Expression of TrkB Receptors in Developing Visual Cortex Is Not Regulated by Light

1. Neurotrophins are very good candidates which relate electrical activity to molecular changes in activity-dependent phenomena. They exert their action through binding to specific tyrosine-kinase receptors: Trk receptors. It is important to consider Trk distribution in order to understand better the role of neurotrophins in the Central Nervous System (CNS). We focused our attention on brain-derived neurotrophic factor (BDNF) Trk receptors (TrkB) during development of the rat visual cortex, since this neurotrophin has been shown to play an important role in visual system development and plasticity.2. We investigated the full length form of TrkB receptors considering both its total amount and its cellular distribution. To address this issue we used an antibody that recognizes the full length form of TrkB and we used it both in Western blot and immunohistochemistry.3. We found that the expression of TrkB receptor increases during development, but that there is no effect on visual experience, since dark-reared animals show the same protein level and pattern of TrkB expression compared to age-matched, normally reared controls.     

Apoptotic Membrane Blebbing Is Regulated by Myosin Light Chain Phosphorylation

The evolutionarily conserved execution phase of apoptosis is defined by characteristic changes occurring during the final stages of death; specifically cell shrinkage, dynamic membrane blebbing, condensation of chromatin, and DNA fragmentation. Mechanisms underlying these hallmark features of apoptosis have previously been elusive, largely because the execution phase is a rapid event whose onset is asynchronous across a population of cells. In the present study, a model system is described for using the caspase inhibitor, z-VAD-FMK, to block apoptosis and generate a synchronous population of cells actively extruding and retracting membrane blebs. This model system allowed us to determine signaling mechanisms underlying this characteristic feature of apoptosis. A screen of kinase inhibitors performed on synchronized blebbing cells indicated that only myosin light chain kinase (MLCK) inhibitors decreased blebbing. Immunoprecipitation of myosin II demonstrated that myosin regulatory light chain (MLC) phosphorylation was increased in blebbing cells and that MLC phosphorylation was prevented by inhibitors of MLCK. MLC phosphorylation is also mediated by the small G protein, Rho. C3 transferase inhibited apoptotic membrane blebbing, supporting a role for a Rho family member in this process. Finally, blebbing was also inhibited by disruption of the actin cytoskeleton. Based on these results, a working model is proposed for how actin/myosin II interactions cause cell contraction and membrane blebbing. Our results provide the first evidence that MLC phosphorylation is critical for apoptotic membrane blebbing and also implicate Rho signaling in these active morphological changes. The model system described here should facilitate future studies of MLCK, Rho, and other signal transduction pathways activated during the execution phase of apoptosis.     

柽柳bZIP基因调控耐盐相关基因的表达

本研究探讨了柽柳（Tamarixhispida）bZIP（basicleucine zipper）基因对抗逆基因表达的调控。我们比较了非盐胁迫和盐胁迫条件下非转基因和转bZIP基因植株的SOD、POD、ATPase、GST、LTP和LEA等基因表达量的变化。结果表明,在非胁迫条件下,bZIP转录因子可能直接调控了poxN1、TOBPXD、TOBLTP和ltp1基因的表达,而其他基因的表达可能不受bZIP转录因子的直接调控。在盐胁迫下,bZIP转录因子能够直接或间接地调控部分抗逆基因的表达,使它们的表达量显著增强。     

Fibrin Fiber Stiffness Is Strongly Affected by Fiber Diameter,but Not by Fibrinogen Glycation

