HST2 mediates SIR2-independent life-span extension by calorie restriction

Calorie restriction (CR) extends the life span of numerous species, from yeast to rodents. Yeast Sir2 is a nicotinamide adenine dinucleotide (NAD+-dependent histone deacetylase that has been proposed to mediate the effects of CR. However, this hypothesis has been challenged by the observation that CR can extend yeast life span in the absence of Sir2. Here, we show that Sir2-independent life-span extension is mediated by Hst2, a Sir2 homolog that promotes the stability of repetitive ribosomal DNA, the same mechanism by which Sir2 extends life span. These findings demonstrate that the maintenance of DNA stability is critical for yeast life-span extension by CR and suggest that, in higher organisms, multiple members of the Sir2 family may regulate life span in response to diet.     

Yeast life-span extension by calorie restriction is independent of NAD fluctuation

Calorie restriction (CR) slows aging in numerous species. In the yeast Saccharomyces cerevisiae, this effect requires Sir2, a conserved NAD+-dependent deacetylase. We report that CR reduces nuclear NAD+ levels in vivo. Moreover, the activity of Sir2 and its human homologue SIRT1 are not affected by physiological alterations in the NAD+:NADH ratio. These data implicate alternate mechanisms of Sir2 regulation by CR.     

Requirement of NAD and SIR2 for life-span extension by calorie restriction in Saccharomyces cerevisiae

Calorie restriction extends life-span in a wide variety of organisms. Although it has been suggested that calorie restriction may work by reducing the levels of reactive oxygen species produced during respiration, the mechanism by which this regimen slows aging is uncertain. Here, we mimicked calorie restriction in yeast by physiological or genetic means and showed a substantial extension in life-span. This extension was not observed in strains mutant for SIR2 (which encodes the silencing protein Sir2p) or NPT1 (a gene in a pathway in the synthesis of NAD, the oxidized form of nicotinamide adenine dinucleotide). These findings suggest that the increased longevity induced by calorie restriction requires the activation of Sir2p by NAD.     

SD大鼠Sirt1基因真核表达的研究

用RT-PCR扩增含有XhoI/EcoRI酶切位点的Sirt1片段,克隆、测序后,构建真核荧光表达载体pEGFP-N1-Sirt1、脂质体介导转染293细胞,最后利用SDS-PAGE检测蛋白表达情况.结果表明,经脂质体介导重组体pEGFP-N1-Sirt1可成功转染293细胞;转染48h后.荧光显微镜下可见绿色荧光蛋白表达;SDS-PAGE证明表达的融合蛋白相对分子质量约为41kD.该结果为进一步研究Sirt1在哺乳动物细胞中的作用奠定了基础.     

Comment on "HST2 mediates SIR2-independent life-span extension by calorie restriction"

Calorie restriction (CR) increases life span in yeast independently of Sir2. Lamming et al. (Reports, 16 September 2005, p. 1861) recently proposed that Sir2-independent life-span extension by CR is mediated by the Sir2 paralogs Hst1 and Hst2. Contradictory to this, we find that CR greatly increases life span in cells lacking Sir2, Hst1, and Hst2, which suggests that CR is not mediated by Sir2, Hst2, or Hst1.     

Adrenocorticotrophin-Releasing Hormone in Peripheral Blood: Increase during Stress

Significant amounts of adrenocorticotrophin-releasing hormone appear in the peripheral blood under conditions of physiological stress. Associated with the appearance of this neurohormone is an increased antidiuretic activity. The neurohormone presumably enters the general circulation by way of the portal vessels of the anterior pituitary gland.     

Increase in the Asian southwest monsoon during the past four centuries

Climate reconstructions reveal unprecedented warming in the past century; however, little is known about trends in aspects such as the monsoon. We reconstructed the monsoon winds for the past 1000 years using fossil Globigerina bulloides abundance in box cores from the Arabian Sea and found that monsoon wind strength increased during the past four centuries as the Northern Hemisphere warmed. We infer that the observed link between Eurasian snow cover and the southwest monsoon persists on a centennial scale. Alternatively, the forcing implicated in the warming trend (volcanic aerosols, solar output, and greenhouse gases) may directly affect the monsoon. Either interpretation is consistent with the hypothesis that the southwest monsoon strength will increase during the coming century as greenhouse gas concentrations continue to rise and northern latitudes continue to warm.     

早期限饲对肉仔鸡蛋白质周转代谢的影响

用 2 16只 7日龄艾维茵肉仔鸡研究早期能量限饲 (ME =10 .5 8MJ·kg-1)或蛋白质限饲 (w(CP) =16 .80 % )对蛋白质周转代谢的影响。结果表明 :限饲阶段 ,能量限饲降低氮的利用率 ,蛋白质限饲提高氮的利用率 ;能量限饲和蛋白质限饲显著降低胸肌和腿肌蛋白质周转率 ,但对肝脏蛋白质周转率无影响。营养恢复阶段 ,能量限饲和蛋白质限饲均提高氮的利用率 ;能量限饲不影响胸肌和肝脏的蛋白质周转率 ,但导致腿肌的蛋白质生长率( 9.4 7% )显著高于对照组 ( 7.4 2 % ) ;蛋白质限饲对胸肌、腿肌和肝脏的蛋白质周转率均无显著影响     

Generation of simian-tropic HIV-1 by restriction factor evasion

Because HIV-1 does not infect most nonhuman primates, animal modeling of human HIV infection and AIDS has primarily consisted of experimentally infecting macaques with related simian immunodeficiency viruses (SIVMAC). However, the usefulness of such models is limited by the substantial divergence between SIVMAC and HIV-1. We derived an HIV-1-based virus that includes only small portions of SIVMAC yet replicates robustly in both transformed and primary rhesus macaque T cells. Derivation of simian-tropic HIV-1 (stHIV-1) has important implications for understanding primate lentivirus zoonosis and should allow the development of improved animal models for studies of AIDS and the evaluation of vaccines and treatments.     

