Dopamine regulates phosphate uptake by opossum kidney cells through multiple counter-regulatory receptors

The purpose of this study was to determine the mechanisms of dopamine regulation of phosphate uptake in opossum kidney (OK) cells, a model of proximal renal tubules. Dopamine stimulated cAMP generation and inhibited radiolabeled phosphate uptake into OK cell monolayers by 14.4 +/- 1.8%. The effect of dopamine was transient, as phosphate uptake returned toward control level by 3 h despite the continued presence of dopamine. Pretreatment with pertussis toxin increased dopamine inhibition of phosphate uptake to 25 +/- 3%, increased the duration of the dopamine effect to at least 3 h, and enhanced cAMP generation. In an OK cell clone that overexpressed cAMP phosphodiesterase, dopamine did not inhibit phosphate uptake, but pharmacologic inhibition of protein kinase A activation did not prevent dopamine inhibition of phosphate uptake. A DA1 receptor agonist inhibited phosphate uptake more potently than dopamine (29.5 +/- 1.1%) or a DA2 receptor agonist (7.9 +/- 2%). However, both DA1 and DA2 receptor antagonists completely blocked dopamine inhibition of phosphate uptake. DA1, but not the DA2, antagonists blocked dopamine-stimulated cAMP generation. Treatment with alpha-adrenergic receptor antagonists potentiated dopamine inhibition of phosphate uptake to the same extent as pertussis toxin and was not additive with pertussis toxin. It is concluded that dopamine inhibits phosphate uptake through DA1 and DA2 receptor stimulation by cAMP-dependent and -independent pathways and activates a pertussis toxin-sensitive counter-regulatory pathway that attenuates this response through alpha-adrenergic receptor stimulation.     

Speculative Versioning Cache

Dependences among loads and stores whose addresses are unknown hinder the extraction of instruction level parallelism during the execution of a sequential program. Such ambiguous memory dependences can be overcome by memory dependence speculation which enables a load or store to be speculatively executed before the addresses of all preceding loads and stores are known. Furthermore, multiple speculative stores to a memory location create multiple speculative versions of the location. Program order among the speculative versions must be tracked to maintain sequential semantics. A previously proposed approach, the Address Resolution Buffer (ARB) uses a centralized buffer to support speculative versions. Our proposal, called the Speculative Versioning Cache (SVC), uses distributed caches to eliminate the latency and bandwidth problems of the ARB. The SVC conceptually unifies cache coherence and speculative versioning by using an organization similar to snooping bus-based coherent caches. Our evaluation for the Multiscalar architecture shows that hit latency is an important factor affecting performance and private cache solutions trade-off hit rate for hit latency     

A systematic review of state-of-the-art noise removal techniques in digital images

Digital Image processing is a subcategory of digital signal processing that lays emphasis on the study of processing techniques used for enhancement or restoration. De-noising of images corrupted with various types of noises falls into this category. De-noising is mainly performed to enhance the understandability of an affected image. Images captured with faulty equipment or being transmitted over long distances are highly prone to be depraved by impulse noise, so, various techniques are presented for removal of this noise from images. Each of the presented technique has its own merits and demerits. This paper presents a comprehensive comparative analysis of these techniques over a wide range of noise densities. All the filtering techniques are implemented in MATLAB and simulated with standard benchmark image data and qualitative metrics namely Peak Signal to Noise Ratio (PSNR) and Structural Similarity Index (SSIM) are evaluated and compared. Therefore, this paper presents a comprehensive comparative analysis of various state-of-the-art noise removal techniques.

     

Bacillus thuringiensis enzyme-digested delta endotoxin: effect on cultured insect cells

Cells from three insect cell lines responded to the enzyme-digested delta endotoxin of Bacillus thuringiensis with swelling, lysis, and vesicle formation. Sufficient toxin was taken up in 1 minute to cause half-maximal cell damage. Cytoxic activity was neutralized by specific antiserum to the endotoxin.     

Performance of DSWC diversity system using suboptimum adaptive switching threshold in independent and correlated nakagami‐m fading channels

The use of dual switched combining (DSWC) diversity reception scheme, for combating the detrimental effects of fading on digital transmissions, is popular due to its simpler implementation. The performance of switched diversity strategy is dependent on the selection of the switching threshold. But, for the analysis and design of the DSWC diversity system, the closed form analytical solution for optimum adaptive switching threshold is not possible for most of the modulation schemes in correlated fading environment. This letter presents an approximate, but simple and closed form, generic expression for adaptive switching threshold, called in this case as suboptimum adaptive switching threshold, in independent and correlated Nakagami‐m fading channels for a wide range of binary and M‐ary modulation schemes. It is shown that the average symbol error rate (ASER) performance obtained using this suboptimum adaptive switching threshold is almost same as obtained using optimum adaptive switching threshold. Copyright © 2005 John Wiley & Sons, Ltd.     