The major structural component of a blood clot is a mesh of fibrin fibers. Our goal was to determine whether fibrinogen glycation and fibrin fiber diameter have an effect on the mechanical properties of single fibrin fibers. We used a combined atomic force microscopy/fluorescence microscopy technique to determine the mechanical properties of individual fibrin fibers formed from blood plasma. Blood samples were taken from uncontrolled diabetic patients as well as age-, gender-, and body-mass-index-matched healthy individuals. The patients then underwent treatment to control blood glucose levels before end blood samples were taken. The fibrinogen glycation of the diabetic patients was reduced from 8.8 to 5.0 mol glucose/mol fibrinogen, and the healthy individuals had a mean fibrinogen glycation of 4.0 mol glucose/mol fibrinogen. We found that fibrinogen glycation had no significant systematic effect on single-fiber modulus, extensibility, or stress relaxation times. However, we did find that the fiber modulus, Y, strongly decreases with increasing fiber diameter, D, as Y ∝ D^?1.6. Thin fibers can be 100 times stiffer than thick fibers. This is unusual because the modulus is a material constant and should not depend on the sample dimensions (diameter) for homogeneous materials. Our finding, therefore, implies that fibrin fibers do not have a homogeneous cross section of uniformly connected protofibrils, as is commonly thought. Instead, the density of protofibril connections, ρ_Pb, strongly decreases with increasing diameter, as ρ_Pb ∝ D^?1.6. Thin fibers are denser and/or have more strongly connected protofibrils than thick fibers. This implies that it is easier to dissolve clots that consist of fewer thick fibers than those that consist of many thin fibers, which is consistent with experimental and clinical observations.     

Nitrate Respiration in Chemoautotrophic Symbionts of the Bivalve Lucinoma aequizonata Is Not Regulated by Oxygen

The marine bivalve Lucinoma aequizonata has intracellular chemoautotrophic symbionts residing in the gill tissue. These bacteria are capable of nitrate respiration even under fully saturated oxygen conditions. Nitrate reductase in the symbionts of L. aequizonata appears to be constitutively expressed and without significant regulation by oxygen or nitrate. We discuss the stationary-phase growth state of the symbionts as an explanation for the lack of enzyme induction.     

Widely Used Enhancer of Eukaryotic Expression Vectors Is Strongly and Differentially Regulated in Fibroblast, Myoblast, and Teratocarcinoma Cell Lines

The expression of transgenes in eukaryotic cells is a powerful approach in cell biology. In most cases, it is based on the activity of strong and constitutive viral cis-acting elements in eukaryotic expression vectors. Here we show that a widely used such element derived from an early gene of human cytomegalovirus is strongly and differentially regulated in mouse cell lines. We analyzed cytomegalovirus promoter-driven expression of stably transfected transgenes in growing, confluent, and differentiating mouse 3T3 fibroblasts, C2C12 myoblasts, and P19 teratocarcinoma cells. In the fibroblasts, transgene expression was strongly downregulated in confluent cultures and was upregulated in growing or confluent cultures by phorbol ester. In contrast, no downregulation by confluency, nor upregulation by phorbol ester, was detected in C2C12 cells. In addition, while marked upregulation was detected in differentiating myotubes, transgene expression was downregulated when differentiating teratocarcinoma cells assumed a neuronal phenotype. These results demonstrate the existence of drastic differences in the regulation of transgene expression in different types of cell lines, indicating that when studying transgene function in cells that are not growing exponentially, viral promoter-driven expression should not be taken for granted.     

Expression of Ethylene Biosynthetic Genes Regulated by Pollination associated Factors in Doritaenopsis hybrida Flowers

Pollination of flowers initiates postpollination development in orchid ( Doritaenopsis hybrida Hort. ) flowers, including perianth senescence, stigma closure, and ovary development. Because ethylene is thought to play a key role in coordinating these developmental changes, the authors studied the temporal and spatial patterns of expression of genes encoding 1-aminocyclopropane-l-carboxylic acid (ACC) synthase and ACC oxidase following pollination-associated factor treatments in orchid flowers. Both ACC synthase and ACC oxidase mRNA accumulation in the various parts of the flowers is induced by auxin, and ethylene, but not by emasculation. The patterns of both ACC synthase and ACC oxidase mRNA accumulation are similar in all floral organs following auxin and ethylene treatments. Further, in situ hybridization analysis indicates that the ACC oxidase mRNA is localized in epidermal and parenchyma cells of the stigma after auxin and ethylene treatments. The putative roles of auxin, ethylene and emasculation are discussed in terms of the regulation of ACC synthase and ACC oxidase gene expression in flowers.     

