MPEG-21 in backpack journalism scenario

The vision of MPEG-21-the multimedia framework-is to enable transparent and augmented use of multimedia resources across a wide range of networks and devices used by different communities. As the initial standardization effort for MPEG-21 reaches its conclusion, this article explores one case scenario and examines whether MPEG-21 can achieve its vision.     

trans-Dominant and non-trans-dominant mutant simian virus 40 large T antigens show distinct responses to ATP

Simian virus 40 (SV40) DNA replication requires the coordinated action of multiple biochemical activities intrinsic to the virus-encoded large tumor antigen (T antigen). We report the preliminary biochemical characterization of the T antigens encoded by three SV40 mutants, 5030, 5031, and 5061, each of which have altered residues within or near the ATP binding pocket. All three mutants are defective for viral DNA replication in cultured cell lines. However, while 5030 and 5031 can be complemented in vivo by providing a wild-type T antigen in trans, 5061 exhibits a strong trans-dominant-negative phenotype. In order to determine the basis for their replication defects and to explore the mechanisms of trans dominance, we purified the T antigens encoded by each of these mutants and examined their activities in vitro. The 5061 T antigen had no measurable ATPase activity and failed to hexamerize in response to ATP, and its affinity for the SV40 origin of DNA replication (ori) DNA was not increased by ATP. In contrast, the 5030 and 5031 T antigens exhibited at least some ATPase activity and both readily formed hexamers in the presence of ATP. These mutants differed in that 5030 was very defective in an ori-dependent unwinding assay while 5031 retained significant activity. Both the 5030 and 5031 T antigens bound to ori-containing DNA, but the binding was less efficient than that of wild-type T antigen and was not affected by the presence of ATP. These results suggest that 5030 and 5031 are defective in some aspect of communication between the ATP binding and DNA binding domains and that the ability of ATP to induce T-antigen hexamerization is distinct from its action to increase the affinity for ori. Finally, all three mutants were defective for the ability to support SV40 DNA replication in vitro. Both the 5031 and 5061 T antigens inhibited wild-type-T-antigen-stimulated replication in vitro, while the 5030 T antigen did not. The fact that the 5031 T antigen was trans dominant in the in vitro assays but not in vivo indicates that the in vitro system does not accurately reflect events occurring in vivo.     

Ovine arylalkylamine N-acetyltransferase in the pineal and pituitary glands: differences in function and regulation

The enzyme arylalkylamine N-acetyltransferase (AANAT; EC 2.3.1.87) has been conventionally linked with the biosynthesis of melatonin within the pineal gland and retina. This study establishes that AANAT messenger RNA (mRNA) and functional enzyme occurs within the pars tuberalis (PT) and to a lesser degree within the pars distalis (PD) of the sheep pituitary gland; expression in these tissues is approximately 1/15th (PT) and 1/300th (PD) of that in the ovine pineal gland. AANAT mRNA in the PT appears to be expressed in the same cells as the Mel1a receptor. No evidence was obtained to indicate that either PT or PD cells have the ability to synthesize melatonin, suggesting that this enzyme plays a different functional role in the pituitary. We also found that cAMP regulation of the abundance of AANAT mRNA differs between the PT and pineal gland. Forskolin (10 microM) has no effect on pineal AANAT mRNA levels, yet represses expression in the PT. This suppressive influence could be mediated by ICER (inducible cAMP response early repressor), which is induced by forskolin in both tissues. Although it appears that the specific function and regulation of AANAT in the pituitary gland differ from that in the pineal gland, it seems likely that AANAT may play a role in the broader area of signal transduction through the biotransformation of amines.     

Transfection of the gene for B7-1 but not B7-2 can induce immunity to murine malignant mesothelioma

A 56-year-old female with rheumatoid arthritis was admitted because of bilateral hip pain. In a few months of her hospitalization, a relatively abrupt renal dysfunction was emerged besides complement breakdown, and renal biopsy revealed crescentic glomerulonephritis. Immunofluorescence study showed peripheral granular deposits of IgG, IgM, and C3 in the glomeruli. Cresents were predominantly composed of macrophages and glomerular epithelial cells. Amyloid nephropathy, renal vasuculitis, and association of other collagen vascular diseases were negligible for the causative factor. It was suggested that immune complexes were formed in the glomeruli, in which both humoral and cellular immune responses were to be induced, that brought cescents formation in the lesions. Crescentic glomerulonephritis in patients with rheumatoid arthritis is rare and a possible pathogenetic mechanisms involved in the development of renal dysfunction are discussed with the special reference to immune complex-induced inflammation.     

Mean-shape vector quantizer for ECG signal compression

A direct waveform mean-shape vector quantization (MSVQ) is proposed here as an alternative for electrocardiographic (ECG) signal compression. In this method, the mean values for short ECG signal segments are quantized as scalars and compression of the single-lead ECG by average beat substraction and residual differencing their waveshapes coded through a vector quantizer. An entropy encoder is applied to both, mean and vector codes, to further increase compression without degrading the quality of the reconstructed signals. In this paper, the fundamentals of MSVQ are discussed, along with various parameters specifications such as duration of signal segments, the wordlength of the mean-value quantization and the size of the vector codebook. The method is assessed through percent-residual-difference measures on reconstructed signals, whereas its computational complexity is analyzed considering its real-time implementation. As a result, MSVQ has been found to be an efficient compression method, leading to high compression ratios (CR's) while maintaining a low level of waveform distortion and, consequently, preserving the main clinically interesting features of the ECG signals. CR's in excess of 39 have been achieved, yielding low data rates of about 140 bps. This compression factor makes this technique especially attractive in the area of ambulatory monitoring.     

Influence of ventilation on indoor radon level

Detailed radon measurements were conducted at different residential units in Hong Kong in winter time when air-conditioners were off and also in summer time when air-conditioners were on. Ventilation rates were measured concurrently to investigate the influence of ventilation on indoor radon level. The ratio of indoor radon level to outdoor radon level was plotted against ventilation rate, and it was found that a critical value existed after which the indoor radon level could be considered identical to the outdoor level. This result is important for use in ventilation design to reduce indoor radon pollution.     

Processing and characterization of a biaxially oriented conducting polymer

Two methods have been developed for the preparation of biaxially oriented poly(phenylene vinylene) from its poly(sulfonium salt) precursor. A two-stage stretching process permits non-equibiaxial stretching over a wide range of deformation ratios and a bubble expansion technique allows equibiaxial planar extension. The resulting films were examined using X-ray diffraction prior to chemical doping with SbF₅ vapor. Biaxial orientation was shown to exert considerable influence over the attainable electrical conductivity.