Secretogranin II: a key AP-1-regulated protein that mediates neuronal differentiation and protection from nitric oxide-induced apoptosis of neuroblastoma cells.

Identification of AP-1 target genes in apoptosis and differentiation has proved elusive. Secretogranin II (SgII) is a protein widely distributed in nervous and endocrine tissues, and abundant in neuroendocrine granules. We addressed whether SgII is regulated by AP-1, and if SgII is involved in neuronal differentiation or the cellular response to nitrosative stress. Nitric oxide (NO) upregulated sgII mRNA dependent on a cyclic AMP response element (CRE) in the sgII promoter, and NO stimulated SgII protein secretion in neuroblastoma cells. Upregulation of sgII mRNA, sgII CRE-driven gene expression and SgII protein synthesis/export were attenuated in cells transformed with dominant-negative c-Jun (TAM67), which became sensitized to NO-induced apoptosis and failed to undergo nerve growth factor-dependent neuronal differentiation. Stable transformation of TAM67 cells with sgII restored neuronal differentiation and resistance to NO. RNAi knockdown of sgII in cells expressing functional c-Jun abolished neuronal differentiation and rendered the cells sensitive to NO-induced apoptosis. Therefore, SgII represents a key AP-1-regulated protein that counteracts NO toxicity and mediates neuronal differentiation of neuroblastoma cells.

Molecular phylogenetics and the classification of honey bee viruses.

We present the phylogenetic relationships of several picorna-like RNA viruses found in honey bees, with respect to 13 additional plant and animal positive-strand RNA viruses. Most of the honey bee viruses fall into an unnamed family of insect RNA viruses typified by the Drosophila C virus. Different bee viruses are broadly distributed within this group, suggesting either that the ability to infect honey bees has evolved multiple times, or that these viruses are generalistic in their abilities to infect insect hosts. At least one major change in gene order has occurred among the bee viruses, based on their phylogenetic affiliations. At the amino-acid level, the bee viruses differed by 15-28% at three conserved loci. Most differed by greater than 50% at the RNA level, indicating that sequence-based methods for bee virus identification must be tailored to at least three different virus clades independently.

ATP-stimulated c-fos and zif268 mRNA expression is inhibited by chemical hypoxia in a rat brain-derived type 2 astrocyte cell line, RBA-2.

The stimulus-transcriptional coupling during ischemia/hypoxia was examined for ATP-stimulated expression of immediate early genes (IEGs; c-fos, zif268, c-myc and nur77) in a rat brain-derived type 2 astrocyte cell line, RBA-2. Incubation of cells with 1 mM of extracellular ATP stimulated time-dependent expression of c-fos and zif268. ATP induced the largest increases in zif268 mRNA and a lesser one in c-fos mRNA. ATP also induced a slight increase in nur77 mRNA but was ineffective in inducing c-myc expression in these cells. Brief exposure of cells to potassium cyanide to simulate chemical hypoxia induced 9-fold and 7-fold transient increases in c-fos and zif268 expression, respectively, but did not affect c-myc or nur77 expression. When cyanide and ATP were added together, the expression of c-fos and zif268 expression was inhibited, and the effect was mimicked by simulating chemical hypoxia with sodium azide. To elucidate the mechanism involved, the effect of cyanide on ATP-stimulated increases in intracellular Ca(2+) concentrations, [Ca(2+)](i), and phospholipase D (PLD) activities were measured. Cyanide induced an increase in [Ca(2&plus);](i) and further enhanced the ATP-stimulated increases in [Ca(2+)](i) and PLD activities. Nevertheless, metabolic inhibitor, iodoacetate, blocked the ATP-induced c-fos and partially inhibited zif268 expression, and deprivation of cells with glucose also inhibited the ATP-induced c-fos expression. Taken together, these results demonstrate that both extracellular ATP and chemical hypoxia induce c-fos and zif268 expression in RBA-2 type 2 astrocytes. The chemical hypoxia inhibited ATP-stimulated c-fos and zif268 expression is not due to alterations in Ca(2+) and PLD signaling, and is at least partially related to metabolic disturbance in these cells.

ATP-stimulated Ca2+ influx and phospholipase D activities of a rat brain-derived type-2 astrocyte cell line, RBA-2, are mediated through P2X7 receptors.

