盐节木同化枝的腋芽丛生与快速繁殖

本文通过同化枝腋芽丛生方式建立了盐生植物盐节木的快速繁殖体系。以在MS附加200 mmol·L-1 Na Cl的培养基上无菌种子萌发、生长共计4~5个月、高约3~4 cm的盐节木小苗为材料,从上截取0.5 cm长的同化枝小段为外植体,培养在MS附加不同浓度的6-BA与NAA的培养基中。结果表明:同化枝腋芽诱导与增殖最佳培养基均为MS+0.05 mg·L-1 6-BA+1mg·L-1 NAA或MS+1 mg·L-1 6-BA,初代培养30 d后,腋芽诱导率达97.5%,平均芽增殖系数为2.50;继代增殖培养时,将同化枝切成1 cm长的小段芽增殖系数提高到4.92;一次性芽苗伸长与生根培养基为MS+0.05 mg·L-1 IBA,生根率达99%;小苗经炼苗后移栽到沙子、营养土和蛭石体积比为1:1:1的基质中,成活率可达91%。     

Quantification of Filamentous Actin (F-actin) Puncta in Rat Cortical Neurons

Filamentous actin protein (F-actin) plays a major role in spinogenesis, synaptic plasticity, and synaptic stability. Changes in dendritic F-actin rich structures suggest alterations in synaptic integrity and connectivity. Here we provide a detailed protocol for culturing primary rat cortical neurons, Phalloidin staining for F-actin puncta, and subsequent quantification techniques. First, the frontal cortex of E18 rat embryos are dissociated into low-density cell culture, then the neurons grown in vitro for at least 12-14 days. Following experimental treatment, the cortical neurons are stained with AlexaFluor 488 Phalloidin (to label the dendritic F-actin puncta) and microtubule-associated protein 2 (MAP2; to validate the neuronal cells and dendritic integrity). Finally, specialized software is used to analyze and quantify randomly selected neuronal dendrites. F-actin rich structures are identified on second order dendritic branches (length range 25-75 µm) with continuous MAP2 immunofluorescence. The protocol presented here will be a useful method for investigating changes in dendritic synapse structures subsequent to experimental treatments.     

Intercellular information transfer in the process of immunogenesis. VI. The induction of antiphage antibody synthesis in the cells of rat transplantable lymphosarcoma under the influence of splenic RNA from rats and mice immunized with phage T2]

It has been proved that nuclear and cytoplasmic RNAs, isolated from spleens of T2 phage immunized rats and mice, can induce T2 phage antibodies in cells of the transplantable rat lymphosarcoma. With the nuclear RNA from rat spleens, the effect is persisting in a number of subsequent cell generations. The data presented are principally in accord with results of the authors' previous studies in which lymphosarcoma cells were treated with RNA extracted from spleens of rat immunized with sheep red cells. These results well compare with the authors' earlier advanced hypothesis suggesting a possible involvement of RNA in deblockation of genes responsible for the synthesis of the antibodies in question.     

Tropomyosin from smooth and skeletal muscles initiates various conformational changes in skeletal F-actin

Changes in F-actin conformation in myosin-free single ghost fibers of rabbit skeletal muscle induced by the binding of skeletal and gizzard tropomyosin to F-actin were studied by measuring intrinsic tryptophan-polarized fluorescence of F-actin. It was found that skeletal and gizzard tropomyosin binding to F-actin initiate different conformational changes in actin filaments. Skeletal tropomyosin inhibits, while gizzard tropomyosin activates the Mg2+-ATPase activity of skeletal actomyosin. It is supposed that in muscle fibers tropomyosin modulates the ATPase activity of actomyosin via conformational changes in F-actin.     

