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.     

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.     

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.     

Modulation of acetylcholine receptor desensitization by forskolin is independent of cAMP

Biochemical and electrophysiological studies suggest that adenosine 3',5'-monophosphate (cAMP)-dependent phosphorylation of the nicotinic acetylcholine receptor channel is functionally significant because it modifies the receptor's rate of desensitization to acetylcholine. In studies that support this conclusion researchers have used forskolin to stimulate cAMP-dependent phosphorylation in intact muscle. It is now shown that although forskolin facilitated desensitization in voltage-clamped rat muscle, this effect was not correlated with the abilities of forskolin and forskolin analogs to activate adenylate cyclase or phosphorylate the receptor. Furthermore, elevation of intracellular cAMP or addition of the catalytic subunit of A-kinase failed to alter desensitization. Therefore, in intact skeletal muscle, cAMP-dependent phosphorylation does not modulate desensitization.     

Theory of mind is independent of episodic memory

Theory of mind (ToM) to infer other people's current mental states and episodic memory of personal happenings have been assumed to be closely related. We report two participants with severely impaired episodic memory who perform indistinguishably from healthy controls on objective ToM tests. These results suggest that ToM can function independently of episodic memory.     

Cellulose metabolism by the flagellate trichonympha from a termite is independent of endosymbiotic bacteria

Continuous axenic cultures were established of Trichonympha sphaerica, a cellulose-digesting symbiotic protozoon in the gut of a termite. The cultured flagellates harbored no endosymbiotic bacteria and metabolized cellulose to acetate, carbon dioxide, and hydrogen. Thus, the cellulolytic activity of this flagellate is an inherent property and is not dependent on endosymbiotic bacteria.     

Regulation of C. elegans life-span by insulinlike signaling in the nervous system

An insulinlike signaling pathway controls Caenorhabditis elegans aging, metabolism, and development. Mutations in the daf-2 insulin receptor-like gene or the downstream age-1 phosphoinositide 3-kinase gene extend adult life-span by two- to threefold. To identify tissues where this pathway regulates aging and metabolism, we restored daf-2 pathway signaling to only neurons, muscle, or intestine. Insulinlike signaling in neurons alone was sufficient to specify wild-type life-span, but muscle or intestinal signaling was not. However, restoring daf-2 pathway signaling to muscle rescued metabolic defects, thus decoupling regulation of life-span and metabolism. These findings point to the nervous system as a central regulator of animal longevity.     

啤酒废酵母制备的富铬酵母对糖尿病小鼠糖代谢的影响

[目的]研究富铬酵母对糖尿病小鼠糖代谢的影响。[方法]利用富集铬元素的啤酒废酵母制备富铬酵母,检测其基本营养指标。通过建立糖尿病小鼠模型考察富铬酵母对糖尿病小鼠的作用和有效剂量,给药试验4周后,检测血糖值、己糖激酶和苹果酸脱氢酶活性。[结果]富铬酵母的蛋白质含量为44.7%,铬含量为810.4±14.3 mg/kg,其中有机铬含量占85%以上。富铬酵母剂量在中剂量（150 mg/kg）时可显示显著的降糖能力,在高剂量时降糖能力更为显著。糖尿病小鼠在补充富铬酵母后,小鼠体内己糖激酶和苹果酸脱氢酶活力均有提高,且酶活力的增加随富铬酵母的添加量的增加而增加。[结论]在试验范围内,小鼠体内苹果酸脱氢酶活力与对照组还有较大差异,而高剂量组富铬酵母己糖激酶活力已与正常对照无显著差异。     

Extension of life-span by loss of CHICO, a Drosophila insulin receptor substrate protein

The Drosophila melanogaster gene chico encodes an insulin receptor substrate that functions in an insulin/insulin-like growth factor (IGF) signaling pathway. In the nematode Caenorhabditis elegans, insulin/IGF signaling regulates adult longevity. We found that mutation of chico extends fruit fly median life-span by up to 48% in homozygotes and 36% in heterozygotes. Extension of life-span was not a result of impaired oogenesis in chico females, nor was it consistently correlated with increased stress resistance. The dwarf phenotype of chico homozygotes was also unnecessary for extension of life-span. The role of insulin/IGF signaling in regulating animal aging is therefore evolutionarily conserved.     

