposure to low concentrations (e.g. 180 µM) of H₂O₂. These results suggest that the increase in mitochondrial mass in replicative senescent cells may result from an increase in ROS production, and that it is dependent on both de novo synthesis of nuclear DNA-encoded proteins and their import into mitochondria, dictated by the membrane potential of mitochondria.     

An economic analysis of biomass gasification and power generation in China

With vast territory and abundant biomass resources China appears to have suitable conditions to develop biomass utilization technologies. As an important decentralized power technology, biomass gasification and power generation (BGPG) has a potential market in making use of biomass wastes. In spite of the relatively high cost for controlling secondary pollution by wastewater, BGPG is economically feasible and can give a financial return owing to the low price of biomass wastes and insufficient power supply at present in some regions of China. In this work, experimental data from 1 MW-scale circulating fluidized bed (CFB) BGPG plants constructed recently in China were analyzed; and it was found that the unit capital cost of BGPG is only 60-70% of coal power station and its operation cost is much lower than that of conventional power plants. However, due to the relatively low efficiency of small-scale plant, the current BGPG technology will lose its economic attraction when its capacity is smaller than 160 kW or the price of biomass is higher than 200 Yuan RMB/ton. The development of medium-scale BGPG plants, with capacity ranging from 1000 to 5000 kW, is recommended; as is the demonstration of BGPG technology in suitable enterprises (e.g. rice mill and timber mill) in developing countries where large amounts of biomass wastes are available so that biomass collection and transportation can be avoided and the operation cost can be lowered.     

化学损毁交感神经后大鼠心内神经节生长抑素的变化

应用免疫组织化学和原位杂交方法研究了大鼠心内神经节细胞中SS的分布及其mRNA表达。结果发现,大鼠心内神经节中有SS－IR阳性神经纤维和细胞,心内神经部分细胞浆中有SSmRNA表达,表明大鼠心内神经节细胞有SS合成和贮存。用小剂量6－OH－DA选择性损毁心内交感神经纤维后,心内神经节中SS－IR阳性神经纤维和细胞的积分光密度均有不同程度增强,反映了心内交感神经和付交感神经的相互抑制作用。     

Depletion of a gamma delta T cell subset can increase host resistance to a bacterial infection

Gammadelta T lymphocytes have been shown to regulate immune responses in diverse experimental systems. Because distinct gammadelta T cell subsets, as defined by the usage of certain TCR V genes, preferentially respond in various diseases and disease models, we have hypothesized that the various gammadelta T cell subsets carry out different functions. To test this, we compared one particular gammadelta T cell subset, the Vgamma1(+) subset, which represents a major gammadelta T cell type in the lymphoid organs and blood of mice, to other subsets and to gammadelta T cells as a whole. Using LISTERIA: monocytogenes infection as an infectious disease model, we found that bacterial containment improves in mice depleted of Vgamma1(+) gammadelta T cells, albeit mice lacking all gammadelta T cells are instead impaired in their ability to control LISTERIA: expansion. Our findings indicate that Vgamma1(+) gammadelta T cells reduce the ability of the innate immune system to destroy LISTERIA:, even though other gammadelta T cells as a whole promote clearance of this pathogen.