Mismatch repair-independent increase in spontaneous mutagenesis in yeast lacking non-essential subunits of DNA polymerase ε

Yeast DNA polymerase ε (Pol ε) is a highly accurate and processive enzyme that participates in nuclear DNA replication of the leading strand template. In addition to a large subunit (Pol2) harboring the polymerase and proofreading exonuclease active sites, Pol ε also has one essential subunit (Dpb2) and two smaller, non-essential subunits (Dpb3 and Dpb4) whose functions are not fully understood. To probe the functions of Dpb3 and Dpb4, here we investigate the consequences of their absence on the biochemical properties of Pol ε in vitro and on genome stability in vivo. The fidelity of DNA synthesis in vitro by purified Pol2/Dpb2, i.e. lacking Dpb3 and Dpb4, is comparable to the four-subunit Pol ε holoenzyme. Nonetheless, deletion of DPB3 and DPB4 elevates spontaneous frameshift and base substitution rates in vivo, to the same extent as the loss of Pol ε proofreading activity in a pol2-4 strain. In contrast to pol2-4, however, the dpb3Δdpb4Δ does not lead to a synergistic increase of mutation rates with defects in DNA mismatch repair. The increased mutation rate in dpb3Δdpb4Δ strains is partly dependent on REV3, as well as the proofreading capacity of Pol δ. Finally, biochemical studies demonstrate that the absence of Dpb3 and Dpb4 destabilizes the interaction between Pol ε and the template DNA during processive DNA synthesis and during processive 3' to 5'exonucleolytic degradation of DNA. Collectively, these data suggest a model wherein Dpb3 and Dpb4 do not directly influence replication fidelity per se, but rather contribute to normal replication fork progression. In their absence, a defective replisome may more frequently leave gaps on the leading strand that are eventually filled by Pol ζ or Pol δ, in a post-replication process that generates errors not corrected by the DNA mismatch repair system.     

Oxidative modification of creatine kinase BB in Alzheimer's disease brain

Creatine kinase (CK) BB, a member of the CK gene family, is a predominantly cytosolic CK isoform in the brain and plays a key role in regulation of the ATP level in neural cells. CK BB levels are reduced in brain regions affected by neurodegeneration in Alzheimer's disease (AD), Pick's disease, and Lewy body dementia, and this reduction is not a result of decreased mRNA levels. This study demonstrates that posttranslational modification of CK BB plays a role in the decrease of CK activity in AD brain. The specific CK BB activity and protein carbonyl content were determined in brain extracts of six AD and six age-matched control subjects. CK BB activity per microgram of immunoreactive CK BB protein was lower in AD than in control brain extracts, indicating the presence of inactive CK BB molecules. The analysis of specific protein carbonyl levels in CK BB, performed by two-dimensional fingerprinting of oxidatively modified proteins, identified CK BB as one of the targets of protein oxidation in the AD brain. The increase of protein carbonyl content in CK BB provides evidence that oxidative posttranslational modification of CK BB plays a role in the loss of CK BB activity in AD.     

Review: Alzheimer's amyloid beta-peptide-associated free radical oxidative stress and neurotoxicity

Alzheimer's disease, the major dementing disorder of the elderly that affects over 4 million Americans, is related to amyloid beta-peptide, the principal component of senile plaques in Alzheimer's disease brain. Oxidative stress, manifested by protein oxidation and lipid peroxidation, among other alterations, is a characteristic of Alzheimer's disease brain. Our laboratory united these two observations in a model to account for neurodegeneration in Alzheimer's disease brain, the amyloid beta-peptide-associated oxidative stress model for neurotoxicity in Alzheimer's disease. Under this model, the aggregated peptide, perhaps in concert with bound redox metal ions, initiates free radical processes resulting in protein oxidation, lipid peroxidation, reactive oxygen species formation, cellular dysfunction leading to calcium ion accumulation, and subsequent neuronal death. Free radical antioxidants abrogate these findings. This review outlines the substantial evidence from multiidisciplinary approaches for amyloid beta-peptide-associated free radical oxidative stress and neurotoxicity and protection against these oxidative processes and cell death by free radical scavengers. In addition, we review the strong evidence supporting the notion that the single methionine residue of amyloid beta-peptide is vital to the oxidative stress and neurotoxicological properties of this peptide. Further, we discuss studies that support the hypothesis that aggregated soluble amyloid beta-peptide and not fibrils per se are necessary for oxidative stress and neurotoxicity associated with amyloid beta-peptide.