酵母菌处理高浓度果汁废水的研究

利用酵母菌对高浓度果汁废水进行了好氧生化降解试验。正交试验结果表明,采用微孔曝气处理方式,在酵母菌接种量为20%,温度30℃,pH 5.0,处理时间48 h的条件下,果汁废水CODcr去除率可达94%以上,回收酵母干菌2.8 g/L。该工艺既可去除果汁废水中的CODcr,又能回收一定量的酵母细胞蛋白,是一种经济有效的处理方法。     

酵母菌处理皂素生产废水的研究

经过富集培养和逐级驯化,从4种酵母菌株中筛选出对皂素废水降解性能较好的产朊假丝酵母;用单因素和正交试验确定产朊假丝酵母对皂素生产废水进行好氧处理的工艺条件.结果表明:当CODCr为24 648.36 mg/L的皂素废水,按m(CODCr)∶m(N)∶m(P)=200∶5∶1 的配比补充尿素和KH2PO4后,在30℃、接种量10%、pH 4.5、处理时间72 h、摇床转速146 r/min的条件下,产朊假丝酵母对废水CODCr的去除率可达86.16 %,处理液中细胞干质量可达20.80 g/L.与传统的厌氧-好氧活性污泥处理工艺比较,该工艺操作简单,对皂素生产废水的CODCr耐受负荷提高1～2倍.     

树脂—海藻酸钠混合凝胶共固定化糖化酶和酵母菌的研究

以D113离子交换树脂—海藻酸钠混合凝胶为载体,2%CaCl2溶液为固化液,采用包埋法共固定化糖化酶和酵母菌,并用于生料液态法白酒生产中。通过研究影响共固定化颗粒糖化发酵性能的因素,确定了共固定化的最佳条件:载体总量40mL,树脂浓度1.0%、海藻酸钠浓度3.5%、二氧化硅添加量为0.8%,糖化酶包埋量150mg,酵母菌包埋量60mg。将共固定化颗粒接入25%高粱粉发酵培养基中,30℃糖化发酵7d,酒度为15.0%。共固定化颗粒重复使用10次后,活力保存率为66.7%。     

Utilization of Exogenous Proline by the Yeast Candida utilis

Utilization of labeled proline by the yeast Candida utilis has been studied. Conversion of the labeled material to biochemically related compounds was observed in the metabolic pools in this organism. The kinetic flow of these molecules into protein was observed, and an explanation is proposed in terms of the absolute cellular concentrations and specific activities of the precursors.     

Phorbol ester action is independent of viral and cellular src kinase levels

Treatment of normal chick embryo fibroblasts with phorbol myristate acetate causes those cells to express many of the phenotypic properties of virally transformed cells and also enhances the expression of transformed properties in Rous sarcoma virus-transformed chick embryo fibroblasts. We report here that phorbol myristate acetate has little or no effect on the level of protein kinases encoded by the viral src or endogenous sarc genes.     

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.     

酵母菌合成的高效生物絮凝剂特性研究

采用白酒废水为碳源从土壤、垃圾、废水、污泥中分离大量菌株中,筛选到一株能够在简单废水和硫酸铵培养基上合成广谱高效絮凝剂的酵母菌株ZC1。运用单因素法考察了模拟悬浊性废水pH值、絮凝剂用量、助凝剂种类及其浓度对絮凝效果的影响,分别在处理时间为0.5h,pH值中性,Al2(SO4)3浓度0.01 g/L,絮凝剂用量为15 mL/L的条件下,对模拟废水絮凝率达到95%。同时发现该絮凝剂对中性到偏酸性(pH值3～7)废水均有较高的处理效果,废水中适量Ca2+、Fe3+的存在对絮凝都有促进作用,该菌株及其产生的絮凝剂对发酵废水处理及回收利用有较大潜力。     

Viability of stored seed: extension by cathodic protection

Placing seeds on a negatively charged conductor extended their viability during artificial aging. Such cathodic protection may reduce free radical attack by providing a source of electrons. The results stupport the hypothesis of free radical damage to cellular components and are consistent with such damage being important in deteriorative senescence changes.     

Effect of forskolin on voltage-gated K+ channels is independent of adenylate cyclase activation

Forskolin is commonly used to stimulate adenylate cyclase in the study of modulation of ion channels and other proteins by adenosine 3',5'-monophosphate (cAMP)-dependent second messenger systems. In addition to its action on adenylate cyclase, forskolin directly alters the gating of a single class of voltage-dependent potassium channels from a clonal pheochromocytoma (PC12) cell line. This alteration occurred in isolated cell-free patches independent of soluble cytoplasmic enzymes. The effect of forskolin was distinct from those of other agents that raise intracellular cAMP levels. The 1,9-dideoxy derivative of forskolin, which is unable to activate the cyclase, was also effective in altering the potassium channel activity. This direct action of forskolin can lead to misinterpretation of results in experiments in which forskolin is assumed to selectively activate adenylate cyclase.