Localization of iron in Arabidopsis seed requires the vacuolar membrane transporter VIT1

Iron deficiency is a major human nutritional problem wherever plant-based diets are common. Using synchrotron x-ray fluorescence microtomography to directly visualize iron in Arabidopsis seeds, we show that iron is localized primarily to the provascular strands of the embryo. This localization is completely abolished when the vacuolar iron uptake transporter VIT1 is disrupted. Vacuolar iron storage is also critical for seedling development because vit1-1 seedlings grow poorly when iron is limiting. We have uncovered a fundamental aspect of seed biology that will ultimately aid the development of nutrient-rich seed, benefiting both human health and agricultural productivity.     

Systemic RNAi in C. elegans requires the putative transmembrane protein SID-1

Double-stranded RNA-mediated gene interference (RNAi) in Caenorhabditis elegans systemically inhibits gene expression throughout the organism. To investigate how gene-specific silencing information is transmitted between cells, we constructed a strain that permits visualization of systemic RNAi. We used this strain to identify systemic RNA interference-deficient (sid) loci required to spread gene-silencing information between tissues but not to initiate or maintain an RNAi response. One of these loci, sid-1, encodes a conserved protein with predicted transmembrane domains. SID-1 is expressed in cells sensitive to RNAi, is localized to the cell periphery, and is required cell-autonomously for systemic RNAi.     

“九五”期间锡盟农民人均收入现状分析与增加收入的建议

锡盟地处内蒙古中部，属浅山丘陵区，所辖5个农区旗县，共34个农业乡，农业人口30万人，耕地面积16.5万hm2。近年来，以农业增效、农民增收、农村稳定为目标，大力实施农业和农村经济结构战略性调整，农村经济结构发生了较大变化，各项工作都取得了新进展，主导产业起到了推动作用。但是，由于本地区农业基础薄弱，生产水平一直比较落后，农民经济水平和经济收入与其它先进地区相比，仍存在很大差距。……     

母猪哺乳期蛋白限饲对后代肉质性状及肌纤维发育的影响

试验采用二因素试验设计,选取12头胎次、体况相近的母猪(民猪、长白猪各6头)进行纯种繁育,旨在探讨哺乳期母猪蛋白限饲对子代肉质及肌纤维发育的影响,每个品种母猪随机分为两组,在哺乳期饲喂不同蛋白水平日粮(对照组日粮蛋白水平为18％,限饲组日粮蛋白水平为9％),哺乳期为28 d,子代断奶后饲喂相同的标准日粮。测定子代猪18...     

新农村建设中促进苏中地区农民增收的对策研究——以江苏省扬州市为例

依据扬州市农民的增收现状,分析了制约扬州市农民增收的原因,并提出促进农民增收的对策。     

浅谈水稻绿色增产增效栽培技术

水稻绿色增产增效栽培技术的推广,对缓解生态环境压力、推动农业增产增效以及提高农民 的收入具有重要意义。本文将从水稻绿色增产增效栽培技术的模式要点、促进水稻栽培结构的完善, 为水稻的增产增效提供参考建议。     

Calorie restriction promotes mammalian cell survival by inducing the SIRT1 deacetylase

A major cause of aging is thought to result from the cumulative effects of cell loss over time. In yeast, caloric restriction (CR) delays aging by activating the Sir2 deacetylase. Here we show that expression of mammalian Sir2 (SIRT1) is induced in CR rats as well as in human cells that are treated with serum from these animals. Insulin and insulin-like growth factor 1 (IGF-1) attenuated this response. SIRT1 deacetylates the DNA repair factor Ku70, causing it to sequester the proapoptotic factor Bax away from mitochondria, thereby inhibiting stress-induced apoptotic cell death. Thus, CR could extend life-span by inducing SIRT1 expression and promoting the long-term survival of irreplaceable cells.     

G1/S transition in normal human T-lymphocytes requires the nuclear protein encoded by c-myb

Exposure of peripheral blood mononuclear cells (PBMC) to an 18-base c-myb antisense oligomer before mitogen or antigen stimulation resulted in almost complete inhibition of c-myb messenger RNA and protein synthesis and blockade of T lymphocyte proliferation. Expression of early and late activation markers, interleukin-2 receptor and transferrin receptor, respectively, by PBMC was unaffected by antisense oligomer exposure as was the expression of c-myc messenger RNA. In contrast, histone H3 messenger RNA levels and DNA content were selectively decreased. These results suggest that c-myb protein deprivation does not perturb T lymphocyte activation or early molecular events that may prepare the cell for subsequent proliferation. Rather, it appears to specifically block cells in late G1 or early S phase of the cell cycle.     

影响新台糖1号甘蔗茎重增长的关键气象因子

采用逐步回归和通径分析的方法,对新台糖1号甘蔗旬茎重增长与11个气象因子之间的关系进行研究。结果表明：分蘖期影响茎重增长的主要气象因子是最低气温和展高气温,其中最低气温对茎重增长的直接效应为正,最高气温的直接效应为负;伸长期的主要气象因子为日照时数、降雨日数和平均风速．均为正效应,次要因子蒸发量的直接效直为负;成熟期的主要气象因子为最低气温和平均风速,均为正效应。并据此提出,在伸长期增加灌溉是甘蔗增产的关键措施。