Dielectric property and electromagnetic interference shielding effectiveness of ethylene vinyl acetate‐based conductive composites: Effect of different type of carbon fillers

Carbon black, short carbon fiber (SCF), and multiwall carbon nano‐tube (MWNT)‐filled conductive composites were prepared from ethylene vinyl acetate copolymer. The dielectric property and electromagnetic interference (EMI) shielding of carbon black, MWNT, and SCF‐filled composites were studied with different filler loadings. The dielectric constant and loss of filled polymer composites is due to the formation of interfacial polarization in the polymer matrix. It was found that the dielectric constant, dielectric loss, and EMI shielding of filled composites depends on amount and type of filler loading. The results of different experiments have been discussed in the light of break down and formation of continuous conductive network in polymer matrix. The results indicate that these composites can be used as effective EMI shielding materials. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers.     

Crystal structure of the zinc-dependent beta-lactamase from Bacillus cereus at 1.9 A resolution: binuclear active site with features of a mononuclear enzyme

The structure of the zinc-dependent beta-lactamase II from Bacillus cereus has been determined at 1.9 A resolution in a crystal form with two molecules in the asymmetric unit and 400 waters (space group P3121; Rcryst = 20.8%). The active site contains two zinc ions: Zn1 is tightly coordinated by His86, His88, and His149, while Zn2 is loosely coordinated by Asp90, Cys168, and His210. A water molecule (W1) lies between the two zinc ions but is significantly closer to Zn1 and at a distance of only 1.9 A is effectively a hydroxide moiety and a potential, preactivated nucleophile. In fact, Asp90 bridges W1 to Zn2, and its location is thus distinct from that of the bridging water molecules in the binuclear zinc peptidases or other binuclear zinc hydrolases. Modeling of penicillin, cephalosporin, and carbapenem binding shows that all are readily accommodated within the shallow active site cleft of the enzyme, and the Zn1-bound hydroxide is ideally located for nucleophilic attack at the beta-lactam carbonyl. This enzyme also functions with only one zinc ion present. The Zn1-Zn2 distances differ in the two independent molecules in the crystal (3.9 and 4.4 A), yet the Zn1-W1 distances are both 1.9 A, arguing against involvement of Zn2 in W1 activation. The role of Zn2 is unclear, but the B. cereus enzyme may be an evolutionary intermediate between the mono- and bizinc metallo-beta-lactamases. The broad specificity of this enzyme, together with the increasing prevalence of zinc-dependent metallo-beta-lactamases, poses a real clinical threat, and this structure provides a basis for understanding its mechanism and designing inhibitors.     

Analysis of ecdysteroid action in Malacosoma disstria cells: cloning selected regions of E75- and MHR3-like genes

IPRI-MD-66 (MD-66) cells respond to 20-hydroxyecdysone (20E, 4 x 10(-6) M) in the medium by producing cytoplasmic extensions, clumping and attaching themselves to the substrate. These morphological changes are at a maximum by 6 days post treatment. Degenerate oligonucleotides, designed on the basis of conserved amino acid sequences in the DNA and ligand binding regions of the members of the steroid hormone receptor superfamily, were used in RNA-PCR to isolate two cDNA fragments, Malacosoma disstria hormone receptor 2 (MdHR2) and Malacosoma disstria hormone receptor 3 (MdHR3) from the MD-66 cells. Comparison of deduced amino acid sequences of these cDNA fragments with the members of the steroid hormone receptor superfamily showed that MdHR2 is most closely related to E75 proteins of Manduca sexta, Galleria mellonella and Drosophila melanogaster. The MdHR3 is most closely related to Manduca hormone receptor 3 (MHR3), Galleria hormone receptor 3 (GHR3) and Drosophila hormone receptor 3 (DHR3) proteins. At a concentration of 4 x 10(-6) M, 20E induces the expression of MdHR2 and MdHR3 beginning at 3 h, reaching maximum levels in 12 h and declining in 24 h. MdHR2 binds to a 2.5 kb mRNA, whereas MdHR3 binds to a 4.5 kb mRNA. Based on sequence similarity, RNA size and ecdysone inducibility, we conclude that these cDNA fragments, cloned from MD-66 cells, are regions of E75- (MdHR2) and MHR3- (MdHR3) like genes.     

Scalable shared-memory multiprocessor architectures

Directory-based and bus-based cache coherence schemes are defined and described. Directory-based schemes can be classified as centralized or distributed. Both categories support local caches to improve processor performance and reduce traffic in the interconnection. Schemes using presence flags, B pointers, and linked lists are discussed. Bus-based systems provide uniform memory access to all processors. This memory organization allows a simpler programming model, making it easier to develop new parallel applications or to move existing applications from a uniprocessor to a parallel system. Two architectural variations of bus-based systems are described: multiple-bus and hierarchical architectures