This study characterizes and examines the P2 receptor-mediated signal transduction pathway of a rat brain-derived type 2 astrocyte cell line, RBA-2. ATP induced Ca2+ influx and activated phospholipase D (PLD). The ATP-stimulated Ca2+ influx was inhibited by pretreating cells with P2 receptor antagonist, pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), in a concentration-dependent manner. The agonist 2'- and 3'-O-(4-benzoylbenzoyl)adenosine 5'-triphosphate (BzATP) stimulated the largest increases in intracellular Ca2+ concentrations ([Ca2+]i); ATP, 2-methylthioadenosine triphosphate tetrasodium, and ATPgammaS were much less effective, whereas UTP, ADP, alpha,beta-methylene-ATP, and beta,gamma-methylene-ATP were ineffective. Furthermore, removal of extracellular Mg2+ enhanced the ATP- and BzATP-stimulated increases in [Ca2+]i. BzATP stimulated PLD in a concentration- and time-dependent manner that could be abolished by removal of extracellular Ca2+ and was inhibited by suramin, PPADS, and oxidized ATP. In addition, PLD activities were activated by the Ca2+ mobilization agent, ionomycin, in an extracellular Ca2+ concentration-dependent manner. Both staurosporine and prolonged phorbol ester treatment inhibited BzATP-stimulated PLD activity. Taken together, these data indicate that activation of the P2X7 receptors induces Ca2+ influx and stimulates a Ca2+-dependent PLD in RBA-2 astrocytes. Furthermore, protein kinase C regulates this PLD.

Multidimensional rotations for robust quantization of image data.

Laplacian and generalized Gaussian data arise in the transform and subband coding of images. This paper describes a method of rotating independent, identically distributed (i.i.d.) Laplacian-like data in multiple dimensions to significantly improve the overload characteristics for quantization. The rotation is motivated by the geometry of the Laplacian probability distribution, and can be achieved with only additions and subtractions using a Walsh-Hadamard transform. Its theoretical and simulated results for scalar, lattice, and polar quantization are presented in this paper, followed by a direct application to image compression. We show that rotating the image data before quantization not only improves compression performance, but also increases robustness to the channel noise and deep fades often encountered in wireless communication.

Error-resilient pyramid vector quantization for image compression.

Pyramid vector quantization (PVQ) uses the lattice points of a pyramidal shape in multidimensional space as the quantizer codebook. It is a fixed-rate quantization technique that can be used for the compression of Laplacian-like sources arising from transform and subband image coding, where its performance approaches the optimal entropy-coded scalar quantizer without the necessity of variable length codes. In this paper, we investigate the use of PVQ for compressed image transmission over noisy channels, where the fixed-rate quantization reduces the susceptibility to bit-error corruption. We propose a new method of deriving the indices of the lattice points of the multidimensional pyramid and describe how these techniques can also improve the channel noise immunity of general symmetric lattice quantizers. Our new indexing scheme improves channel robustness by up to 3 dB over previous indexing methods, and can be performed with similar computational cost. The final fixed-rate coding algorithm surpasses the performance of typical Joint Photographic Experts Group (JPEG) implementations and exhibits much greater error resilience.

Development of continuous cell lines from the egg parasitoids Trichogramma confusum and T. exiguum.

Although numerous insect cell lines have been developed over the past three decades, few of these have been from the order Hymenoptera. This report describes two new continuous cell lines from trichogrammid wasps. The extremely small size of these insects has made physiological and biochemical studies difficult. Now, with the development of the cell lines, a limitless supply of biologically active material is available for a wide variety of basic biological studies. The Trichogramma confusum and T. exiguum cell lines (designated IPLB-Tcon1 and IPLB-Tex2) were characterized by chromosome and isozymes techniques. Evidence of their utility is shown by morphological response to the developmental hormone, 20-hydroxyecdysone. The morphological change in IPLB-Tex2 is accompanied by an induction of highly contractile cells which indicates this cell line may be composed of myoblast cells.

Insemination-induced histolysis of the flight musculature in fire ants (Solenopsis, spp.): an ultrastructural study (1).

The fine structure of the insemination-induced flight muscle degeneration (histolysis) in the queen fire ant (Solenopsis spp.) has been investigated. Within 2 hours post-insemination, degenerative changes are detectable in the most peripheral fasciculi of the fibrillar flight muscle. Histolysis proceeds internally with time. Myofibril (sarcomere) dissolution begins with myofilament breakdown and continues until only free Z-line material remains. The latter subsequently disappears leaving, at the terminal stages, only nuclei, lamellar bodies (myelin figures), and tracheoles as residual myoid elements. Lysosomes and/or phagocytes do not appear to play a primary role in the initiation and continuance of this process.

Interspecific hybridization and caste specificity of protein in fire ant.

One natural population of fire ant in Texas was found to be a hybrid between Solenopsis geminata and S. xyloni. Evidence from isozyme studies and breeding experiments is provided to demonstrate interspecific hybridization in ants. In this hybrid population, all worker ants have both parental types of nicotinamide adenine dinucleotide-malate dehydrogenase isozymes, but 95 percent of queens possess only the maternal type.