AtSTP3启动子控制的外源基因在转基因水稻中的特异表达研究

利用PCR技术从哥伦比亚型拟南芥基因组DNA中分离了AtSTP3绿色组织特异表达的启动子,序列分析表明,扩增片段(1774bp)与已报道序列的相应区域同源性达99.9%。将其与GUS报告基因融合在一起,构建了植物表达载体,并由农杆菌介导法导入水稻品种‘中花11’中。对转基因水稻植株中的GUS活性进行定性与定量测定结果表明,AtSTP3启动子可驱动GUS报告基因在转基因水稻植株叶片中特异性表达,而在根和种子等器官中不表达或表达活性极弱,AtSTP3启动子表现出明显的组织特异性。     

与授粉有关的因子调节的乙烯生物合成基因在兰花花器官中的表达

分析了与授粉有关的因子调节的ＡＣＣ合酶和ＡＣＣ氧化酶基因在朵丽蝶兰（ＤｏｒｉｔａｅｎｏｐｓｉｓｈｙｂｒｉｄａＨｏｒｔ．）花中的表达。生长素和乙烯均可诱导ＡＣＣ合酶和ＡＣＣ氧化酶的ｍＲＮＡ在花器官中积累。然而,去雄却不能诱导这两个基因在花器官中表达。生长素和乙烯所诱导的ＡＣＣ合酶和ＡＣＣ氧化酶的ｍＲＮＡ在花器官中的积累模式相似。原位杂交结果表明,生长素和乙烯处理后ＡＣＣ氧化酶的ｍＲＮＡ在柱头的表皮和薄壁细胞中积累。根据ＡＣＣ合酶和ＡＣＣ氧化酶基因表达的结果,对生长素、乙烯和去雄在兰花授粉后乙烯生物合成过程中的作用进行了分析。     

The Expression of Three Opsin Genes from the Compound Eye of Helicoverpa armigera (Lepidoptera: Noctuidae) Is Regulated by a Circadian Clock,Light Conditions and Nutritional Status

Visual genes may become inactive in species that inhabit poor light environments, and the function and regulation of opsin components in nocturnal moths are interesting topics. In this study, we cloned the ultraviolet (UV), blue (BL) and long-wavelength-sensitive (LW) opsin genes from the compound eye of the cotton bollworm and then measured their mRNA levels using quantitative real-time PCR. The mRNA levels fluctuated over a daily cycle, which might be an adaptation of a nocturnal lifestyle, and were dependent on a circadian clock. Cycling of opsin mRNA levels was disturbed by constant light or constant darkness, and the UV opsin gene was up-regulated after light exposure. Furthermore, the opsin genes tended to be down-regulated upon starvation. Thus, this study illustrates that opsin gene expression is determined by multiple endogenous and exogenous factors and is adapted to the need for nocturnal vision, suggesting that color vision may play an important role in the sensory ecology of nocturnal moths.     

Intensity of Mutualism Breakdown Is Determined by Temperature Not Amplification of Wolbachia Genes

Wolbachia are maternally transmitted intracellular bacterial symbionts that infect approximately 40% of all insect species. Though several strains of Wolbachia naturally infect Drosophila melanogaster and provide resistance against viral pathogens, or provision metabolites during periods of nutritional stress, one virulent strain, wMelPop, reduces fly lifespan by half, possibly as a consequence of over-replication. While the mechanisms that allow wMelPop to over-replicate are still of debate, a unique tandem repeat locus in the wMelPop genome that contains eight genes, referred to as the “Octomom” locus has been identified and is thought to play an important regulatory role. Estimates of Octomom locus copy number correlated increasing copy number to both Wolbachia bacterial density and increased pathology. Here we demonstrate that infected fly pathology is not dependent on an increased Octomom copy number, but does strongly correlate with increasing temperature. When measured across developmental time, we also show Octomom copy number to be highly variable across developmental time within a single generation. Using a second pathogenic strain of Wolbachia, we further demonstrate reduced insect lifespan can occur independently of a high Octomom locus copy number. Taken together, this data demonstrates that the mechanism/s of wMelPop virulence is more complex than has been previously described.